Automobile - PDF

Document Sample
Automobile - PDF Powered By Docstoc
					The Car Maintenance Bibles

Everything the DIY car enthusiast needs to know about basic car maintenance, wheels, tyres or tires, engine oil or motor oil, suspension (including springs and shock absorbers), brakes (disc brakes and drum brakes), gearboxes, transmissions, engines, motors, petrol, gasoline and general car maintenance.

Choose your entry point: The Engine Oil Bible The Brake Bible The Transmission Bible The Suspension Bible The Fuel & Engine Bible The Steering Bible Basic Car Maintenance Tips The Wheel & Tyre Bible The Motorbike Suspension Bible Product Reviews

What's New?

Used cars for sale

http://www.carbibles.com/ (1 of 2) [2/6/2008 7:10:10 AM]

The Car Maintenance Bibles

This site and all contents unless otherwise noted are copyrighted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Technorati Profile

Elements of my title graphic come from CarArtz.com Click their logo to visit them.

The car maintenance bibles relate to all DIY aspects of basic car maintenance but are focused primarily on suspension, brakes, tyres or tires, wheels, oils and engines.

http://www.carbibles.com/ (2 of 2) [2/6/2008 7:10:10 AM]

Car Bibles : The Engine Oil Bible

The engine oil Bibles, covering everything you need to know about engine or motor oil including viscosity, friction reducers, additives, oil types, sludge, SAE and API classifications and ratings, what all the codes and markings mean, how your engine oil works, how to keep your engine running at peak fitness and much mode.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

How much do you value the engine in your car? Think about it, because the life of your engine depends in no small part on the quality of the oil you put in it - oil is the lifeblood of your car's engine. From the mid 80's for 8 or 9 years there was a veritable revolution in car engine oil. All oils were no longer the same thanks to the popularity of hot hatches, 16valve engines and turbos as the tuner scene started to rise. Combined with the devastating problems of black death, the days of one oil catering for everyone were over. Take Castrol for example. They led the field for years with GTX. This was surpassed a few years back by semi-synthetic and fully synthetic oils, including GTX2 and GTX3 Lightec. Now, that's been surpassed by Formula SLX which can cost upwards of £50 ($75) for 5 litres. And most recently, Castrol GTX Magnatec which is muscling in on the hitherto separate world of friction reducers (and we'll deal with them later, on the additives page.).

What does my oil actually do?
An engine oil's job is primarily to stop all the metal surfaces in your engine from grinding together and tearing themselves apart from friction whilst transferring heat away from the combustion cycle. Engine oil must also be able to hold all the nasty by-products of combustion, such as silica (silicon oxide) and acids in suspension. It cleans the engine of these chemicals and build-ups, and keeps the moving parts coated in oil. Finally, engine oil minimises the exposure to oxygen and thus oxidation at higher temperatures. It does all of these things under tremendous heat and pressure.

What the heck was Black Death?
Black Death first appeared in the early 80's when a horrible sticky black substance was found to be the cause of many engine seizures in Europe. Many engines were affected but Ford and Vauxhall (GM) suffered the most. Faster roads, higher under-hood temperatures, tighter engineering tolerances and overworked engine oils turned out to be contributors to the problem. The oils just couldn't handle it and changed their chemical makeup under pressure into a sort of tar-like glue. This blocked all the oil channels in the engines, starved them of lubrication and caused them to
http://www.carbibles.com/engineoil_bible.html (1 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

seize. I don't recommend this but you can reproduce the effect with a frying pan, cooking oil and a blowtorch. The cooking oil will heat up far quicker than it's designed to and will turn to a sticky black tar in your pan. Either that or it will set fire to your kitchen, which is why I said "don't do this". Anyway, burning kitchens aside, Black Death was the catalyst for the production of newer higher quality oils, many of them man-made rather than mineral-based.

Black death for the 21st century
There's a snappy new moniker for Black Death now, and it's called sludge. The cause is the same as Black Death and it seems to be regardless of maintenance or mileage. The chemical compounds in engine oils break down over time due to prolonged exposure to high temperatures and poor maintenance habits. When the oil oxidises, the additives separate from the oil and begin to chemically break down and solidify, leading to the baked-on oil deposits turning gelatinous, and that nasty compound is what is lovingly referred to nowadays as sludge. It's like black yoghurt. What doesn't help is that modern engines, due to packaging, have smaller sumps than in the "good old days" and so hold less oil. This means that the oil that is present in the engine can't hold as much crap (for want of a better word) and can lead to earlier chemical breakdown. The most common factor in sludge buildup is mineral oils combined with a lack of maintenance by the car owner combined with harsh driving conditions. But this isn't true in all cases. For some reason, a 2005 Consumer Reports article discovered that some engines from Audi, Chrysler, Saab, Toyota, and Volkswagen appear prone to sludge almost no matter how often the oil is changed.

What does sludge look like?
I was contacted by a BMW driver who's been having a particularly harsh time with sludge and has been discussing it on the Bimmerfest forums. He posted some images of his problem and other readers posted similarly-framed images of the same engine components in "normal" condition. Below are two of those photos. On the left is what the cam case should look like in a well maintained engine when photographed through the oil filler cap. On the right is what the same type of engine looks like when suffering sludge buildup.

http://www.carbibles.com/engineoil_bible.html (2 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible Picture credit: 'ketchup' at Bimmerfest

In this example, the consensus was that the sludge buildup was caused by an overheating engine, oil that hadn't been changed for 20,000 miles of stop-go city driving, a lot of cold starts and a period of about 12 months in storage without an oil change. Most of this happened before the current owner got it.

Curing sludge
There are no hard and fast rules for curing an engine of sludge buildup. If it's really bad, flushing the engine might be the only cure, but that could also cause even more problems. If flushing the engine results in bits of sludge getting lodged where they can do more damage, you're actually worse off. It's interesting to note that some race techs have reported sludge buildup in race engines as a result of aftermarket additives being used in conjunction with the regular oil. The chemical composition of the additives isn't as neutral as some companies would lead us to believe, and combined with particular types of oil and high-stress driving, they can cause oil breakdown and sludge to appear. The lesson from them appears to be "don't use additives".

When is sludge not sludge?
Easy. When it's an oil and water emulsion from a leaking or blown head gasket. If this happens, you get a whitish cream coloured sludge on the inside of the oil filler cap. The filler cap is typically cooler than the rest of the cam case and so the oil/water mix tends to condense there. So if you take the oil filler cap off and it looks like it's covered in vanilla yoghurt or mayonnaise, you've got a blown head gasket. A surefire way to confirm this is if your oil level is going up and your coolant level is going down. The coolant is getting through the breaks in the head gasket and mixing with the oil. When it gets to the sump it separates out and the oil floats on top. A slightly more accurate way to check for this condition is to use a combustion leak tester, or block tester. If you're in America, NAPA sell them for about $45 (part #BK 7001006). If you're in England, Sealey sell them for about £70 (model number VS0061). Combustion leak testers are basically a turkey baster filled with PH liquid, with a non-return valve at the bottom. To use one, run your engine for a few minutes until its warm (not hot) then turn it off. Use a protective glove (like an oven glove) and take the radiator or reservoir cap off. Plug the bottom of the combustion leak tester into the hole and squeeze the rubber bulb on top. It will suck air from the top of the coolant through the non-return valve and bubble it through the PH liquid. If the liquid changes colour (normally blue to yellow), it means there is combustion gas in the coolant, which means a head gasket leak. There is one other possible cause for this yellow goop : a blocked scavenger hose. Most engines have a hose which comes off the cam cover and returns to the engine block somewhere via a vacuum line. This is the scavenger hose which scavenges oil vapour and gasses that build up in the cam cover. If it's blocked you can end up with a buildup of condensation inside the cam cover, which can manifest itself as the yellow goop inside the filler cap.

VW / Audi sludge problems
While the the 1.8T engines in Audi A4's, Audi TT, VW Passat, Jetta, Golf, New Bettle, are all very prone to sludge build-up, Audi/VW does not have an extended warranty for them from the factory. The factory warranty is 4 year/50,000 miles but it can be extended if purchased. Although Audi/VW now has 10,000 mile service intervals, oil changes can be done between "services", and should be done if the vehicle is driven in heavy traffic, offroad, and non-highway use. Also, Audi/ VW will only warrant an engine if the customer has proof of all their oil changes. As of 2004 I belive all 1.8T engines must use synthetic oil. So if you own one of these sludge-prone engines, what can you do? Obviously, Volkswagen Audi Group (VAG) recommends that you use only VW/AUDI recommended oil which at the time of writing is Castrol Syntec 5W-40. You should also keep up on your oil changes, making them more frequent if you drive hard or haul a lot of cargo. The most important thing for the VW or Audi owner is this: if the oil light comes on and beeps the high pitch beep that most everyone ignores, pull over and shut the engine down immediately. Many VAG engines can be saved by this procedure. Have the vehicled towed to a VAG dealer. Their standard procedure is to inspect the cam bearings; if they're not scored, the oil pan will be removed and cleaned out and all the crankcase breather hoses and the oil pickup tube will be replaced. They'll do an oil pressure test with a mechanical gauge, and hopefully will also replace the turbo lines. Finally, the turbo will be checked for bearing free-play. The VAG turbos run really hot even with proper oil and coolant supply that's why you need a good quality synthetic in them.
http://www.carbibles.com/engineoil_bible.html (3 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

Toyota sludge problems
For their part, Toyota have the dubious honour of having the most complaints about sludge buildup in their engines - 3,400 at the last count. At the time of writing there is a class action suit going on against them. Details can be found at www.oilgelsettlement.com

Saab sludge problems
For an example of sludge in a Saab 9 5 Aero with only 42,000 miles on it, you might be interested to read my case study on this engine, put together with the help of a reader. Our sludge case study.

Mineral or synthetic?
Mineral oils are based on oil that comes from dear old Mother Earth which has been refined. Synthetic oils are entirely concocted by chemists wearing white lab coats in oil company laboratories. For more info, see the section on synthetics further down the page. The only other type is semi-synthetic, sometimes called premium, which is a blend of the two. It is safe to mix the different types, but it's wiser to switch completely to a new type rather than mixing.

Synthetics
Despite their name, most synthetic derived motor oils (ie Mobil 1, Castrol Formula RS etc ) are actually derived from mineral oils - they are mostly Polyalphaolifins and these come from the purest part of the mineral oil refraction process, the gas. PAO oils will mix with normal mineral oils which means Joe public can add synthetic to his mineral, or mineral to his synthetic without his car engine seizing up. (In truth, Mobil 1 is actually made by reformulating ethanol). The most stable bases are polyol-ester (not polyester, you fool). When I say 'stable' I mean 'less likely to react adversely with other compounds.' Synthetic oil bases tend not to contain reactive carbon atoms for this reason. Reactive carbon has a tendency to combine with oxygen creating an acid. As you can imagine, in an oil, this would be A Bad Thing. So think of synthetic oils as custom-built oils. They're designed to do the job efficiently but without any of the excess baggage that can accompany mineral based oils.

Pure synthetics
Pure synthetic oils (polyalkyleneglycol) are the types used almost exclusively within the industrial sector in polyglycol gearbox oils for heavily loaded gearboxes. These are typically concocted by intelligent blokes in white lab coats. These chaps break apart the molecules that make up a variety of substances, like vegetable and animal oils, and then recombine the individual atoms that make up those molecules to build new, synthetic molecules. This process allows the chemists to actually "fine tune" the molecules as they build them. Clever stuff. But Polyglycols don't mix with normal mineral oils. While we're on synthetic oils, I should mention Amsoil. I originally had them down as an additive. I was wrong. I've got to say I've had no experience of the product myself so I can't vent my spleen about it. However, there is a particularly good page with a ton of info about it here. I recommend you pop over and read this and see what you think. I've been contacted by Amsoil themselves and asked to point out the following: Amsoil do NOT produce or market oil additives and do not wish to be associated with oil additives. They are a formulator of synthetic lubricants for automotive and industrial applications and have been in business for 30+ years. They are not a half-hour infomercial or fly-by-night product, nor have they ever been involved in a legal suit regarding their product claims in that 30+ year span. Many Amsoil products are API certified, and ALL of our products meet and in most cases exceed the specifications of ILSAC, AGMA etc..... Their lubricants also exceed manufacturers specifications and Amsoil are on many manufacturers approval lists. They base their claims on ASTM certified tests and are very open to anyone, with nothing to hide. It turns out that Amsoil actually have the stance that they recommend engine oil additives are NOT to be used with
http://www.carbibles.com/engineoil_bible.html (4 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

their products. This will become relevant later on this page, and in the additives section. They have a pretty good FAQ on the Amsoil website, which you can find here.

Mixing Mineral and Synthetic oils - the old and busted concepts
For the longest time, I had this to say about mixing mineral and synthetic oils:
●

●

●

If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. I learned this lesson the hard way! It's wise to use a flushing oil first. If you do decide to change, only go up the scale. If you've been running around on synthetic, don't change down to a mineral-based oil - your engine might not be able to cope with the degradation in lubrication. Consequently, if you've been using mineral oil, try a semi or a full synthetic oil. By degradation, I'm speaking of the wear tolerances that an engine develops based on the oil that it's using. Thicker mineral oils mean thicker layers of oil coating the moving parts (by microns though). Switching to a thinner synthetic oil can cause piston rings to leak and in some very rare cases, piston slap or crank vibration. Gaskets and seals! With the makeup of synthetic oils being different from mineral oils, mineral-oil-soaked gaskets and seals have been known to leak when exposed to synthetic oils. Perhaps not that common an occurrence, but worth bearing in mind nevertheless.

Mixing Mineral and Synthetic oils - the new hotness
That's the thing with progress - stuff becomes out-of-date. Fortunately for you, dear reader, the web is a great place to keep things up-to-date, so here's the current thinking on the subject of mixing mineral and synthetic oils. This information is based on the answer to a technical question posed on the Shell Oil website. There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synetics. Polyglycols don't mix with normal mineral oils.) There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months. There was a time, years ago, when switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal material have taken care of those issues. And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what newfangled additives the oil companies are putting in their products.

Flushing oils
These are special compound oils that are very, very thin. They almost have the consistency of tap water when cold as well as hot. Typically they are 0W/20 oils. Don't ever drive with these oils in the engine - it won't last. (Caveat : some hybrid vehicles now require 0W20, so if you're a hybrid driver, check your owner's manual). Their purpose is for cleaning out all the gunk which builds up inside an engine. Note that Mobil1 0W40 is okay, because the '40' denotes that it's actually thick enough at temperature to work. 0W20 just doesn't get that viscous! To use them, drain your engine of all it's oil, but leave the old oil filter in place. Next fill it up with flushing oil and run it at a fast idle for about 20 minutes. Finally, drain all this off (and marvel at the crap that comes out with it), replace the oil filter, refill with a good synthetic oil and voila! Clean engine. Of course, like most things nowadays, there's a condition attached when using flushing oils. In an old engine you really don't want to remove all the deposits. Some of these deposits help seal rings, lifters and even some of the flanges between the heads, covers, pan and the block, where the gaskets are thin. I have heard of engines with over 280,000km that worked fine, but when flushed it failed in a month because the blow-by past the scraper ring(now really clean) contaminated the oil and screwed the rod bearings.
http://www.carbibles.com/engineoil_bible.html (5 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

Using Diesel oil for flushing
A question came up some time ago about using diesel-rated oils to flush out petrol engines. The idea was that because of the higher detergent levels in diesel engine oil, it might be a good cleaner / flusher for a non-diesel engine. Well most of the diesel oil specification oils can be used in old petrol engines for cleaning, but you want to use a low specification oil to ensure that you do not over clean your engine and lose compression for example. Generally speaking, an SAE 15W/40 diesel engine oil for about 500 miles might do the trick.

The question of phosphorus.
Phosphorus is the key component for valve train protection in an engine, and 1600ppm (parts per million) used to be the standard for phosphorus in engine oil. In 1996 that was dropped to 800ppm and then more recently to 400ppm - a quarter of the original spec. Valvetrains and their components are not especially cheap to replace and this drop in phosphorus content has been a problem for many engines. So why was the level dropped? Money. Next to lead, it's the second most destructive substance to shove through a catalytic converter. The US government mandated a 150,000 mile liftime on catalytic converters and the quickest way to do that was to drop phosphorous levels and bugger the valvetrain problem. Literally. In the US, Mobil 1 originally came out with the 0W40 as a 'European Formula' as it was always above 1000 ppm. This initially got them out of the 1996 800ppm jam and knowledgeable consumers sought it out for obvious reasons. Their 15W50 has also maintained a very high level of phosphorus and all of the extended life Mobil synthetics now have at least 1000ppm. How do they get away with this? They're not classified as energy/fuel conserving oils and thus do not interfere with the precious government CAFE (corporate average fuel economy) ratings. (See my section on the EPA and fuel economy in the Fuel and Engine Bible for more info on this). This also means that they don't get the coveted ratings of other oils but they do protect your valvetrain.

A quick guide to the different grades of oil.
Fully Synthetic 0W-30 0W-40 5W-40 Semi-synthetic 5W-30 10W-40 15W-40 Mineral 10W-40 15W-40 Characteristics Fuel economy savings Enhances engine performance and power Ensures engine is protected from wear and deposit build-up Ensures good cold starting and quick circulation in freezing temperatures Gets to moving parts of the engine quickly Characteristics Better protection Good protection within the first 10 minutes after starting out Roughly three times better at reducing engine wear Increased oil change intervals - don't need to change it quite so often Characteristics Basic protection for a variety of engines Oil needs to be changed more often

So what should I buy?
Quality Counts! It doesn't matter what sort of fancy marketing goes into an engine oil, how many naked babes smear it all over their bodies, how bright and colourful the packaging is, it's what's written on the packaging which counts. Specifications and approvals are everything. There are two established testing bodies. The API (American Petroleum Institute), and the European counterpart, the ACEA (Association des Constructeurs Europeens d'Automobiles - which was the CCMC). You've probably never heard of either of them, but their stamp of approval will be seen on the side of every reputable can of engine oil.

http://www.carbibles.com/engineoil_bible.html (6 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

The API The API classifications are different for petrol and diesel engines: For petrol, listings start with 'S' (meaning Service category, but you can also think of it as Spark-plug ignition), followed by another code to denote standard. 'SM' is the current top grade, which recently replaced 'SL' and 'SH'. 'SH' will be found on most expensive oils, and almost all the new synthetics. It's basically an upgraded 'SG' oil which has been tested more sternly. r For diesel oils, the first letter is 'C' (meaning Commercial category, but you can also think of it as Compression ignition). 'CH' is the highest grade at the moment, (technically CH-4 for heavy-duty) but 'CF' is the most popular and is well adequate for passenger vehicle applications. Note about Castrol oils: Castrol have recently upgraded all their oils and for some reason, Castrol diesels now use the 'S' rating, thus completely negating my little aid-memoir above. So the older CC,CD,CE and CF ratings no longer exist, but have been replaced by an 'SH' grade diesel oil. This link is a service bulletin from Castrol themselves, explaining the situation. The CCMC/ACEA The ACEA standards are prefixed with a 'G' for petrol engines and a 'D' or 'PD' for diesel. Coupled with this are numerous approvals by car manufacturers which many oil containers sport with pride. ACEA replaced CCMC in 1996 primarily to allow for greater read-across in test programs (eg. for viscosity, viscosity modifiers and base oil). The CCMC specifications were G (1 to 5) for gasoline, D (1 to 5) or heavy duty diesel and PD1 and PD2 for passenger car diesel. ACEA though have a slightly different nomenclature they can be summarised as A for petrol, B for passenger car diesel and E for heavy duty diesel. The ACEA grades may also be followed by the year of issue which will be either '96, '98 (current) but coming soon is 2000. Full ACEA specs are: r A1 Fuel Economy Petrol r A2 Standard performance level r A3 High performance and / or extended drain r B1 Fuel Economy diesel r B2 Standard performance level r B3 High performance and / or extended drain r B4 For direct injection passenger car diesel engines r E1 Non-turbo charged light duty diesel r E2 Standard performance level r E3 High performance extended drain r E4 Higher performance and longer extended drain r E5 (1999) High performance / long drain plus American/API performances. - This is ACEAs first attempt at a global spec.
r

Typically, these markings will be found in a statement similar to: Meets the requirements of API SH/CD along the label somewhere. Also, you ought to be able to see the API Service Symbol somewhere on the packaging:

Beware the fake API symbol Some unscrupulous manufacturers (and there's not many left that do this) will put a symbol on their packaging designed to look like the API symbol without actually being the API symbol. They do this in an effort to pump up the 'quality' of their product by relying on people not really knowing exactly what the proper API symbol should look like. To the left is an example of a fake symbol - it looks similar but as long as you remember what to look for, you won't get taken by this scam.
http://www.carbibles.com/engineoil_bible.html (7 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

Amsoil are one of the biggest inadvertent offenders of the fake API symbol. Take a look at one of their labels here on the right. See that little starburst that says "Fuel efficient formula SL-CF"? It can say all it likes, but the fact of the matter is that this is absolutely not an API-certified SL or CF oil. That doesn't mean it doesn't perform to those levels, but for warranty purposes, this is not an API certified product. To be fair, some Amsoil products are API certified and they do have the correct labelling, but their top-tier products do not. The issue of fake API labelling and non-compliance has caused such a stir at Amsoil that they had to put an entire page up on their site dedicated to answering this particular question. You can find it here. Basically what it boils down to is money. Amsoil don't want to pay the $300,000 it can cost for an API certification of a single oil formulation, and getting API certification can limit them to single vendors for some of the raw products they use. If those vendors put their prices up or go out of business, Amsoil need to either pass the increase in price on to the consumer, or go through the whole API thing again from scratch.

If this is all confusing you, then rest assured that all top oils safely conform to the current standards. What you should treat with caution are the real cheapies and those with nothing but a maker's name on the pack. Anything below about £12 ($18) for 5 litres just isn't going to be worth it. A Brief History of Time API ratings Some people have asked about the old standards, and although they're not especially relevant, some rampant plagiarism from an API service bulletin means I can bring you all the API ratings right back from when the earth was cooling.
Petrol Engines Category Status Service Category Status Diesel Engines Service

CJ-4

Introduced in 2006 for high-speed four-stroke engines. Designed to meet 2007 on-highway exhaust emission standards. CJ-4 oils are compounded for use in all applications with diesel fuels ranging in sulphur content up to 500ppm (0.05% by weight). However, use of Current these oils with greater than 15ppm sulfur fuel may impact exhaust aftertreatment system durability and/or oil drain intervals. CJ-4 oils are effective at sustaining emission control system durability where particulate filters and other advanced aftertreatment systems are used. CJ-4 oils exceed the performance criteria of CF-4, CG-4, CH-4 and CI-4. Introduced in 2002 for high-speed four-stroke engines. Designed to meet 2004 exhaust emission standards implemented in 2002. CI-4 oils are formulated to sustain engine durability where exhaust gas Current recirculation (EGR) is used and are intented for use with diesel fuels ranging in sulphur content up to 0.5% weight. Can be used in place of CD, CE, CF-4, CG-4 and CH-4 Introduced in 1998 for high-speed four-stroke engines. CH-4 oils are Current specifically designed for use with diesel fuels ranging in sulphur content up to 0.5% weight. Can be used in place of CD, CE, CF-4 and CG-4. Current Introduced in 1995 for high-speed four-stroke engines. CG-4 oils are specifically designed for use with diesel fuels ranging in sulphur content less than 0.5% weight. CG-4 oil needs to be used for engines meeting 1994 emission standards. Can be used in place of CD, CE and CF-4. Introduced in 1990 for high-speed four-stroke naturally aspirated and turbo engines. Can be used in place of CD and CE. Introduced in 1994 for severe duty, two stroke motorcycle engines. Can be used in place of CD-II.

CI-4

SM

Current

For all automotive engines presently in use. Introduced in the API service symbol in November 2004 For all automotive engines presently in use. Introduced in the API service symbol in 1998 For all automotive engines presently in use. Introduced in the API service symbol in 1996 For model year 1996 and older engines. For model year 1993 and older engines. For model year 1988 and older engines. For model year 1979 and older engines. For model year 1971 and older engines.

CH-4

SL

Current

CG-4

SJ SH SG SF SE SD

Still current but nearly obsolete Obsolete Obsolete Obsolete Obsolete Obsolete

CF-4 CF-2 CF CE CD-II CD

Current Current

Introduced in 1994 for off-road, indirect-injected and other diesel Current engines including those using fuel over0.5% weight sulphur. Can be used in place of CD. Obsolete Introduced in 1987 for high-speed four-stroke naturally aspirated and turbo engines. Can be used in place of CC and CD.

Obsolete Introduced in 1987 for two-stroke motorcycle engines. Obsolete Introduced in 1955 for certain naturally aspirated and turbo engines.

http://www.carbibles.com/engineoil_bible.html (8 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible SC SB SA Obsolete Obsolete Obsolete For model year 1967 and older engines. For older engines. Use this only when specifically recommended by the manufacturer. For much older engines with no performance requirement. Use this only when specifically recommended by the manufacturer. CC CB CA Obsolete Introduced in 1961 for all diesels. Obsolete Introduced in 1949 for moderate-duty engines. Obsolete Introduced in 1940 for light-duty engines.

Grade counts too!The API/ACEA ratings only refer to an oil's quality. For grade, you need to look at the SAE (Society of Automotive Engineers) ratings. These describe the oil's function and viscosity standard. Viscosity means the substance and clinging properties of the lubricant. When cold, oil can become like treacle so it is important that any lube is kept as thin as possible. It's cold performance is denoted by the letter 'W', meaning 'winter'. At the other end of the scale, a scorching hot oil can be as thin as water and about as useful too. So it needs to be as thick as possible when warm. Thin when cold but thick when warm? That's where MultiGrade oil comes in. For ages, good old 20W/50 was the oil to have. But as engines progressed and tolerances decreased, a lighter, thinner oil was required, especially when cold. Thus 15W/50, 15W/40 and even 15W/30 oils are now commonplace. Synthetics can go down as far as 5W which seemed unbeatable until Castrol came up with SLX - a 0W30 formulation! 'Free flowing' just doesn't describe it! It's predominantly a workshop oil retailing at around £10 ($15) a litre, but recommended for use in places like Canada in the winter. The latest offering to this 0W30 engineering miracle comes from AMSOIL. So again: what should I buy? That all depends on your car, your pocket and how you intend to drive and service the car. All brands claim theirs offers the best protection available - until they launch a superior alternative. It's like washing powders - whiter than white until new Super-Nukem-Dazzo comes out. For most motorists and most cars, a quality mainline oil is the best. Ones which are known to be good at their job. Stuff like Castrol GTX. They're not too dear either. Don't believe the sales hype - they all perform to the same standards once they're out of the can and into your engine. Moving up a step, you could look at Duckhams QXR and Castrol Protection Plus and GTX3 Lightec. The latter two of these are designed specifically for engines with catalytic converters. They're also a good choice for GTi's and turbo'd engines. Go up a step again and you're looking at synthetic oils aimed squarely at the performance market. To get more money out of you, the manufacturers sell this stuff in smaller amounts which makes an oil change more expensive.

Marine Diesels and other special considerations.
Inland Marine Diesels (and certain road vehicles under special conditions) can, and do, glaze their bores due the low cylinder wall temperature causing the oil (and more importantly the additive pack) to undergo a chemical change to a varnish-like substance. The low temperature is caused by operating under light load for long periods. This is related to engine design, some engines being nearly immune to it and others susceptible. The old Sherpa van diesel engines were notorious for this problem. The "cure" such as it is, is to use a low API specification oil, such as CC. Certain engine manufacturers/marinisers are now marketing the API CC oil for this purpose under their own name (and at a premium). You'll find some modern engines where its' industrial/vehicle manual states API CF and the marinised manual states API CC/CD. {Thanks to Tony Brooks for this information.}

Marine Oils.
I sometimes get asked "why are marine engine oils so expensive and why can't I just use regular motor oil in my marine engine instead?". Well, the National Marine Manufacturers Association Oil Certification Committee (click here for more info) introduced a four-stroke engine oil test and standard called the 4T certification. This specification is meant to assist boaters and manufacturers in identifying four-stroke cycle engine oils that have been specially formulated to withstand the rigors of marine engine operation. The certification was prompted by the growing influence of fourstroke engines in the marine market and their unique lubrication demands. So the simple answer is that regular roadbased engine oil products don't contain rust inhibitors and won't pass the 4T certification. Lakes, waterways and the sea is a lot more aggressive an environment for an engine to operate around than on land. Note : the NMMA have long had a similar specification for 2-stroke oils destined for marine use, called the TCW3® certification.

http://www.carbibles.com/engineoil_bible.html (9 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

The eBay problem
This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at www.carbibles.com, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to www.carbibles.com to see the full site and find my contact details. And now, back to the meat of the subject.... Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Engine Oil Shelf Life.
I couldn't decide whether to put this in the FAQ or the main page, so it's in both, because I get asked this question a lot. Typically, the question is along the lines of "GenericAutoSuperStore are having a sale on WickedlySlippy Brand synthetic oil. If I buy it now, how long can I keep if before I use it?" In general, liquid lubricants (ie. oils, not greases) will remain intact for a number of years. The main factor affecting the life of the oil is the storage condition for the products. Exposure to extreme temperature changes, and moisture will reduce the shelf life of the lubricants. ie. don't leave in the sun with the lid off. Best to keep them sealed and unopened. Technically, engine oils have shelf lives of four to five years. However, as years pass, unused engine oils can become obsolete and fail to meet the technical requirements of current engines. The specs get updated regularly based on new scientific testing procedures and engine requirements. But this is only really a concern if you've bought a brand new car but have engine oil you bought for the previous car. An oil that is a number of years old might not be formulated to meet the requirements set for your newer engine. If your unopened containers of engine oil are more than three years old, read the labels to make sure they meet the latest industry standards. If they do meet the current standards, you might want to take the extra precaution of obtaining oil analysis before using them. An oil analysis will check for key properties of the oil and ensure that it still meets the original manufacturing specs. Of course the cost of getting an analysis done on old oil is probably going to outweigh going and buying fresh stuff. So it's a double-edged sword. As a general rule, the simpler the oil formulation, the longer the shelf life. The following is a guideline under protected conditions:
Product Base Oils, Process Oils Engine Oils and Transmission Oils Industrial and Automotive Gear Oils Metal Working and Cutting Oils Shelf Life 3 years 3 years 2 years 1 year

Hydraulic Oils, Compressor Oils, General Purpose Lubricating Oils 2 years

The following are signs of storage instability in a lubricant:
● ● ● ●

Settling out of the additives as a gel or sticky liquid Floc or haze Precipitates/solid material Colour change or haziness

Water contamination in a lubricant can be detected by a "milky" appearance of the product.

"High mileage" oils.
http://www.carbibles.com/engineoil_bible.html (10 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

More and more oil companies are coming out with "high mileage" oils now, some recommended for engines with as few as 75,000 miles on them. So what is a "high mileage" oil you ask? Well very generally speaking, these oils have two additives in them which are more suited to older engines. The first is normally a burnoffinhibitor which helps prevent the oil from burning off if it gets past an engine seal into the combustion chamber. The second is a "seal conditioner", the exact makeup of which I'm not sure of, but it's designed to soak into seals such as head- and rockercover gaskets and force them to expand. Thus if one of the seals is a bit leaky, the seal conditioner will attempt to minimise the leak. I've not had experience of high mileage oils myself, but a few people who've e-mailed me have passed on various tales from it being the miracle cure to it making no difference at all. I think the general rule-of-thumb though should be "if it 'aint broke, don't fix it." Just because your engine has over 75,000 miles on it, doesn't automatically mean you need high mileage oil. Is the exhaust sooty or smokey? Are you noticing oil leaks? Is the engine consuming oil? If your engine is working fine, the exhaust is clean and you're not noticing any problems, my guess is that it doesn't need high-mileage oil.

What about own-brands?
If you can't afford the big-name players, you could look at own-brand oils. These are usually badged oils from one of the larger companies but sold without the name, they are cheaper. Check the standards and grade ratings on the pack first! The example on the right is a local store in Chelmsford in England who sell their own label oil which is bottled for them by a volume retailer. The label tells you all you need to know.

Viscosity and Viscosity Index (VI).
The proper viscosity is the single most important criteria of a lubricating oil. The basic performance of machinery is based on the viscosity of the lubricant. Viscosity is, if you like, the resistance to the flowability of the oil. The thicker an oil, the higher its viscosity. The chart on the right shows a rough guide to ambient temperatures vs oil viscosity performance in both multigrade (top half) and single grade (lower half) oils. Multigrade oils work by having a polymer added to a light base oil which prevents the oil from thinning too much as it warms up. At low temperatures, the polymers are coiled up and allow the oil to flow as it's low number (W number) indicates. As the oil heats up, the polymers unwind into long chains which prevent the oil from thinning as much as it normally would. The result is that at 100°C, the oil has thinned only as much as it's higher rating. Think of it like this: a 10W30 oil is a 10-weight oil that will not thin more than a 30-weight oil when it gets hot. The viscosity index of a lubricant is an empirical formula that allows the change in viscosity in the presence of heat to be calculated. This tells the user how much the oil will thin when it is subjected to heat. The higher the viscosity index, the less an oil will thin at a specified temperature. Multi-viscosity motor oils will have a viscosity index well over 100, while single viscosity motor oils and most industrial oils will have a VI of about 100 or less. Viscosity and oil weight numbers is quite a nauseatingly detailed topic. So if you're curious about why a 15W50 oil is so-called, then put on the geek shield and pop over to the Viscosity Page.....

Servicing and checking
For God's sake don't skimp on either of these. You can never check your engine oil too often. Use the dipstick http://www.carbibles.com/engineoil_bible.html (11 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

that's what it's there for - and don't run below the 'min' mark. Below that, there isn't enough oil for the pump to be able to supply the top of the engine whilst keeping a reserve in the sump. All oils, no matter what their type, are made of long-chained molecules which get sheared into shorter chains in a running engine. This in turn means that the oil begins to lose it's viscosity over time, and it uses up the additives in it that prevent scuffing between cams and followers, rings and cylinder walls etc etc. When this happens, fresh oil is the key. And don't worry about the engine oil turning black. It will lose it's golden-brown colour within a few hundred miles of being put in to the engine. That doesn't mean it's not working. Quite the contrary - it means it is working well. It changes colour as it traps oxidised oil, clots and the flakes of metal that pop off heavily loaded engine parts. Just don't leave it too long between oil changes.

So how often should I change my oil?
You can never change your engine oil too frequently. The more you do it, the longer the engine will last. The whole debate about exactly when you change your oil is somewhat of a grey area. Manufacturers tell you every 10,000 miles or so. Your mate with a classic car tells you every 3,000 miles. Ole' Bob with the bad breath who drives a truck tells you he's never once changed the oil in his car. Fact is, large quantities of water are produced by the normal combustion process and, depending on engine wear, some of it gets into the crank case. If you have a good crank case breathing system it gets removed from there PDQ, but even so, in cold weather a lot of condensation will take place. This is bad enough in itself, since water is not noted for its lubrication qualities in an engine, but even worse, that water dissolves any nitrates formed during the combustion process. If my memory of chemistry serves me right, that leaves you with a mixture of Nitric (HNO3) and Nitrous (HNO2) acid circulating round your engine! So not only do you suffer a high rate of wear at start-up and when the engine is cold, you suffer a high rate of subsequent corrosion during normal running or even when stationary. The point I'm trying to make is that the optimum time for changing oil ought to be related to a number of factors, of which distance travelled is probably one of the least important in most cases. Here is my selection in rough order of importance: 1. 2. 3. 4. 5. 6. Number of cold starts (more condensation in a cold engine) Ambient temperature (how long before warm enough to stop serious condensation) Effectiveness of crank case scavenging (more of that anon) State of wear of the engine (piston blow-by multiplies the problem) Accuracy of carburation during warm-up period (extra gook produced) Distance travelled (well, lets get that one out of the way)

If you were clever (or anal) enough, you could probably come up with a really clever formula incorporating all those factors. However, I would give 1, 2, and 3 equal top weighting. Items 1 to 3 have to be taken together since a given number of "cold" starts in the Dakar in summer is not the same as an equal number conducted in Fargo in January. The effect in either case will be modified by how much gas gets past the pistons. What we are really after is the severity and duration of the initial condensation period. All other things being equal, that will give you how much condensate will be produced and I would suggest that more than anything else determines when the oil should be dumped.

Dammit Chris, get to the point already!
Hang on a tic - if you really want the answer, there's a couple more factors you need to take account of: Crankcase scavenging (that's the clever term for sucking the nasty fumes back out of the crank-case) - or lack of it - is a crucial multiplying factor affecting all the other items listed above. As an example, the worst I've heard of was a Ford Fiesta of the mid 70s or so. It's crank-case fume extraction was via a tiny orifice directly into the inlet manifold which obviously could not handle any significant volume of crank-case fumes without upsetting the carburation. The car in question had been used almost exclusively for 5 mile journeys to/from work, shopping etc, and it had always been serviced "by the

http://www.carbibles.com/engineoil_bible.html (12 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

book". Despite (or because of) this, the engine was totally buggered at 40,000 miles. Alternatively you might get a car that by virtue of excellent crank case fume scavenging could tolerate many more cold starts than one without. Taking all these into consideration, my philosophy would be to totally ignore the distance and change the oil three times a year - about November, February and May. Move these dates a bit according to the severity of the winter. An average family car will do around 14,000 miles per year and about 2/3 of that will fall in the May - November period. At the end of that period, the car will have just about touched on the recommended oil change distance - but all done at reasonable temperatures and including long distance runs during vacations and good weather. During the Nov - Feb. period it may accumulate only 2 or 3 thousand miles, all low temperature starts and mostly short runs. The Feb. to May period is likely to be about the same. About 10 or 15 years ago, an article in the ANWB journal (ANWB is the Dutch equivalent of the AA - or the AAA in the American case) reached more or less the same conclusion that distance was not very important. In their case they applied this to their road service fleet, which typically once started in the morning never got cold. In effect, they hardly ever changed the oil! I seem to remember 30,000 miles between oil changes being quoted. I also seem to remember that they had some kind of water or acid indicator attached to the end of the dipstick and went by that rather than distance.

That's a politician's answer - you've dodged the entire issue!
Have I? I don't know how far you drive in a year, where you live, the style of your driving or anything else so I can't tell you what's right for your car. Personally, I changed the oil and filter in my 1985 Audi Coupe every 5,000 miles. It had done over 150,000 miles when I sold it, wasn't leaking and didn't consume any oil. If you must have a figure from me, then 5,000 is it.

What else happens when I change the oil then?
Engines pump about 10,000 litres of air for every litre of fuel consumed, and along with all that air, they suck in plenty of dirt and grit. A good air filter will stop everything bigger than a micron in diameter - everything smaller mostly just floats around harmlessly in the 0.001inch minimum thickness oil films that separate all the moving parts. Despite all of this, there will always be submicron particles that get in and there will be places in the engines oilways where they will gather. Every time you empty the oil from your sump, you're also draining this fine grit with it.

Checking the oil in your engine, and topping up.
Note that this section only applies to wet sump engines - the type found in most consumer vehicles. For more info on sump types, see Wet sumps vs. dry sumps below. To a lot of people, this little section could be categorised by the rearranging the words "granny eggs teaching suck your to". But you'd be surprised by the number of people that don't know how to do even this basic task. When checking the level of oil in the engine, the car should be on a level plane, and should be relatively cold. I've run into several people lately who insist
http://www.carbibles.com/engineoil_bible.html (13 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

in keeping the crankcase topped off completely, and they invariably check the dipstick just after shutting down the engine. Reading the oil in this way results in an erroneous reading because a quantity of oil (usually about half a litre) is still confined in the oilways and passages (galleries) of the engine, and takes some time to drain back into the crankcase. (On the image, the blue areas are where oil is likely to still be running back down to the sump). On seeing what appears to be an abnormally low level on the dipstick, these people then add more oil to the oil filler at the top of the engine. The oilways and passages all empty, and suddenly the engine becomes over-filled with oil, going way above the 'MAX' mark on the dipstick.

What happens when an engine is overfilled with oil?
So you topped up the engine when it was warm after getting a faulty dipstick reading, or you put too much oil in when you changed it yourself. What's the worst that could happen? Well the problem with this is that the next time the engine is run, the windage in the crankcase and other pressures generated by the oil pump, etc. place a great strain on the seal on the rear main bearing. Eventually, often much sooner than the ordinary man in the street might expect, the rear main bearing seal ruptures, and the engine becomes a 'leaker'. If you've got a manual gearbox, this means one thing: this oil goes right onto the flywheel and the face of the clutch disc. A lubricated clutch is A Bad Thing. If this still goes unnoticed, the front seal is the next to go, and the engine then becomes a 'gusher' (or to be more colourful, it starts pissing oil all over the place). As well as smothering the clutch with oil from the rear, the oil now coming from the front leak will be neatly distributed about the engine bay as it hits the front pulley - often propelling it out as far as the brake discs. At the same time as this Hollywood disaster movie is unfolding outside the engine, things aren't working out any better on the inside. As you can see from the diagram, the correct oil level is really close to the rotating crank. Overfilling will mean the crank dips into the oil and churns it into a froth. Froth is good on certain types of coffee but not good in an engine. The mixture of aerated oil will be forced into the bearings and in case you didn't know, air is not a lubricant. Typically this means that bearing damage will follow quite rapidly, especially if you are driving on a motorway. You'll know bearing damage when you get it. The engine smells like a garage mechanic cooking over an open flame and the noise coming from the engine is the sort of thing you'd normally hear in vaudeville plays when a piano is pushed down a flight of stairs. As if that all wasn't bad enough, the excess oil gets thrown up into the piston bores where the piston rings have a hard time coping with the excess oil and pressure. It gets into the combustion chamber and some of it will get out into the exhaust system unburned resulting in a nice patina of oil all over the platinum surfaces of your catalytic converter. This renders it utterly useless for good. Well, you did ask.

So what's the best way to check the oil level?
If your engine is cold (for example it has been parked overnight) you can check the oil level right away. The oil will have had time to settle back into the sump. Just make sure the car is level before you do. If the engine is warm or hot (after you've been driving) then you should wait for 30 minutes or so to let as much oil as possible drain back into the sump. Checking it first thing the next morning is ideal. It's worth pointing out that you should double-check your owner's manual too - some cars, like I the '92 Porcshe Carrera, require that the oil is checked while the engine is running and the oil is at temperature. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Wet sumps vs. dry sumps.
http://www.carbibles.com/engineoil_bible.html (14 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

Almost all passenger cars, trucks and SUVs use what's called a wet sump system. If you look at the diagram above you can see the sump (or oil pan) is the lowest part of the engine. In a wet sump system, excess oil drains back into the sump when it has passed through the engine, and the oil pump then sucks it out of the sump and pumps it back to the top of the engine. The advantage of a wet sump is that it's cost effective to build and maintain and it makes oil-checking easy for the average driver. The disadvantage is that cornering and braking can cause the oil to slosh around in the sump. This can cause the oil to not cover the oil pump pickup tube, which could starve the top end of oil, or it could get deep enough in a severe cornering maneuver to bog-down the crank, which is A Bad Thing. To counter these problems, a lot of wet sumps now have baffles in them to stop the oil moving around so much, and for your average road-going consumer-level vehicle, this is a fine compromise.

Dry sumps
When it comes to racing vehicles, wet sumps simply have too many disadvantages. Instead, race engines typically use a dry sump. As its name implies, the sump of the engine is dry - it never fills with oil. In a wet-sump system, the sump has to be large enough to accommodate all the oil from the engine when it is turned off. In a dry sump system, that requirement is gone so the sump can be much much smaller. (In the image on the right, the right-most sump is representative of a dry sump). A smaller sump means the engine can be mounted lower down in the vehicle, which in turn lowers the centre of gravity. So how can this be? Well a dry sump system uses a remote oil reservoir or tank, and a either a second oil pump, or a single multi-stage pump. In a double pump system, one oil pump works just like a wet sump - it distributes oil to the top end of the engine, but it pulls the oil from the reservoir instead of the sump. The second pump scavenges the oil from the sump and returns it to the reservoir. In a single pump system, one pump is either a three- or four-stage pump. It has multiple circuits running off the same pump to pressurise the engine and scavenge oil back from the sump. The advantages of dry sumps for racing become obvious when you examine the design. The engine can be mounted lower in the chassis because of the shallow oil pan. The pumps typically don't run off the crank-driven belts so no engine power is sapped in driving them. The remote tank or reservoir can be pretty much any size you like and be mounted anywhere in the vehicle (usually low down again for centre of gravity reasons). There isn't oil sloshing around in the sump so you don't run the risk of bogging down the crank. For all these reasons, dry sumps are considered to be safer and far more dependable than their wet counterparts. So if it's that much better, why don't you find this system in consumer vehicles? Simple. The increased weight, complexity and cost of having larger or more pumps and a remote reservoir with all the additional high pressure oil lines involved. For a racing team, this isn't an issue, but for Toyota or Ford, adding that sort of cost and complexity to their passenger vehicles is just a no-go.

Can I use car engine oil in my motorbike then?
No you can't. Or at least I wouldn't recommend it.... The real answer to this question lies in the type of motorbike you own. If you own a bike with a wet clutch (ie. where the clutch sits partially submerged in the sump oil) and you dump car oil into it, all sorts of nasty things happen. Oils formulated for car engines have friction modifiers in them. When the engine oil gets into the clutch, the friction modifiers get to work and you'll end up with a clutch that won't bite. In addition, the chemical makeup of some car oils has been known to soften the clutch material on motorbikes to the point where the entire clutch pack fails. Bike oils generally don't have friction modifiers, so they don't have this problem. If you're not sure, check for a JASO MA spec on the bottle. If you see that on the label, then it means the oil has been tested and confirmed to work with a wet clutch. Mobil have cautionary information on exactly this subject on their Motorcycle Oils FAQ page. The other side of this coin is if you have a dry clutch bike, like some BMWs. In this case, the clutch is configured similar to a car in that it's never in contact with the engine oil, and if that's the case, then regular car engine oil might provide all the protection and lubrication you need for your bike. The issue then becomes a question of the exact formulation of the oil. The additive packages for car engine oil are typically balanced differently than those for motorbikes with fuel economy and emission system protection being the higher priorities. Your typical passenger car doesn't rev to 12,000 rpm either so stuffing normal car engine oil in a motorbike engine that can run to double or even triple the rpm of a car engine could cause all sorts of problems. The debate about whether any of this is true is burning in many forums across the internet. One site in particular casts some doubt on the issue, claiming the only difference between car and bike oil is the price. I don't subscribe to that theory but in order for you to make your own decision, here's a link: Testing motorcycle oil.

http://www.carbibles.com/engineoil_bible.html (15 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

Can I use diesel engine oil in my petrol engine?
Not really. Diesel engines run much higher compression ratios than petrol engines and they run a lot hotter, so the oil is formulated to deal with this. Plus they produce a lot more dirt in terms of combustion by-products. Diesel-rated oils typically have more detergents in them to deal with this (see Using Diesel oil for flushing above). It's not unheard of for diesel oils to clean a petrol engine so well that it loses compression. Diesel-rated oils also have an anti-foaming agent in them which is unique to diesel engines, and not needed in petrol engines.

And so to engine additives
Think what you will of these. Whatever you call them, they are an addition to the engine which it was not designed to take. Engines are designed to use engine oil, not Teflon®. Make up your own mind - read this report and see what you think. In my opinion (and that doesn't mean I'm right) the majority of these are primarily a placebo to put uneducated minds at rest whilst making a nice profit for the additive manufacturer. The additive part of this site started quite small, but as more and more of the companies got into lawsuits and legal actions, and lost, this page became far too long to read all in one go. So if you're considering Duralube, ProLong, Slick50 or any of the other brand-name placebos, you'll be wanting to hot-step it over to my additives page pretty darned quickly.....

Nanolubricants
Not something off Star Trek, although it sounds like it. Nanolubricants use the geometrical properties of miniature particles to provide lubrication. A couple of companies are working on these new generation lubricants; New York-based Applied Nanomaterials (ApNano) is one of them. Their R&D lab in the commercial arm of the Weizmann Institute of Science in Israel is initially developing an onion-type nanostructure, i.e. a multilayered hollow structure of nested spheres called NanoLubTM. According to the theory of the company's founders, such a structure can replace lubricants, because it works like a box moving along a near infinite layer of super-miniaturized ball bearings. They claim that respected institutes worldwide have proved that powder made from these nanostructures is six to ten times more effective than regular lubricants. In their case, the nanospheres are built from tungsten disulfide (WS2). The layers slide past each other, reducing friction, while the hollow cores provide flexibility. Applied Nanomaterials claims the materials can withstand immense pressures. The material acts as a kind of solid ball bearing between the metal layers, rather like the wheels of a tank tread. In addition, the nanostructures insert themselves within each metal layer, while other nanostructures slide over them, creating a smooth layer at the molecular level. The idea is that unlike oil, the nanolubricant never wears down; it is permanent and requires no maintenance. Theoretically, a nanolubricant can be used for various friction reducing applications, such as on the outer coating of ships and planes to reduce water and air friction, respectively. If you're that way inclined, think of what it could do to the sex toy industry.... The powder will eventually stand on its own as a lubricant, however Applied Nanomaterials realizes that recognition of the technology requires collaboration with lubricant manufacturers as an additive to existing lubricants. The problem of course is that if this lubricant never needs changing, anyone who decides to mass manufacture and market it is going to lose a chunk of revenue - once you dump it in your engine, you never buy any more. Great for you and me, bad business model for the company who dares to market it. Applied Nanomaterials competitors are developing similar materials, but based on nested carbon nanotube structures that over time tend to disintegrate under friction from the materials they lubricate. Don't expect to see NanoLubTM on the shelves just yet though. It can take a day to manufacture just 750g of the stuff.

An alternative to engine additives: pre-pressurisation
What the additive manufacturers tell you is true - when you start your engine, there really is very little oil in the right place - most of it is in the sump. There is another alternative. I found a site called AutoEngineLube.com and they seem to be
http://www.carbibles.com/engineoil_bible.html (16 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

offering an interesting alternative. They have a system which uses a cylinder of pressurised oil and a solenoid valve, all connected to the regular oil system. It works with only one moving part, (the solenoid valve - duh!). When the key is turned on it opens the valve and the oil that was trapped in the tank the previous time it was running goes back into the oil gallery in 1 or 2 seconds and the low oil pressure light will flash off. There's likely to still be a little lag before fullon lubrication gets to the main bearings, but from what I can tell, this system will massively reduce that lag compared to starting from cold - it pressurises the system before the starter engages. Of course an engine that has set up for a few months and is completely dry will take a few more seconds. When the engine is turned off the solenoid valve shuts off in 30 milliseconds so you end up with pressure on the tank equal to the pressure the last time it was running. The tank will hold more than enough oil to accomplish this. Its completely over engineered as the tank is rated for over a thousand pounds and the hose is good for 300lb. Because the valve is designed for an industrial application with an expected duty life of several million cycles, AutoEngineLube give it a lifetime warranty. It only uses previously filtered oil from the gallery so no damage can be done by it in any way. Their system comes as a kit and requires some menial installation - most savvy home mechanics should be able to do it. I'm not sure how it would affect the warranty on a car engine. In theory, if it works, it ought to make no difference but you know what manufacturers are like - if you even sneeze on your engine, it's likely to void the warranty. Pop over and check them out if you're interested. If you end up buying one of these, I'd like to know what sort of results you get so I can add an objective review to my site. AutoEngineLube.com can be found here. Another site sells a similar product - PreLuber.com can be found here. It's worth pointing out that pre-lubers have been around for quite a while; the original systems featured an electric pump that circulated the oil from the sump before the starter turned. The pump would bring the oil up to full operating pressure before you attempted to start the engine. A reader of this site e-mailed me about this. He had one on an old MGTD, because the car got very infrequent use; it worked rather well and he never had any major engine problems with it installed. Enginelube.com still do the "old style" pre-lubers but their website has vanished so I don't have a good link for them now.

Case study: MOROSO Accumulater (pistonless upright bottle type) pre-oiler on V8 Zephyrs
Picture credit: MkIII Zephyr V8s

A reader contacted me about using pre-oilers on classic vehicles. Here's what he had to say: "I use the MOROSO Accumulater 2 which is a pistonless upright bottle type. I researched these after experiencing oil pressure drops of 20psi on uphill right hand corners at speed. The Moroso 2 cured it right away. I plumbed it directly into where the oil sender went and used a tee for the oil light sender. I have a ½" ball valve at the bottle I use but intend to rig a choke cable to use it from inside the car. Electric solenoid valves are available too. To do an oil change the factory fitted tire valve is pumped with 20psi of air and the tap opened, old oil is then fully pushed out into the sump via the oil feeds. The car if used for racing etc is driven with the ball valve open, any drop in oil pressure is taken over by the accumulater until the oil pump pick up is covered again. I also use the oiler to lube the engine (Ford V8) by turning the valve with the engine off, the oil pressure goes up to about 20-30psi (you can hear it gurgle in the rocker covers!). After 10-15 seconds I then start the engine. You turn the valve off with the engine running to trap oil for the next start up.Racers run these on engines that can be "claimed" after a race as if the engine had a high doller sump pan they would lose it with the engine. The Accumulater works better than any trap door or baffled sump if you spin backwards off a track too!" There are further writeups of this particular installation available at the MKIII Zephyr V8 site and at StockCarRacing.com.

Oil filters and filtration.
Thanks to one reader who noted that in all of this page, until mid-2001 I had not given much, if any space, to the topic
http://www.carbibles.com/engineoil_bible.html (17 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

of filters and filtration. So here we go. It's all very well changing your oil often, but it's not just the oil that helps prevent engine wear. The oil filter does its part too. Dirt is the prime cause of engine wear. Not big dirt, like you'd see in a yard, but minute particles of dirt. It's dirt nevertheless, and it's abrasive. These contaminants vary from road dust (which are razor-like flakes from an engine's perspective) that doesn't get filtered out by the air filter, up to actual metal particles - the byproducts of the casting scarf from the original engine manufacture, and basic engine wear. All this nastiness is carried around by the oil into the minute parts of your engine, being rammed into the precision clearances between bearings and other moving parts. Once in, they don't come out easy, but tend to stay there, wearing grooves, grinding and generally messing up your engine. Other debris that causes problems are a by-product of the mere way an engine works - sooty particles from the combustion process can be forced past the piston rings and transported around in the oil too. This is definitely A Bad Thing - the soot acts like a sponge and soaks up other oil additives reducing the oil's anti-wear properties, and messing up it's viscosity. All this dirt is why oil goes black when it's used. That lovely syrup-like yellow that it is when you put it in is pure oil. The black stuff that comes out at an oil change is the same oil full of contaminants and by-products from wear and tear. That's where the oil filter comes in. It's job is to catch all this crap floating around in the oil, and to stop it from recirculating. Most oil filters that you or I will ever see are the spin-on type. They're shaped like an aluminium can and spin on to a threaded oil feeder poking out of the side of the engine somewhere. They're called 'full-flow' oil filters because they sit in the normal flow of the oil through the engine. Sort of like an electrical component in series with all the other electrical component. Because it sits in-line, it has to be designed not to restrict the flow of oil around the circuit, and thus can only really be effective at stopping the larger particles. Large, in this case, is around the 20micron size. So here's the catch. The smallest contaminants are in the 10-20micron size range. Not only is that "extremely small", but it means that they pass right through the oil filter and back out into circulation. This is why regular oil changes are a necessity, because these tiny little things can be the most damaging.

http://www.carbibles.com/engineoil_bible.html (18 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

This is an exploded view of a typical spin-on oil filter used in automotive applications. I've sliced the filter element (the brownishyellow part) so you can see the internal structure of the filter). Typically the engine oil enters through the ring of 5 or 6 holes in the base and into the main cannister. From there it is forced inwards through the filter element, through the drain holes in the central core and out through the central, threaded hole in the base.

There is another alternative, but it's only really used in heavy applications or for racing. That alternative is to fit a secondary bypass oil filter. This is sort of like a filter in parallel with the primary one. It doesn't restrict the flow of oil in the main circuit, but the oil that passes through it is filtered down to the 5 micron range, thus removing even the smallest contaminants. The newest filters claim to work down to 1 micron, though I can't confirm nor deny those claims. The upside is that by cleaning the oil so completely, bypass oil filters increase not only engine life, but also the life of the oil itself. This means longer service intervals.

Magnetised oil traps
Recently, magnetic filter additions have started to surface. I was sent one in 2001 to try out and it really did seem to work. The product in question was called the Bear Trap BT500. Their website can be found here (now owned by One Eye Industries). It's basically a sleeve made of foam rubber and plastic with some magnets in it. It bends to clamp around the outside of your regular spin-on oil filter. The idea is that the magnets will attract any metal debris in your oil and stick them to the inside of the oil filter wall, thus preventing them from going back into the oil circulation. Being of a curious nature (or stupid, depending on how you look at it) I decided to dismantle my oil filter after using the Bear Trap for 5000 miles. I learned a couple of things.
http://www.carbibles.com/engineoil_bible.html (19 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

1. You shouldn't try to do this yourself. 2. It's bloody messy. 3. But most importantly, after a brief period in accident and emergency to stitch up the gash in my hand, I discovered that sure enough, there were tiny arrangements of metal filings clustered around the inside of the oil filter wall where the magnets from the beartrap had been. You'll excuse the lack of photos to prove the point, but I had other things to worry about. If you visit their website or that of FilterMag (below) you'll see similar cutaway photos. So can I recommend their product? Yes. Another alternative to the Bear Trap is the FilterMag - essentially the same style of product but from a different manufacturer. FilterMag can be found at this link.

An alternative to custom magnetised oil traps.
Thanks to John Nightingale who read my pages and then felt he should contribute something. For those of you who do more than just change your filter - ie. take off the oil pan completely, John writes: " Next time you are in the mall or high street, drop into the Radio Shack or a hardware store and purchase a package of modern, powerful ceramic magnets. These are available in various shapes and they are cheap. Radio Shack sells a package of two wafer shaped magnets, for instance. Stroll out to your car at the end of your shopping trip, bend down and stick these magnets onto convenient flat surfaces the bottom of your oil pan either side of the drain hole or as convenient. Now the magnets will magnetize the steel of the oil pan in their area. On the inside, particles coming through the field established by a magnet will be sequestered by being stuck to the bottom of the oil pan. Next time you take off the oil pan, clean it out in the usual way, pull off the magnets from the outside, clean them up and then stick them onto the inside of the oil pan at the bottom but clear of the drain hole. This will give an even better result since now the oil is exposed to the naked magnets themselves. The bottom of the oil pan in the area of each of the magnets is also magnetized, of course, and contributing to the effect. Resist the temptation to stand the magnets on edge to expose more of their surface to the oil. Placing the magnets flat on the oil pan uses the oil pan's steel as a keeper for the magnets and will ensure that they stay powerful. Placing the magnets flat will increase the area of the oil pan that is part of the magnetic circuit so you will loose no particle pick up area by having the magnets lying flat. "

Magnetised oil traps - doing it yourself.
There's nothing really special about magnetised oil traps other than the type of magnet they use. Bear Trap and FilterMag basically offer a consumer-oriented product. But if you're a tinkerer, there's nothing to stop you doing it yourself. The magnets normally used are Neodymium, nearly the most powerful nonelectric magnet type. They are the kind of magnet used in computer hard drives, often coming in pairs held just a few millimeters apart with the back end of the hard drive head assembly (the part being made of coiled wire) in between. If you can find a couple of old hard drives - try the local computer junk store - you ought to be able to disassemble them and take the magnets out to stick to your own oil filter. John Nicholas Sarris, a reader of my site, suggested this and provided the following photos as an example.

http://www.carbibles.com/engineoil_bible.html (20 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

An open hard drive. The magnets (one visible) are in the upper left corner and are crescent shaped.

The top magnet plate has been removed. As you can see on the lower magnet it is attached to a metal plate. I presume this it to keep the magnetic field from the magnets between the two magnets and not extend outside the hard drive case.

The hard drive's head assembly has been removed. The lower magnet attached to its plate is clearly visible.

http://www.carbibles.com/engineoil_bible.html (21 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

A pair of hard drive magnets side-by-side. They are still attached to their metal plates because the adhesive used to attach them is immensely strong. I once removed a hard drive magnet from its plate, but broke it in half in the process.

The same magnets holding themselves to my hand. I could have them stick to each other through my palm, but it was hard to take a good picture. This actually hurt my fingers a bit. As you can see they are strong despite being only 2mm thick. The plate they are attached to itself is 3mm thick.

The importance of neodynium magnets
I thought it worth pointing out here what a potential disaster awaits the home tinkerer if you just grab any old magnet and stick it on the outside of your oil filter. Your common or garden ferrous magnet, like those horrible souvenir magnets stuck to your fridge (you know you've got some) are usually made from iron, and thus have a limited life span which in some cases can be as short as 6 or 12 months. During this time they progressively lose thier power. Not enough for that hideous magnetic photo frame to drop off the fridge, but enough to be a problem if it was stuck to your oil filter. Why's that then? Well, come the end of the filters life, just as the magnet is weakening and the collection of metal particles is at it's highest, one good jolt and it could dislodge, and a large collection of metal shavings and filings could detach from the inside of the filter and find its way back into your engine all in one go. That would be bad. So as much as you might like the magnetic photo of granny and the giraffe from Whipsnade zoo to be stuck in a filthy oily place on your car, don't do it.

Larger filters on standard cars?
There's a school of thought which says that enlarging the oil filter on your car is A Good Thing. Why is this? The small oil filters fitted to engines these days run with quite a high back pressure, and the bypass valve trips at about 3500rpm. That means that your oil is not being filtered when the engine is spinning faster than 3500rpm. As the oil filter does its job and starts to clog up, that rpm value can be lower. If you increase the size of the filter, this will raise the rpm at which the bypass valve will switch. With a bigger filter and lower back pressure, for the same rpm (prior to bypass valve operation) less engine power will be lost in the filter. Bigger filter means better filtering and more power at low to mid revs. Clever eh? But there's some things you need to be aware of if you're going to try this approach, all of which are relevant, and none of which I can confirm or deny
●

Bigger filter = more "dead" space = more oil. Remember you'd need to add more oil to the engine to keep the oil level at

http://www.carbibles.com/engineoil_bible.html (22 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

●

●

the correct mark on the dipstick. This isn't necessarily a bad thing - more oil doing the same job theoretically means less stress on the oil. Oil may take a little longer to circulate around the engine after startup, as the pump may have to fill up the larger capacity oil filter. With modern filters this ought not to be a problem though because all but the cheapest filters have backflow preventers which keep oil in the filter when the engine is off. Availability of filters and fouling. If you put a larger filter on it might foul something else in the engine bay. That is if you can find a larger filter to start with. The rule of thumb is to go to a motor factors shop, and find the oil filter that was designed for your engine .Then look through the myriad of larger oil filter boxes for a bigger filter that has the same screw thread and sealing ring diameter. Nowadays most spin-on filters have a 20mm screw thread so that's not going to be the hard part. Finding the same sealing ring diameter is the thing to be careful of. And don't ask the people at the parts counter. Because of liability issues, they're unlikely to sell you anything other than exact filter for your make and model of vehicle. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

A Practical example of the proper procedures saving an engine.
I started these pages back in 1994 and have been adding to them ever since. I've always followed my own advice and in 2005, it paid off big time. I'll tell this in the past tense because it'll get lost in the page and I'll forget to update it when I change motorbikes. So I owned a 2001 BMW R1150GS motorbike. I bought it pre-owned from my local dealer who assured me it had been through the workshops as part of the "standard procedure" of them taking a bike in and re-selling it. For 2 years I'd been riding it with horrible engine noise and engine detonation (pre-ignition). Every time I took it back to the dealer, they were adamant there was nothing wrong with the engine, and that "they all do that". Not believing them, I finally found an independent BMW specialist who took the engine apart for me. It turned out the BMW dealership had lied - the bike had never been in their service department. This was evidenced by the fact that the cylinders had sand in them. The dealership had never bothered to check the bike and wouldn't believe my complaints about the noisy engine. The independent mechanic fixed it all up for me - an $1100 repair bill that involved basically stripping down the entire engine, honing the cylinder barrels, putting in new piston rings, cleaning the pistons, barrels, heads, throttle and airbox, flushing and cleaning the whole thing and putting it all back together. The point is that during the two years I'd been riding it with sand in the engine, I'd been religiously topping up the oil and changing the filter. It's a testament to BMW engineering that the engine ran without seizing up, but it's also a testament to paying attention to your oil changes. If I'd let it slide, or not done the filter, that engine would not have been a rebuild - it would have been a far more costly brand new engine.

This is all great. Now how do I actually change my oil?
A good number of readers will get to this point in the page and think "this is easy - I could do this!", and for the most part, you can. Below is a generic, idiots-guide to changing the oil in your engine. It's not specific to any particular car but ought to cover most engines. Before you start, you'll need the following :
● ● ● ● ● ● ● ● ●

new oil (duh!) a drain pan an oil funnel rags a socket wrench set and / or hex wrench set (allen wrenches) an oil filter remover a new crush washer nitrile gloves (not latex - mineral oil eats latex gloves) engineer / shop manual, if one is available

http://www.carbibles.com/engineoil_bible.html (23 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

1. Start your engine and run it for a couple of minutes to get some heat into the oil 2. Leave the engine to stand for 5 or 10 minutes. When you started it, it heated the oil but it also filled the oilways. You want the oil to drain back to the sump. 3. Take the dipstick out or loosen it off and break the seal where it plugs into the engine dipstick tube. This prevents a vacuum building up behind the oil when you start to drain it. 4. Get your drain pan / oil container and stuff it under the sump. Make sure it's sitting under the sump drain plug. I Really like the combined drainer / container types. They look like regular oil containers but if you lay them on their side, there's a popout plug. When you drain the oil, it runs into the side of the container, then you can put the plug back in and use the same container to take the oil away.

5. Put your rubber gloves on. Try to use the disposable type. Your mum / wife will never forgive you if you use the washingup gloves. Remember - used oil is toxic and carcinogenic. If you get it on your skin, it could cause problems. Use your socket wrench or allen wrench to loosen the sump plug just slightly. Once it's loose, remove it by hand.

6. Be amazed as the black syrup runs out of the engine and into your container. Be more amazed how, if it's windy, those last dregs just won't hit the container no matter where you put it. They will however go all over the road/garage floor/cat. 7. Remove the old crush washer from the sump plug and throw it away. Replace it with a new one. Use some of the oil from the drain container on the end of a rag to wipe around the drain hole in the sump. This will help clean any mess away and leave you with a smooth surface. Screw the sump plug back in by hand until it's finger tight and then use your wrench to crush the washer. This can vary from a quarter turn to a half turn. Don't overdo it or you'll strip the threads. Similarly, don't leave it too loose or it will fall out. If in doubt, use a torque wrench set to the value indicated in your shop manual.

8. Now get your oil filter remover out. Push the oil drain container under the oil filter - when you spin it off, there will be a lot
http://www.carbibles.com/engineoil_bible.html (24 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

of oil comes out. Use the filter remover to grip the oil filter and spin it off anticlockwise. 99.9% of oil filters take some muscle to get going. This is why a filter remover is a must-have. Stabbing the filter with a screwdriver and using brute force may work, but you'll be finding oil all over yourself for weeks to come if you use that method. Apart from that, some cars have aluminium inserts that protrude out of the engine block into the body of the filter, so firing a screw driver into the filter near its base (the strongest part) may shear that aluminium bit off the engine block. That Would Be Bad. Once the filter is finger-loose, spin it off by hand. (these things below are filter removers)

9. Clean off the face of the oil filter mount on the side of the engine block using a rag. Use a little oil on a rag to wipe around the seal of the new filter and spin it on by hand. Once it's locked against the side of the engine block, another quarter-turn by hand is normally enough to secure it in place. 10. Pull the drain container out from under the car and use a rag to wipe down any excess oil that has spilled down the side of the engine block. Pay attention around the sump plug and the filter. These are places you'll be checking later for leaks so the cleaner they are now, the better. 11. Use a little WD40 on the oil container and an old rag to clean the remaining oil down into the container. Put the plug back in and make sure it fits snug. That's your waste oil. Don't drink it. 12. Up to the top of the again engine now. Put the dipstick back in. Find the oil filler cap and take it off. It might say "OIL" or it might say "710". It is not a "710 cap" as one person once asked for. "710" is "OIL" upside-down. Some people need to be told.... 13. Look in your shop manual for the system capacity with filter change. This will be more than the capacity without a filter change. A lot of oil containers now come with capacity marks on the side of them. Put your oil funnel into the oil filler hole and pour in the right amount of oil. Do it slowly. If you do it quick, you'll get airlocks and the funnel will burp oil in your face. 14. Once you're happy you've got enough oil in there (check it with the dipstick if you're not sure), remove the funnel, replace the oil cap and replace the dipstick. 15. Pull the main high tension wire from the distributor cap or in some way disable the engine so that you can crank it over but it WILL NOT start. (Note : you might want to pull out the fuel pump fuse too - if you crank the engine without it starting, it will still be pumping fuel - that could cause a backfire or damage the catalyst). Crank it over until the low pressure light goes off, and another 15-20 seconds for good measure. You are pumping new oil into the empty filter and then expelling all the air from the oil lines and cavities. 16. Replace the high tension lead (and fuel pump fuse) and start the engine and let it idle for a minute or so. Stop the engine. I don't want you crawling under a car to look for leaks when the engine is running. There's so many things that can go wrong with spinning fan blades, belts, human hair, clothes, fingers and the odd dodgy auto-gearbox that will slip into "D" and run you over. 17. With the engine off have a look at the side of the engine block around the oil filter. Check the area around the sump drain too. Both should be as clean as you left them with no sign of leaks. If there's a leak, a little tightening of the drain plug or filter should cure it. One reader suggested and additional step before (9) above. When he changes his filter, he fills the new one up with clean oil and waits for it to soak into the filter itself. Once he's satisfied that the filter is soaked, he pours the excess oil out of the filter and then screws it on to the engine. Job well done. Now you should have hands that smell of talcum powder and rubber (from the gloves), a couple of greasy, slippery tools and a container full of old oil. Oh, and a crush washer and filter. If you've got more than this, you took something off that I didn't tell you to. If you turned the engine off before checking for leaks, you should also have a full complement of fingers, hair (if you had it to start with) and you should still be fully clothed. Congratulations. You've changed your engine oil.

Using oil extractors
http://www.carbibles.com/engineoil_bible.html (25 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible

There's another way of getting the oil out of your car's engine during an oil change - oil extractors. The typical extractor uses a vacuum mechanism either generated by you pumping a handle to build up a vacuum in the reservoir, or by a powered vacuum pump. The example on the right is a manual style. Basically you pump the handle to build up a vacuum, then poke the extractor hose into the oil and let her rip. Extractors are a convenience item designed to eliminate the need to get your vehicle up on a ramp, or for you to crawl under it and deal with the drain plug. The only problem with an extractor is that you can never be 100% guaranteed that you get all the oil out. For it to work best, the suction hose needs to be in the lowest point of the sump pan, where the drain bolt is. The problem is that first of all, the sump isn't transparent, so you can't tell where the suction hose really is. (Remember you'll be feeding it in through dipstick tube). Second, a lot of sumps have anti-slosh baffles in them both horizontally and vertically. If you don't get the extractor pipe through one of the baffle holes, you'll be leaving the entire sump's-worth of oil in there. Third, and finally, any congealed oil, clogs or clumps of sludge will likely get stuck in the extractor hose causing a blockage. That would mean taking the hose out, cleaning out the blockage, then feeding it back in again which subjects you to the initial two problems all over again. Oil extractors are more commonly used for getting oil out of smaller engines like lawnmowers. I've never used one in a car engine but because of the problems mentioned above, I can't imagine it would be especially efficient. Having said that, the Smart car has no sump drain so the only way to get oil out of those things in a service is to use an extractor.

Finally, and just as importantly: Disposing of used engine oil.
Think about it for a minute. What did you do with that last oil change? Pour it away down a drain? Seal it and bin it? The annual average for oil which is just washed away is 720Million gallons! About 120Million of that is from tanker spills which leaves another 600Million from domestic and business disposal. This all ends up polluting the groundwater. So what can you do? Well, you can dispose of your used oil properly. Firstly, it's worth noting that engine oils which have been used are mildly carcinogenic. This means cancer, specifically skin cancer. To be safe, wash any off quickly with a degreaser like GUNK. For heavens sake, don't use petrol (gasoline) - most fuels contain long chain hydrocarbons, which when exposed to skin pass right through to the blood stream. (This can mean liver damage, and possibly failure) Better still, wear protective gloves. Once the oil is drained into a suitable container, try your local garage. All garage workshops must have disposal barrels and many will allow you to dump your oil into their barrels. In the UK, many DIY superstores now have oil disposal banks where you can empty your used oil, and it's collected every couple of days by a tanker. So next time, just think about first. If only for the fact that in most civilised countries, it's actually an arrestable offence to dispose of oil in the public sewerage system. If you live in the UK, phone 0800 663366 to find the location of your nearest oil bank. Alternatively, you can use the postcode search on the oilbank website.

A CHEAP ENGINE OIL MAY SAVE YOU MONEY IN THE SHORT TERM, BUT IT WILL COST YOU IN THE LONG TERM! DON'T SKIMP! Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

http://www.carbibles.com/engineoil_bible.html (26 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Engine Oil Bible These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/engineoil_bible.html (27 of 27) [2/6/2008 7:10:42 AM]

Car Bibles : The Car Suspension Bible

The car suspension bible. Everything you need to know about car suspension including shocks, struts, springs, raising and lowering your suspension, different types of suspension, all the technologies involved, DIY car maintenance and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

What does it do?
Apart from your car's tyres and seats, the suspension is the prime mechanism that separates your bum (arse for the American) from the road. It also prevents your car from shaking itself to pieces. No matter how smooth you think the road is, it's a bad, bad place to propel over a ton of metal at high speed. So we rely upon suspension. People who travel on underground trains wish that those vehicles relied on suspension too, but they don't and that's why the ride is so harsh. Actually it's harsh because underground trains have no lateral suspension to speak of. So as the rails deviate sideto-side slightly, so does the entire train, and it's passengers. In a car, the rubber in your tyre helps with this little problem. In it's most basic form, suspension consists of two basic components: Springs These come in three types. They are coil springs, torsion bars and leaf springs. Coil springs are what most people are familiar with, and are actually coiled torsion bars. Leaf springs are what you would find on most American cars up to about 1985 and almost all heavy duty vehicles. They look like layers of metal connected to the axle. The layers are called leaves, hence leaf-spring. The torsion bar on its own is a bizarre little contraption which gives coiled-springhttp://www.carbibles.com/suspension_bible.html (1 of 38) [2/6/2008 7:11:17 AM]

Car Bibles : The Car Suspension Bible

like performance based on the twisting properties of a steel bar. It's used in the suspension of VW Beetles and Karmann Ghias, air-cooled Porsches (356 and 911 until 1989 when they went to springs), and the rear suspension of Peugeot 205s amongst other cars. Instead of having a coiled spring, the axle is attached to one end of a steel shaft. The other end is slotted into a tube and held there by splines. As the suspension moves, it twists the shaft along it's length, which in turn resist. Now image that same shaft but instead of being straight, it's coiled up. As you press on the top of the coil, you're actually inducing a twisting in the shaft, all the way down the coil. I know it's hard to visualise, but believe me, that's what is happening. There's a whole section further down the page specifically on torsion bars and progressive springs. Shock absorbers Strangely enough, absorb shocks. Actually they dampen the vertical motion induced by driving your car along a rough surface. If your car only had springs, it would boat and wallow along the road until you got physically sick and had to get out. Or at least until it fell apart. Shock absorbers perform two functions. Firstly, they absorb any larger-than-average bumps in the road so that the shock isn't transmitted to the car chassis. Secondly, they keep the suspension at as full a travel as possible for the given road conditions. Shock absorbers keep your wheels planted on the road. Without them, your car would be a travelling deathtrap. You want more technical terms? Technically they are called dampers. Even more technically, they are velocitysensitive hydraulic damping devices - in other words, the faster they move, the more resistance there is to that movement. They work in conjunction with the springs. The spring allows movement of the wheel to allow the energy in the road shock to be transformed into kinetic energy of the unsprung mass, whereupon it is dissipated by the damper. The damper does this by forcing gas or oil through a constriction valve (a small hole). Adjustable shock absorbers allow you to change the size of this constriction, and thus control the rate of damping. The smaller the constriction, the stiffer the suspension. Phew!....and you thought they just leaked oil didn't you?

A modern coil-over-oil unit
The image above shows a typical modern coil-over-oil unit. This is an all-in-one system that carries both the spring and the shock absorber. The type illustrated here is more likely to be an aftermarket item - it's unlikely you'd get this level of adjustment on your regular passenger car. The adjustable spring plate can be used to make the springs stiffer and looser, whilst the adjustable damping valve can be used to adjust the rebound damping of the shock absorber. More sophisticated units have adjustable compression damping as well as a remote reservoir. Whilst you don't typically get
http://www.carbibles.com/suspension_bible.html (2 of 38) [2/6/2008 7:11:17 AM]

Car Bibles : The Car Suspension Bible

this level of engineering on car suspension, most motorbikes do have preload, rebound and spring tension adjustment. See the section later on in this page about the ins and outs of complex suspension units.

Suspension Types
In their infinite wisdom, car manufacturers have set out to baffle use with the sheer number of different types of suspension available for both front and rear axles. The main groupings are dependent and independent suspension types. If you know of any not listed here, e-mail me and let me know - I would like this page to be as complete as possible.

Front suspension - dependent systems
So-called because the front wheel's suspension systems are physically linked. For everyday use, they are, in a word, shite. I hate to be offensive, but they are. There is only one type of dependent system you need to know about. It is basically a solid bar under the front of the car, kept in place by leaf springs and shock absorbers. It's still common to find these on trucks, but if you find a car with one of these you should sell it to a museum. They haven't been used on mainstream cars for years for three main reasons:
●

●

●

Shimmy - because the wheels are physically linked, the beam can be set into oscillation if one wheel hits a bump and the other doesn't. It sets up a gyroscopic torque about the steering axis which starts to turn the axle left-to-right. Because of the axle's inertia, this in turn feeds back to amplify the original motion. Weight - or more specifically unsprung weight. Solid front axles weigh a lot and either need sturdy, heavy leaf springs or heavy suspension linkages to keep their wheels on the road. Alignment - simply put, you can't adjust the alignment of wheels on a rigid axis. From the factory, they're perfectly set, but if the beam gets even slightly distorted, you can't adjust the wheels to compensate. I frequently get pulled-up on the above statements from people jumping to defend solid-axle suspension. They usually send me pictures like this and claim it's the best suspension system for off-road use. I have to admit, for off-road stuff, it probably is pretty good. But let's face it; how many people with these vehicles ever go off-road? The closest they come to having maximum wheel deflection is when the mother double-parks the thing with one wheel on the kerb during the school-run.......

Picture credit: Landrover Owner's Group

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Front suspension - independent systems
So-named because the front wheel's suspension systems are independent of each other (except where joined by an antiroll bar) These came into existence around 1930 and have been in use in one form or another pretty much ever since then.

http://www.carbibles.com/suspension_bible.html (3 of 38) [2/6/2008 7:11:17 AM]

Car Bibles : The Car Suspension Bible

MacPherson Strut or McPherson strut
This is currently, without doubt, the most widely used front suspension system in cars of European origin. It is simplicity itself. The system basically comprises of a strut-type spring and shock absorber combo, which pivots on a ball joint on the single, lower arm. At the top end there is a needle roller bearing on some more sophisticated systems. The strut itself is the load-bearing member in this assembly, with the spring and shock absorber merely performing their duty as oppose to actually holding the car up. In the picture here, you can't see the shock absorber because it is encased in the black gaiter inside the spring. The steering gear is either connected directly to the lower shock absorber housing, or to an arm from the front or back of the spindle (in this case). When you steer, it physically twists the strut and shock absorber housing (and consequently the spring) to turn the wheel. Simple. The spring is seated in a special plate at the top of the assembly which allows this twisting to take place. If the spring or this plate are worn, you'll get a loud 'clonk' on full lock as the spring frees up and jumps into place. This is sometimes confused for CV joint knock. Rover 2000 MacPherson derivative During WWII, the British car maker Rover worked on experimental gas-turbine engines, and after the war, retained a lot of knowledge about them. The gas-turbine Rover T4, which looked a lot like the Rover P6, Rover 2000 and Rover 3500, was one of the prototypes. The chassis was fundamentally the same as the other Rovers and the net result was the the 2000 and 3500 ended up with a very odd front suspension layout. The gas turbine wasn't exactly small, and Rover needed as much room as possible in the engine bay to fit it. The suspension was derived from a normal MacPherson strut but with an added bellcrank. This allowed the suspension unit to sit horizontally along the outside of the engine bay rather than protruding into it and taking up space. The bellcrank transferred the upward forces from the suspension into rearward forces for the spring / shock combo to deal with. In the end, the gas turbine never made it into production and the Rover 2000 was fitted with a 2-litre 4cylinder engine, whilst the Rover 3500 was fitted with an 'evergreen' 3.5litre V8. Open the hood of either of these classics and the engine looks a bit lost in there because there's so much room around it that was never utilised. The image on the left shows the Rover-derivative MacPherson strut. Potted history of MacPherson: Earle S. MacPherson of General Motors developed the MacPherson strut in 1947. GM cars were originally designbound by accountants. If it cost too much or wasn't tried and tested, then it didn't get built/used. Major GM innovations including the MacPherson Strut suspension system sat stifled on the shelf for years because innovation cannot be proven on a spreadsheet until after the product has been produced or manufactured. Consequently, Earle MacPherson went to work for Ford UK in 1950, where Ford started using his design on the 1950 'English' Ford models straight away. Today the strut type is referred to both with and without the "a" in the name, so both McPherson Strut and MacPherson Strut can be used to describe it. Further note: Earle MacPherson should never be confused with Elle McPherson - the Australian über-babe. In her case, the McPherson Strut is something she does on a catwalk, or in your dreams if you like that sort of thing. And if you're a bloke, then you ought to....

http://www.carbibles.com/suspension_bible.html (4 of 38) [2/6/2008 7:11:17 AM]

Car Bibles : The Car Suspension Bible

Double wishbone suspension systems.
The following three examples are all variations on the same theme.

Coil Spring type 1
This is a type of double-A or double wishbone suspension. The wheel spindles are supported by an upper and lower 'A' shaped arm. In this type, the lower arm carries most of the load. If you look headon at this type of system, what you'll find is that it's a very parallelogram system that allows the spindles to travel vertically up and down. When they do this, they also have a slight side-to-side motion caused by the arc that the wishbones describe around their pivot points. This side-to-side motion is known as scrub. Unless the links are infinitely long the scrub motion is always present. There are two other types of motion of the wheel relative to the body when the suspension articulates. The first and most important is a toe angle (steer angle). The second and least important, but the one which produces most pub talk is the camber angle, or lean angle. Steer and camber are the ones which wear tyres.

Coil Spring type 2
This is also a type of double-A arm suspension although the lower arm in these systems can sometimes be replaced with a single solid arm (as in my picture). The only real difference between this and the previous system mentioned above is that the spring/shock combo is moved from between the arms to above the upper arm. This transfers the load-bearing capability of the suspension almost entirely to the upper arm and the spring mounts. The lower arm in this instance becomes a control arm. This particular type of system isn't so popular in cars as it takes up a lot room.

http://www.carbibles.com/suspension_bible.html (5 of 38) [2/6/2008 7:11:17 AM]

Car Bibles : The Car Suspension Bible

Multi-link suspension
This is the latest incarnation of the double wishbone system described above. It's currently being used in the Audi A8 and A4 amongst other cars. The basic principle of it is the same, but instead of solid upper and lower wishbones, each 'arm' of the wishbone is a separate item. These are joined at the top and bottom of the spindle thus forming the wishbone shape. The super-weird thing about this is that as the spindle turns for steering, it alters the geometry of the suspension by torquing all four suspension arms. They have complex pivot systems designed to allow this to happen. Car manufacturers claim that this system gives even better road-holding properties, because all the various joints make the suspension almost infinitely adjustable. There are a lot of variations on this theme appearing at the moment, with huge differences in the numbers and complexities of joints, numbers of arms, positioning of the parts etc. but they are all fundamentally the same. Note that in this system the spring (red) is separate from the shock absorber (yellow). Click on the image for a reverse view of the same system (this will popup a separate window).

Trailing-arm suspension
The trailing arm system is literally that - a shaped suspension arm is joined at the front to the chassis, allowing the rear to swing up and down. Pairs of these become twin-trailing-arm systems and work on exactly the same principle as the double wishbones in the systems described above. The difference is that instead of the arms sticking out from the side of the chassis, they travel back parallel to it. This is an older system not used so much any more because of the space it takes up, but it doesn't suffer from the side-to-side scrubbing problem of double wishbone systems. If you want to know what I mean, find a VW beetle and stick your head in the front wheel arch - that's a double-trailing-arm suspension setup. Simple.

http://www.carbibles.com/suspension_bible.html (6 of 38) [2/6/2008 7:11:17 AM]

Car Bibles : The Car Suspension Bible

Moulton rubber suspension
This suspension system is based on the compression of a solid mass of rubber - red in both these images. The two types are essentially derivatives of the same design. It is named after Dr. Alex Moulton - one of the original design team on the Mini, and the engineer who designed its suspension system in 1959. This system is known by a few different names including cone and trumpet suspension (due to the shape of the rubber bung shown in the right hand picture). The rear suspension system on the original Mini also used Moulton's rubber suspension system, but laid out horizontally rather than vertically, to save space again. The Mini was originally intended to have Moulton's fluid-filled Hydrolastic suspension, but that remained on the drawing board for a few more years. Eventually, Hydrolastic was developed into Hydragas (see later on this page), and revised versions were adopted on the Mini Metro and the current MGF-sportscar. Ultimately, Moulton rubber suspension is now used in a lot of bicycles - racing and mountain bikes. Due to the compact design and the simplicity of its operation and maintenance, it's an ideal solution.

Front suspension - semi-independent (linked) systems

http://www.carbibles.com/suspension_bible.html (7 of 38) [2/6/2008 7:11:17 AM]

Car Bibles : The Car Suspension Bible

Transverse leaf-spring
This system is a bit odd in that it combines independent double wishbone suspension with a leaf spring like you'd normally find on the rear suspension. Famously used on the Corvette, it involves one leaf spring mounted across the vehicle, connected at each end to the lower wishbone. The centre of the spring is connected to the front subframe in the middle of the car. There are still two shock absorbers, mounted one to each side on the lower wishbones. Chevy insist that this is the best thing since sliced bread for a suspension system but there are plenty of other experts, manufacturers and race drivers who think it's junk. It's never been clear if this was a performance and design decision or a cost issue, but this type of system is very rare.

Historically, Triumph used transverse leaf spring suspension on their small chassis cars (Herald, Vitesse, Spitfire & GT6). In the good old British school of thought, they did this because it was cheap. The spring was bolted to the differential, rather than the chassis, and under (very) hard cornering you got jacking and tuck-under. If you got this whilst driving and panicked enough to let off the gas, or worse, step on the brake, you got massive over-steer, and pirouetted off into the nearest tree. There were plenty of complaints about this suspension system in the late 60's, so Triumph changed to a 'swing spring' system on some cars (no longer bolted to the diff), and what they called 'rotoflex' on the GT6. Again from the good old British school of thought, the replacement system was unnecessarily complicated and allegedly very fragile. Photo credit : Triumph Herald Tricks & Tips

Rear suspension - dependent (linked) systems

http://www.carbibles.com/suspension_bible.html (8 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Solid-axle, leaf-spring
This system was favoured by the Americans for years because it was dead simple and cheap to build. The ride quality is decidedly questionable though. The drive axle is clamped to the leaf springs and the shock absorbers normally bolt directly to the axle. The ends of the leaf springs are attached directly to the chassis, as are the tops of the shock absorbers. Simple, not particularly elegant, but cheap. The main drawback with this arrangement is the lack of lateral location for the axle, meaning it has a lot of side-to-side slop in it.

Solid-axle, coil-spring
This is a variation and update on the system described above. The basic idea is the same, but the leaf springs have been removed in favour of either 'coil-overoil' spring and shock combos, or as shown here, separate coil springs and shock absorbers. Because the leaf springs have been removed, the axle now needs to have lateral support from a pair control arms. The front ends of these are attached to the chassis, the rear ends to the axle. The variation shown here is more compact than the coil-over-oil type, and it means you can have smaller or shorter springs. This in turn allows the system to fit in a smaller area under the car.

http://www.carbibles.com/suspension_bible.html (9 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Beam Axle
This system is used in front wheel drive cars, where the rear axle isn't driven. (hence it's full description as a "dead beam"). Again, it is a relatively simple system. The beam runs across under the car with the wheels attached to either end of it. Spring / shock units or struts are bolted to either end and seat up into suspension wells in the car body or chassis. The beam has two integral trailing arms built in instead of the separate control arms required by the solid-axle coil-spring system. Variations on this system can have either separate springs and shocks, or the combined 'coil-over-oil' variety as shown here. One notable feature of this system is the track bar (or panhard rod). This is a diagonal bar which runs from one end the beam to a point either just in front of the opposite control arm (as here) or sometimes diagonally up to the top of the opposite spring mount (which takes up more room). This is to prevent side-to-side movement in the beam which would cause all manner of nasty handling problems. A variation on this them is the twist axle which is identical with the exception of the panhard rod. In a twist axle, the axle is designed to twist slightly. This gives, in effect, a semi-independent system whereby a bump on one wheel is partially soaked up by the twisting action of the beam. Yet another variation on this system does away with the springs and replaces them with torsion bars running across the chassis, and attached to the leading edge of the control arms. These beam types are currently very popular because of their simplicity and low cost.

4-Bar
4-bar suspension can be used on the front and rear of vehicles - I've chosen to show it in the "rear" section of this page because that's where it's normally found. 4-bar suspension comes in two varieties. Triangulated, shown on the right here, and parallel, shown on the left. The parallel design operates on the principal of a "constant motion parallelogram". The design of the 4-bar is such that the rear end housing is always perpendicular to the ground, and the pinion angle never changes. This, combined with the lateral stability of the Panhard Bar, does an excellent job of locating the rear end and keeping it in proper alignment. If you were to compare this suspension system on a truck with a 4-link or ladder-bar setup, you'd notice that the rear frame "kick up" of the 4-bar setup is far less severe. This, combined with the relatively compact installation design means that it's ideal for cars and trucks where space is at a premium. You'll find this setup on a lot of street rods and American style classic hot rods. The triangulated design operates on the same principle, but the top two bars are skewed inwards and joined to the rear end housing much closer to the centre. This eliminates the need for the separate panhard bar, which in turn means the whole setup is even more compact.

http://www.carbibles.com/suspension_bible.html (10 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Derivatives of the 4-Bar system
There are many variations on the 4-bar systems I've illustrated above. For example, if the four angled bars go from the axle outboard to the chassis near the centreline, this is called a "Satchell link". (Satchell is a US designer, who used the above linkage on some of Paul Newmans Datsun road racers some years back.) It has certain advantages over the above examples. Both of the these angled linkages can be reversed to have the angled links below the axle and the parallel links above. The roll centre will be lowered with the angled bars under the axle, a function which is difficult to accomplish without this design. The other variation on the "four bars" not shown are the Watts and Jacobs bar linkages to replace the Panhard rod for lateral positioning. Another linkage is the two parallel bars above the axle and a triangulated link underneath - a design you will find on the Lotus 7 - where the lower link has its base on the chassis and the apex under the differential. Then there is the Mallock Woblink, which could be described as half way between a Jacobs ladder and a Watts link, and makes it possible to place the rear roll centre quite low without sacrificing ground clearance. Watts links are pretty popular with the hydraulic lowrider/truck bed dancer types. The Jacobs ladder is used almost exclusively on US midget and sprintcar dirt track rear ends. The Mallock Woblink is used mostly on the Mallock U2 Clubman cars in Great Britain.

de Dion suspension, or the de Dion tube
The de Dion tube - not part of the London underground, but rather a semi-independent rear suspension system designed to combat the twin evils of unsprung weight and poor ride quality in live axle systems. de Dion suspension is a weird bastardisation of live-axle solid-beam suspension and fully independent trailing-arm suspension. It's neither one, but at the same time it's both. Weird! With this system, the wheels are interconnected by a de Dion Tube, which is essentially a laterally-telescoping part of the suspension designed to allow the wheel track to vary during suspension movement. This is necessary because the wheels are always kept parallel to each other, and thus perpendicular to the road surface regardless of what the car body is doing. This setup means that when the wheels rebound, there is also no camber change which is great for traction, and that's the first advantage of a de Dion Tube. The second advantage is that it contributes to reduced unsprung weight in the vehicle because the transfer case / differential is attached to the chassis of the car rather than the suspension
http://www.carbibles.com/suspension_bible.html (11 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

itself. Naturally, the advantages are equalled by disadvantages, and in the case of de Dion systems, the disadvantages would seem to win out. First off, it needs two CV joints per axle instead of only one. That adds complexity and weight. Well one of the advantages of not having the differential as part of the suspension is a reduction in weight, so adding more weight back into the system to compensate for the design is a definite distadvantage. Second, the brakes are mounted inboard with the calipers attached to the transfer case, which means to change a brake disc, you need to dismantle the entire suspension system to get the driveshaft out. (Working on the brake calipers is no walk in the park either.) Finally, de Dion units can be used with a leaf-spring or coil-spring arrangement. With coil spring (as shown here) it needs extra lateral location links, such as a panhard rod, wishbones or trailing links. Again - more weight and complexity. de Dion suspension was used mostly used from the mid 60's to the late 70's and could be found on some Rovers, the Alfa Romeo GTV6, one or two Lancias a smattering of exotic racing cars and budget sports cars or coupes. More recently deDion suspension has had somewhat of a renaissance in the specialist sports car and kit car market such as those from Caterham, Westfield and Dax. These all uniformly now use outboard brake setups for ease-of-use, and a non-telescoping tube, usually with trailing links and an A-bar for lateral location (rather than a Watts linkage or Panhard rod.) Whilst a properly setup independent suspension system will always win hands-down on poorly maintained roads, when you get on to the track, the advantage is not so clear cut and a well set up deDion system can often match it turnfor-turn now, espeically for flyweight cars.

Rear suspension - independent systems
It follows, that what can be fitted to the front of a car, can be fitted to the rear to without the complexities of the steering gear. Simplified versions of all the independent systems described above can be found on the rear axles of cars. The multilink system is currently becoming more and more popular. In advertising, it's put across as '4-wheel independent suspension'. This means all the wheels are independently mounted and sprung. There are two schools of thought as to whether this system is better or worse for handling than, for example, Macpherson struts and a twist axle. The drive towards 4-wheel independent suspension is primarily to improve ride quality without degrading handling.

The eBay problem
This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at www.carbibles.com, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to www.carbibles.com to see the full site and find my contact details. And now, back to the meat of the subject....

Ford Control Blade™ Suspension
A lot of attention and marketing has been coming out of Ford recently about their new Control Blade™ rear suspension. Details and engineering facts are predictably sketchy but the glossy marketing brochures will tell you this revolution in rear suspension will make your Ford Focus handle better, grip the road better, and brake better than everything else on the road. It warrants some investigation when they make claims like that, but it turns out what they mean is "we've got a new suspension system", and not much else. It actually started out its life sometime around 1998 in Ford of Australia and I believe Holden had something to do with it too. Since then its become far more mainstream. So "Control Blade™" is the snappy marketing name that Ford use to describe their new system. It sounds good, looks good on paper, and has an aura of 21st century-ness about it. "Blade". Ooh. Cool. The reality isn't quite so cool though - control blade is basically an evolution of trailing-arm suspension. However its still an interesting development and it does serve the purpose for which Ford designed it. The primary purpose of Control Blade suspension is to increase the interior space available in the vehicle. Most suspension systems used in daily drivers have strut towers front and rear. In the front it's not really a problem, but in the rear it impedes on boot (or trunk) space. Ford wanted to give more space in the back and needed to find a good way to remove or reduce the size of the strut towers. The result is their Control Blade™ system which in essence separates the shock absorber from the springs. To do
http://www.carbibles.com/suspension_bible.html (12 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

this, Ford needed to use a trailing-arm type suspension so that they didn't have swingarms up under the wheel arches. The springs were shortened and moved inboard and underneath. In one variation, the shock absorbers still sit vertically but the space they take up now is hugely reduced because they no longer have the coil springs around the outside. In the second variation the shock absorber is a subminiature unit mounted inboard of the springs underneath the vehicle. I'm not sure of the merits of the super-short shock absorber but Ford seem to think it works. The control blades themselves are basically the trailing arms which give lateral support and provide the vertical pivot point for the entire unit. The Ford spiel says this about Control Blade™: "It has the key function of promoting ride and reducing road noise transmission, while providing the freedom to let the lateral links define toe and camber by absorbing any rearward forces and allowing the rest of the suspension to do it's job uninterrupted. Effectively isolating the handling components of the new IRS from the road noise and impact harshness components of the suspension.". In English? It means better handling and less road noise. Looking at the basic design it's not difficult to see that this system has a much lower centre of gravity than a Macpherson strut (for example). Lower C-of-G in a vehicle is always a good thing. The geometry of the Control Blade™ system also provides significant 'anti-dive' under braking force, which means a the car body will dive less when you jump on the brakes which in turn translates into more well-behaved braking response. Lower C-of-G, less roll and less pitch during braking all add up to better handling, althouth whether the average driver would notice or not is a different matter. Another function of this system is that they've separated the two basic functions of suspension. With the springs and shock absorbers being mounted in different places, Ford have managed to optimise the function of these components. It's similar in concept to what BMW did with the telelever front suspension on motorbikes - separating braking from suspension forces, only in the control blade system, it separates the springing support of the suspension from the shock reducing functions of the shock absorbers. The images below are currently from other sources as I've not had the time to render up my own just yet, but they show the basic layout of each variation of control blade suspension and I've annotated them accordingly.

http://www.carbibles.com/suspension_bible.html (13 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Picture credits: Ford press kit

Aftermarket work on Control Blade™ vehicles.
There's one thing worth noting about this suspension system. Because the spring and shock are in different locations, and because of the reduced or removed strut towers, it makes it very difficult to bolt-on aftermarket suspension kits to these vehicles. For the daily driver, that's probably not an issue but if you're looking at spiffing up the suspension on a Ford Focus for track days or racing, it's not going to be quite so straightforward as it is on other cars. Just so you know. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Hydrolastic Suspension
If you've got this far, you'll remember that Dr. Alex Moulton originally wanted the Mini to have Hydrolastic suspension a system where the front and rear suspension systems were connected together in order to better level the car when driving. The principle is simple. The front and rear suspension units have Hydrolastic displacers, one per side. These are interconnected by a small bore pipe. Each displacer incorporates a rubber spring (as in the Moulton rubber suspension system), and damping of the system is achieved by rubber valves. So when a front wheel is deflected, fluid is displaced to the corresponding suspension unit. That pressurises the interconnecting pipe which in turn stiffens the rear wheel damping and lowers it. The rubber springs are only slightly brought into play and the car is effectively kept level and freed from any tendency to pitch. That's clever enough, but the fact that it can do this without hindering the full range of motion of either suspension unit is even more clever, because it has the effect of producing a soft ride. Pictures and images of anything to do with hydrolastic suspension are few and far between now, so you'll have to excuse the plagiarism of the following image. The animation below shows the self-leveling effect - notice the body stays level and doesn't pitch.

http://www.carbibles.com/suspension_bible.html (14 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

But what happens when the front and rear wheels encounter bumps or dips together? One cannot take precedent over the other, so the fluid suspension stiffens in response to the combined upward motion and, while acting as a damper, transfers the load to the rubber springs instead, giving a controlled, vertical, but level motion to the car. Remember I said the units were connected with a small bore pipe? The restriction of the fluid flow, imposed by this pipe, rises with the speed of the car. This means a steadier ride at high speed, and a softer more comfortable ride at low speed. Hydrolastic suspension is hermetically sealed and thus shouldn't require much, if any, attention or maintenance during its normal working life. Bear in mind that hydrolastic suspension was introduced in 1964 (on the prototype BMC ADO16) and you'd be lucky to find a unit today that has had any work done to it. The image below shows a typical lateral installation for hydrolastic rear suspension. The suspension swingarms are attached to the main subframe. The red cylinders are the displacer units containing the fluid and the rubber spring. The pipes leading from the units can be seen and they would connect to the corresponding units at the front of the vehicle.

Hydrolastic suspension shouldn't be confused with Citroën's hydropneumatic suspension (see below). That system uses a hydraulic pump that raises and lowers the car to different heights. Sure it's a superior system but it's also a lot more costly to manufacture and maintain. That's due in part to the fact that they don't use o-rings as seals; the pistons and
http://www.carbibles.com/suspension_bible.html (15 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

bores are machined to incredible tolerances (microns), that it makes seals unnecessary. Downside : if something leaks, you need a whole new cylinder assembly. Hydrolastic was eventually refined into Hydragas suspension.......

Hydragas Suspension
Hydragas is an evolution of Hydrolastic, and essentially, the design and installation of the system is the same. The difference is in the displacer unit itself. In the older systems, fluid was used in the displacer units with a rubber spring cushion builtin. With Hydragas, the rubber spring is removed completely. The fluid still exists but above the fluid there is now a separating membrane or diaphragm, and above that is a cylinder or sphere which is charged with nitrogen gas. The nitrogen section is what has become the spring and damping unit whilst the fluid is still free to run from the front to the rear units and back.

Hydragas suspension was famously used in the 1986 Porsche 959 Rally car that entered the Paris-Dakar Rally, and today you can find it on the MGF Roadster. There are a lot of resources on Hydragas available at one of the MGF club sites on the internet: http://www.mgfcar. de/hydragas

Hydropneumatic Suspension
{Thanks to Julian Marsh, Jonathan Bruce, Simon Byrnand and Pieter Melissen for some updates to this information.} Since the early fifties, Citroën have been running a fundamentally different system
http://www.carbibles.com/suspension_bible.html (16 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

to the rest of the auto industry. Its called hydropneumatic suspension, and it is a whole-car solution which can include the brakes and steering as well as the suspension itself. The core technology of hydropneumatic suspension is as you might guess from the name, hydraulics. Ultra-smooth suspension is provided by the fluid's interaction with a pressurised gas, and in this respect, its very similar to the hydragas system described above. Citroën pioneered the system in the rear suspension of the 15 (Traction Avant) model, and it has been fitted to many of their cars since. Because of the complexity of the system, the rest of this section gets a bit wordy but hopefully not so much that I'll lose you half way through. Because this page is about all types of suspension, for clarity I decided to concentrate on the simplified version of this as installed in the "BX" model. If you're desperate to know every last nut and bolt of hydropneumatics, just do a google search for it. On we go.... The system is powered by a large hydraulic pump, typically belt-driven by the engine like an alternator or an air conditioner. the pump provides fluid to an accumulator at pressure, where it is stored ready to be delivered to servo a system. This pump may also be used for the power steering and the brakes, and in the DS for the semi-automatic gearbox. Note - the C5 and C6 only use the high pressure hydraulics for the suspension - brakes and steering are conventnional. Under the company's new Peugot management, Citroën produced the LN, followed by the Visa and then the LNA and then the BX. The BX was a major turning point in Citroën's history. As a direct consequence of the Peugeot influence, the car was somewhat more conventional than its bulkier predecessors like the CX. This Peugeot-enforced "normalisation" of the design makes it fairly easy to examine as an illustration of how hydropneumatic suspension works. The BX employed pseudo-McPherson struts at the front with a hydropneumatic unit replacing the coil spring and damper. At the rear a 'conventional' trailing arm was used with the hydropneumatic unit mounted horizontally. Apart from the pump, the two most obvious components in the system are the spheres on top of each suspension strut, and the struts themselves. The spheres are like the springs in regular suspension, and the struts are the hydraulic components that make the fluid act like a spring. The spring in this suspension system is provided by a hydraulic component called a suspension sphere. The accumulator is an additional sphere (which holds a reserve of hydraulic fluid under pressure to even out the load on the pump caused by varying demand) acting rather like a battery. The accumulator is is gas (typically nitrogen) under pressure in a bottle contained within a diaphragm. This is effectively a balloon which allows pressurised fluid to compress the gas, and then as pressure drops the gas pushes the fluid back to keep the system's pressure up. In the image here, the nitrogen gas is represented in red and the LHM fluid is represented in green. As the pressure in the fluid overcomes the gas pressure, the nitrogen is compressed by the diaphragm being pushed back. Then as the pressure in the fluid reduces, the gas pushes back the diaphragm which expels the fluid from the sphere, returning gas and fluid to equilibrium. This is the hydropneumatic equivalent to the spring being compressed and then rebounding. Still with me? We can keep going... So how can the interaction of compressing gas, hydraulic fluid and a diaphragm form a spring? Simple(ish): The pressure of the gas is the equivalent to the spring weight. The inlet hole at the bottom of the sphere restricts the flow of the fluid and provides an element of damping. By replacing the spheres for ones of different specifications, it's possible to adjust the ride characteristics of these cars.

http://www.carbibles.com/suspension_bible.html (17 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Before we go any further it is pretty important that you understand where the fluid acting on the diaphragm in the sphere gets its force from, and to do that we are going to have to look at the operation of the other key component in the Citroën system - the strut. The sphere in these systems is actually mounted at the end of the strut. The strut itself acts like a syringe to inject fluid into the sphere. When the wheel hits a bump it rises, pushes the piston back and this squeezes fluid through the tiny hole in the sphere to let the gas spring absorb the energy of the bump. Then when the car is over the bump, the gas pushes the diaphragm back out, pushing the fluid down to the strut, pushing the wheel down to the ground. Some interesting possibilities were opened up when Citroën decided to use this system to spring their cars. One or two of the more obvious ones are that since the system is hydraulic, the ride height can easily be altered; Citroën put fancy valves called height correctors in the system. They are designed to correct for long-term/static errors in height. To do this there is a clamp on the middle of each roll bar connected by a linkage to the height corrector. This linkage varies by model - on DS, CX, GS, BX it is a simple torsion bar about 8mm diameter and about 400mm long, on the XM and Xantia it is a coil spring assembly with a double acting override linkage, but the functionality is the same. By measuring the height at the middle of the rollbar, it automatically takes the average of the left and right wheel height on that axle, and therefore cannot detect body roll. This prevents it from spuriously trying to react to body roll, as it can't do anything to counter it anyway - it can only make both sides go up or down together. Additionally the height correctors have a hydraulic damping chamber in them which restricts and delays their movement - typically it takes a suspension movement of at least 20mm in one direction for at least 5 seconds before the height corrector will respond. Even fully bottoming the suspension still takes at least 5 seconds for a response. This works as a simple averaging system and prevents the height correctors from responding to bumps or road undulations, (which would be undesirable). The slight exception here is the rear suspension which is subject to squat due to acceleration because of the front wheel drive. Prolonged heavy accleration of more than 5 seconds (particularly noticable on an automatic) will cause a height correction response - an undesirable side effect. (Hydractive 2 models take steps to try and avoid this response by stiffening the suspension during heavy acceleration). Another noteworthy feature of Citroën system is its ability to "pre-set" a car for bumps in the road, keeping the car on an even keel. This is a result of the cross-piping between left and right struts on the same axle. They are connected permanently via a 3.5mm pipe, (except in Hydractive and Activa systems). The height corrector connects to a T-junction of this cross piping, but when the height corrector is "closed" (which is nearly all the time while driving) it represents a dead end, so only the piping from left to right comes into play. When the wheel on one side hits a bump some oil will flow into
http://www.carbibles.com/suspension_bible.html (18 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

the sphere on that side via the damping valve, and some will flow across to the other side and extend the wheel on that side, which gives a slight roll stabalizing response. This tends to make the car more steady in the roll axis, and reduces the side to side rocking motion on transverse undulations. A side effect of this cross piping is that it gives the suspension very soft compliance for "warp mode" movements, as the suspension spheres (springing) don't resist slow roll movements like conventional springs do - only the rollbar does. (This improves traction a lot at very slow speeds over very uneven ground) In fact without the rollbars the suspension would be completely unstable on the roll axis - you could sit on the left and it would go right down and the other side would go right up... The downside of the cross connection is the same - the long term roll stiffness is provided only by the rollbar - and there is no damping control of the flow of oil from one side to the other, other than some restriction caused by the small pipe diameter - hence the tendency of older Citroëns to have a lot of very slow body roll. Hydractive 2 overcomes these shortcomings by modifying the side to side connection - it is increased from 3.5mm to 10mm, but at the mid point there is a unit with an additional sphere, an on/off valve, and two damper valves. In the "soft mode" (selected dynamically by computer) this additional middle sphere is connected in circuit and provides additional springing, via the two damping valves in the unit. The system effectively has two parallel paths for the oil to flow for each bump, with different damping rates. The damper valves in the struts spheres on Hydractive 2 are very stiff, while the ones in the middle unit are softer, giving a net result of 3 stage damping in the soft mode, and 2 stage damping in the hard mode. Any body roll requires oil to either flow into and out of the very stiff damping valves in the strut spheres - where the opening thresholds are above that produced by roll movement - or to flow from side to side - where it must pass through two damping valves in series in the centre unit. This means roll movements are hydraulically damped in Hydractive systems, unlike Hydropneumatic. This contributes towards the reduced roll on later models like XM and Xantia. Because of the large gauge of pipe there is the potential for greater instantaneous flow when hitting large bumps, so the roll axis stability of the car is actually improved over older models. In the "hard mode", again selected dynamically by the computer based on inputs such as steering wheel angle and road speed, the central unit is isolated, completely blocking the cross-flow of oil and isolating the middle sphere, giving stiffer springing, much stiffer damping, and much reduced body roll. The Activa refinements and developments were quite effective. The main setback was that ride comfort was even worse than a BMW (although cornering speeds were fantastic) which did not go too well with the traditional Citroën clientele. The current adjustable systems (computer controlled) lack this anti roll characteristic, and there are owners who always prefer the "comfort" setting rather than the "sporty" one, because again, that is not what Citroën is about. The following cars were fitted with hydropneumatic suspension: Traction Avant 15 Six H, D series, GS/GSA, SM, BX, some XMs and most Xantias. The following were fitted with Hydractive 1 or Hydractive 2 suspension (the difference between H1 and H2 are mainly concerned with computer parameters): most XMs and some Xantias. The Xantia Activa was fitted with Hydractive suspension. The C5 is fitted with Hydractive 2 suspension and the C6 with Hydractive 3. A further mechanical advantage of hydraulic suspension is that the car is able to link its braking effort to the weight on the wheels. In the Citroën BX, the rear braking effort comes from the pressure exerted on the LHM fluid by the weight on those struts. This means that as the weight travels forward under braking, there is less pressure on the back suspension. The suspension then exerts less pressure on its fluid, and as weight and grip diminish on the wheels, so does the braking effort, thus the hydropneumatic system prevents rear wheel lock ups. Since the rear brakes use the rear suspension fluid, the tail is pulled down allowing for level braking. In addition to these benefits, Citroën pioneered computer controlled suspension in the early nineties by inserting a computer to take readings from the cars' chassis and control systems and let the computer make informed decisions about how to handle the cars suspension. The computer could then effect these decisions by things like servo valves, and offered benefits like soft suspension for cruising, but stiffer, sportier suspension for faster harder driving, allowing the driver to cruise in comfort and still enjoy a responsive car. It also moves substantially towards eliminating body roll and if used for a sportier driver will save tyre wear as well (they claim).

http://www.carbibles.com/suspension_bible.html (19 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Its worth noting that when Mercedes launched their latest 600 SLC version with a computer controlled anti roll system, Auto Motor und Sport then proudly claimed that to be the first such anti roll system in world, only having to correct that one issue later by having to mention a French invention. Rolls Royce was the only company ever to buy the patent and they used in in the rear suspension of the Silver Shadow. When Citroën was the owner of Maserati some of their cars were also hydropneumatised. More in-depth information can be found here: http://www.citroenet.org.uk/miscellaneous/suspension/suspension8.html http://web.actwin.com/toaph/citroen/work/work.html http://www.tramontana.co.hu/citroen/guide/guide.php. Meanwhile, the rest of us can hopefully feel satisfied with our newly enriched understandings of hydropneumatic suspension. If you're still awake.

Hydraulic Suspension
Hydraulic suspension is an innovation making its way into motor sports, no doubt to trickle down to consumer vehicles eventually. It has been designed by a Spanish company called Creuat and pioneered by the Racing For Holland Dome S101 sports car team. In the image below you can see both the traditional coilover system (the yellow/blue/red units) at the front of the car. This photo was taken before scrutineering for the 2005 24 Hours of Le Mans race. The team had both systems online and when scrutineering passed the car, the coilover units were removed, to race for the first time completely with hydraulic suspension. Central to their system is a control unit mounted next to the cockpit. They tell me the system can't be compared to the hydropneumatic suspension Citroën uses because this system doesn't use a pump and has less than a litre of hydraulic fluid in the entire system. Instead of springs and dampers, this central Hydropneumatic unit takes care of each suspension mode in an independent manner. This allows the car to be tuned to avoid most of the compromises which arise out of the use of conventional suspension made of springs and dampers. This system is so new that the best source of information on it is Creuat's own website. You can find it at this link and you need to look for the Le Mans Project in their menu on the left side of their page. The hydraulic suspension page is a workin-progress project and its content changes almost weekly at the moment. Racecar Engineering magazine have a feature article about this suspension system at this link but you need a subscription to read the whole thing. Fortunately Creuat have scanned the article and made it available as a 6.2Mb PDF file which you can read here. Thanks to Sander van Dijk for sending me this photo, plus a ton of others of their racing car.

http://www.carbibles.com/suspension_bible.html (20 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

http://www.carbibles.com/suspension_bible.html (21 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Ferrofluid or magneto-rheological fluid dampers - Audi Magnetic Ride.
In 2006, Audi launched the new TT model and one of the innovations that it came with is their magnetic semi-active suspension. It is a totally new form of damping technology refined from Delphi's MagneRide system. Delphi used to be a division of GM when they developed the first version of Magneride in conjunction with LORD Corp. (The initial version was used in the 2002 Cadillac Seville STS). It is designed once again to attempt to resolve the long-standing conflict between cabin comfort and driving dynamics. The Audi system is a coninuously adaptive system - ie it's a closed feedback loop that can react to changes both in the road surface and the gear-changes (frontto-back weight shift) within milliseconds. So how does this work? Well, the dampers in the Audi system are not filled with your regular old shock absorber oil. Nope. They're filled with (wait for it) magneto-rheological fluid. This is a synthetic hydrocarbon oil containing subminiature magnetic particles. When a voltage is applied to a coil inside the damper piston, it creates a magnetic field (physics 101 - get that old textbook out and check the left- and right-handed electro-magnetic rules that make electric motors work). Inside the magnetic field, all the magnetic particles in the oil change alignment in microseconds to lie predominantly across the damper. Because the damper is trying to squeeze oil up and down through the flow channels, having the
http://www.carbibles.com/suspension_bible.html (22 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

particles lined up transverse to this motion makes the oil 'stiffer'. Stiffer oil flows less, which stiffens up the suspension. Neat. You might have seen a demo of a similar system on TV in 2005 when an artist in New York started making living art using a ferromagnetic liquid (ferrofluid) and electromagnets. The principle is exactly the same - apply a magnetic field and the fluid lines up along the lines of magnetism. The image on the left shows a ferrofluid demonstration. The Audi system has a centralised control unit which sends signals to the coils on each damper. Hooked up to complex force and acceleration sensing gauges, the control unit constantly analyses what's going on with the car and adjusts the damping settings accordingly. Because there are no moving parts - no valves to open or close - the system reacts within microseconds; far quicker than any other active suspension technology on the market today. And because the amount of voltage applied to the coils can be varied nearly infinitely, the dampers have a similarly near-infinite number of settings. The power usage for each strut is around 5Watts, and the entire thing takes up no more room than a regular coil-over-oil unit. Vorsprung durch Technik indeed. The diagram below shows the basic principle of magnetised vs. unmagnetised ferrofluid, as well as a cutaway of the piston assembly in a Magneride-type damper. The little blue balls represent the particles of fluid, and yes I know they're huge - that's artistic licence so you can see them.

Linear Electromagnetic Suspension
http://www.carbibles.com/suspension_bible.html (23 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible Picture credits: Bose Learning Center & Bose press kit.

This is the latest innovation in suspension systems, invented by Bose®. The idea is that instead of springs and shock absorbers on each corner of the car, a single liner electromagnetic motor and power amplifier can be used instead. Inside the linear electromagnetic motor are magnets and coils of wire. When electrical power is applied to the coils, the motor retracts and extends, creating motion between the wheel and car body. It's like the electromagnetic effect used to propel some newer rollercoaster cars on launch, or if you're into videogames and sci-fi, it's like a railgun. One of the big advantages of an electromagnetic approach is speed. The linear electromagnetic motor responds quickly enough to counter the effects of bumps and potholes, thus allowing it to perform the actions previously reserved for shock absorbers. In it's second mode of operation, the system can be used to counter body roll by stiffening the suspension in corners. As well as these functions, it can also be used to raise and lower ride height dynamically. So you could drop the car down low for motorway cruising, but raise it up for the pot-hole ridden city streets. It's all very clever. The power amplifier delivers electrical power to the motor in response to signals from the control algorithms. These mathematical algorithms have been developed over 24 years of research. They operate by observing sensor measurements taken from around the car and sending commands to the power amps installed with each linear motor. The goal of the control algorithms is to allow the car to glide smoothly over roads and to eliminate roll and pitch during driving. The amplifiers themselves are based on switching amplification technologies pioneered by Dr. Bose at MIT in the early 1960s. The really smart thing about the power amps is that they are regenerative. So for example, when the suspension encounters a pothole, power is used to extend the motor and isolate the vehicle's occupants from the disturbance. On the far side of the pothole, the motor operates as a generator and returns power back through the amplifier. By doing this, the Bose® system requires less than a third of the power of a typical vehicle's air conditioner system. Clever, eh? Bose have also managed to package this little wonder of technology into a two-point harness - ie it basically needs two bolts to attach it to your vehicle and that's it. It's a pretty compact design, not much bigger than a normal shock absorber.

The official Bose suspension page can be found here if you want more info. It's worth noting that a company called Aura Systems devised (or at least tried to market)
http://www.carbibles.com/suspension_bible.html (24 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

a similar linear electromagnetic suspension system around 1991. They published an article in the Automotive Engineering Journal claiming that electromagnetic actuators could be used for vehicle suspensions and it said that small devices could be designed with a typical thrust capability of about 2500 Newtons and for a reasonable power demand. This happened at the same time that linear electromagnetic rams were being developed for entertainment simulators and full flight simulators to replace hydraulic systems. In fact, it could be argued that the Aura Systems ram was a direct descendant of the rams found on Super-X entertainment simulators. The units looked very similar to the Bose devices and had the same limitation - they couldn't carry the dead weight of the vehicle. Aura Systems ran into financial troubles in 2000, and filed for Chapter 11 in 2005. The time scales fit quite nicely into the declared Bose time frame (start of development versus going public). Of course they could have been parallel developments, but the bigger question is why was Aura not able to sell their system to an OEM at some time during the previous 15 years? Could it be to do with mechanical limitations - that the sway bars carrying vertical loads are very good at transmitting road inputs into the vehicle structure even if the bar rate is low? Time will tell if Bose manage to succeed where Aura Systems failed.

Air suspension
In days gone by, air suspension was limited to expensive logistics trucks - heavy goods vehicles that needed to be able to maintain a level ride no matter what the road condition. Nowadays, you can retrofit air suspension to just about any vehicle you like from a Range Rover to a Ferrari. Air suspension replaces the springs in your car with either an air bag or an air strut made of high-tensile super flexible polyurethane rubber. Each air bag or strut is connected to valve to control the amount of air allowed into it. The valves are in turn connected to an air compressor and a small compressed air reservoir. By opening and closing the four valves, the amount of air sent to each unit can be varied. By letting the same amount of air out of all the units, reducing the pressure in the bags, your car gets lowered, whilst increasing the air pressure by the same amount in each unit results in your car lifting higher off the ground. The rubber bags filled with air provide the springing action that used to be the realm of metal springs, and you have the option to maintain the factory (or aftermarket) shock absorbers for - well - absorbing shocks. That's it in a nutshell.

Why air suspension?
Simple : ride quality. A well set up air suspension system can surpass metal spring suspension in just about any situation. If you want a luxurious, smooth, supple ride that will iron out the deepest of ruts and crevasses in the road, air suspension is what you're looking for. It's why logistics firms have used it in their trucks since the year dot - air suspension transmits much less road vibration into the vehicle chassis. There are literally hundreds of combinations and permutations of air bags and struts that can be adapted to fit just about any vehicle and the big hitter in the aftermarket segment at the moment is Air Ride Technologies if you're in America. In England, Rayvern Hydraulics have a similarly complete range of aftermarket solutions. One point to note: for some reason the imperial fittings used on some American systems are all but impossible to get hold of in the UK, so if you're in England and looking for air suspension, Rayvern would be a good choice, or BSS or GAS in Germany. In factory fit systems, almost any sports sedan that has variable ride height (like a lot of the current crop of Audis) is using air suspension to accomplish this.

Bags and struts
Air bag systems come in two different flavours - air bags and air struts. The bags are typically used for leaf-spring suspension vehicles, but can easily be adapted (through the use of bolt-on brackets) to almost any swinging-arm type suspension system. Air bags are the most reliable systems because of their simplicity. Air struts are a little more complex and come in two flavours - simple struts and pivoting struts. It used to be that you could only have a simple strut because none of the manufacturers had figured out how to keep the air strut sealed when it twisted - a function that is required if you're going to replace a MacPherson strut. Now though, there are a couple of different options for MacPherson strut replacement, the most complex being the twisting double-doughnut style strut that still allows the
http://www.carbibles.com/suspension_bible.html (25 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

shock absorber to pass through the middle of it. The two images below show an air bag system as applied to the rear leaf spring suspension on a truck, and a simple non-twisting air strut system as applied to a double swingarm unit.

Ride height sensors
Simple air suspension is pretty much what I've outlined above, but most systems are far more sophisticated. For example each unit will normally work in conjunction with a ride-height sensor. This is a mechanical lever linked to the suspension arm at one end, and to an electronic resistance pot at the other. The pot is connected to the chassis or frame so that the lever spins the pot as the suspension moves up and down. A computer can use this to read the height of the vehicle in that corner, and with that data, all sorts of wonderful things can happen. For example, if you mash the accelerator pedal, a car will typically squat under acceleration. When this happens, the ride height at the rear of the car gets less. An air suspension system can register this and either send more air to the rear, or reduce the pressure at the front to level off the car again. Same goes for side-to-side roll in corners - air suspension can compensate somewhat for body roll when connected to ride-height sensors. New generation systems also incorporate air pressure sensors to add another level of feedback to the system.

Control panels
In a factory-fit air suspension system, the control panel will either be integrated into the onboard computer (like BMW's i-Drive), or be accessible via a ride-height adjustment control. For aftermarket systems, the control panel is normally a hand-held device with a series of control buttons and LED readouts on it. Either way, the control panel is how you determine what you want the suspension to do, be it hunkered down for sporty driving, or high off the ground for extra clearance.

Low-riders
Love 'em or hate 'em, there's no getting around the fact that some petrolheads just love to slam their rides down to the floor but put air suspension systems in capable of making the cars hop, jump and dance. The only real difference with these systems is that they have a much larger high-pressure reservoir normally in the boot or trunk, connected to valves that
http://www.carbibles.com/suspension_bible.html (26 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

can open very rapidly. Instead of the smooth, gentle ride-height adjustment of a factory-fit system, these valves can bang open and discharge huge quantities of air from the reservoir into the air bags extremely quickly. The result is the suspension elongating extremely quickly and with enough force to propel the car into the air. In truth, the extreme low riders like this tend to go more for hydraulic actuators than air suspension. Hydraulics give far more power, far more quickly and are a lot more robust when it comes to the constant hammering they get from competitions and shows. The principle is exactly the same though - a reservoir, a compressor, a set of valves and a set of hydraulic lifters connected to the suspension components. The downside? No suspension to speak of because the hydraulic actuators have no give in them like the rubber air bags do.
Picture credit: Wikipedia / Public Domain

Variable-camber suspension for steering
If you've read the wheel and tyre bible, you'll know that camber is the lateral tilt of the suspension (and hence the wheel and the tyre) to the road surface. Proper camber (along with toe and caster) make sure that the tyre tread surface is as flat as possible on the road surface. The problem with regular fixed-geometry suspension is that the camber is set up to be ideal when driving straight. This means that however much you dislike the idea, when you corner, less of the tyre's tread is in contact with the road surface because the tyre has to tilt slightly when the steering is turned. In 2006, OnCamber LLC patented their variable camber steering system which they launched at SEMA in Las Vegas. Matthew Kim, OnCamber's founder and president was kind enough to send some pictures of their development system which you can see here. The idea is simple - as the steering wheel is turned, the steering input shifts the top mounts of a McPherson strut type suspension system laterally. In other words, the top of the strut is no longer solidly bolted to the strut tower. When the top mount point is moved, the camber of the suspension system changes. Turn to the left, and the mounting points shift to the left tilting the wheels over to the left giving a larger contact patch whilst cornering. ie. the inside wheel tilts and goes into positive camber(almost parallel to the outside wheel), which in turn contributes to the overall grip of the car. The variable camber action also gives even tyre wear. Pyrometer readings during testing have shown that the inside, mid, and outside tyre tread temperatures are all within 2° of each other. With regular fixed-camber steering, the inside of the tyre was 20° higher. OnCamber's development car is an RSX although they have designs on the table for double-wishbone variants of their system too. On the RSX testbed the camber plates are attached together by linear guides which permits them to move freely. The top connecting rods are mechanically connected to the steering rack. The degree of camber applied with steering is adjustable by varying the distance of the rods from the pivot point. ie: when the rods are mounted closer to pivot point you get more camber with less steering input. On track, this system has shaved 3 seconds off the development vehicle's lap times in race conditions. Whether this sytem will trickle down into consumer level cars is debatable. It's doubtful that a manufacturer would add this as standard but the racing and aftermarket scenes will undoubtedly welcome this development with open arms. 3 seconds off your lap time for a change of suspension components? Why wouldn't you? The images below show a camber plate at the top of one of the strut towers, and the mechanical steering linkage.

http://www.carbibles.com/suspension_bible.html (27 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Picture credits: Matthew Kim, OnCamber LLC

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Anti-roll Bars & Strut Braces
Strut Braces
If you're serious about your car's handling performance, you will first be looking at lowering the suspension. In most cases, unless you're a complete petrolhead, this will be more than adequate. However, if you are a keen driver, you will be able to get far better handling out of your car by fitting a couple of other accessories to it. The first thing you should look at is a strut brace. When you corner, the whole car's chassis is twisting slightly. In the front (and perhaps at the back, but not so often) the suspension pillars will be moving relative to each other because there's no direct physical link between them. They are connected via the car body, which can flex depending on its stiffness. A strut brace bolts across the top of the engine to the tops of the two suspension posts and makes that direct physical contact. The result is that the whole front suspension setup becomes a lot more rigid and there will be virtually no movement relative to each side. In effect, you're adding the fourth side to the open box created by the subframe and the two suspension pillars.

Simple straight brace(highlighted). Complex brace (highlighted).
http://www.carbibles.com/suspension_bible.html (28 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Anti-roll Bars (Sway Bars/Stabilizers)
No, these aren't the things that are bolted inside the car in case you turn it over - those are rollover cages. Anti-roll bars do precisely what their name implies - they combat the roll of a car on it's suspension as it corners. They're also known as sway-bars or anti-sway-bars. Almost all cars have them fitted as standard, and if you're a boy-racer, all have scope for improvement. From the factory they are biased towards ride comfort. Stiffer aftermarket items will increase the road-holding but you'll get reduced comfort because of it. It's a catch-22 situation. Fiddling with your roll stiffness distribution can make a car uncomfortable to ride in and extremely hard to handle if you get it wrong. The anti-roll bar is usually connected to the front, lower edge of the bottom suspension joint. It passes through two pivot points under the chassis, usually on the subframe and is attached to the same point on the opposite suspension setup. Effectively, it joins the bottom of the suspension parts together. When you head into a corner, the car begins to roll out of the corner. For example, if you're cornering to the left, the car body rolls to the right. In doing this, it's compressing the suspension on the right hand side. With a good anti-roll bar, as the lower part of the suspension moves upward relative to the car chassis, it transfers some of that movement to the same component on the other side. In effect, it tries to lift the left suspension component by the same amount. Because this isn't physically possible, the left suspension effectively becomes a fixed point and the anti-roll bar twists along its length because the other end is effectively anchored in place. It's this twisting that provides the resistance to the suspension movement.

If you're loaded, you can buy cars with active anti-roll technology now. These sense the roll of the car into a corner and deflate the relevant suspension leg accordingly by pumping fluid in and out of the shock absorber. It's a high-tech, super expensive version of the good old mechanical anti-roll bar. You can buy anti-roll bars as an aftermarket add-on. They're relatively easy to fit because most cars have
http://www.carbibles.com/suspension_bible.html (29 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

anti-roll bars already. Take the old one off and fit the new one. In the case of rear suspension, the fittings will probably already be there even if the anti-roll bar isn't. Typical anti-roll bar (swaybar) kits include the uprated bar, a set of new mounting clamps with polyurethane bushes, rose joints for the ends which connect to the suspension components, and all the bolts etc that will be needed.

Suspension bushes
These are the rubber grommets which separate most of the parts of your suspension from each other. They're used at the link of an A-Arm with the subframe. They're used on anti-roll bar links and mountings. They're used all over the place, and from the factory, I can almost guarantee they're made of rubber. Rubber doesn't last. It perishes in the cold and splits in the heat. Perished, split rubber was what brought the Challenger space shuttle down. This is one of those little parts which hardly anyone pays any attention to, but it's vitally important for your car's handling, as well as your own safety, that these little things are in good condition. My advice? Replace them with polyurethane or polygraphite bushes - they are hard-wearing and last a heck of a lot longer. And, if you're into presenting your car at shows, they look better than the naff little black rubber jobs. Like all suspension-related items though, bushes are a tradeoff between performance and comfort. The harder the bush compound, the less comfort in the cabin. You pays your money and makes your choice.

Variable stiffness anti-roll bars
Some sportier vehicles have the capability to stiffen up the suspension for more aggressive handling by altering how the anti-roll bar behaves. The system itself isn't especially complex. Instead of simple rubber or urethane bushes to clamp the anti-roll bar to the frame of the car, these systems use a motor-driven or electromagnetically clamped bush instead. When the driver decides they want 'sport' mode, the car can increase the friction in the mounting bushes by clamping them more tightly around the anti-roll bar. This better resists the anti-roll bar's ability to twist across the width of the vehicle, which in turn provides more resistance at the ends where it joins the suspension components. The end result is that the suspension components have to take on a lot more load to deflect by the same amount. Or conversely, under the same load, they move less, thus stiffening up the suspension.

The Ins and Outs of complex suspension units.
Generally speaking, this section will be more relevant to you if you ride a motorbike, but you can get high-end spring / shock combos for cars that have all these features on them. The thing to realise is that if you're going to start messing with all these adjustments, for God's sake take a digital photo of the unit first, or somehow mark where it all started out. It's a slippery slope and you can very quickly bugger up the ride quality of your vehicle. If you don't know what the "stock" setting was, you'll never get it back.

Compression damping.
http://www.carbibles.com/suspension_bible.html (30 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

This is the damping that a shock absorber provides as it's being compressed, ie. as you hit a bump in the road. It's the resistance of the unit to alter from its steady state to its compressed state. Imagine you're riding along and you hit a bump. If there is too little compression damping, the wheel will not meet enough resistance as the suspension compresses. Not enough energy is dissipated by the time you reach the crest of the bump and because the wheel and other unsprung components have their own mass, the wheel will continue to move upwards. This unweights or unloads the tyre and in extreme cases, it can lose contact with the road. Either way, you briefly lose traction and control. The opposite is true if compression damping is too heavy. As the wheel encounters the bump in the road, the resistance to moving is high and so at the crest of the bump, the remaining energy from the upward motion through the shock absorber is transferred into the frame of the bike or the chassis of the car, lifting it up.

Rebound damping.
Go on - have a guess at what this is. Well in case you're not following along, this is the damping that a shock absorber provides as it returns from its compressed state to its steady state, ie. after you've crested the bump in the road. Too light, and the feeling of control in your vehicle is minimised because the wheel will move very quickly. The feeling is the soft, plush ride you find in a lot of American cars. Or mushy as we like to call it. Too heavy, and the shock absorber can't return quickly enough. As the contour of the road drops away after the bump, the wheel has a hard time "catching up". This can result in reduced traction, and a downward shift in the height of the vehicle. If that happens, you can overload the tyre when the weight of the vehicle bottoms-out the suspension.

Damping controllers.
High-end kit has controls on the shock absorber for both compression and rebound damping. Typically the rebound damping will be a screwdriver slot at the top of the shock absorber, and compression damping will be a knob either on the side or on the remote reservoir. Ultra-high-end kit has separate controls for high- and low-speed damping. ie. you can make the shock absorber behave differently over small bumps (low speed compression and rebound) than it does over large bumps (high speed compression and rebound). Of course you could buy yourself a nice big TV, a DVD player, dark curtains, a new couch and a year's supply of popcorn for the same cost as four of these units.

http://www.carbibles.com/suspension_bible.html (31 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Spring preload.
Some motorbike suspension units, as well as some found on cars, give you the ability to alter the spring preload or pre-tension. This means that you're artificially compressing the spring a little which will alter the vehicle's static sag the amount of suspension travel the vehicle consumes all by itself. For example, if you ride a motorbike on your own, the preload might work on the factory setup. But if you put a passenger on the back, the tendency is for the bike to sag because there's now more sprung weight. Increasing the preload on the spring plate will help compensate for this.

Sprung vs. unsprung weight.
Simply put, sprung weight is everything from the springs up, and unsprung weight is everything from the springs down. Wheels, shock absorbers, springs, knuckle joints and tyres contribute to the unsprung weight. The car, engine, fluids, you, your passenger, the kids, the bags of candy and the portable Playstation all contribute to the sprung weight. Reducing unsprung weight is the key to increasing performance of the car. If you can make the wheels, tyres and swingarms lighter, then the suspension will spend more time compensating for bumps in the road, and less time compensating for the mass of the wheels etc. The greater the unsprung weight, the greater the inertia of the suspension, which will be unable to respond as quickly to rapid changes in the road surface. As an added benefit, putting lighter wheels on the car can increase your engine's apparent power. Why? Well the engine has to turn the gearbox and driveshafts, and at the end of that, the wheels and tyres. Heavier wheels and tyres require more torque to get turning, which saps engine power. Lighter wheels and tyres allow more of the engine's torque to go into getting you going than spinning the wheels. That's why sports cars have carbon fibre driveshafts and ultra light alloy wheels.

Progressively wound springs
These are the things to go for when you upgrade your springs. In actual fact, it's difficult not to get progressive springs when you upgrade - most of the aftermarket manufacturers make them like this. Most factory-fit car springs are normally wound. That is to say that their coil pitch stays the same all the way up the spring. If you get progressively wound springs, the coil pitch gets tighter the closer to the top of the spring you get. This has the effect of giving the spring increasing resistance, the more it is compressed. The spring constant (stiffness) of a coil spring equals: k = compression / force = D^4 * G / (64*N*R^3) where D is the wire diameter, G an elastic material property, N the number of coils in the spring, and R the radius of the spring. So increasing the number of coils decreases the stiffness of the spring. Thus, a progressive spring is progressive because the two parts are compressed equally until the tightly wound part locks up, effectively shortening the spring and reducing its compliance. So for normal driving, you'll be using mostly the upper 3 or 4 'tight' winds to soak up the average bumps and potholes. When you get into harder driving, like cornering at speed for example, because the springs are being compressed more, they resist more. The effect is to reduce the suspension travel at the top end resulting in less body roll, and better road-holding. Invariably, the fact that the springs are progressively wound is what accounts for the lowering factor. The springs aren't made shorter - they're just wound differently. Of course the material that aftermarket springs are made of is usually a higher grade than factory spec simply because it's going to be expected to handle more loads. Note:Make sure you get powder-coated springs! This means they've been treated with a good anti-corrosion system and then covered in powdered paint. The whole lot is then baked to make the paint seal and stick and bring out it's polyurethane elastic properties. It's the best type. If you just get normally painted springs, the paint will start to flake on the first bump, and surface rust will appear within days of the first sign of dampness. Not good. Besides - powder coated springs look cool too!

http://www.carbibles.com/suspension_bible.html (32 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Electronic damping force controllers.
Remember way back at the top of the page I mentioned that some dampers allowed you to change the damping rate by altering the size of the constriction hole? That's all very well and good but you have to stop your car, get out and twiddle a knob or screw on the top or side of the strut each time you want to make a change. In 2005 the aftermarket saw the first appearance of an EDFC - electronic damping force controller. The premise is really simple. Four servo motors (the four smaller boxes in the picture here), one for each strut, each one designed to replace the manual screw adjuster. A control unit mounts inside the car and allows you to change the damping force of the shocks front and rear without leaving the drivers seat. The way it works is dead simple. When you first install the system and power it up, all the servos spin clockwise for a few seconds. This ensures the adjusters are screwed all the way in on all four struts. From that point, you can dial in any number from 0 to 20 on the control unit. When you do, the servo motors spin a certain amount - the same as you getting out of the car and spinning the adjuster with your finely calibrated fingers. The units currently have three memory settings so you can store motorway, city and track-day settings (for example), and recall them at the push of a button. Installing the current-generation EDFCs is pretty simple - about the most difficult thing you'll face is running the wires from each servo back to the control unit inside the car. There's a few different companies selling EDFCs right now. This link will take you to a googlesearch for further info.
Picture credit: TEIN

Torsion bars
Torsion bars deserve their own section because they are a type of spring which can be used in place of coil- or leaf-springs. It's one of the topics I get the most e-mail on, so instead of
http://www.carbibles.com/suspension_bible.html (33 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

continually sending the same answer, I thought I'd cover it on this page. A torsion bar is a solid bar of steel which is connected to the car chassis at one end, and free to move at the other end. They are almost always mounted across the car, one for each side of the suspension. The springing motion is provided by the metal bar's resistance to twisting. To over-simplify, stick your arm out straight and get someone to twist your wrist. Presuming that your mate doesn't snap your wrist, at a certain point, resistance in your arm (and pain) will cause you to twist your wrist back the other way. That is the principle of a torsion bar. Torsion bars are normally locked to the chassis and the suspension parts with splined ends. This allows them to be removed, twisted round a few splines and re-inserted, which can be used to raise or lower a car, or to compensate for the natural 'sag' of a suspension system over time. They can be connected to just about any type of suspension system listed on this page but are commonly found on trailing arm suspension.

Lift Kits
Because of the mechanical nature of suspension, all sorts of mods are available. Lifting suspension is a popular mod used to try to increase ground clearance. This is often a source of misunderstanding. A lift kit doesn't really give you more ground clearance. What it does is increase the height between the axle and the underside of the body. Whilst this does give more ground clearance for the bodywork, the lowest point on the vehicle is still the axles - or on a 4-wheel-drive, the bottom of the transfer case. For this reason, you'll often see trucks and SUVs with lift kits and larger wheels and tyres. The lift kit boosts the clearance under the bodywork whilst the larger wheels and tyres result in the axles being lifted higher off the ground. Technically of course, in a 4-wheel-drive, you don't really need a lift kit - bigger wheels and tyres would do it. BUT lift kits typically end up being required because adding on the larger wheels and tyres can often mean they will no longer fit in the wheel arches. The lift kit will help solve that problem. Lift kits come in literally hundreds of shapes and sizes, all dependent on the final application as well as the design of the vehicle the kit is going to be used on. For street cars, typically with independent suspension, the kit will basically be
http://www.carbibles.com/suspension_bible.html (34 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

longer struts, longer springs and remounted shocks. For off-roaders with beam axles and transfer cases, the suspension system is typically leaf-spring, so the kit will be a set of blocks that fit between the beam axle and the bottom of the leaf spring. Alternatively, some kits have blocks which lower the spring mounts themselves so that the spring-toaxle joint isn't changed. The image below shows an example of a typical leaf-spring beam-axle suspension system along with two examples of how it can be raised.

Fitting a lift kit is pretty basic engineering but it's really difficult to do without access to a hydraulic lift, so its best to either get a garage to do it, or to find a mechanic friend who has a decent sized hydraulic lift. Trying to mess with the suspension whilst a vehicle is on the ground is just asking for trouble.

Speaking of trouble...
Lifting a vehicle is going to affect its handling. Most obviously, you're going to add height to the centre of gravity, which in turn is going to make the vehicle more prone to roll in corners. At the extreme, an already roll-happy SUV or truck will become even more likely to turn over in the event of an accident. Similarly, just because you've lifted your truck, don't think you can instantly go off-road with it like a pro. If you're doing it for off-road functionality rather than just pose value, spend the extra cash and get a one-day off-road course. You'll have a blast and it will make you infinitely safer when you do take your vehicle off the beaten track. It's also worth pointing out that putting larger wheels on simply to increase ground clearance can come with all its own problems including the legality of it, changes to the steering and suspension geometry and steering load. It's also
http://www.carbibles.com/suspension_bible.html (35 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

a possibility on some types of 4WD vehicle that larger tyres and steering load can result in tearing the steering box off the chassis. Other things which tend to fail quicker when this is done are items like pitman arms, track rods, knuckle and ball joints - all of these get stressed beyond their normal design limits when you stuff massive tyres and wheels on a truck. One other point to consider when doing this: if your speedometer is based on a mechanical link to the gearbox, your speedo will become so innacurate that it will basically be useless. You'll be driving at an indicated 30mph but could be doing 40mph if the tyres are big enough. Just be warned.

Lowering Kits
The opposite of lift kits - lowering kits. These are designed to (wait for it....) lower your car. Also at the other of the scale - lowering kits are almost exclusively used on cars, whereas lift kits are almost exclusively used on trucks and SUVs. (Having said that, the number of pimped-out low-rider trucks on the road does seem to be increasing by the day.) Lowering your car will similarly affect the handling, just like a lift kit. But again it's the opposite end of the spectrum a lowered car will typically handle much better than factory suspension, and it will lower the centre of gravity, making it less likely to tip or roll in an accident. I'm a European, and as far as I'm concerned, if you're going for pose value, lowering your car is the quickest way to do it, hotly pursued by larger wheels and tyres to make the car appear even more ground-hugging. Lowering kits typically consist of shorter, stiffer springs and gas shocks - often nitrogen-filled. Don't do it by halves. Get a matched kit from someone like Spax or Jamex. Matched kits have springs and shocks designed to work together. If you get shorter springs, your factory shocks will be under a lot of stress because they'll be operating a much shorter throw than they were designed for, and ultimately, they'll normally fail much quicker. Similarly, don't get shorter shocks and the cut the springs. Cutting the springs is the epitome of A Really Bad Idea. You're weaking the spring's structural integrity and the chances are that when you've finished a ham-fisted attempt at hacking off all 4 springs with a grinder, the result will be 4 springs all slightly different lengths. There's something else worth mentioning here - do not try to disassemble a shock absorber. Ever. Those things are like little bombs, and unless you have all the right tools, you could easily loose a hand as the shock explodes into its component parts when you get that last twist off the collar. Please - just don't. I know your mate Guido might have told you it's a "sure fire" way to shorten the shock, but he's lying. Matched lowering kits typically assume you're going for sportier handling, so a lot of times, you'll get a whole slew of new adjustments which you never had before. Spring height, rebound damping, compression damping etc. My recommendation is to leave everything as it is to start with. Right out of the box they're normally set up pretty well. The following renderings show an example "before and after" of a lowering kit fitted to a car:

http://www.carbibles.com/suspension_bible.html (36 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Lowering kit questions.
What if I get shorter springs to lower the car? Will I need to adjust my caster and camber angles and/or my shock absorbers? Generally the answer would be no for caster/camber angles. Most cars have a good 10-13cm (4-5 inches) movement in their suspension from the factory. As most of the lowering springs you can buy only lower by 2-7cm (1-3 inches), your suspension should still be well within it's designed operating limits. Therefore, caster and camber angles shouldn't need looking at. As for the shocks, see the FAQ page. What if I get shorter springs to lower the car? Will my tyres rub on my arches? They shouldn't unless you start messing about with wheel and tyre sizes. Again, given that most suspension kits lower within the car's normal operating limits, there shouldn't be a problem. If there was, then every time you went over a big hump with standard suspension, the tyres would rub. Rubbing against the arches will almost certainly only occur if you lower the car and widen the wheels. See the Wheel & Tyre Bible for more info on this.

http://www.carbibles.com/suspension_bible.html (37 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Car Suspension Bible

Where can I buy a good kit to lower or lift my truck?
There are a lot of local and internet stores that offer you ready to go suspension kits. For instance, www. streetbeatcustoms.com has a Truck Suspension section and a lot of Lowering and Lifting Truck Kits.

Where can I buy a good kit to lower or lift my car?
Again, a lot of local and internet stores that offer you ready to go suspension kits. Spax and Jamex are two big names for car suspension kits.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/suspension_bible.html (38 of 38) [2/6/2008 7:11:18 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

The wheel and tyre Bible, covering everything you need to know about wheels, tyres or tires, rim sizes, tyre tread, tread depth and tread wear, tyre markings, aquaplaning, wheel balancing, aftermarket wheels, alloys, TPMS tyre pressure monitoring systems and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Page 1 ------ Page 2

Are you confused by your car's tyres? (or tires if you're American). Don't know your rolling radius from your radial? Then take a good long look through this page where I hope to be able to shift some of the mystery from it all for you. At the very least, you'll be able to sound like you know what you're talking about the next time you go to get some new tyres.

Decoding all that information on the sidewall
It's confusing isn't it? All numbers, letters, symbols, mysterious codes. Actually, most of that information is surplus to what you need to know. So here's the important stuff:
http://www.carbibles.com/tyre_bible.html (1 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Key
A

Description
Manufacturers or brand name, and commercial name or identity. Tyre size, construction and speed rating designations. Tubeless designates a tyre which requires no inner tube. See tyre sizes and speed ratings below. DIN-type marking also has the load index encoded in it. These go from a load index of 50 (190kg) up to an index of 169 (5800kg). Denotes type of tyre construction. M&S denotes a tyre designed for mud and snow. Reinforced marking only where applicable. Pressure marking requirement. ECE (not EEC) type approval mark and number. North American Dept of Transport compliance symbols and identification numbers. Country of manufacture.

B

C D E F G H

Also on the sidewall, you might find the following info embossed in the rubber. The temperature rating - an indicator of how well the tire withstands heat buildup. "A" is the highest rating; "C" is the lowest. The traction rating - an indicator of how well the tire is capable of stopping on wet pavement. "A" is the highest rating; "C" is the lowest. The tread-wear rating - a comparative rating for the useful life of the tire's tread. A tire with a tread-wear rating of 200, for example, could be expected to last twice as long as one with a rating of 100. Tread-wear grades typically range between 60 and 600 in 20-point increments. It is important to consider that this is a relative indicator, and the actual life of a tire's tread will be affected by quality of road surfaces, type of driving, correct tire inflation, proper wheel alignment and other variable factors. In other words, don't think that a tread-wear rating of 100 means a 30,000 mile tyre. Encoded in the US DOT information (G on the diagram above) is a two-letter code that identifies where the tyre was manufactured in detail. In other words, what factory and in some cases, what city it was manufactured in. It's the first two letters after the 'DOT' - in this case "FA" denoting Yokohama. This two-letter identifier is worth knowing in case you see a tyre recall on the evening news where they tell you a certain factory is recalling tyres. Armed with the two-letter identifier list, you can figure out if you are affected. It's a nauseatingly long list, and I've not put it on this page. But if you click here it will popup a separate window with just those codes in it.

DOT Codes and the 6-year shelf life
As part of the DOT code (G above), there is a tyre manufacture date stamped on the sidewall. Take a look at yours - there will be a three- or four-digit code. This code denotes when the tyre was manufactured, and as a ruleof-thumb, you should never use tyres more than 6 years old. The rubber in tyres degrades over time, irrespective of whether the tyre is being used or not. When you get a tyre change, if you can, see if the tyre place will allow you to inspect the new tyres first. It's not uncommon for these shops to have stuff in stock which is more than 6 years old. The tyre might look brand new, but it will delaminate or have some other failure within weeks of being put on a vehicle.
http://www.carbibles.com/tyre_bible.html (2 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Reading the code. The code is pretty simple. The three-digit code was used for tyres manufactured before 2000. So for example 1 7 6 means it was manufactured in the 17th week of 6th year of the decade. In this case it means 1986. For tyres manufactured in the 90's, the same code holds true but there is a little triangle after the DOT code. So for this example, a tyre manufactured in the 17th week of 1996 would have the code 176 After 2000, the code was switched to a 4-digit code. Same rules apply, so for example 3 0 0 3 means the tyre was manufactured in the 30th week of 2003.

Check your spare
I had a reader email me about the age code and he pointed out that it's wise to check your spare tyre too. In his case, he had an older vehicle but his running tyres were all nice and fresh. It was his spare that was the problem - it had a date code on it of 081 meaning it was manufactured in the 8th week of 1991. At the time of writing, that was a 16 year old tyre. So you've been warned - if you're driving an older car, check the date code of your spare. If you get a flat and your spare is gently corroding in the boot (or trunk), it won't do you much good at all.

DOT Age Code Calculator
The calculation built in to this page is up-to-date based on today's date. If the DOT age code on your tyres is older than this code, change your tyres.

DOT AGE CODE: 0602
Interesting note : in June 2005, Ford and GM admitted that tyres older than 6 years posed a hazard and from their 2006 model year onwards, started printing warnings to this effect in their drivers handbooks for all their vehicles.

The E-Mark
Item F in the diagram above is the E-mark. All tyres sold in Europe after July 1997 must carry an E-mark. The mark itself is either an upper or lower case "E" followed by a number in a circle or rectangle, followed by a further number. An "E" (upper case) indicates that the tyre is certified to comply with the dimensional, performance and marking requirements of ECE regulation 30. An "e" (lower case) indicates that the tyre is certified to comply with the dimensional, performance and marking requirements of Directive 92/33/EEC. The number in the circle or rectangle denotes the country code of the government that granted the type approval. 11 is the UK. The last number outside the circle or rectangle is the number of the type approval certificate issued for that particular tyre size and type.

A Word on "guaranteed" tyres
When I moved to America, I noticed a lot of tyre shops offering tyres with x,000 mile guarantees. It's not unusual to see 60,000 mile guarantees on tyres. It amazed me that anyone would be foolish enough to put a guarantee on a consumable product given that the life of the tyre is entirely dependent on the suspension geometry of the car it is being used on, the style of driving, the types of road, and the weather. Yet many manufacturers and dealers offer an unconditional* guarantee. There's the catch though. The '*' after the word "unconditional" takes you elsewhere on their information flyer, to the conditions attached to the unconditional guarantee. If you want to claim on that guarantee, typically you'll have to prove the tyres were inflated to the correct pressure all the time, prove they were rotated every 3000 miles, prove the suspension geometry of your car has always been 100%, prove you never drove over 80mph, prove you never left them parked in the baking hot sun or freezing cold ice, and prove you never drove on the freeways. Wording in the guarantee will be similar to: "used in normal service on the vehicle on which they were originally fitted and in accordance with the maintenance recommendations and safety warnings contained in the attached owner's manual"

http://www.carbibles.com/tyre_bible.html (3 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

and "The tyres have been rotated and inspected by a participating (tyre brand) tyre retailer every 7,500 miles, and the attached Mounting and Rotation Service Record has been fully completed and signed" There will typically also be a long list of what isn't covered. For example: Road hazard injury (e.g., a cut, snag, bruise, impact damage, or puncture), incorrect mounting of the tire, tire/ wheel imbalance, or improper repair, misapplication, improper maintenance, racing, underinflation, overinflation or other abuse, uneven or rapid wear which is caused by mechanical irregularity in the vehicle such as wheel misalignment, accident, fire, chemical corrosion, tire alteration, or vandalism, ozone or exposure to weather. Given that you really can't prove any of this, the guarantee is, therefore, worthless because it is left wide open to interpretation by the dealer and/or manufacturer. For a good example, check out the Michelin warranty or guarantee, available on their website (PDF file). Don't be taken in by this - it's a sales ploy and nothing more. Nobody - not even the manufacturers - can guarantee that their tyre won't de-laminate or catch a puncture the moment you leave the tyre shop. Buy your tyres based on reviews, recommendations, previous experience and the recommendation of friends. Do not buy one simply because of the guarantee.

Big-chain dealers vs. manufacturer warranties.
A reader pointed out to me that the dealer he worked for honoured tyre warranties in a no-fuss manner requiring simply the original receipt for when they were purchased and one small form to be filled out. They then typically used a prorated refund applied to the new tyre. For example if someone paid $100 for a tyre guaranteed for 60,000 miles and it was dead after 40,000, pro-rata the customer had 34% of the warranty mileage left in the tyre. They would either refund $34 (34% of $100) or apply it against the cost of a replacement. I suspect this no-fuss attitude is down to buying power. Large chain stores like CostCo or Sears will have far more clout with the manufacturers than you or I with our 4 tyres. After all they buy bulk in he hundreds if not thousands. For the consumer, it makes them look good because you get a fair trade. They can argue the toss with the manufacturers later, leveraging their position as a bulk buyer in the market to get the guarantees honoured.

Tyre size notations.
Okay, so you look at your car and discover that it is shod with a nice, but worn set of 185-65HR13's. Any tyre mechanic will tell you that he can replace them, and he will. You'll cough up and drive away safe in the knowledge that he's just put some more rubber on each corner of the car that has the same shamanic symbols on it as those he took off. So what does it all mean?

http://www.carbibles.com/tyre_bible.html (4 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2 This is the width in mm of the tyre from sidewall to sidewall when it's unstressed and you're looking at it head on (or topdown). This is known as the section width. This is the ratio of the height of the tyre sidewall, (section height), expressed as a This is the speed percentage of the width. It is known as the aspect ratio. In this rating of the tyre. case, 65% of 185mm is 120.25mm - the section height.

This tells you that the tyre is a radial construction. Check out tyre construction if you want to know what that means.

This is the diameter in inches of the rim of the wheel that the tyre has been designed to fit on. Don't ask me why tyre sizes mix imperial and metric measurements. They just do. Okay?

More recently, there has been a move (especially in Europe) to adjust tyre designations to conform to DIN. This is the German Institute for standardisation - Deutsches Institut fuer Normung, often truncated to Deutsche Industrie Normal. DIN sizing means a slight change in the way the information is presented to the following:

Section width

Aspect ratio

Radial

Rim diameter

Load rating

Speed rating.

Ultra high speed tyre size notations.
There is a subtle difference in the notation used on ultra high speed tyres, in particular motorcycle tyres. For the most part, the notation is the same as the DIN style described above. The difference is in the way the speed rating is displayed. For these tyres, if the speed rating is above 149mph, then a 'Z' must appear in the dimension part of the notation, as well as the actual speed rating shown elsewhere. The 'Z' is a quick way to see that the tyre is rated for over 149mph.

Section width

Aspect ratio

149+ mph rated

Radial

Rim diameter

Load rating

Speed rating.

Classic / vintage / imperial crossply tyre sizes.
What ho. Fabulous morning for a ride in the Bentley. Problem is your 1955 Bentley is running on 7.6x15 tyres. What, you ask, is 7.6x15? Well it's for older vehicles with imperial measurements and crossply tyres. Both measurements are in inches - in this case a 7.6inch tyre designed to fit a 15inch wheel. There is one piece of information missing though - aspect ratio. Aspect ratios only began to be reduced at the end of the 1960s to improve cornering. Previously no aspect ratio was given on radial or crossply tyres. For crossply tyres, the initial number is both the tread width and the sidewall height. So in my example, 7.6x15 denotes a tyre 7.6 inches across with a sidewall height which is also 7.6 inches. After conversion to the newer notation, this is the equivalent to a 195/100 15. If you're plugging numbers into the tyre size calculator lower down this page, I've included an aspect ratio value of 100 for imperial calculations. Note: I put 195/100 15 instead of 195/100R15 because technically the "R" means radial. If you're trying to get
http://www.carbibles.com/tyre_bible.html (5 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

replacement crossply tyres, the "R" won't be in the specification. However if you're trying to replace your old crossply tyres with metric radial bias tyres, then the size does have the "R" in it. Here is a javascript calculator to turn your imperial tyre size into a radial metric tyre size: Your imperial tyre size: 7.6 x 15 /100 R
Click to calculate equivalent standard size

Equivalent standard tyre size is :

Classic / vintage radial tyre sizes.
Remember above that I said aspect ratios only started to come into play in the 1960s? Unlike the 100% aspect ratio for crossply tyres, for radial tyres, it's slightly different - here an aspect ratio of 80% is be assumed. So for example, if you come across on older tyre with 185R16 stamped on it, this describes a tyre with a tread width of 185mm and a sidewall height which is assumed to be 80% of that; 148mm. The question of the aspect ratio for radial sizes has been the subject of a lot of email to me. I've had varying figures from 80% up to 85% and everyone claims they're right. Well one reader took it to heart and did some in-depth research. It seem there is actually no fixed standard for aspect ratio when it is not expressly stated in the tyre size. Different manufacturers use slightly different figures. The english MOT (road-worthiness test) manual states: Unless marked otherwise, "standard" car tyres have a nominal aspect ratio of 82%. Some tyres have an aspect ratio of 80%. These have "/80" included in their size marking e.g. 165/80 R13. Note: Tyres with aspect ratios of 80% and 82% are almost identical in size and can be safely mixed in any configuration on a vehicle. See http://www.motuk.co.uk/manual_410.htm for the online version. If you're plugging vintage radial numbers into the tyre size calculator, I've included aspect ratios of 80 and 82 for these calculations.

Vintage radial letter load-ratings vs. tyre size.
On some vintage vehicles, notably the Jensen Interceptor, the tyre sizes were denoted as ER70VR15. The '70' refers to the section height as you might expect, and the '15' is the wheel dimension, but on first inspection there appears to be no section width. Actually there is, but it's in yet another odd format. In this case, the first letter is the thing to look at. The letter itself has no direct equivalent to modern dimensional sizes but instead relates to load ratings; the higher the letter the more load it can carry. With vintage tyres, higher loads translated into bigger tyres, so the close approximations between old load and new size these days are: C = 185 D = 195 E = 205 F = 215 G = 225 H = 235 etc. In this example then, ER70VR15 means 205/70 R15 with a 'V' speed rating. Frankly that's a little optimistic for something like a Jensen Interceptor, so if you're looking to replace tyres for this type of vehicle, an 'H' speed rated tyre is the better choice, and it's cheaper.

Picture credit: Jensen Intercepter Club

Metric Tyre sizes and the BMW blurb.
Fab! You've bought a BMW 525TD. Tyres look a bit shoddy so you go to replace them. What the....? TD230/55ZR390? What the hell does that mean? Well my friend, you've bought a car with metric tyres. Not that there's any real difference, but certain manufacturers experiment with different things. For a while, (mid 1990s) the 525TD came with arguably experimental 390x180 alloy wheels. These buggers required huge and non-conformal tyres. I'll break down that classification into chunks you can understand with your new-found knowledge: TD - ignore that. 230 = cross section 230mm. 55 = 55% sidewall height. Z=very high speed rating. R390=390mm diameter wheels. These are the equivalent of about a
http://www.carbibles.com/tyre_bible.html (6 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

15.5" wheel. There's a nice standard size for you. And you, my friend, have bought in to the long-raging debate about those tyres. They are an odd size, 180x390. Very few manufacturers make them now and if you've been shopping around for them, you'll have had the odd heart-stopper at the high price. The advice from the BMWcar magazine forum is to change the wheels to standard sized 16" so there's more choice of tyres. 215-55R16 for example. The technical reason for the 390s apparently is that they should run flat in the event of a puncture but that started a whole debate on their forum and serious doubts were expressed. You've been warned... If you're European, you'll know that there's one country bound to throw a spanner in the works of just about anything. To assist BMW in the confusion of buyers everywhere, the French, or more specifically Michelin have decided to go one step further out of line with their Pax tyre system. See the section later on to do with run-flat tyres to find out how they've decided to mark their wheels and tyres.

Land Rovers and other off-road tyre sizes.
On older Land Rovers (on the LWB/110 vehicles and many "off-roaders"), you'll often find tyres with a size like 750x16. This is another weird notation which defies logic. In this case, the 750 refers to a decimalised notation of an inch measurement. 750 = 7.50 inches, referring to the "normal inflated width" of the tyre - i.e. the external maximum width of the inflated, unladen tyre. (This is helpfully also not necessarily the width of the tread itself). The 16 still means 16 inch rims. Weird eh? The next question if you came to this page looking for info on Land Rover tyres will be "What size tyre is that the equivalent of in modern notation?". Simple. It has no aspect ratio and the original tyres would likely be cross-ply, so from what you've learned a couple of paragraphs above, assume 100% aspect ratio. Convert 7.5inches to be 190mm. That gives you a 190/100 R16 tyre. (You could use the calculator in the section on Classic / vintage / imperial crossply tyre sizes above to get the same result.) Generally speaking, the Land Rover folks reckon a 265/65R16 is a good replacement for the "750", although the tread is slightly wider and might give some fouling problems on full lock. It's also 5% smaller in rolling radius so your speed will over-read by about 4mph at 70mph. If you can't fit those, then the other size that is recommended by Landrover anoraks is 235/86R16. On Discoveries, Range Rovers, or the SWB Defenders/Series land rovers you'll find "205" tyres, denoting 205mm x 16 inches. The 205 type tyres can generally be replaced with 235/70R16 or 225/75R16. The 235 is a wider tyre and the general consensus in Land Rover circles is that it holds the road better when being pushed. If you're really into this stuff, you ought to read Tom Sheppard's Off Roader Driving (ISBN 0953232425). It's a Land Rover publication first published in 1993 as "The Land Rover Experience". It's been steadily revised and you can now get the current edition from Amazon. I've even helpfully provided you with this link so you can go straight to it....

LT (Light Truck) imperial tyre sizes.
Confused yet? Okay how about this: 30x9.5 R15 LT or LT30x9.5/15. Yet another mix-and-match notation, this time for (amongst other things) light truck classification tyres. All the information you need to figure out a standard size is in there, but in the usual weird order. In this case the 30 refers to a 30 inch overall diamter. The 9.5 refers to a 9.5 inch wide tread. The R15 refers to a 15 inch diameter wheel. In order to figure out the closest standard notation, you know the tread width which (in this example) is 9.5 inches or 240mm. The sidewall height is the overall height minus the wheel diameter all divided by 2. So 30 inches minus 15 inches, which gives you 15 inches. Half that to get 7.5 inches and that's the sidewall height - 190mm. Remember the section value is a percentage of the tread width - in this case 190mm/240mm gives us a section of 80% (near enough). So the standard size for 30x9.5R15 works out to be 240/80R15. In truth you can barely find a tyre that size so most off-roaders with that sort of tyre size go for 245/70R15 which is more common. For your convenience, another calculator then. Your LT tyre size: 30 x 9.5 R 15 / R
Click to calculate equivalent standard size

Equivalent standard tyre size is :

Porsche N-rated tyres.
http://www.carbibles.com/tyre_bible.html (7 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

of the butt-ugly Cayenne). All this design and performance is worth nothing if you put cheap Korean tyres on your Porsche though, and because of that prospect, Porsche introduced the N rating or N specification system. In order for a manufacturer to be an OE (original equipment) supplier of tyres for Porsches, they must work with the Porsche engineers at the development and testing stage. They concentrate on supreme dry-weather handling but they also spend a considerable amount of time working on wet-weather handling. Porsches are typically very tail-heavy because of the position of the engine relative to the rear wheels, and with traction control off, it's extremely easy to spin one in the wet. Because of this, Porsche specify a set of wet-grip properties which is way above and beyond the requirements of any other car manufacturer. OE tyres for Porsches must successfully pass lab tests to prove that they would be capable of adequately supporting a Porsche at top speed on a German Autobahn. Once the lab tests are done, they must go on to track and race tests where prototypes are evaluated by Porsche engineers for their high-speed durability, uniformity and serviceability. If they pass all the tests, Porsche give the manufacturer the go-ahead to put the tyres into production and then they can proudly claim they are an N-rated Porsche OEM (Original Equipment Modifier). The N-ratings go from 0 (zero) to 4, marked as N-0, N-1 etc. This N-rating, stamped into a tyre sidewall, clearly identifies these tyres as having gone through all the nauseating R&D and testing required by Porsche as described above. The number designates the revision of the design. So for a totally new design, the first approved version of it will be N-0. When the design is improved in some way, it will be re-rated as an N-1. If the design changes completely so as to become a totally new tyre, it will be re-rated at N-0. If you've got a Porsche, then you ought to be aware that as well as using N-rated tyres, you ought to use matching tyres all around because many Porsches have different sizes tyres front and rear. So for example if you have a Porsche with N3 rated tyres and the rear ones need replacing but the model has been discontinued, you should not get N-0's and put them on the back leaving the old N-3's on the front. You should replace all of them with the newer-designed re-rated N-0 tyres. But then you own a Porsche so you can certainly afford four new tyres.... One final point. You may go into a tyre warehouse and find two tyres with all identical markings, sizes and speed ratings, but one set has an N-rating. Despite everything else being the same, the non-N-rated tyres have not been certified for use on a Porsche. You can buy them, and you can put them on your car, but if you stuff it into the armco at 150mph, Porsche will just look at you and with a very teutonic expression ask why you didn't use N-rated tyres.

Porsche designs and manufacturers some of the highest performance cars in the world (with the exception

http://www.carbibles.com/tyre_bible.html (8 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Lies, Damn Lies and Speed ratings.
All tyres are rated with a speed letter. This indicates the maximum speed that the tyre can sustain for a ten minute endurance without coming to pieces and destroying itself, your car, the car next to you and anyone else within a suitable radius at the time.

Speed Symbol
L M N P Q R

Max Speed Capability Km/h
120 130 140 150 160 170

MPH
75 81 87 95 100 105

Speed Symbol
S T U

Max Speed Capability Km/h
180 190 200

MPH
113 118 125

H
V W Y Z

210
240 270 300 240+

130
150 168 186 150+

'H' rated tyres are becoming the most commonplace and widely used tyres, replacing 'S' and 'T' ratings. Percentage-wise, the current split is something like this: S/T=67%, H=23%, V=8%. Certain performance cars come with 'V' or 'Z' rated tyres as standard. This is good because it matches the performance capability of the car, but bad because you need to remortgage your house to buy a new set of tyres.

UTQG Ratings
http://www.carbibles.com/tyre_bible.html (9 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

The UTQG - Uniform Tyre Quality Grade - test is required of all dry-weather tyres ("snow" tyres are exempt) before they may be sold in the United States. This is a rather simple-minded test that produces three index numbers : Tread life, Traction and Temperature.
●

●

●

The tread life index measures the relative tread life of the tyre compared to a "government reference". An index of 100 is equivalent to an estimated tread life of 30,000 miles of highway driving. The traction test is a measure of wet braking performance of a new tyre. There is no minimum stopping distance, therefore a grade "C" tyre can be very poor in the wet. The temperature test is run at high speeds and high ambient temperatures until the tyre fails. To achieve a minimum grade of "C" the tyre must safely run at 85mph for 30 minutes, higher grades are indicative of surviving higher speeds (a rating of "B" is, for some reason, roughly equivalent to a European "S" rating, a rating of "A" is equivalent to an "H" rating.)

There are some exceptions: Yokohama A008's are temperature rated "C" yet are sold as "H" speed rated tyres. These UTQC tests should be used only as a rough guide for stopping. If you drive in the snow, seriously consider a pair of (if not four "Snow Tyres" Like life, this tyre test is entirely subjective.

Load indices.
The load index on a tyre is a numerical code associated with the maximum load the tyre can carry. These are generally valid for speed under 210km/h (130mph). Once you get above these speeds, the load-carrying capacity of tyres decreases and you're in highly technical territory the likes of which I'm not going into on this page. The table below gives you most of the Load Index (LI) values you're likely to come across. For the sake of simplicity, if you know your car weighs 2 tons - 2000kg - then assume an even weight on each wheel. 4 wheels at 2000kg = 500kg per wheel. This is a load rating of 84. The engineer in you should add 10% or more for safety's sake. For this example, I'd probably add 20% for a weight capacity of 600kg - a load rating of 90. Generally speaking, the average car tyre is going to have a much higher load rating than you'd ever need. It's better to have something that will fail at speeds and stress levels you physically can't achieve, than have something that will fail if you nudge over 60mph with a six pack in the trunk.
LI kg LI kg LI kg LI kg LI kg LI kg

50 190 51 195 52 200 53 206 54 212 55 218 56 224 57 230 58 236 59 243 60 250 61 257 62 265 63 272 64 280 65 290 66 300 67 307 68 315 69 325

70 335 71 345 72 355 73 365 74 375 75 387 76 400 77 412 78 425 79 437 80 450 81 462 82 475 83 487 84 500 85 515 86 530 87 545 88 560 89 580

90 600 91 615 92 630 93 650 94 670 95 690 96 710 97 730 98 750 99 775 100 800 101 825 102 850 103 875 104 900 105 925 106 950 107 975 108 1000 109 1030

110 1060 111 1090 112 1120 113 1150 114 1180 115 1215 116 1250 117 1285 118 1320 119 1360 120 1400 121 1450 122 1500 123 1550 124 1600 125 1650 126 1700 127 1750 128 1800 129 1850

130 1900 131 1950 132 2000 133 2060 134 2120 135 2180 136 2240 137 2300 138 2360 139 2430 140 2500 141 2575 142 2650 143 2725 144 2800 145 2900 146 3000 147 3075 148 3150 149 3250

150 3350 151 3450 152 3550 153 3650 154 3750 155 3875 156 4000 157 4125 158 4250 159 4375 160 4500 161 4625 162 4750 163 4875 164 5000 165 5150 166 5300 167 5450 168 5600 169 5800

http://www.carbibles.com/tyre_bible.html (10 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Tyre types for passenger cars.
There are several different types of tyre that you, the humble consumer, can buy for your car. What you choose depends on how you use your car, where you live, how you like the ride of your car and a variety of other factors. The different classifications are as follows, and some representative examples are shown in the image on the right. Performance tyres or summer tyres Performance tyres are designed for faster cars or for people who prefer to drive harder than the average consumer. They typically put performance and grip ahead of longevity by using a softer rubber compound. Tread block design is normally biased towards outright grip rather than the ability to pump water out of the way on a wet road. The extreme example of performance tyres are "slicks" used in motor racing, so-called because they have no tread at all. All-round or all-season tyres These tyres are what you'll typically find on every production car that comes out of a factory. They're designed to be a compromise between grip, performance, longevity, noise and wet-weather safety. For increased tyre life, they are made with a harder rubber compound, which sacrifices outright grip and cornering performance. For 90% of the world's drivers, this isn't an issue. The tread block design is normally a compromise between quiet running and water dispersion - the tyre should not be too noisy in normal use but should work fairly well in downpours and on wet roads. All-season tyres are neither excellent dry-weather, nor excellent wet-weather tyres, but are, at best, a compromise. Wet-weather tyres Rather than use an even harder rubber compound than all-season tyres, wet weather tyres actually use a softer compound than performance tyres. The rubber needs to heat up quicker in cold or wet conditions and needs to have as much mechanical grip as possible. They'll normally also have a lot more siping to try to disperse water from the contact patch. Aquachannel tyres are a subset of winter or wet-weather tyres and I have a little section on them further down the page. Snow & mud or ice : special winter tyres Winter tyres come at the other end of the spectrum to performance tyres, obviously. They're designed to work well in wintery conditions with snow and ice on the roads. Winter tyres typically have larger, and thus noiser tread block patterns. In extreme climates, true snow tyres have tiny metal studs fabricated into the tread for biting into the snow and ice. The downside of this is that they are incredibly noisy on dry roads and wear out both the tyre and the road surface extremely quickly if driven in the dry. Mud & snow tyres typically either have 'M&S' stamped on the tyre sidewall. Snow & Ice tyres have a snowflake symbol. All-terrain tyres All-terrain tyres are typically used on SUVs and light trucks. They are larger tyres with stiffer sidewalls and bigger tread block patterns. The larger tread block means the tyres are very noisy on normal roads but grip loose sand and dirt very well when you take the car or truck off-road. As well as the noise, the larger tread block pattern means less tyre surface in contact with the road. The rubber compound used in these tyres is normally middle-of-the-road - neither soft nor hard. Mud tyres At the extreme end of the all-terrain tyre classification are mud tyres. These have massive, super-chunky tread blocks and really shouldn't ever be driven anywhere other than loose mud and dirt. The tread sometimes doesn't even come in blocks any more but looks more like paddles built in to the tyre carcass.

Tyre constructions.
Simply put, if you bought a car in the last 20 years or so, you should be riding on radial tyres. If you're not, then it's a small miracle you're still alive to be reading this. Radial tyres wear much better and have a far greater rigidity for when cars are cornering and the tyres are deforming.

http://www.carbibles.com/tyre_bible.html (11 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Cross-ply components

Radial components

The tread consists of specially compounded/vulcanised rubber which can have unique characteristics ranging from wear resistance, cut resistance, heat resistance, low rolling resistance, or any combination of these. The purpose of the tread is to transmit the forces between the rest of the tyre and the ground. The sidewall is a protective rubber coating on the outer sides of the tyre. It is designed to resist cutting, scuffing, weather checking, and cracking. The chafer protects the bead and body from chafing (wear from rubbing) where the tyre is in contact with the rim. The chafer of a radial tire acts as a reinforcement. It increases the overall stiffness of the bead area, which in turn restricts deflection and deformation and increases the durability of the bead area. It also assists the bead in transforming the torque forces from the rim to the radial ply.

The liner is an integral part of all tubeless pneumatic tires. It covers the inside of the tire from bead to bead and prevents the air from escaping through the tire. The bead of a cross-ply tyre consists of bundles of bronze coated high tensile strength steel wire strands which are insulated with rubber. A cross-ply tyre designed for off-road use typically has two or three bundles. A radial on-road tyre normally only has one. The bead is considered the foundation of the tire. It anchors the bead on the rim. The cord body is also known as the tyre carcass. It consists of layers of nylon plies. The cord body confines the pressure, which supports the tyre load and absorbs shocks encountered during driving. Each cord in each ply is completely surrounded by resilient rubber. These cords run diagonally to the direction of motion and transmit the forces from the tread down to the bead. The breakers are also know as belts. They provide protection for the cord body from cutting. They also increase tread stability which resists cutting. Breakers can be made of nylon, aralon, or steel wire. The body ply of a radial tire is made up of a single layer of steel cord wire. The wire runs from bead to bead laterally to the direction of motion (hence the term "radial plies"). The body ply is a primary component restricting the pressure which ultimately carries the load. The body ply also transmits the forces (torque, torsion, etc.) from the belts to the bead and eventually to the rim. The belts are layers of steel cord wires located between the tread and the body ply. Off-road tyres can have up to five belts. Road tyres typically have one or two. The steel wire of the belts run diagonally to the direction of motion. The belts increase the rigidity of the tread which increases the cut resistance of the tire. They also transmit the torque forces to the radial ply and restrict tire growth which prevents cutting, cut growth and cracking.

http://www.carbibles.com/tyre_bible.html (12 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Comparison of Radial vs. Cross-ply performance
This little table gives you some idea of the advantages and disadvantages of the two types of tyre construction. You can see the primary reasons why radial tyres are almost used on almost all the world's passenger vehicles now, including their resistance to tearing and cutting in the tread, as well as the better overall performance and fuel economy.

Cross-ply
Vehicle Steadiness Cut Resistance - Tread Cut Resistance - Sidewall Repairability Self Cleaning Traction Heat Resistance Wear Resistance Flotation Fuel Economy

Radial

A subset of tyre construction : tyre tread.
You thought tread was the shape of the rubber blocks around the outside of your tyre didn't you? Well it is, but it's also so much more. The proper choice of tread design for a specific application can mean the difference between a comfortable, quiet ride, and a piss poor excuse for a tyre that leaves you feeling exhausted whenever you get out of your car. A proper tread design improves traction, improves handling and increases Durability. It also has a direct effect on ride comfort, noise level and fuel efficiency. Believe it or not, each part of the tread of your tyre has a different name, and a different function and effect on the overall tyre. Your tyres might not have all these features, but here's a rundown of what they look like, what they're called and why the tyre manufacturers spend millions each year fiddling with all this stuff.

Sipes are the small, slit-like grooves in the tread blocks that allow the blocks to flex. This added flexibility increases traction by creating an additional biting edge. Sipes are especially helpful on ice, light snow and loose dirt.
http://www.carbibles.com/tyre_bible.html (13 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Grooves create voids for better water channeling on wet road surfaces (like the Aquachannel tyres below). Grooves are the most efficient way of channeling water from in front of the tyres to behind it. By designing grooves circumferentially, water has less distance to be channeled. Blocks are the segments that make up the majority of a tyre's tread. Their primary function is to provide traction. Ribs are the straight-lined row of blocks that create a circumferential contact "band." Dimples are the indentations in the tread, normally towards the outer edge of the tyre. They improve cooling. Shoulders provide continuous contact with the road while maneuvering. The shoulders wrap slightly over the inner and outer sidewall of a tyre. The Void Ratio is the amount of open space in the tread. A low void ratio means a tyre has more rubber is in contact with the road. A high void ratio increases the ability to drain water. Sports, dry-weather and high performance tyres have a low void ratio for grip and traction. Wet-weather and snow tyres have high void ratios.

Tread patterns
There are hundreds if not thousands of tyre tread patterns available. The actual pattern itself is a mix of functionality and aesthetics. Companies like Yokohama specialise in high performance tyres with good-looking tread patterns. Believe it or not, the look of the pattern is very important. People want to be safe with their new tyres, but there's a vanity element to them too. For example, in the following comparison, which would you prefer to have on your car?

The thought process you're going through whilst looking at those two tyres is an example of the sort of thing the tyre manufacturers are interested in. Sometimes they have focus groups and public show-and-tells for new designs to gauge public reaction. For example, given the choice, I'd prefer the tread pattern on the right. The challenge for the manufacturers is to make functionally safe tyres without making them look like a random assortment of rubber that's just been glued to a wheel in a random fashion. In amongst all this, there are three basic types of tread pattern that the manufacturers can choose to go with: Symmetrical: consistent across the tyre's face. Both halves of the treadface are the same design. Asymmetrical: the tread pattern changes across the face of the tyre. These designs normally incorporates larger tread blocks on the outer portion for increased stability during cornering. The smaller inner blocks and greater use of grooves help to disperse water and heat. Asymmetrical tyres tend to also be unidirectional tyres. Unidirectional: designed to rotate in only one direction, these tyres enhance straight-line acceleration by reducing
http://www.carbibles.com/tyre_bible.html (14 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

rolling resistance. They also provide shorter stopping distance. Unidirectional tyres must be dedicated to a specific side of the vehicle, so the information on the sidewall will always include a rotational direction arrow. Make sure the tyres rotate in this direction or you'll get into all sorts of trouble.

Tread depth and tread wear indicators
For the most part, motoring law in most countries determines that your tyres need a minimum tread depth to be legal. This varies from country to country but is normally around 1.6mm. To assist you in figuring out when you're getting close to that value, most tyres have tread wear indicators built into them. If you look around the tread carefully, at some point you'll see a bar of rubber which goes across the tread and isn't part of the regular pattern (see the picture here for an example). This is the wear indicator. It's really basic, but it's also pretty foolproof. The tread wear indicator is moulded into the rubber at a depth of about 2mm normally. As the rubber in your tyres wears away due to everyday use, the tread wears down. At some point, the tyre tread will become flush with the wear indicator (which is normally recessed into the tread). At this point you have about 2mm of tread left in other words it is time to change tyres.

Minimum legal tread depth does not mean "safe".
Actually it's wise to change your tyres before you get to the wear indicator, as by this point, the effectiveness of the tyre in the wet is pretty limited, and its grip in the dry won't be as sharp as it was when new. In 2006, Auto Express magazine in the UK did some pretty rigorous testing on "legal" tyres. They are campaigning to have the legal minimum in England increased from 1.6mm up to 3mm. Their reasons are backed up by testing : at 1.6mm, despite still being perfectly legal, the stopping distance is increased by 40% in the wet over tyres that have 3mm of tread left. They performed the test using the same car, under the same conditions with the same driver. The only thing that changed was the tyres. The Fifth Gear TV program performed a graphic demonstration of the problem by equipping two cars with different tyres. The lead car had 3mm of tread left, the trailing car had 1.6mm. The cars were driven at 50mph at a distance of 3 car lengths apart - not safe, but representative of the real-world. When the lead driver performed an emergency stop, the trailing driver reacted nearly instantly, but despite years of training and an ABS-equipped car, he slammed into the lead vehicle still doing 35mph. This was the result:

http://www.carbibles.com/tyre_bible.html (15 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

I've sliced up the video into a short clip so you can see what happened. Download the clip here. You'll need the DiVX codec installed to play it. The clip is, of course, ©2006 Channel Five in the UK. Despite knowledge like this, there are always going to be people who ignore their tyres and at the point where the tread is gone completely, they are within a couple of hundred miles of driving on the metal overbanding in the tyre carcass itself. There's really no excuse for not changing your tyres when the tread gets low. Sure, when you go to get them done, the price will seem steep - it always does with tyres. But it will seem like a wise investment next time you find yourself pirouetting across three lanes of wet motorway traffic towards the crash barrier. Which leads us nicely on to the subject of.....

Aquaplaning / hydroplaning.
By this point you probably understand that one of the functions of your car's tyres is to pump water out of the tread on wet road surfaces. As the tyre spins, the tread blocks force water into the sipes and grooves and those channel water out and away from the contact patch where the tyre meets the road. As your tread wears down, the depth of the grooves and sipes gets less, which in turn reduces the tyre's ability to remove water. At some point, the tread will get down to a point where all but the lightest of showers will turn any road into a skating rink for you. This is called aquaplaning and how it happens is really simple: as you drive in the wet, your tyres form a natural but slight bow wave on the road surface. Some of the water escapes around the side of the tyre as spray whilst the rest goes under the tyre. The tyre tread pumps the water out to the sides and the contact patch remains in good contact with the road. As the amount of water becomes more or deeper (heavier rain, or travelling faster for example), you end up with the tyre riding on a cushion of water as the volume of water in the 'bow wave' overcomes the tyre's ability to disperse it. At this point, it doesn't matter what you do - braking, accelerating and steering have no effect because the tyre is actually making no contact with the road surface any more. In fact, the worst thing you can do is to brake, because stopping the rotation of the wheels removes any last chance the tyres have at removing the water. If you let off the accelerator instead, as wind resistance and other factors begin to slow you down, at some point you'll go back through the critical depth of water and the tyres will begin to grip again.

Under good conditions, with adequate tread, light water buildup and good road drainage, the tyre tread is able to disperse the water from the road surface so that the tyre's contact patch remains in good contact with the road.

As conditions worsen - less drainage, higher speed or more rain, the amount of water on the road surface increases. The tread is only able to disperse so much water, and begins to become innundated.

At this point, the tread is overwhelmed with water and is no longer effective. Water is incompressible so the tyre is lifted off the road and skates across the surface of the water.

Aquaplaning doesn't just happen because of dodgy tyre tread depth. You can get into just as much trouble with brand
http://www.carbibles.com/tyre_bible.html (16 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

new tyres if you go careening through a deep puddle. The new tyres may have their full complement of tread depth with nice deep grooves and sipes, but the depth of the water in the puddle might be so much that the volume of water can't be removed quickly enough. Every tyre has a finite limit to the amount of water it can pump out of the way. Exceed that limit and you're aquaplaning.

Road surface design
It's worth spending a moment whilst we're on the subject of aquaplaning to talk about road surface design. I know your morning commute along pot-holed roads full of cracks might lead you to believe otherwise, but for the most part, roads, especially motorways, are designed to lessen the risk of aquaplaning in the first place. Most roads are built with a slope to one side or the other, or are crowned in the middle (ie. the road surface is higher in the middle than at the sides). The idea being that any water buildup is encouraged to run off the road surface to drainage ditches at the sides. Some newer designs of asphalt are more porous than the old stuff, and when laid on top of a subsurface drainage system, will allow a certain amount of water to run down through the road surface as well as off to the sides. Slip sliding in a summer downpour. If you've driven for any length of time and ever been caught in a downpour on a hot summer day, you'll have seen how a super-glue sticky surface can turn into a teflon ice rink at the drop of a hat. This unusual phenomenon occurs because of the way most road surfaces are manufactured and put down. There's a lot of oil and tar involved in laying asphalt and over the course of its lifetime, a road surface will naturally leech out these products. During normal dry-weather driving or a light rain storm, they get dispersed gradually by the action of trucks, cars and motorbikes driving on the road. However, in a downpour, the road surface cools off extremely quickly. As it contracts slightly, the oils and tars are squeezed out at a quicker rate than normal and because oil is less dense than water, any residue floats to the top of the layer of rain water on the road. The result is oil-on-water which has zero grip. Next time you drive through a sudden summer downpour, look at the road surface once it has stopped raining - you'll see it covered in rainbow artifacts where the sunlight is reflecting off the wet, oily layer. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Aquachannel tyres.
Towards the end of the 90's, there was a gradually increasing trend for manufacturers to design and build so-called aquachannel tyres. Brand names you might recognise are Goodyear Aquatread and Continental Aquacontact. These differ noticeably from the normal type of tyre you would expect to see on a car in that the have a central groove running around the tread pattern. This, combined with the new tread patterns themselves lead the manufacturers to startling waterremoval figures. According to Goodyear, their versions of these tyres can expel up to two gallons of water a second from under the tyre when travelling at motorway speeds. My personal experience of these tyres is that they work. Very well in fact - they grip like superglue in the wet. The downside is that they are generally made of a very soft compound rubber which leads to greatly reduced tyre life. You've got to weigh it up - if you spend most of the year driving around in the wet, then they're possibly worth the extra expense. If you drive around over 50% of the time in the dry, then you should think carefully about these tyres because it's a lot of money to spend for tyres which will need replacing every 10,000 miles in the dry.

TwinTire™
This was an idea from the USA based on the twin tyres used in Western Australia on their police vehicles. It's long been the practice for closed-wheel racing cars, such as NASCAR vehicles, to use two inner tubes inside each tyre, allowing for different pressures inside the same tyre. They also allow for proper run-flat puncture capability. TwinTires tried putting the same principle into effect for those of us with
http://www.carbibles.com/tyre_bible.html (17 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

road-going cars. Their system used specially designed wheel rims to go with their own unique type of tyres. Each wheel rim was actually molded as two half-width rims joined together. The TwinTires tyres then fitted those double rims. Effectively, you got two independent tyres per wheel, each with their own inner tube or tubeless pressure. The most obvious advantage of this system was that it was an almost failsafe puncture proof tyre. As most punctures are caused by single objects entering the tyre at a single point, with this system, only one tyre would deflate, leaving the other untouched so that your vehicle was still controllable. TwinTires claimed a reduction in braking distance too, typically from 150ft down to 120ft when braking from a fixed 70mph. The other advantage was that the system was effectively an evolution of the Aquatread type single tyres that can be bought over the counter. In the dry, you had more or less the same contact area as a normal tyre. In the wet, most of the water was channeled into the gap between the two tyres leaving (supposedly) a much more efficient wet contact patch. History is cruel to those who buck the trend, and as it turned out this system was just a passing fad. Their products disappeared around 2001 and the website vanished shortly thereafter. I've not seen any trace of them since. Daunltess Motor Corp are the last remaining suppliers and they have all the remaining stock. For an independent opinion on TwinTyre systems from someone who used them avidly, have a read of his e-mail to me which has a lot of information in it.

Run-Flat Tyres.
Yikes! Tyres for the accident-prone. As it's name implies, it's a tyre designed to run when flat. ie. when you've driven over a cunningly placed plank full of nails, you can blow out the tyre and still drive for miles without needing to repair or reinflate it. I should just put one thing straight here - this doesn't mean you can drive on forever with a deflated tyre. It means you won't careen out of control across the motorway and nail some innocent wildlife when you blowout a tyre. It's more of a safety thing - it's designed to allow you to continue driving to a point where you can safely get the tyre changed (or fixed). The way it works is to have a reinforced sidewall on the tyre. When a normal tyre deflates, the sidewalls squash outwards and are sliced off by the wheel rims, wrecking the whole show. With run-flat tyres, the reinforced sidewall maintains some height in the tyre allowing you to drive on. Most run-flat tyres come with a TPMS to alert that you've got a puncture (see TPMS later in the page) Both Goodyear (Run-flat Radials) and Michelin (Zero Pressure System) introduced run-flat tyres to their ranges in 2000. Goodyear named their technology "EMT", meaning Extended Mobility Tyre.

Not content with their Zero Pressure System, Michelin developed the PAX system too in late 2000 which is a variation on a theme. Rather than super-supportive sidewalls, the PAX system relies on a wheel-rim and tyre combination to provide a derivative run-flat capability. As well as the usual air-filled tyre, there is now a reinforced polymer support ring inside. This solid ring clips the air-filled tyre by it's bead to the wheel rim which is the first bonus - it prevents the air-filled tyre from coming off the rim. The second bonus, of course, is that if you get a puncture, the air-filled tyre deflates, and the support ring takes the strain. Michelin say this system is good for over 100 miles at 80km/h (50mph). The downside is that I believe the PAX system is just that - a system. ie. you can't use PAX tyres on standard rims and you can't use standard tyres on PAX rims. This is because PAX tyres have asymmetric beads. In English this means that the inside bead and outside bead are a different diameter. Typically a 410 PAX tyre will have bead diameters of 400mm on the outside and 420mm on the inside. Remember up the top of this page where I was talking about tyre sizes and mentioned that Michelin had come up with a new 'standard' ? Imagine you're used to seeing tyre sizes written like this : 205/60 R16. If you've read my page this far, you ought to know what that means. But for the PAX system, that same tyres size now becomes : 205-650 R410 A. Decoding this, the 205 is the same as it always was - tyre width in mm. The 650 now means 650mm in overall diameter, rather than a sidewall height of 65% of 205mm. The 410 is the metric equivalent of a 16inch wheel rim. Finally, the 'A' means "This is a PAX system wheel or tyre with an asymmetric bead".
Picture credits: Michelin press kit

http://www.carbibles.com/tyre_bible.html (18 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

The Michelin PAX tyre size converter
You can use this little script to convert Michelin PAX sizes into the closest conventional tyre size. ie. it's not going to be exact, but the resulting size is as close as you can get in standard tyre sizes. Remember though that the PAX system uses asymmetric beads so this typically means you can't fit a standard tyre to a PAX rim. Your PAX tyre size: 205 / 650 R 410
Click to calculate standard tyre size

/

R

What about the criminals? My immediate thought when I heard about run-flat tyres was "so now criminals can outfit their cars with these, and not be prone to the police stinger devices used to slow down getaway cars." I e-mailed all the major tyre companies for their response on this matter, and so far have only had one reply - from Michelin. Here's what they have to say on the matter:

"Michelin's aim is to propose products allowing people to drive in enhanced conditions of security. From this point of view, run-flat tyres and PAX System represent great progress in the history of the automotive industry. Indeed, these two developments allow drivers to go on driving even after a puncture, if, for instance, they do not feel safe to stop on the hard shoulder of a highway to repair their tyre, or they are in a hazardous area. Michelin is of course aware that such inventions, like any other innovations can be used in a distorted way : cheques for example are meant to facilitate transactions, however the signature on a cheque can be falsified and money can go into the wrong hands ; run flat tyres are designed to provide better security to a driver, but could be used for other purposes by somebody having other intentions. Michelin is very sorry that it is unable to control any abuses made of its tyres by individuals intent on breaking the law."

Michelin Tweels.
In 2005, Michelin unveiled their "Tweel" concept - a word made up of the combination of Tyre and Wheel. After decades of riding around on air-filled tyres, Michelin would like to convince us that there is a better way. They're working on a totally air-less tyre. Airless = puncture proof. The Tweel is the creation of Michelin's American technology centre - no doubt working with the sound of the Ford Explorer / Bridgestone Firestone lawsuit still ringing in their ears. The Tweel is a combined single-piece tyre and wheel combination, hence the name, though it actually begins as an assembly of four pieces bonded together: the hub, a polyurethane spoke section, a "shear band" surrounding the spokes, and the tread band - the rubber layer that wraps around the circumference and touches the road. The Tweel's hub functions just like your everyday wheel right now - a rigid attachment point to the axle. The polyurethane spokes are flexible to help absorb road impacts. These act sort of like the sidewall in a current tyre. But turn a tweel side-on and you can see right through it. The shear band surrounding the spokes effectively takes the place of the air pressure, distributing the load. Finally, the tread is similar in appearance to a conventional tyre. The image on the right is my own rendering based on the teeny tiny images I found from the Michelin press release. It gives you some idea what the new Tweel could look like. One of the basic shortcomings of a tyre filled with air is that the inflation pressure is distributed equally around the tire, both up and down (vertically) as well as side-to side (laterally). That property keeps the tire round, but it also means that raising the pressure to improve cornering - increasing lateral stiffness - also adds up-down stiffness, making the ride harsher. With the Tweel's injection-molded spokes, those characteristics are no longer linked. Only the spokes toward the bottom of the tyre at any point in its rotation are determining the grip / ride quality. Those spokes rotating around the top of the tyre are free to flex to full extension without affecting the grip or ride quality. The Tweel offers a number of benefits beyond the obvious attraction of being impervious to nails in the road. The tread will last two to three times as long as today's radial tires, Michelin says, and when it does wear thin it can be retreaded. For manufacturers, the Tweel offers an opportunity to reduce the number of parts, eliminating most of the 23 components of a typical new tire as well as the costly air-pressure monitors now required on all new vehicles in the United States. (See TPMS below). Another benefit? No spare wheels. That leaves more room for boot/trunk space, and reduces the carried weight in the vehicle. Reporters who took the change to drive an Audi A4 sedan equipped with Tweels early in 2005 complained of harsh
http://www.carbibles.com/tyre_bible.html (19 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

vibration and an overly noisy ride. Michelin are well aware of these shortfalls - mostly due to vibration in the spoke system. (They admit they're in extremely-alpha-test mode.) Another problem is that the wheels transmit a lot more force and vibration into the cabin than regular tyres. A plus point though is cornering ability. Because of the rigidity of the spokes and the lack of a flexing sidewall, cornering grip, response and feel is excellent. There are other negatives: the flexibility, at this early stage, contributes to greater friction, though it is within 5% of that generated by a conventional radial tyre. And so far, the Tweel is no lighter than the tyre and wheel it replaces. Almost everything else about the Tweel is undetermined at this early stage of development, including serious matters like cost and frivolous questions like the possibilities of chrome-plating. Either way, it's a promising look into the future. Tweels are being tested out on the iBot - Dean Kamen's (the Segway inventor) new prototype wheelchair, and by the military. The military are interested because the Tweel is incredibly resistant to damage, even caused by explosions. Michelin hope to bring this technology to everyday road car use, construction equipment, and potentially even aircraft tyres.

Picture credits: Michelin press kit

Stiffened sidewalls - Goodyear Eagle with ResponsEdge.

http://www.carbibles.com/tyre_bible.html (20 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

In 2007, Goodyear added a new tyre to their Eagle range, called the Eagle Responsedge. The tyre has the same basic construction as all modern tyres but Goodyear added a carbon-fibre insert to the outer sidewall. If you've seen footage of cars cornering hard in racing, you'll have seen how the sidewalls deform under extreme cornering loads. The idea of putting a carbon fibre insert in the outer sidewall is that it stiffens the sidewall to help prevent compression and sideways shearing. That in turn helps to keep more of the contact patch on the road during cornering as the tyre isn't trying to roll out of the corner so much. Ultimately the idea is improved cornering speed and handling characteristics. It's another of the trickledown technologies from Formula 1 motor racing that has finally hit the streets for the consumer. From the Goodyear markering blurb:"Featuring a dual-compound asymmetric tread design, the tire sports a sound- and shock-absorbing InsuLayer made with DuPont KEVLAR, to help provide a smooth, quiet ride and to promote even treadwear. On the inboard side of the tread, an All Season Zone offers an open tread pattern, Aquachutes and lateral grooves for water dispersion, and a high number of TredLock technology microgrooves. All of these tread features are supported by a new silica tread compound. Combined, the All Season Zone provides all-season traction and handling confidence in wet and wintery conditions."

Picture credit: Goodyear press kit

Kevlar puncture resistence - Goodyear Wrangler 'SilentArmor'.
In 2007, Goodyear added another new tyre to their range which they advertised as having 'SilentArmor' (note the spelling - this is a tyre for the American market). This is a truck and SUV tyre that is essentially constructed identically to a normal radial except that one of the steel belts has been replaced with a Kevlar® belt. Kevlar® is a particularly light but very strong synthetic fiber that doesn't rust or corrode and is five times stronger than steel for the equivalent weight. (It's one of the many things found in bulletproof jackets). The idea here is that the Kevlar® belt helps absorb some of the road noise of the tyre as well as making the tread more resistent to punctures. It's interesting to note that Kevlar® is being advertised in this way as if its something new. In fact, DuPont originally intended their ballistic fabric to replace the steel belts in car tyres but it never quite made it that far. In addition to the Kevlar® belt, the tyre also has strengthened sidewalls as well as an extended rubber lip around the sidewall to try to help prevent kerbing from damaging your wheels. Goodyear site

Coloured dots and stripes - whats that all about?
When you're looking for new tyres, you'll often see some coloured dots on the tyre sidewall, and bands of colour in the tread. These are all here for a reason, but it's more for the tyre fitter than for your benefit. The dots on the sidewall typically denote unformity and weight. It's impossible to manufacture a tyre which is perfectly balanced and perfectly manufactured in the belts. As a result, all tyres have a point on the tread which is lighter than the rest of the tyre - a thin spot if you like. It's fractional - you'd never notice it unless you used tyre manufacturing equipment to find it, but its there. When the tyre is manufactured, this point is found and a coloured dot is put on the sidewall of the tyre corresponding to the light spot. Typically this is a yellow dot (although some manufacturers use different colours just to confuse us) and is known as the weight mark. Typically the yellow dot should end up aligned to the valve stem on your wheel and tyre combo. This is because you can help minimize the amount of weight needed to balance the tyre and wheel combo by mounting the tire so that its light point is matched up with the wheel's heavy balance point. Every wheel has a valve stem which cannot be moved so that is considered to be the heavy balance point for the wheel. As well as not being able to manufacture perfectly weighted tyres, it's also nearly impossible to make a tyre which is perfectly circular. By perfectly circular, I mean down to some nauseating number of decimal places. Again, you'd be hard pushed to actually be able to tell that a tyre wasn't round without specialist equipment. Every tyre has a high and a low spot, the difference of which is called radial runout. Using sophisticated computer analysis, tyre manufacturers spin each tyre and look for the 'wobble' in the tyre at certain RPMs. It's all about harmonic frequency (you know - the frequency at which something vibrates, like the Tacoma Narrows bridge collapse). Where the first
http://www.carbibles.com/tyre_bible.html (21 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

harmonic curve from the tyre wobble hits its high point, that's where the tyre's high spot is. Manufacturers typically mark this point with a red dot on the tyre sidewall, although again, some tyres have no marks, and others use different colours. This is called the uniformity mark. Correspondingly, most wheel rims are also not 100% circular, and will have a notch or a dimple stamped into the wheel rim somewhere indicating their low point. It makes sense then, that the high point of the tyre should be matched with the low point of the wheel rim to balance out the radial runout.

What if both dots are present?
Generally speaking, if you get a tyre with both a red and a yellow dot on it, it should be mounted according to the red dot - ie. the uniformity mark should line up with the dimple on the wheel rim, and the yellow mark should be ignored.

What about the coloured stripes in the tread?
Often when you buy tyres, there will be a coloured band or stripe running around the tyre inside the tread. These can be any colour and can be placed laterally almost anyhwere across the tread. Some are on the tread blocks whilst others are on the tyre carcass. For ages I thought this was a uniformity check - a painted mark used to check the "roundness" of the tyre. But I had a tyre dealer contact me with a far more feasible answer. The same tyre is often made with slightly tweaked specifications for different vehicles. To easily identify these same labelled tyres when they are warehoused or in storage, different markings and stripes are used. Sometimes stripes are added for huge bulk orders to various manufactures. Eg All the red outside stripes are for Toyota next week. This gives anyone in the warehouse a very quick visual check of the different types of tyres without needing to pull them all down and read the sidewall on each one. As well as the colour, the actual position of the lines is something to take note of too. They're a measure of something called runout. Depending on how the belts are laid on the tyre during manufacturing, they can cause the tire to "run out" to not track perfectly straight, but pull to the left or right. The closer to the centre of the tyre that these lines are, the less runout the tyre has and the straighter it will track when mounted on your car. So for example, if you were looking at your car from the front and you saw the coloured striped running around the right side of both your front tyres, the car would likely have a tendency to pull to that side. The best thing is to have the coloured stripes on opposite sides of the tyres for opposite sides of the car, so that the runout on each side will counteract the other and help maintain a good straight running. This is something that not many tyre fitting places know about or take any notice of. The obvious solution to having the stripes both on one side is to flip one of the tyres around, but that will only work if they're not unidirectional tyres. If they are unidirectional (and thus must be mounted to rotate a specific way) then you should try to find another tyre from the same batch with the stripe on the opposite side.

http://www.carbibles.com/tyre_bible.html (22 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

Running in your new tyres
It may sound like an odd concept, but if you buy brand new tyres and slap them on your car, then try to drive the nuts off it, you're going to come a cropper. The reason, believe it or not, is that all tyres need a running-in (or scrubbing-in) period. When tyres are made, they're typically injection-moulded in a heat press. In order to get the tyres out of the mould, it is first lined with a non-stick coating. When the tyres pop out, some of that releasing agent sticks to the tyres themselves. What you get is a nice shiny new tyre, with 'shiny' being the operative word. The releasing agent can take as much as 500 miles to scrub off. Now for the everyday Joe, this isn't really so much of an issue, but for people who are fast drivers, or think they're fast drivers, this can lead to a distressing loss-of-grip mid-corner and a visit to something large and solid. It's doubly important for motorcyclists because they have half the number of tyres and a much smaller contact patch per tyre to boot.

Getting the same results with tyre-black polish or dress-up polish
If you're proud of your car (or vain) you might have been tempted at one point or another to use a Back-to-Black type substance on them to blacken up the sidewalls of the tyres. These things are over-the-counter items that you can buy in just about any car parts store and they're designed to remove the dirt and muck from your sidewalls whilst (allegedly) conditioning the rubber and restoring that factory-fresh look to your tyres. This is all very good until you use a little too much and/or park the car in the sun. When that happens, this stuff starts to run down your tyres and into the tread. Worse, I've seen people using tyre-black on the tread on purpose. This stuff is basically teflon mixed with WD-40 and if you get it on the tyre tread, your car is going to take on the handling dynamics of a drunk ice skater. Not in a "ha ha that was funny" sort of way but in a "holy snot that's gonna hurt!" sort of way. You've been warned.

Learning from others - tyre reviews
http://www.carbibles.com/tyre_bible.html (23 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2

With the sheer number of tyres available to you, you might wonder how to choose the one that's going to suit your driving style. Most tyre websites will have a section for customer reviews but you need to be careful because the bigname sites (like TyreRack etc) typically attract people with an axe to grind or those who can never review anything other than positively. As a result, you'll find the same tyre being given 5-star ratings and 1-star ratings and nothing in between, and the reviews will not be especially objective. Tyrereviews.co.uk is a new independent site which seems pretty good - it has a broad spectrum of comments and their reviews are sorted by tyre type as well as by vehicle. If you can't get what you want from the web, go all old-fashioned and use your mouth - ask your friends. I know it's an out-of-date concept, but you'd be surprised what talking to people can reveal, instead of emailing them or worse, txtng yr bff 4 hlp. They will likely have an opinion one way or another and any opinion is worth listening to when you're trying to gather information.

So Chris - what do you like?
My personal favourite tyre brand is Yokohama. I've had them on every vehicle I've owned since 1993. That doesn't necessarily mean they're fabulous tyres, it just means I like them, I like the way they handle, how they wear and how they make the car feel. That's the crux of the matter though. Essentially you're never going to know whether a tyre will suit your needs until you've got them on your car and are driving it the way you normally drive. My advice: if you find a good brand and style that you like, stick with it. It might take a few tyre changes to find one but eventually you'll likely find something that makes you think "hey - this isn't a bad tyre". Just stick with big name brands. Anything that costs less than about $80 or £50 a tyre will be junk. Trust me.

The eBay problem
This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at www.carbibles.com, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to www.carbibles.com to see the full site and find my contact details. And now, back to the meat of the subject....

Page 1 ------ Page 2

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

http://www.carbibles.com/tyre_bible.html (24 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Wheel and Tyre Bible Page 1 of 2 These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/tyre_bible.html (25 of 25) [2/6/2008 7:11:48 AM]

Car Bibles : The Brake Bible

The car brake bible. Everything you need to know about car brakes, discs, drums, calipers, hoses, brake fluid and general brake maintenance, current and future brake technologies, DIY car maintenance and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Brakes - what do they do?
The simple answer : they slow you down. The complex answer : brakes are designed to slow down your vehicle but probably not by the means that you think. The common misconception is that brakes squeeze against a drum or disc, and the pressure of the squeezing action is what slows you down. This in fact is only part of the reason you slow down. Brakes are essentially a mechanism to change energy types. When you're travelling at speed, your vehicle has kinetic energy. When you apply the brakes, the pads or shoes that press against the brake drum or rotor convert that energy into thermal energy via friction. The cooling of the brakes dissipates the heat and the vehicle slows down. This is all to do with The First Law of Thermodynamics, sometimes known as the law of conservation of energy. This states that energy cannot be created nor destroyed, it can only be converted from one form to another. In the case of brakes, it is converted from kinetic energy to thermal energy. Angular force. Because of the configuration of the brake pads and rotor in a disc brake, the location of the point of contact where the friction is generated also provides a mechanical moment to resist the turning motion of the rotor.

http://www.carbibles.com/brake_bible.html (1 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Thermodynamics, brake fade and drilled rotors.
Picture credit: Formula1.com

If you ride a motorbike or drive a race car, you're probably familiar with the term brake fade which is used to describe what happens to brakes when they get too hot. A good example is coming down a mountain pass using your brakes rather than your engine to slow you down. By the First Law of Thermodynamics, as you start to come down the pass, the brakes on your vehicle heat up, slowing you down. But if you keep using the brakes, the drums or discs and brake pads will stay hot and get no chance to cool off. The next time you try to brake, because the brake components are already so hot, they cannot absorb much more heat. Once they get to this stage, you have to look at the brake pads themselves. In every brake pad there is the friction material which is held together with some sort of resin. Once this lot starts to get too hot, the resin holding the pad material together starts to vapourise, forming a gas. That gas has to have somewhere to go, because it can't stay between the pad and the rotor, so if forms a thin layer between the two trying to escape. The result is very similar to hydroplaning while going too fast in the rain; the pads lose contact with the rotor, thus reducing the amount of friction. Voila. Brake fade. The typical symptom of this would be to get the vehicle to a stop and wait for a few minutes. As the brake components cool down, their ability to absorb heat returns, the pads cool off which means they have more chance to heat up again before the resin vapourises, hence the next time you use the brakes, they seem to work just fine. This type of brake fade was more common in older vehicles. Newer vehicles tend to have less outgassing from the brake pad compounds but they still suffer brake fade. So why? Well it is again to do with the pads getting too hot. With newer brake pad compounds where outgassing isn't so much of a problem, the pads transfer heat into the calipers because the rotors are already too hot and the brake fluid starts to boil as a result. As this happens, bubbles form in the brake fluid. Air is compressible, brake fluid isn't, so you can put your foot on the brake pedal and get full travel but have no braking effect at the other end. This is because you're now compressing the gas bubbles and not actually forcing the pads against the rotors. Voila. Brake fade again. So how do the engineers design brakes to reduce or eliminate brake fade? For older vehicles, you give that vapourised gas somewhere to go. For newer vehicles, you find some way to cool the rotors off more effectively. Either way you end up with cross-drilled or grooved brake rotors. While grooving the surface may reduce the specific heat capacity of the rotor, its effect is negligible in the grand scheme of things. The rotors will heat up to cool down no faster or slower. However, under heavy braking once everything is hot and the resin is vapourising, the grooves give the gas somewhere to go, so the pad can continue to contact the rotor, allowing you to stop. The whole understanding of the conversion of energy is critical in understanding how and why brakes do what they do, and why they are designed like they are. If you've ever watched Formula-1 racing, you'll see the front wheels have huge scoops inside the wheel pointing to the front (see the picture on the right). This is to duct air to the brake rotors to help them cool off because in Formula-1 racing, the brakes are used viciously every few seconds and spend a lot of their time trying to stay hot. Without some form of cooling assistance, the brakes would be fine for the first few corners but then would fade and become near useless by half way around the track. Rotor technology. If a brake rotor was a single cast chunk of steel, it would have terrible heat dissipation properties and leave nowhere for the vapourised gas to go. Because of this, brake rotors are typically modified with all manner of extra design features to help them cool down as quickly as possible as well as dissapate any gas from between the pads and rotors. The following diagram shows some examples of rotor types with the various modification that can be done to them to help them create more friction, disperse more heat more quickly, and ventilate gas. From left to right. 1. Basic brake rotor. 2. Grooved rotor. The grooves give more bite and thus more friction as they pass between the brake pads They also allow gas to vent from between the pads and the rotor. 3. Grooved, drilled rotor. The drilled holes again give more bite, but also allow air currents (eddies) to blow through the brake disc to assist cooling and ventilating gas. 4. Dual ventilated rotors. Same as before but now with two rotors instead of one, and with vanes in between them to generate a vortex which will cool the rotors even further whilst trying to actually 'suck' any gas away from the pads. An important note about drilled rotors: Drilled rotors are typically only found (and to be used on) race cars. The drilling weakens the rotors and typically results in microfractures to the rotor. On race cars this isn't a problem - the brakes are changed after each race or weekend. But on a road car, this can eventually lead to brake rotor failure - not what you want. I only mention this because of a lot of performance suppliers will supply you with drilled rotors for street cars without mentioning this little fact.

http://www.carbibles.com/brake_bible.html (2 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Big rotors. You know I've been drumming into you the whole mechanism that causes you to stop? How does it apply to bigger brake rotors; a common sports car upgrade? Well sports cars and race bikes typically have much bigger discs or rotors than your average family saloon car. The reason again is to do with heat and friction. A bigger rotor has more material in it so it can absorb more heat. More material also means a larger surface area, which as well as meaning more area for the pads to generate friction with, also translates to better heat dissipation. On top of that, the larger rotors mean that the brake pads make contact further away from the axle of rotation. This provides a larger mechanical advantage to resist the turning of the rotor itself. To best illustrate how this works, imagine a spinning steel disc on a pivot in front of you. If you clamped your thumbs either side of the disc close to the middle, your thumbs would heat up very quickly and you'd need to push pretty hard to generate the friction required to slow the disc down. Now imagine doing the same thing but clamping your thumbs together close to the outer rim of the disc. The disc will stop spinning much more quickly and your thumbs won't get as hot. That, in a nutshell explains the whole principle behind why bigger rotors = better stopping power. Taking it one step further, composite brake rotors, as found on high-end Ferraris, the McLaren F1, and most Formula-1 race cars, are even better again at heat transfer. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

The different types of brake.
All brakes work by friction. Friction causes heat which is part of the kinetic energy conversion process. How they create friction is down to the various designs.

Bicycle wheel brakes
I thought I'd cover these because they're about the most basic type of functioning brake that you can see, watch working, and understand. The construction is very simple and out-in-the-open. A pair of rubber blocks are attached to a pair of calipers which are pivoted on the frame. When you pull the brake cable, the pads are pressed against the side or inner edge of the bicycle wheel rim. The rubber creates friction, which creates heat, which is the transfer of kinetic energy that slows you down. There's only really two types of bicycle brake - those on which each brake shoe shares the same pivot point, and those with two pivot points. If you can look at a bicycle brake and not understand what's going on, the rest of this page is going to cause you a bit of a headache.

http://www.carbibles.com/brake_bible.html (3 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Drum brakes - single leading edge
The next, more complicated type of brake is a drum brake. The concept here is simple. Two semicircular brake shoes sit inside a spinning drum which is attached to the wheel. When you apply the brakes, the shoes are expanded outwards to press against the inside of the drum. This creates friction, which creates heat, which transfers kinetic energy, which slows you down. The example below shows a simple model. The actuator in this case is the blue elliptical object. As that is twisted, it forces against the brake shoes and in turn forces them to expand outwards. The return spring is what pulls the shoes back away from the surface of the brake drum when the brakes are released. See the later section for more information on actuator types.

http://www.carbibles.com/brake_bible.html (4 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

The "single leading edge" refers to the number of parts of the brake shoe which actually contact the spinning drum. Because the brake shoe pivots at one end, simple geometry means that the entire brake pad cannot contact the brake drum. The leading edge is the term given to the part of the brake pad which does contact the drum, and in the case of a single leading edge system, it's the part of the pad closest to the actuator. The diagram below shows what happens as the brakes are applied. The shoes are pressed outwards and the part of the brake pad which first contacts the drum is the leading edge. The action of the drum spinning actually helps to draw the brake pad outwards because of friction, which causes the brakes to "bite". The trailing edge of the brake shoe makes virtually no contact with the drum at all. This simple geometry explains why it's really difficult to stop a vehicle rolling backwards if it's equipped only with single leading edge drum brakes. As the drum spins backwards, the leading edge of the shoe becomes the trailing edge and thus doesn't bite.

http://www.carbibles.com/brake_bible.html (5 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Drum brakes - double leading edge
The drawbacks of the single leading edge style of drum brake can be eliminated by adding a second return spring and turning the pivot point into a second actuator. Now when the brakes are applied, the shoes are pressed outwards at two points. So each brake pad now has one leading and one trailing edge. Because there are two brake shoes, there are two brake pads, which means there are two leading edges. Hence the name double leading edge.

http://www.carbibles.com/brake_bible.html (6 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Disc brakes
Some background. Disc brakes were invented in 1902 and patented by Birmingham car maker Frederick William Lanchester. His original design had two discs which pressed against each other to generate friction and slow his car down. It wasn't until 1949 that disc brakes appeared on a production car though. The obscure American car builder Crosley made a vehicle called the Hotshot which used the more familiar brake rotor and calipers that we all know and love today. His original design was a bit crap though - the brakes lasted less than a year each. Finally in 1954 Citroën launched the wayahead-of-its-time DS which had the first modern incarnation of disc brakes along with other nifty stuff like selflevelling suspension, semi-automatic gearbox, active headlights and composite body panels. (all things which were re-introduced as "new" by car makers in the 90's). Disc brakes are an order of magnitude better at stopping vehicles than drum brakes, which is why you'll find disc brakes on the front of almost every car and motorbike built today. Sportier vehicles with higher speeds need better brakes to slow them down, so you'll likely see disc brakes on the rear of those too. Disc brakes are again a two-part system. Instead of the drum, you have a disc or rotor, and instead of the brake shoes, you now have brake caliper assemblies. The caliper assemblies contain one or more hydraulic pistons which push against the back of the brake pads, clamping them together around the spinning rotor. The harder they clamp together, the more friction is generated, which means more heat, which means more kinetic energy transfer, which slows you down. You get the idea by now.

http://www.carbibles.com/brake_bible.html (7 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Standard disc brakes have one or two cylinders in them - also know as one or two-pot calipers. Where more force is required, three, or more cylinders can be used. Sports bikes have 4- or 6-pot calipers arranged in pairs. The disadvantage of disc brakes is that they are extremely intolerant of faulty workmanship or bad machining. If you have a regular car disc rotor which is off by so much as 0.07mm (3/1000 inch) it will be Hell when you step on the brakes. That ever-soslight warp or misalignment is going to spin through the clamped calipers at some ungodly speed and the resulting vibration will make you wonder if you're driving down stairs. To combat this problem, which is particularly critical on motorbikes, floating rotors were invented. The floating rotor. Standard brake rotors are cast in a single piece which bolts directly to the wheel or drive plate. If the mounting surface of your wheel or drive plate isn't perfectly flat, you'll get vibration at speed. Floating rotors are typically cast in two pieces the rotor and the carrier. The carrier is bolted to the wheel and the rotor is attached to the carrier using float buttons. The other method of floating a brake rotor is to have the rotor bolted directly to the wheel itself without a carrier, but the bolts have float buttons built into them.

http://www.carbibles.com/brake_bible.html (8 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

These buttons allow the brake rotor some freedom to move laterally, but restrict the angular and rotational movement as if they were bolted directly to the wheel. This slight lateral motion which can be less than 0.03mm, is just enough to prevent vibration in the brake system. Because the calipers are mounted solidly, and warping or misalignment in the wheel or brake rotor mounting face can be compensated for because the rotor will "float" laterally on the float buttons. This sideto-side vibration is separated from the carrier by the float buttons themselves, so none of the resulting motion is transferred into the suspension or steering. Clever eh? The rendering below shows an extreme close-up of the brake disc shown above. I've rendered the components slightly transparent so you can see what's going on.

http://www.carbibles.com/brake_bible.html (9 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Radial calipers / radial brakes. Around the year 2003, motorbikes started to hit the showrooms with a new feature - radial brakes. The magazines and testers will all tell you that radial brakes make the bike stop quicker. Not true - they have nothing to do with stopping power and everything to do with the design of the front forks of the bike. More and more bikes are coming out with upside-down forks. ie. instead of the fat canister part of the fork being at the bottom of the assembly, it's at the top. This means that the fork pistons are now the part of the suspension with the wheel attached to them. It also means that it's impossible to put a stiffening fork brace down there now because the brace would need to move with the wheel, and the length of the fork pistons precludes that. The stiffness of the front end is now entirely dependent on the size of the front axle. Bigger axle = stiffer front end. A side-effect of this design was that traditionallymounted brake calipers could cause a lot of vibration in the steering because of flex between the wheel (with the brake disc bolted to it), and the fork leg (with the caliper). The slight tolerance allowed by floating brake rotors couldn't compensate for the amount of flexing in the forks. To reduce the brake-induced fork vibration, the brake calipers were moved around the rotors slightly so that they fell into the front-rear alignment of the wheel axle. This is because there is less lateral flex at that point, which means less or no vibration. The caliper mounts were changed too. Traditional calipers bolt on to the forks with bolts going through them at 90 degrees to the face of the brake rotor. With radial calipers, the bolts are aligned parallel to the brake rotor - effectively also in the front-rear alignment of the wheel. This design is a trickle-down technology from superbike racing where a radial caliper mount allows the racing teams to use different diameters of brake rotor by simply adding spacers to the caliper mounts. The image on the right here shows the difference between traditional and radially mounted brake calipers.

http://www.carbibles.com/brake_bible.html (10 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Full-contact Disc brakes.
There is a quiet but major revolution happening in the world of brakes, and its being brought about by a Canadian company called NewTech. Rather than the piecemeal improvements we've seen over the last few years, with slight design changes, and materials improvements, the new system is a radical redesign from the ground up. NewTech have designed a disc brake system called "full contact disc brakes". They looked at traditional pad and rotor design and figured that the pads only contact about 15% of the rotor surface at any one time. With a change of design, NewTech have been able to add 5 more pads to the system so that 75% of the brake rotor is in contact with the pads at any one time. With traditional pads and rotors, the brake rotor is clamped between the pad. With the NewTech design, the brake rotor itself becomes a floating rotor, similar to those found on motorbikes. It is covered with a 'spider' (the red structure in my renderings below) and the spider has 6 brake pads on the inside of it. The hydraulic system acts on fully circular elastomer composite diaphragm behind the brake disc, mounted in the black structure in the renderings. This had 6 pads on it which push the entire disc out against the 6 pads inside the spider. This provides and even force across the entire disc to push it out, and the disc gets an even contact with all 12 pads. To ensure the brakes remain cool, the system is covered in cooling fins connected to the outer pads to dissipate heat. The inner pads are fitted with a moulded thermal barrier made of a composite material. Special inserts made of a variety of frictional materials are distributed evenly on the entire surface of the pad. The range of materials is used to ensure performance under diverse conditions. NewTech believe that the system has considerable advantages over conventional brakes with better cooling, higher strength and reduced noise and vibration. NewTech have sold truck and bus versions of these brakes into the haulage and public transport industry, but now Renault is considering introducing this system on its cars in conjunction with a new brake-by-wire system. Newtech's first OEM customer was to be Saleen who were going to put the system on their S7 supercar, but in the end went with conventional six-piston monoblock calipers instead. NewTech's website can be found here.

http://www.carbibles.com/brake_bible.html (11 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

It's worth nothing that this isn't actually the first time this has been tried in cars. Bugatti experimented with a system like this in the late 80's for inclusion on their 1991 EB110 supercar; it was going to be available as an option for the car. People who had experienced the brakes said they were just otherworldy, that the braking power was way beyond capabilities of the average driver. They came from Aerospatiale, the French aerospace company, who also designed the chassis for the EB110 (this type of brake was being used in aircraft at the time). Bugatti dropped the idea because the brakes would have cost more than the rest of the EB110, which at $350,000 was by no means a cheap car.

The Siemens VDO Electric Wedge Brake.
Siemens VDO in Germany are trying to bring a prototype electric wedge brake (EWB) to the market. As much as it sounds like a high school prank involving underwear, it's actually the latest attempt to remove hydraulics from the braking circuit in a car. The EWB is an innovative idea based on technology developed by a company called eStop. Siemens acquired eStop early in 2005 and have been continuing their work on the wedge system ever since. The principle is both simple and clever. The brake pad is pressed against the brake rotor by means of a wedge-shaped thrust plate. The more the brake rotor turns, the harder the slope of the wedge forces the pads against it. Because of the shape of the wedge bearings and thrust plate and the rotation of the brake rotor, the pad is actually forced against the rotor harder the faster the rotor is spinning. In effect, a lot of braking force for very little input. The system runs off a normal 12v vehicle electrical system which means no more hydraulics. It also allows the system to eliminate all the plumbing associated with ABS as the EWB is entirely electronically controlled. The final advantage, if you could call it that, is that it allows the first true all-electronic brake-by-wire system. Current brake-by-wire systems use electronics behind the brake pedal to send signals to actuators in the hydraulic system. With the EWB there is no
http://www.carbibles.com/brake_bible.html (12 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

hydraulic system so the only link from the brake pedal to the brake caliper is a 12v electrical feed and signal actuation wire. The operation of the wedge system is based on several roller bearings and a wedge-shaped thrust plate connected to a pair of 12v electric motors. As the brake pedal is depressed, the signal is sent to the motors to start moving the thrust plate. Because of its shape and the design of the roller bearings, as the thrust plate moves, it forces the brake pad to press against the brake rotor. The reaction time of the electric motors can be measured in milliseconds - far quicker than any hydraulic system could react, so in theory, when connected to a full computer-monitored brake-by-wire system, the EWB ought to be able to shave milliseconds off brake reaction time. Doesn't sound like much but if it means a few less metres in stopping distance, that can only be a good thing. The brake caliper unit itself has an intelligent wheel-braking module built into it. As well as the motors, bearings and wedges, the module also has a sensor system for monitoring movement and force - basically this is what replaces the traditional ABS items so each brake caliper becomes a self-governing ABS unit. Because there's no physical link back to the brake pedal any more, the ABS doesn't force the brake pedal to judder when it activates which will make it far more acceptable for a lot more drivers. Finally, because the system is totally electronic, the traditional cable-pulled handbrake can also be eliminated and replaced with a parking switch that simply activates all four EWB modules. Of course there are pros and cons to any new system like this. Obviously reducing the weight and complexity of the braking system is a good thing, and because of the design of the EWB, there's a lot less space taken up in the engine bay, freeing up more room for the car designers to work with. But by removing the hydraulic lines, ABS actuators and sensors, and master and slave brake cylinders, the EWB concept becomes entirely reliant on the 12v electrical system and the vagaries of a computer. Knowing how often a single dodgy earth connections in a car can totally screw up the electrics, I've got to wonder what would happen if a grounding strap came loose and the electronic brake system started playing up. Will these brakes have a fail-safe or backup system like the double hydraulic circuits we use now, or will you sail off into some solid object because you've got no brakes left? Siemens aren't clear on this matter. Until I get the chance to render up some illustrations of my own to better show how the system works, the one you see here is from the Siemens press pack. If you want to see a video demonstrating the EWB, Siemens VDO have one available here (27.8Mb mpeg).

http://www.carbibles.com/brake_bible.html (13 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible Picture credit: Siemens press kit

Brake pad compounds.
Just a quick word on brake pad compounds. Most pads used to use asbestos but we all know what that stuff is like. Today they use all manner of combinations of materials. The pads themselves are made up of a friction material bonded to the backing plate. The brake caliper piston pushes against the backing plate and the friction material is pushed against the brake rotor. The material combinations typically fall into the following broad categories now. Organic These pads are well-suited for street driving because they wear well, are easy on the ears, don't chew up the rotors and don't spew dust everywhere. They're favoured for your average family saloon because they work well when they're cold. Of course the drawback is that they don't work so well when they get hot. Semi-metallic / sintered This is a good compromise between street and track. These seem to be the pad of choice for sportier vehicles such as the Subaru Impreza WRX. They won't work as well as organic pads when they are cold, so you need to be a bit wary of the first couple of stops. Conversely they do work well when hot. Occasionally the weak link in semi-metallic pads is the bonding material that holds the friction pad to the backing plate. There have been occasions where the friction material has come away completely. That's infrequent though. Metallic These pads are typically reserved for racing or the extremely rich. They squeal and dust like crazy, are hard on rotors and don't work well when cold. Ceramic Ceramic pads still have metal fibers (about 15% vs. about 40% for semi-metallic) but they are copper instead of steel and therefore cause less wear and transfer heat better. They don't fade as easily as other pads, cool faster, last longer, and are effectively silent, as the sound they genereate is outside of the human range of hearing. Dogs will go crazy thought. The dust created by ceramic pads is also very light in color so your wheels look cleaner.

Brake squeal.
Squealing brakes are a sign of one of two things : the friction material is all gone and you're jamming the backing plate against the brake rotor, or the fit of the brake pad against the caliper piston isn't as snug as it could be. Either way, the squealing is the result of an extremely high-frequency vibration between the pad, the caliper piston and the brake rotor. Some vehicles have problems with squealy brakes right from the factory. In those cases, simply changing brake pad manufacturer can often cure the problem as the different pads will have a slightly different harmonic frequency, which is harder to attain. A classic example was one of the BMW R1100 touring bikes. From the factory, they'd squeal like crazy, and BMW redesigned the brake calipers and rotors a couple of times until they finally just switched to a different brand of pads and the problem vanished.

Solving brake squeal.
A good way to solve brake squeal is to put some copper-based grease on the back of your brake pads. That's very important so I'll say it again in CAPS : THE BACK. Copper grease is extremely resistant to pressure and heat and if you get any on the front of your pads, you'll need new pads and rotors or discs. The picture here shows a cutaway of a disc brake assembly. The blue caliper housing on the right is missing to show the two silver brake pistons. The idea is that it creates a small pocket of sticky lubrication between the front side of the brake pistons and the back side of the brake pads. This is usually enough to prevent the high-frequency squeal. If you're not happy doing this yourself (working on a safety-critical part of your car like the brakes isn't something just everybody should be doing) then ask your friendly greasemonkey to do it for you. There's a couple of products on the market that I've heard of and/or used in the past. Noisefree is one of them and Copaslip is the other. I've used Copaslip on my vehicles before with
http://www.carbibles.com/brake_bible.html (14 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

no problems. Noisefree is a new player so if you've used their product and have any comments, drop me a line. I believe both are available in America, but I think only Copaslip is available in Europe.

Copper grease and rubber
Whilst copper grease such as Copaslip works well in the short term to solve brake squeal, long-term, it has an adverse affect on the rubber dust seals of the caliper pistons. This can lead to the seal deteriorating or failing completely. If that happens, it leaves the piston and it's surface exposed to the very elements from which it should be protected. Just so you know.

The other solution to brake squeal
Whilst the ultra high frequency vibration is one cause of brake squeal, the other biggie is related to suspension alignment. Driving on badly-maintained roads, mountaineering through pot-holes or kerbing your wheels all make the suspension move around in ways it was never really designed to cope with, and this in turn leads to the suspension bushes becoming stressed. Normally, re-aligning the wheels on a vehicle is corrected by mechanical adjustment only. If the mounting rubbers are not de-stressed first, then it leads to the transfer of the sound generated during braking into the chassis and body which then amplifies it to where we can hear it. Sort of like a giant record player with the suspension as the pickup needle and the entire car as the speaker. If you have squealing brakes that copper grease doesn't solve, look into a proper suspension realignment and possibly new suspension bushes.

The eBay problem
This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at www.carbibles.com, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to www.carbibles.com to see the full site and find my contact details. And now, back to the meat of the subject....

Brake actuators.
Brakes are all well and good, but you need some method of applying them in order for them to work. The method by which the force from your hand or foot reaches the brake itself is all to do with the brake actuator system.

Cable-operated
This is about as basic as you get. A cable is connected to a lever at each end. You press on one lever with your foot or squeeze it with your hand, and it pulls the lever at the other end. On the back of the brake-end lever there's an elliptical cam which rotates inside a circular cup in the brake shoe. As the long axis of the ellipse rotates, it forces the brake shoes to move apart. In the case of a bicycle brake, the brake-end of the cable just pulls the two calipers together.

http://www.carbibles.com/brake_bible.html (15 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Solid bar connection
One step up, and found on the rear brake of older motorbikes, the solid bar connection. This allows the use of mechanical advantage (see below) to amplify your force on the pedal or lever before it gets to the brakes themselves. Typically these systems are used on drum brakes with the elliptical actuator described above. The disadvantage of this system is that it needs hinge and pivot points that match the position of the suspension components. If they're not present, going over a bump could put the brakes on as the suspension moves relative to the lever.

Single-circuit hydraulic
Another step up and we get to the type of brake system used on most cars and motorbikes today. Gone are the cables and bars, replaced instead with a system of plungers, reservoirs and hydraulic fluid. Single-circuit hydraulic systems have three basic components - the master cylinder, the slave cylinder and the reservoir. They're joined together with hydraulic hose and filled with a non-compressible hydraulic fluid (see brake fluid below). When you press your foot on the brake, or squeeze the brake lever, you compress a small piston assembly in the master cylinder. Because the brake fluid does not compress, that pressure is instantaneously transferred through the hydraulic brake line to the slave cylinder where it acts on another piston assembly, pushing it out. That slave assembly is either connected to a lever to activate the brakes, or more commonly, is the brake caliper itself, with the slave cylinder being the piston that acts directly on the brake pads. Because of the arrangement of the slave cylinder, heat from the brakes can be transferred back into the brake fluid.

http://www.carbibles.com/brake_bible.html (16 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Dual-circuit hydraulic
Dual-circuit hydraulic systems are available on high-end luxury vehicles and newer motorbikes, in particular BMW bikes. These have two separate circuits. One is the command circuit - that's the one you act on with your hand or foot. The second is a separate circuit controlled by an onboard computer, and that's the one which is actually connected to the brakes. As you apply the brakes, you're sending a pressure signal via the command circuit to the brake computer. It measures the amount of force you're applying, and using a servo / pump system, applies the same force to the secondary circuit to activate the brakes. If you do something stupid like trying to slam on the brakes at 100mph, the computer will realise that this would result in a skid or spin, and will not send the full pressure down the secondary circuit, instead deciding to use it's speed and ABS sensors to determine the optimal brake pressure to maintain control of the vehicle. The advantage of a dual-circuit system is that the command circuit never gets heat transferred into it because it is totally separated from the brakes themselves. The disadvantage of course is that you now have two hydraulic circuits to maintain.

http://www.carbibles.com/brake_bible.html (17 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Brake-by-wire
The most advanced system of brakes to date are brake-by-wire. These are a direct copy of some styles of racing brakes and are very similar to the dual-circuit hydraulic system described above, but instead of the command circuit being hydraulic, its replaced with electronics. The brake pedal or lever is connected to a hypersensitive rheostat (measures electrical resistance). The more you push it, the greater the electrical signal sent to the brake computer. From there on, it performs just like the secondary circuit described above. The advantage to this system is that the brake pedal or lever can be placed just about anywhere you like as it no longer is encumbered by the plumbing that goes with a hydraulic circuit. To combat driver complaints of "lack of feel" in the brakes, most brake-by-wire systems have a reverse feedback loop built in. This measures the pressure being applied to the brakes on the secondary circuit, and actuates an electrical resistor in the pedal or lever assembly to provide resistance. This is needed because there is no physical connection to any part of the brake system at all.

http://www.carbibles.com/brake_bible.html (18 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Mechanical advantage - why you can stop a 2-ton car with one foot.
If you did any sort of physics classes when you were back in school, you might remember something called mechanical advantage. In its most basic form, mechanical advantage is the ratio of force-in to force-out in a mechanical system. Mechanical Advantage = Effort Torque/Load Torque. For example a 20kg weight 1 metre from a pivot can lift a 40kg weight 0.5m from the pivot on the other side. The effort torque and load torque calculations are to do with force in Newtons and distance from pivot point. Hence torque is measured in Newton-metres, or Nm. A Newton is the amount of force required to accelerate a mass of one kilogram by one metre per second². On Earth, where acceleration due to gravity is 9.8m/s², the force exerted upon a mass of 1kg is 9.8N (usually rounded up to 10N). Another popular notation is lbf.ft - pound-force-feet, commonly referred to as foot-pounds. 1 Newton-metre is equivalent to 0.737 foot-pounds. The diagram below shows a simple lever system on a pivot. The load torque is 200Nm, and the effort torque is also 200Nm. Mechanical advantage = effort / load, which in this case is 200 / 200, which is 1. ie. the system is balanced.

http://www.carbibles.com/brake_bible.html (19 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Now imagine increasing the weight on the effort side to 30kg instead of 20kg, but leaving everything else the same. The load torque is still 200Nm, but the effort torque is now 300Nm. Mechanical advantage = effort / load, which is 300 / 200, which is 1.5. Any mechanical advantage value larger than 1.0 means that the effort has the advantage. In this case, a 30kg weight which is lighter than the 40kg load, is able to lift it off the ground.

If you now take your new-found / remembered knowledge about physics and look at the simple lever brake system, you'll realise how it's possible to generate enough force using your foot to stop a car or motorbike. Look at this diagram of the lever-operated cam brake.

http://www.carbibles.com/brake_bible.html (20 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

This system has 4 levers in it. The middle two have no mechanical advantage as the levers are connected the same distance from the pivot in each case. However, look at the pedal. The values I've put in are arbitrary but they serve the purpose. On the pedal we have some amount of force 20cm from the pivot, but the other end of the lever is only 5cm from the pivot. This gives us a mechanical advantage of 4 on the brake lever (20cm / 5cm). At the other end, the lever attached to the cam is still a lever system - it's just bent. The input lever is 10cm long but the cam is only 4cm across - or 2cm to the tip from the pivot. So at the brake cam we have a mechanical advantage of 5. (10cm / 2cm). So across this entire system, we have a total mechanical advantage of 20 - 4 from the brake pedal and 5 from the lever and cam. Apply force to this little system and be amazed. The units of force used are irrelevant they're multiplied just the same. To use easier-to-comprehend values, let's imagine that when you're braking, your foot is pushing on the brake pedal with about 60pounds of force - 27Kg. Through the brake pedal, that is amplified 4 times to 240pounds, and through the lever and cam its amplified a further 5 times from 240pounds to 1200pounds. You pushed the pedal with 60pounds of force, but the cam inside the drum brake is being forced out against the brake drum with 1200pounds of force - about 544Kg. Sweet.

Mechanical advantage as applied to hydraulics.
Most braking systems now use hydraulics. This is a slight change in the equation but the concept of mechanical advantage still exists, this time by the use of pressure equations. Pressure = force / area. If you apply 20 Newtons of pressure to 1m², it's the same as applying 200 Newtons to 10m². Why? Because 20 Newtons of force divided by 1m² of area generates 20 Pascals of pressure. Similarly, 200N / 10m² is also 20Pa.

http://www.carbibles.com/brake_bible.html (21 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

If you now think of that in terms of a hydraulic braking system, it becomes clear how mechanical advantage works for you. Brake fluid is incompressible - it has to be. This is good because it makes calculation for hydraulic brake systems quite easy - you can eliminate the internal pressure from the equation. Split the system into two parts - input and output - the brake pedal and the brake caliper piston. For each part, Pressure = Force / Area. The Pressure is the same at all points in the system, so some basic algebra gives a simple formula:

Using our previous example, we apply 60pounds (27Kg) of input force to the brake pedal. This is attached to a master
http://www.carbibles.com/brake_bible.html (22 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

piston which (for example) is 1.25cm across - ie. it has a surface area of 0.000491m² (remember your maths? area = PI x r²). At the other end of the system is the caliper piston, which for example is 2cm across - ie. it has a surface area of 0.001257m². Using our sparkly new formula, the output force from the caliper piston is 60 x (0.001257m² / 0.000491m²) Get your calculator out and that comes out to 154pounds (69.8Kg) - more than double the force at the brake pedal. The ratio of output area to input area is sometimes referred to as the area differential. So that, my friend, is why you can stop a speeding vehicle with a single foot. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Power Brakes and master cylinders.
Power brakes (also known as power assisted brakes) are designed to use the power of the engine and/or battery to enhance your braking power. Whilst you can generate a fair amount of force using your foot, using systems from elsewhere in the car to help you apply even more force means that you get more powerful brakes as a result. The four most common types of power brakes are: vacuum suspended; air suspended; hydraulic booster, and electrohydraulic booster. Most cars use vacuum suspended units (vacuum boosters). In this type of system, when you press the brake pedal, the push rod to the master cylinder opens a vacuum control valve. This allows vacuum pressure (normally from the intake manifold) to "suck" on a diaphragm inside the vacuum assist unit. This extra vacuum suction helps you to produce more force at the pedal end of the brake system. Hydraulic booster systems usually utilise pressure from the power steering system to augment pressure on the master brake cylinder. Electrohydraulic booster systems use an electric motor to pressurize the hydraulic system downwind of the brake pedal which has the effect of amplifying the internal pressure in the whole system.The advantage to this system is that as long as you have battery power, you have power brakes even if the engine fails. With vacuum-assist brakes, no engine means no assistance. If you're curious about how power brakes work, go out to your car and with the engine off, step on the brakes. They'll have a slightly solid, almost wooden feel to them. Turn the engine on and do it again and you'll notice a lot less back-pressure on the pedal. This is the power assist which is making it easier for you to depress the pedal.

The components of a master cylinder.
Brake master cylinders are complicated affairs involving finely manufactured parts, minute tolerances, springs, o-rings and rubber seals. The diagram below is a simplified representation of a dual-circuit master brake cylinder. When you step on the brake, its connected to the main plunger (on the right side of this image). As this is pushed into the master cylinder it acts on the components inside. The rear plunger (in blue) is the first one to start moving. As it moves forward, brake fluid from the reservoir is sucked in through the fluid intake and return port. At the same time, fluid is sucked in through the equalisation port. As the second circuit rear seal passes the intake and return port (about 1.5mm after the plunger starts moving), it creates a fixed volume of fluid between the rear and front plungers. The more you step on the brake pedal, the more this fluid is now forced out into the second brake circuit to apply those brakes. At the same time, the pressure building up in this area overcomes the strength of the first circuit return spring and the front plunger (red) begins to move too. As with the rear plunger, it too sucks fluid from the reservoir until the first circuit rear seal passes the fluid intake and return port (again about 1.5mm), trapping fluid between it and the front of the master cylinder. This fluid is then forced out into the first brake circuit, applying those brakes. When you take your foot off the brakes, the return springs push the plungers back into their neutral position. Fluid returns to the brake fluid reservoir and the system goes back to an unpressurised state.

http://www.carbibles.com/brake_bible.html (23 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

One last thing about brake master cylinders : they cost an absolute bomb to replace. If you find yours is leaking, patching it up is not an option. Brand new master cylinders can go for around $1500 without labour costs. Remanufactured ones come in slightly cheaper at around $900. Bear that in mind when your 20 year old beater develops a leak - it's probably cheaper to buy another used car than to replace the master cylinder.

Cross-linked brakes - why there are two brake circuits.
In the rendering of the master brake cylinder above, you'll see there are two plungers and two brake circuits. This is the most common design for cars today. It's a form of redundancy in the brake system. The idea is that only two brakes, one front and one rear, are on either of the brake circuits. For four brakes, you therefore need two circuits. But why? Well imagine one of your brake lines springs a leak - for the sake of argument, the front-left brake. If all four brakes were on a single circuit, when the master cylinder began to pressurise the brake system, fluid would spurt out of the broken line and pressure would never build up. In turn, that means none of the brakes would ever come on and you'll sail merrily into the back of the vehicle in front of you. Imagine the same scenario with two circuits. As the first circuit pressurises the front-left and rear-right brakes, fluid spurts out of the broken line and those brakes are never applied. However because the master cylinder is also pressurising a separate second circuit connected to the front-right and rear-left wheels, those brakes do apply and you've still got braking force. Sure, it's reduced, but it's a hell of a lot better than no brakes at all. Because of the front-left to rear-right and front-right to rear-left linking of the brake circuits, this type of system is known as cross-linked brakes. The rendering below shows an example arrangement of cross-linked brakes.

http://www.carbibles.com/brake_bible.html (24 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

A word about handbrakes.
It's worth spending a moment here to talk about handbrakes. Or parking brakes, e-brakes or emergency brakes depending on where you come from. Whilst they're good for doing handbrake turns, they're not especially effective at actually slowing you down. They will - don't get me wrong - but you won't be seeing any stellar performance out of them so the term 'emergency brake' is a bit of a misnomer. So why is this? Well, handbrakes are cable-actuated for a start so the amount of power they have is wholly dependent on the amount of tug you have in your arm. There's no hydraulic system to help you out. Apart from that, they only work on the rear wheels, so you're not getting four-wheel braking. On drumbrakes, the handbrake is connected to a small lever that pivots against the end of one of the brake actuating pistons. When you pull the handbrake, the lever gets pulled and the brake shoes are pressed out against the inside of the drum. On disc brakes, the handbrake normally works a second set of brake pads in the rear caliper. They're little spots, about the size of a grown man's thumbprint and they're clamped mechanically against the brake rotor. These pads never need changing because they're normally only used at standstill so generally don't wear much. Their small size is the other reason you shouldn't expect stellar stopping performance if you yank on the handbrake. That being said, there are derivatives of disc-based handbrakes that use a mechanical arm to press the main brake pads against the rotor although these are less common as far as I know.

When to use handbrakes
Typically you ought to use your handbrake whenever you're stopped somewhere, be it parked, on a hill or waiting at traffic lights. The reason is simple : if you're parked or stopped, you generally don't want the car to run off without you. At traffic lights, it's an accident minimisation function as much as anything. If you're sitting there with your foot on the brake and someone drives into the back of you, the impact will cause you to take your foot off the brake and you'll go sailing into the car in front, causing more accidents. If you have the handbrake on in the same scenario, your car will largely stay put (apart from the initial shove across the ground as the energy from the impact is dissapated through your tyres). Of course there are personal habits and mechanical complications to contend with here. For example in a car with an automatic gearbox, it's force of habit to just use the footbrake. Even so, you should still use the handbrake when you're parked, especially on an incline. The 'park' setting on automatic gearboxes isn't sufficient to hold a car on a hill, and apart from that, it puts incredible strain on the transmission and clutch system if you let the whole weight of the car transfer into the transmission to try to keep it from moving. In some American cars, the handbrake isn't a handbrake at all, it's a second footbrake on the far left side of the footwell, which is basically totally useless because it's a pain to put on and even more of a pain to get off because it's a one-way ratchet system (you have to force the pedal all the way down to get it to release). Then there's the ignorance factor. When I went to my new owners orientation evening after buying a Subaru in America, one lady asked what the parking brake was for. (Apparently the name wasn't obvious enough). The dealer representative told her it was a relic of days gone by, not
http://www.carbibles.com/brake_bible.html (25 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

to be used, and he didn't understand why manufacturers even put them in cars any more!

When not to use handbrakes
The first and most obvious answer to this is : when you're going at any speed. If you yank on the handbrake at any speed much over 30km/h, the back end of your car will start to slide. Great for stunts and tricks, not so great if you're trying to stop in 5 lanes of crowded motorway traffic. The other time you should not use your handbrake is in post-snow, freezing conditions. With the salt and grit that gets put down on the roads, you'll be driving through a salty, snowy slush and it will be spraying all over the underside of your car. If you park and put the handbrake on, you risk it binding on by freezing. Why? Well handbrake cables are almost always exposed to the elements at some point under your car. If you put the handbrake on and the cable is covered in slush, as it freezes again it will lock the handbrake on. There's no solution to this other than waiting for the weather to warm up. Well, not unless you fancy a crack at the Darwin Awards, because some people have tried using blowtorches to thaw the ice, not understanding that they were working right underneath the petrol tank. So here's a tip : don't. If you need to park in those types of conditions, try to find level ground and leave your automatic gearbox in "p" or your manual gearbox either in first or reverse gears.

Regional variations
One last thing to know about handbrakes : for some reason, from-the-factory settings on handbrakes vary largely with region. In Europe for example, the handbrake is easily capable of exerting enough friction to prevent the engine from being able to move the car from standstill. In America, it's not uncommon to see handbrakes adjusted to lightly that even when fully on, you can just drive off. The only way you'll notice is the handbrake light on the dash, the lack of performance, or the smell of burning as your rear brakes burn off.

Anti lock Braking Systems - ABS
Stop without skidding, and maintain control of the vehicle. That's the premise of ABS. It was first introduced in the 1980's and has been undergoing constant refinement ever since. The system is typically comprised of 4 ABS rings, 4 sensors, an ABS computer and a number of pressure-management circuits in the brake lines. The ABS rings are attached either to the wheels, or more often, to the brake discs. They look like a notched ring - see the image to the right. The sensors are magnetic field sensors which are held very close to the ABS rings and can detect the slight change in magnetic field as the teeth on the ring pass them. The pulsing field tells the ABS computer that the wheels are spinning, and how fast they're spinning. When you brake, the wheel rotation starts to slow down. The ABS computer "listens" to the input from the sensors and can detect if one wheel is slowing down much quicker than the others - the precursor to the wheel locking up. (This all happens in milliseconds, by the way). When the computer detects this condition, a pressure regulator in the brake circuit interrupts the pressure in the brake lines by momentarily reducing it so that the brakes release just enough to give the wheels a chance to keep spinning rather than locking up. The computer then instructs the regulator to re-apply full pressure and again measures the wheel rotation. This on/off/measure cycle happens around 15 to 30 times a second. If the ABS kicks in, you'll feel it through the brake pedal as a vibration because the pulsing in the brake circuit affects all the components.

Newer generation ABS systems
As technology marches on, so does the control / feedback system used in ABS. It used to be the case that any single wheel approaching lockup would cause the ABS system to pulse the brake pressure for all the wheels. With the latest vehicles, the ABS computer is connected to 4 pressure regulators instead of just the one. This means it can selectively apply pulsed braking only to the wheel(s) that need it. So if three of the tyres are gripping well, but the front-left is beginning to skid, the ABS can unlock the front-left brake and pulse it to try to regain grip. It's called three- or four-circuit ABS and it's all very James Bond. When hooked up to the traction control system, this type of multi-circuit ABS can also be used to influence the overall traction of a car in extreme
http://www.carbibles.com/brake_bible.html (26 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

maneuvers, such as helping to prevent rollover and inside-wheel-lifting.

ABS and skid control
So how to talk about the biggest misconception about ABS - that it will make you come to a stop more quickly? This is a prickly subject to talk about. In one camp you have drivers like me who just can't stomach the idea of a computer breaking the physical connection between my right foot and the brake system. Whilst in the other camp you have people who believe that ABS is the best thing since sliced bread. It's these people in the second camp who have the all-out belief that ABS will help you stop faster, and in certain conditions, this is true. On a wet or greasy road surface where the traction is severely reduced, an ABS system can pulse the brakes and prevent lockup much better than a human can. But why? The whole point of brakes is to slow you down. To do that they rely on friction in two places - between the brake pads and the rotors, and between the tyres and road surface. If one of those factors is taken out of the equation, the brakes become useless. The most typical situation is that a driver will panic-react to something and step on the brakes with as much power as they can muster. The brake system amplifies this power, grabs hold of the brake rotors and the wheels stop turning almost instantly. This causes the tyres to now skid across the road surface, and as they do so, they become subject to dynamic attrition. In other words, if a tyre is rotating and gripping the road, the "stick" factor is much higher than if the wheel is locked and skating across the same surface. So that's what ABS does - in an emergency, it ensures that the wheels don't lock up but instead keep spinning so that the tyres maintain grip with the road. (That's where ABS gets its name - Anti-Lock Brakes.) This is where the real benefit of ABS comes into play. If you're going to attempt to avoid an accident, the best thing to do is to try to steer around it. If your tyres are skidding on the road surface, you can point your wheels pretty much wherever you want because the actual direction you end up going will have nothing to do with the wheels and everything to do with the direction you were travelling, combined with the camber of the road. Once the tyres lose grip, all bets are off. With ABS, if those wheels keep turning and the tyres keep gripping, then when you ham-fistedly grab the steering and yank it to one side, the car will still turn and you might be able to avoid the accident. So that's the true essence of ABS - to maintain control over the direction of the car.

So why the negativity, Chris?
My bone of contention with ABS is not so much to do with the technology as the placebo effect is has on drivers. ABS is widely misunderstood and if you ask most drivers, they'll tell you that ABS helps them to stop more quickly, and as I illustrated above, in certain conditions this is true. But even the most well-trained driver is going to be subject to panic in an emergency, and more often than not, will lock their arms on the steering wheel bracing for the coming impact. Once you do this, you're no longer steering so the ABS is trying to give you control over your car but you're not taking advantage of it. Given that this is the most natural human instinct, people accept this as "the way of crashes" but somehow believe that if they have ABS, they'll be able to stop before they get to the point of impact, and that's simply not true. I believe too many people think ABS gives them a license to drive faster, because they mistakenly believe that it will get them out of any situation. It's yet another technical placebo that has been put into vehicles which is making the standard of driving worse. The more gadgets and "driver aids" that get put into a car, the worse the drivers become because they live in a rose-spectacled world where they believe that it's the car's responsibility to get them out of any sticky situation that might arise. It bothers me so much I have a "rant" page dedicated to it here : Nanny Cars.

Political correctness and the push for ABS in every vehicle
It's a widely perpetrated myth that speeding is the cause of most accidents, so it follows that if you can develop a method of helping drivers to bring their vehicles to a stop in a more controlled fashion, you'll help to reduce the number of accidents. Good idea, but it doesn't have a lot of substance to it. If you check my page with studies on the facts vs. the fiction of speeding, you'll see that only 4% of all accidents are caused by loss of control of the vehicle with excessive speed as the primary contributing factor. So ABS wasn't really designed for that - it's difficult to reduce the incidence of the already lowest cause of motoring-related accidents. In truth, distracted drivers (like I mentioned above, driving in their cosetted mobile living rooms), their actual ability to drive properly (training and advanced driver courses) and their ability to have some form of spatial awareness are much bigger factors than speed itself and none of those can be overcome by clever braking systems. Shouldn't we be pushing for more driver training programs to attempt to treat the real cause of the accidents rather than simply putting a bandage on the result? So what about the emotive issue of pedestrian accidents? What if you, the driver, could stop quicker? It's a staggering fact that 84% of vehicle-pedestrian accidents are actually the pedestrian's fault and in most of those cases, even if you could
http://www.carbibles.com/brake_bible.html (27 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

have stopped on a dime, the accident would not have been prevented. Seriously. Read the the facts vs. the fiction of speeding page - you'll be astonished. I'm not condoning running over pedestrians - that would be stupid. I know firsthand what it's like - I had one of those 84% jog out in front of me using his cellphone when I was riding my motorcycle some years ago. I hit him square in the back despite being hard on the brakes, and threw him a good 10 metres down the road. He survived with some scrapes and bruises but I still think about it to this day. I can't begin to imagine what it would have been like if the stupid bugger had actually died.

ABS in snow and ice, and on gravel
Ah yes. The subject of a good 75% of the emails I get about ABS. The two camps for this argument are split almost exactly 50/50. In one camp, those like me who from experience would rather have their tyres lock up in deep snow to give me at least a fleeting chance of having them dig through the snow to find some road. Those who have anecdotal evidence that ABS is total crap in snow and ice. Whilst in the other camp, those who again believe ABS will somehow magically stop them from crashing in the same conditions. Those who have similar anecdotal evidence disproving all those in the first camp. ABS by its very nature is designed to stop the wheels from skidding by allowing them to keep turning. On deep packed snow and ice, that's exactly what they're going to do - skid, so ABS effectively removes a considerable amount of your braking in an emergency in these conditions. It's why some cars have ABS disable systems for snow and ice, and it's why ice racers yank the fuse to the ABS system before they even get in a car to race. The ABS Education Alliance, a group aiming to help educate drivers on how ABS will best benefit them, has this to say on the subject: Even in fresh snow conditions, you gain the advantages of better steerability and stability with four-wheel ABS than with a conventional system that could result in locked wheels. In exchange for an increased stopping distance, the vehicle will remain stable and maintain full steering since the wheels won't be locked. The gain in stability makes the increase in stopping distances an acceptable compromise for most drivers. So the short answer to this debate is that ABS is worse in snow and ice for overall stopping distance, but better for controlability.

The hidden gremlin of ABS - what they don't advertise.
If you look at the statistics for crashes, a large percentage of them are "fender benders" - low-speed impacts that only do a little damage and so slow that the vehicle occupants are in no danger; less than 15mph normally. I'll give you one guess what the typical "minimum activation speed" is for ABS. That's right. Your average ABS system is useless much below 15mph. Seriously. Try it yourself. Find an empty road on a slight downhill grade - even better if its on a dewy morning. Run your ABS-equipped car up to about 15mph and jam on the brakes as hard as you can. The car will skid to a stop and the ABS system will remain totally silent.

Aftermarket ABS systems
To the best of my knowledge, there's no such thing. A few years back a couple of companies tried to market what they called ABS systems that could be retrofitted to any vehicle. The product was a cylinder with a pressure-relief valve in it. The idea was that you inserted this system into the brake circuit somewhere. When you stomped on the brakes symptomatic of locking up the wheels - the pressure relief valve opened and bled off some brake fluid into the cylinder, thus lowering the braking pressure being sent to the wheels. The idea was to take the "spike" off the initial push of the brake pedal so it wasn't ABS at all. The whole idea of putting something like this into a brake circuit makes me shudder I wouldn't want to be the person trying to get their insurance and medical claims through after an accident when the investigators found one of these contraptions in their brake line!

A final thought on ABS
Consider this: if you're in an accident and your ABS works perfectly, you'll leave no skidmarks on the road surface. An inspection of the car will show the brakes and ABS system are working perfectly but the absence of skidmarks could
http://www.carbibles.com/brake_bible.html (28 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

lead the police accident scene investigator to believe you didn't brake at all. That in turn could lead to you being the "at fault" driver with all the consequences that involves. Think about it. This exact scenario happens many times every day. Amongst all those ABS-related emails I get, at least one a week is telling me about someone who's had this problem.....

Remember : ABS attempts to ensure that your car stops in the shortest distance possible for most road surfaces. It is not a substitute for you, the driver, paying attention to the road and your driving.

Brake-assist and collision warning systems
By 2006, brake-assist and accident warning systems were starting to find their way into consumer cars. I for one just don't like the idea. The manufacturers are reinforcing the misconception that the driver is no longer responsible for their actions. Volvo's collision warning system (CWS), for example, constantly monitors your speed and uses a radar with a 15° forward field of view to determine the distance to any object in front of you. If the distance begins to shrink but you don't slow down, the system sounds a buzzer and flashes a bright red light in a heads-up display to alert you. The brake pads are automatically placed against the discs and when the driver finally does use the brakes, the system monitors the pedal pressure. If the pressure is determined to be too light, the braking power is amplified by the system. It's a great idea, but the TV commercials for this system need some serious attention. Volvo's commercials actually show a woman driving a Volvo, arranging papers on her passenger seat and talking on a cellphone. When the collision warning system activates and she looks up, bemused, then applies the brakes to avoid running into a truck in front of her a truck that she would have seen and presumably slowed down for had she been paying attention. I know it's not meant to be taken this way, but that Volvo commercial actually appears to be promoting distracted driving - Volvo will attempt to save you from your own ineptitude because apparently it's just too inconvenient now to be paying attention to the road ahead. Rather than train drivers to understand that they need to be responsible for their actions, that they need to be alert to their surroundings and that they need to pay attention when they're driving, collision warning systems essentially attempt to treat the symptoms rather than trying to cure the problem itself. Brake-assist and auto-brakes go one step further. In some high end vehicle now (top end BMWs and Mercedes' for example), the collision-detection system is linked into the brakes like it is with the Volvo system, but it's also been given the flexibility to do all the braking for you. Adaptive cruise control, for example, will control the throttle just like a normal cruise control system, but will also apply the brakes if it determines that you're getting too close to the vehicle in front. Full auto-brakes will actually stop the car for you if you fail to respond. All these systems work in essentially the same way - they monitor the brake use and distance to the vehicle in front. If the computer thinks you're not braking hard enough, it will assist you. These systems are all very clever but they tread the thin ethical line. Just because engineers can make their vehicles do this doesn't mean they should. Consider this: with in-vehicle monitoring and tracking systems like OnStar, and the impending satellite-tracking systems for road tolling, it's not too hard to imagine all those systems chained together in such a way that the vehicle will literally prevent you from speeding by limiting the throttle availability and controlling the brakes. If you really want to be driven like that in a vehicle over which you have no control at all, take the bus. Now don't misunderstand me here - I think a lot of what Volvo do in vehicle safety is a good idea - the transparent Apillars, the blind-spot assist and things like that - they all go towards eliminating problems inherent with the design of cars. But I believe putting systems into a car that attempt to compensate for the ineptitude of the person behind the wheel is a mistake. But that's just my opinion.
Picture credit: Volvo

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

http://www.carbibles.com/brake_bible.html (29 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Other Brake Technologies
There are other brake technologies that are becoming available in vehicles now, and a lot of them are gathered together in the 2006 / 2007 BMW models. They're the rolling embodiment of clever brake engineers just showing off. Three of the more notable features are:
●

●

●

Brake Drying. The X3 has rain-sensing windscreen wipers. When they sense rain, they also send information to the onboard computer. In turn, it goes into a cycle of occasionally bringing the pads into light contact with the brake rotors. This generates enough friction to eliminate any film of water that might be on the surface of the rotors, but not enough that it slows the car down or is even detectable by the driver. Brake Stand-by. This is a pre-emptive system that attempts to detect when sharp braking is about to happen. Potentiometers attached the accelerator can detect when the driver takes their foot off it very quickly. That would normally be followed by the brake being applied very quickly. When the onboard computer senses this condition, it moves the brake pads right up to the rotors using the same mechanism that the brake drying system uses. Ultimately, if the driver does jump on the brakes, they're ready to work the millisecond the driver's foot touches the pedal. It may not sound much but that tiny difference in distance moved, translates into a saving in time between putting your foot on the brake and the car actually slowing down. That in turn translates into forward distance - or less of it. Brake Fade Compensation. Right up at the top of the page I explained what brake fade was. If the brake rotor temperature begins to rise, this system increases the hydraulic pressure used to press the pads against the rotors without requiring any more pressure on the brake pedal. I'm not sure if this system has a warning light or not, but it should otherwise drivers could end up driving on horribly faded brakes without realising it, and eventually, even the extra hydraulic pressure isn't going to help.

All the above devices fall into that ethical grey area again, but unlike the brake-assist and collision-detection systems outlined earlier, these three brake technologies don't actually attempt to compensate for any wrongdoing on the driver's behalf. They simply help prepare the car for when the driver chooses to use the brakes. From that point of view, I would regard these as better technologies than those which go the whole hog and interfere with your driving.

Brake hoses - not just rubber.
Obviously with all the pressure in your brake system, the last thing you need is for the brake lines themselves to deform and flex. If they do, you lose brake pressure, and thus lose braking. Steel brake lines are no problem, but for the flexible areas of the brake lines, you need hoses. Brake hoses come in two basic flavours.

Rubber hoses.
Ah the humble rubber hose. Only on your brake lines, not so humble. I don't recommend this but if you were to get under your car and cut one of your hoses in half, you'd notice a couple of things. First, it's amazing how quick all the brake fluid that spills out will stain your clothes and literally eat the paint off your car right in front of you. But second, and more importantly, the hose itself is actually made of three parts. The inner liner is a corrosion and brake-fluid resistant compound designed (normally PTFE / Teflon® based) purely to keep the brake fluid in. Around the outside of that, there's a steel webbed mesh. This is what gives the brake hose its strength and stops it from bulging and deforming. And around the outside of that there's a slightly thicker rubber coating, which is there to weatherproof the steel mesh. The three layers together give strength, flexibility and durability.

http://www.carbibles.com/brake_bible.html (30 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Steel-braided hoses.
Steel-braided hoses are a slightly different design. They only really have two components - the inner hose which carries the brake fluid and is lined with a PTFE compound, and the outer steel braid which contains and flexing or bulging. Steel-braided lines resist bulging a lot better which is why a lot of aftermarket tuners opt to put them on their vehicles. One downside is that the steel braiding itself is totally merciless and if it finds something to rub against in the vehicle, it will rub right through it, even if it's an alloy. For that reason, a lot of braided brake hose manufacturers put a third layer a thin transparent rubber sheath around the outside simply to keep everything in check and prevent scuffing and rubbing. I upgraded the lines on my Audi when I still owned it and put Goodridge steel braided hoses on. For a 15 year old car it did make a difference to the feel of the brake pedal. It didn't bring it up to modern standards, but it was better than the flexible, bendy rubber hoses that were on it from the factory.

http://www.carbibles.com/brake_bible.html (31 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

Where to get brake part replacements.
This seems like as opportune a place as any to mention that there are plenty of places on the internet and locally that will do you proud for brake parts and components if you decide to do it yourself. If you're looking for a good place to start shopping online, the brake lines and brake pads sections at AutoAnything seem as good a place to start as any. I mention them only because they sell the same Goodridge kits I mentioned above, and I was well chuffed with what that kit did to my Audi. One other thing : if you're going to be doing it yourself, a good shop manual is an absolute necessity because if there's one system on your car you don't want to be cocking up, it's the brakes.

Brake fluids.
As mentioned elsewhere on the page, brake fluid does not compress. It's a good job too - if you put your foot on the brake pedal and it went all the way to the floor, you'd be worried. But that's exactly what can happen if you disregard the "health" of your brake fluid. Brake fluid is hygroscopic - that means it attracts and soaks up water. This is why it comes in sealed containers when you buy it, and why when the crazy guy four doors down offers you some of the 15 gallons of brake fluid he's had in his garage since the war, you should turn him down. The problem with it being hygroscopic is that if it does start to take on water, Bad Things can happen. Pull up a chair and allow me to explain. Your typical DOT 4 brake fluid (see later for DOT ratings) boils at about 446°F (230°C). Water boils at 212°F (100°C). Imagine your brakes are getting hot because of a long downhill stretch. Whilst the brake fluid is quite OK, the temperature of the brake components might get up over the boiling point of water. If that happens, the water boils out of the brake fluid and forms steam - a compressible gas. Next time you put your foot on the brake, rather than braking, all the pressure
http://www.carbibles.com/brake_bible.html (32 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

in the brake system is taken up with compressing the steam. Your brakes go out, you don't stop. Getting a little more complex, the boiling point of a liquid goes up with its pressure (Physics 101). So when you step on the brake, the boiling point of the brake fluid might actually go up to 500°F (260°C) and the boiling point of the water content might raise up to 250°F (121°C). This is great, you might think, because now the boiling point is higher than the temperature of the brake fluid. At least it is until you take your foot off the brake again. Now the pressure in the system returns to normal, the boiling points revert to normal and instantly the water boils off into steam again. The symptoms are slightly different now. Under this scenario, the brakes work the first one or two times, but on the third or fourth press, they stop working because now the temperature and pressures have conspired to boil the water. The worst possible scenario is brake-fade (see right at the top) combined with air in the system. If this has happened to you, then you're likely reading this page from beyond the grave, because in most accidents where weak brakes become no brakes, there aren't any survivors.

D.O.T ratings
All brake fluids are DOT rated. Your owners handbook for your car or motorbike probably tells you to use DOT3 or DOT4 from a sealed container. The DOT ratings are a set of minimum standards the fluid must adhere to in order to get the rating, and thus work in your braking system. The following table shows the various properties of DOT ratings. Remember that the values here are the minimum values. Most manufacturers make sure their product far exceeds minimum ratings.
Boiling Point DOT 3 DOT 4 DOT 5 (silicone-based) DOT 5.1 (non-silicone based) Dry Wet 401°F 284°F 446°F 311°F 500°F 365°F 500°F 365°F

The "dry" and "wet" boiling points in the table above are for brake fluid which is fresh from the bottle (dry) and which has a 10% water content (wet). A DOT study in 2000 discovered that on average, the brake fluid in a vehicle absorbs about 2% water every 12 months. The two types of brake fluids shown in the table are DOT3/DOT4/DOT5.1 which are glycol (Polyalkylene Glycol Ether) based, and DOT5 which is silicone based. DOT3 and DOT4 fluids are interchangeable* - the only real difference is their boiling point. Theoretically you could interchange DOT4 and DOT5.1 fluids too but I wouldn't recommend it. DOT3/4/5.1 and DOT5 fluids cannot be mixed or interchanged under any circumstances. They mix like oil and water (ie. they don't) and the silicon based fluids can destroy the seals in brake systems which rely on the moisturiser additives that are present in DOT3/4/5.1 fluids. Other things you ought to know about silicone based fluids: - they are resistant to absorbing water, which is why their wet boiling points are so high. Problem is that any water content eventually pools in the low spots of the brake system and causes rust. - they don't strip paint. - they are not compatible with most ABS system because they doesn't lubricate the ABS pump like a glycol based fluid. - putting this fluid in systems which have had DOT3/4 fluid in will cause the seals in the caliper and master cylinders to malfunction. Which means they need replacing. Which is expensive. Oh, and don't ask me why DOT5.1 is glycol and DOT5 is silicon based. It doesn't make and sense to me either. * There has been some discussion as to the use of DOT4 fluid in Toyotas that recommend DOT3 fluid - apparently something in the Toyota braking system doesn't play well with DOT4 fluid, particularly the master brake cylinder seals. The discussion about this can be found in the archives at the UK Pruis yahoo group.

Brake warning lights
Most cars nowadays have a brake warning light on the dash. Its purpose is to alert you that something is wrong in the braking system somewhere. If it comes on, check your owner's manual to find out its meaning. Unlike the single-purpose ABS warning light, the brake warning light doesn't have a standard meaning; it could be used for multiple purposes. For example, the same light may be used to show that the hand brake (parking brake for the Americans amongst you) is on. If that's the case and you're driving, you ought to have noticed the smell of burning brake dust by now.
http://www.carbibles.com/brake_bible.html (33 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

The light can also indicate that the fluid in the master cylinder is low. Each manufacturer has a different use and standard for this light. Which is nice. Because it would be such a drag if the same indicator meant the same thing in every vehicle.

If you've got an ABS-equipped car, you also have a second light - the ABS light. If it comes on, get it seen to as soon as possible. It means the ABS computer has diagnosed that something is amiss in the system. It could be something as simple as dirt in one of the sensors, or something as costly as an entire ABS unit replacement. Either way, if that light is on, then you, my friend, have got 1970's brakes. It's important to note that this light normally comes on when you start the car and then switches off a few seconds later. If it stays on, blinks, throbs, flashes or in any other way draws your attention to itself, take note. It's not doing it just to please itself.

If you see this light on your dashboard, then congratulations - you're flying the service module on an Apollo mission. The bad news is that you've got a current drain somewhere and your main batteries are critically low. Either way, drop me a line and let me know how you snagged a seat on a spaceflight - I'm dying to know.

And finally....LED replacement bulbs
You might have seen websites and automotive shops stocking LED replacement bulbs for cars and motorbikes. The most basic replacements look like those on the right - a cluster of 19 or 24 LEDS (light emitting diodes) in a housing with a regular push-fit or bayonet plug on the back. The idea is that if you want brighter lights, you can replace your tail or turn lights with these LED replacements. There is a gotcha though that the manufacturers often hide in the smallest of small print. A lot of vehicles (cars and motorbikes) have onboard diagnostics which include a light check. Some of these use resistance to figure out if a bulb has blown. LED clusters have a radically different resistance to a filament bulb and its possible that when you replace your bulbs with LED versions, your car will continuously tell you that one or more bulbs is burned out. Getting one step more severe, if you use LED turn bulbs, your indicators could flash quicker or slower than you're used to (indicator circuits use the natural resistance of the bulbs in conjunction with the relay to dictate the flash speed). The worst case scenario though is ABS; some motorbikes have very tightly regulated voltages in their ABS systems and taking the filament bulb out of the brake light to replace it with an LED bulb can cause ABS errors and theoretically, an ABS shutdown. Granted thats worst-case scenario, but it is a possibility. The way around all these electrical load problems is to add resistance or ballast to the bulb replacement, and this is becoming more common now. Essentially, resistors are added in-line with the LEDs to provide the same sort of resistance to current flow that an incandescent bulb would, thus making the retrofit kits far more compatible with existing car or motorbike electrical systems. CycoActive make kits like this for motorbikes now. You can see an example on the left here which shows the LED unit as a complete replacement for the tail unit on a bike, with a bayonet connector to fit into the old socket. The blue items are the ballast resistors designed to induce sufficient load in the electrical system for
http://www.carbibles.com/brake_bible.html (34 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Brake Bible

the diagnostics to register the unit as a regular lightbulb.

Picture credits: Cycoactive

Truck Accessories: Brake Pads, Brake Kit.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/brake_bible.html (35 of 35) [2/6/2008 7:12:17 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

The Fuel and Engine Bible, covering everything you need to know about fuel, petrol, gasoline, octane rating, power, bhp, gas types and grades, 4-stroke and 2-stroke engines, how combustion engines work, carburettors, fuel injection, tuning, tweaking, nitrous, turbos, superchargers, chipping, hybrids, how to keep your engine running at peak fitness and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Page 1 ------ Page 2 ------ Page 3

Suck, squeeze, bang, blow.
Not a sexual maneuver, but rather the common description for how an internal combustion engine works. The basic way all internal combustion engines work is to suck in a mixture of fuel and air, compress it, ignite it either with a spark plug or by self-igntion (in the case of a diesel engine), allow the explosion of combusting gasses to force the piston back down and then expel the exhaust gas. The vertical movement of the piston is converted into rotary motion in the crank via connecting rods. The crank then goes out to the gearbox via a flywheel and clutch, and the gearbox sends the rotary motion to the wheels, driving the vehicle forwards. The following diagram is for reference for the technical jargon that will pop out on the rest of this page. It shows an inline4 engine with dual overhead cams.

http://www.carbibles.com/fuel_engine_bible.html (1 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

Engine layouts
Below are some illustrations of the most common types of cylinder layout you'll find in engines today. Singles are typically used in motorbikes, snowblowers, chainsaws etc. V-twins are also found in motorbikes. The triple is almost unique to Triumph motorbikes where they call it the Speed Triple, or the 675. Inline-fours are the mainstay of car engines, as well as being found in some motorbikes too such as the BMW K1200S. Inline fives used to be used a lot in Audis but have found a new home in current Volvos. The V5 is something you'll find in some VWs. The V6 has the benefits of being smoother than an inline-four but without the fuel economy issues of a V8. Boxer engines are found in BMW motorbikes (twins) and Porsches and Subarus (fours and sixes). You had no idea, did you?

http://www.carbibles.com/fuel_engine_bible.html (2 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

The difference between 4-stroke and 2-stroke engines
First, some basic concepts. Well one basic concept really - the most common types of internal combustion engine and how they work. It's worth reading this bit first otherwise the whole section on octane later in the page will seem a bit odd.
http://www.carbibles.com/fuel_engine_bible.html (3 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

Almost every car sold today has a 4-stroke engine. So do a lot of motorbikes, lawnmowers, snowblowers and other mechanical equipment. But there are still a lot of 2-stroke engines about in smaller motorbikes, smaller lawnmowers, leaf-blowers, snowblowers and such. The difference between the two engine types is the number of times the piston moves up and down in the cylinder for a single combustion cycle. A combustion cycle is the entire process of sucking fuel and air into the piston, igniting it and expelling the exhaust. There are two other types of engines - rotary or wankel engines, only used by Mazda in their "R" sports cars, and diesel engines. As this page gets updated, those will be dealt with accordingly.

2-stroke engines
A 2-stroke engine is different from a 4-stroke engine in two basic ways. First, the combustion cycle is completed within a single piston stroke as oppose to two piston strokes, and second, the lubricating oil for the engine is mixed in with the petrol or fuel. In some cases, such as lawnmowers, you are expected to premix the oil and petrol yourself in a container, then pour it into the fuel tank. In other cases, such as small motorbikes, the bike has a secondary oil tank that you fill with 2-stroke oil and then the engine has a small pump which mixes the oil and petrol together for you. The simplicity of a 2-stroke engine lies in the reed valve and the design of the piston itself. The picture on the right shows a 4-stroke piston (left) and a 2-stroke piston (right). The 2-stroke piston is generally taller than the 4-stroke version, and it has two slots cut into one side of it. These slots, combined with the reed valve, are what make a 2-stroke engine work the way it does. The following animation shows a 2-stroke combustion cycle. As the piston (red) reaches the top of its stroke, the spark plug ignites the fuel-air-oil mixture. The piston begins to retreat. As it does, the slots cut into the piston on the right begin to align with the bypass port in the cylinder wall (the green oblong on the right). The receding piston pressurises the crank case which forces the reed or flapper valve (purple in this animation) to close, and at the same time forces the fuel-airoil mixture already in the crankcase out through the piston slots and into the bypass port. This effectively routes the mixture up the side of the cylinder and squirts it into the combustion chamber above the piston, forcing the exhaust gas to expel through the green exhaust port on the left. Once the piston begins to advance again, it generates a vacuum in the crank case. The reed or flapper valve is sucked open and a fresh charge of fuel-air-oil mix is sucked into the crank case. When the piston reaches the top of its travel, the spark plug ignites the mixture and the cycle begins again.

http://www.carbibles.com/fuel_engine_bible.html (4 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

For the same cylinder capacity, 2-stroke engines are typically more powerful than 4-stroke versions. The downside is the pollutants in the exhaust; because oil is mixed with the petrol, every 2-stroke engine expels burned oil with the exhaust. 2-stroke oils are typically designed to burn cleaner than their 4-stroke counterparts, but nevertheless, the 2-stroke engine can be a smoky beast. If, like me, you grew up somewhere in Europe where scooters were all the rage for teenagers, then the mere smell of 2-stroke exhaust can bring back fond memories. The other disadvantage of 2-stroke engines is that they are noisy compared to 4-stroke engines. Typically the noise is described as "buzzy".

4-stroke engines
4-stroke engines are typically much larger capacity than 2-stroke ones, and have a lot more complexity to them. Rather than relying on the simple mechanical concept of reed valves, 4-stroke engines typically have valves at the top of the combustion chamber. The simplest type has one intake and one exhaust valve. More complex engines have two of one and one of the other, or two of each. So when you see "16v" on the badge on the back of a car, it means it's a 4cylinder engine with 4 valves per cylinder - two intake and two exhaust - thus 16 valves, or "16v". The valves are opened and closed by a rotating camshaft at the top of the engine. The camshaft is driven by either gears directly from the crank, or more commonly by a timing belt. The following animation shows a 4-stroke combustion cycle. As the piston (red) retreats on the first stroke, the intake valve (left green valve) is opened and the fuel-air mixture is sucked into the combustion chamber. The valve closes as the piston bottoms out. As the piston begins to advance, it compresses the fuel-air mix. As it reaches the top of it's stroke, the spark plug ignites the fuel-air mix and it burns. The expanding gasses force the piston back down on its second stroke. At the bottom of this stroke, the exhaust valve (right green valve) opens, and as the piston advances for a second time,
http://www.carbibles.com/fuel_engine_bible.html (5 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

it forces the spent gasses out of the exhaust port. As the piston begins to retreat again, the cycle starts over, sucking a fresh charge of fuel-air mix into the combustion chamber.

Because of the nature of 4-stroke engines, you won't often find a single-cylinder 4-stroke engine. They do exist in some off-road motorbikes but they have such a thump-thump-thump motion to them that they require some large balancing shafts or counterweights on the crank to try to make the ride smoother. They also take a little longer to start from cold because you need to crank the single piston at least twice before a combustion cycle can start. Any more than one piston and the engine gets a lot smoother, starts better, and is nowhere near as thumpy. That's one of the advantages of V6 and V-8 engines. Apart from the increased capacity, more cylinders typically means a smoother engine because it will be more in balance. Geek trivia: Mercedes-Benz needed to increase the performance of their diesel passenger cars back in the 70's as their market share in the US was increasing. As professionals with big V-8 luxury cars were trading them in for 2.4l diesels, the demand for performance had to be addressed. Mercedes did not want to retool their 114/115 series chassis and there wasn't enough room in the engine bay for a six cylinder diesel. There was, however, room for a straight-5. Benz engineers just hung another cylinder on the back of the 4 cyl block and presto! The five cylinder engine was born. This engine acquired a lot of status among the high line car owners. When Audi introduced the C2 series cars (the 5000 in America, the 100 in Europe) in 1976, they offered a 5-cylinder petrol engine too. It was basically a 1.8 litre 4cylinder engine with an extra cylinder. That took it up to 2.0 litres but the fifth piston made such an enormous difference to the smoothness of the engine that it was often mistaken for a V6 or V8. Why only 5 cylinders instead of going for a V6? Partly for the same rationale as Mercedes (and it was a really tight fit) but primarily because Benz had made the straight5 configuration fashionable. A straight-5 was also more fuel-efficient than a V6. It's also worth pointing out that nowadays, both Audi and VW have V5 engines with three cylinders in one bank and two in the other. Same smoothness,
http://www.carbibles.com/fuel_engine_bible.html (6 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

better gas-mileage.

4-stroke Diesel Engines
Mechanically, 4-stroke diesel engines work identically to four-stroke petrol engines in terms of piston movement and crank rotation. (To be historically accurate, petrol engines are mechanically similar to diesel engines - diesel engines came first) It's in the combustion cycle where the differences come through. First, during the intake cycle, the engine only sucks air into the combustion chamber through the intake valve - not a fuel/air mix. Second, there is no spark plug. Diesel engines work on self-ignition, or detonation - the one thing you don't want in a petrol engine (see the section on Octane later). At the top of the compression stroke, the air is highly compressed (over 500psi), and very hot (around 700 °C - 1292°F). The fuel is injected directly into that environment and because of the heat and pressure, it spontaneously combusts (this system is known as direct-injection). This gives the characteristic knocking sound that diesel engines make, and is also why pre-igniting petrol engines are sometimes refered to as 'dieseling'. Petrol engines typically run compression rations around 10:1, with lower end engines down as low as 8:1 and sportier engines up near 12:1. Diesel engines on the other hand typically run around 14:1 compression ratio and can go up as high as 25:1. Combined with the higher energy content of diesel fuel (around 147,000 BTU per gallon versus 125,000 BTU for a gallon of petrol), this means that the typical diesel engine is also a lot more efficient than your common or garden petrol engine, hence the much higher gas-mileage ratings. Because of the design of the diesel engine, the injector is the most critical part and has been subjected to literally hundreds of variations in both design and position. It has to be able to withstand massive pressures and temperatures, yet still deliver the fuel in a fine mist. One other component that some diesel engines have is a glowplug. From cold, some lowertech engines can't retard the ignition enough, or get the air temperature high enough on startup for the spontaneous combustion to happen. In those engines, the glowplug is literally a hot wire in the top of the cylinder designed to increase the temperature of the compressed air to the point where the fuel will combust. These engines typically have a pictograph on the dashboard that looks like a lightbulb. When starting the engine cold, you need to wait for that light to go out - basically you're waiting for the glowplugs to get up to temperature. In really old diesel designs, this could be as long as 10 seconds. Nowadays it's nearly instantaneous, or in the case of advanced ECM systems, not needed at all.

2-stroke Diesel Engines
Would you believe there is such a thing as a 2-stroke diesel engine? The two-stroke cycle described above turns out to be highly beneficial for the diesel model, the major difference being the inclusion of exhaust valves at the top of the cylinder. The burn cycle works similarly too. At the top of the piston travel, the air is hot and compressed, just like in a 4-stroke diesel. And like the 4-stroke, the injector sprays fuel in at that point and it self-combusts. As the gasses expand, the piston is forced downwards and towards the bottom of its stroke, the exhaust valves on the top of the cylinder open. Because the gas is still expanding at this point, the combustion chamber empties itself through the open valves. At the very bottom of the power stroke, the piston uncovers the air intake and pressurised air fills the combustion chamber forcing the last remnants of the exhaust gas out. As the piston begins its compression stroke, the exhaust valves close and the air is compressed and voila - a two-stroke diesel engine. The other difference between a 4-stroke and 2-stroke diesel engine is that the 2-stroke variety must have a turbocharger or supercharger; you'll notice I mentioned the air intake fills the cylinder with pressurised air. That doesn't happen by magic. As with 2-stroke petrol engines, every downward piston stroke is a power stroke, meaning the 2-stroke engine has the potential to product twice as much power as its 4-stroke sibling. Typically you'll find 2-stroke diesels in maritime engines (like those on freighters, tankers and cruise ships) and diesel-electric trains where more power is needed for the same size of engine.

Interference vs. non-interference engines
It's worth mentioning the two sub-types of 4-stroke engine at this point. Because the valves always open inwards, into the combustion chamber, they take up some space at the top of the chamber. In an interference engine, the position of the piston at the top of its stroke will occupy the same physical space that the open valves do whilst the piston is at the bottom of its stroke. It's important to know if your engine is an interference engine because if the timing belt breaks, at least one set of valves will stop in the open position and the momentum of the engine will ram the piston in that cylinder up into the valves requiring a very expensive engine repair or replacement. In a non-interference engine, the valves do not occupy any space that the piston could move into, so if your timing belt snaps on one of these engines, in 99% of
http://www.carbibles.com/fuel_engine_bible.html (7 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

cases you won't suffer any valve damage because the piston cannot physically touch the open valves. That is the technical explanation of why its important to get your timing belt changed at the manufacturer-specified mileage. The following picture shows the difference between the two types. On the left, circled in red is where the open valve interferes with the position of the piston at the top of its travel. On the right, a non-interference engine shows there is still a gap at the same point (exaggerated for my picture).

Top Dead Centre (TDC) and ignition timing
When a piston in an engine reaches the top of its travel, that point is known as Top Dead Centre or TDC. This is important to know because I don't think any engine actually fires the spark plug with the pistons at TDC. More often than not, they fire slightly before TDC. So how does your ignition system work, and what is ignition timing all about? Well generating the spark is the easy part. The electrical system in your car supplies voltage to your coil and ignition unit. The engine will have a trigger for each cylinder, be it a mechanical trigger (points), electronic module or crank trigger. Whatever it is, at that point, the engine effectively sends a signal to the coil to discharge into the high voltage system. That charge travels into the distributor cap and is routed to the relevant spark plug where it is turned into a spark. The key to this, though, is the timing of the spark in relation to the position of the piston in the cylinder. Hence ignition timing. Having the spark ignite the fuel-air mixture too soon is basically the same as detonation and is bad for all the mechanical components of your engine. Having the spark come along too late will cause it to try to ignite the fuelair mixture after the piston has already started to recede down the cylinder, which is inefficient and loses power. Timing the spark nowadays is usually done with the engine management system. It measures airflow, ambient temperature, takes input from knock sensors and literally dozens of sensors all over the engine. It then has an ignition timing map built into its memory and it cross references the input from all the sensors to determine the precise time that it should fire the spark plug, based on the ignition timing map. At 3000rpm, in a 4 cylinder engine, it does this about 100 times a second. In older systems, the spark timing was done using simple mechanical systems which had nowhere near the ability to compensate for the all the variables involved in a running combustion engine. Typically as an engine revs quicker, the ignition timing needs to advance because the spark needs to get to the cylinder more quickly due to the engine running faster. In modern systems, this is all taken account of in the ignition timing map. On older mechanical system, they used mechanical or vacuum advance systems, so that the more vacuum generated in the intake manifold (due to the engine running quicker), the more advanced the timing became.

Checking ignition timing
Despite the speed that an engine turns, it is possible for mere mortals like you and me to be able to check the ignition timing or an engine using (and you'd have never guessed this) an ignition timing light. Timing lights are typically strobe
http://www.carbibles.com/fuel_engine_bible.html (8 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

lights. They work by being connected to the battery directly and then having an induction coil clamped around one of the spark plug leads - normally the first or last cylinder in the engine depending on the manufacturer. When the engine fires the spark plug for that cylinder, the inductive loop detects the current in the wire and flashes the strobe light once. So if the engine is ticking over at 1100rpm, the strobe will flash 550 times a minute (four stroke engine, remember?). Fantastic. So you're now holding a portable rave lighting rig but how does this help you see the timing of an engine? Well it's simple. You must have seen strobe lights working somewhere - a rave, a stage show - they're used to effectively freeze the position of something in time and space by illuminating it only at a certain point and for a fraction of a second. Shooting a strobe at someone walking in a dark room will result in you seeing them walk as if they were a flip-book animation on a reel of film. This effect is what's used to visualise the timing of your engine. Somewhere on the front of the engine there will be a notch near one of the timing belt pulleys and stamped into the metal next to it will be timing marks in degrees. On the pulley itself there will be a bump, recess or white-painted blob. When you point the strobe light down towards the timing belt pulley, remember it fires once for each firing of the cylinders? Each time it fires, the white blob on the pulley should be at the same position in its rotation - the strobe fires once for each ignition spark at which point the mark should be in the same place, and the effect to you is that the whole pulley, timing mark and all, are now standing still in the strobe light. The mark on the pulley will line up with one of the degree marks stamped on the engine, so for example if the white dot always aligns with the 10° mark, it means your engine is firing at 10 degrees before TDC. When you rev the engine, the timing will change so the mark will move closer or further away from the TDC mark depending on how fast the engine is spinning. Note that in some engines, the two marks are simply painted or stamped, and there are no degree markings. In this case, the marks align when the first piston is exactly at TDC.

Check the timing marks first
After all that, it's worth pointing out that crank timing marks can be way off so it's worth confirming that your TDC marker is actually TDC before pratting about with the timing. It's not as bad now as it used to be, but in the bad old days, Rover V8's were particularly bad for this, with some being as much as 12° off! So how you do confirm your TDC really is TDC? Small cameras, a good set of feeler gauges, some cash and someone who knows what they're doing.

Timing marks on cam belt pulleys
The same timing marks exist stamped into the metal near, and on the pulley on the end the cam. Essentially these marks are used to line up the cam to the correct position when you're changing the timing belt. You have to make sure the engine is rotated to TDC and that the cams are properly aligned too. If you don't, the cams will spin permanently out-of-synch with the engine crank and the engine will run badly, if at all. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Spark plugs
And engine without a spark plug is useless, unless it's a diesel engine in which case it uses a glowplug instead. But we're talking about regular petrol engines here so the next topic to get to grips with is the spark plug. It does exactly what it says on the tin - it's a plug that generates a spark. Duh. So why spend time talking about it? Well with apologies to George Orwell not all spark plugs are created equal. Some are more equal than others. They'll all do the job but the more you pay, the better the plug. All spark plugs share the same basic design and construction though.

http://www.carbibles.com/fuel_engine_bible.html (9 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

The high voltage from your vehicle's high-tension electrical system is fed into the terminal at the top of the spark plug. It travels down through the core of the plug (normally via some noise-suppression components to prevent electrical noise) and arrives at the centre electrode at the bottom where it jumps to the ground electrode creating a spark. The crush washer is designed to be crushed by tightening the spark plug down when it's screwed into the cylinder head, and as such, it helps keep the screw threads under tension to stop the spark plug from shaking loose or backing out. The insulator basically keeps the high-tension charge away from the cylinder head so that the spark plug doesn't ground before it gets a chance to generate the spark. The type of plug I've illustrated here is known as a projected nose type plug, because the tip extends below the bottom of the spark plug itself. The other main type of spark plug has the centre electrode recessed into the plug itself and merely grounds to the collar at the bottom. The advantage of the projected nose type is that the spark is better exposed to the fuel-air mixture. Ground electrode (ground strap) types.There are plenty of different types of grounding electrodes kicking around in spark plug designs nowadays, from 'Y' shaped electrodes (like SplitFire plugs) to grooved electrodes like you'll find on Champion plugs all the way up to triple-electrode plugs like the high-end Bosch items. They're all designed to try to get a better spark, and to that end, you'll now find all sorts of exotic materials turning up too. Titanium plugs, for example, have better electrical conductivity than brass and steel plugs, and the theory is that they'll generate a stronger, more reliable spark. Gapping a spark plug. Gapping a spark plug is the process of ensuring the gap between the two electrodes is correct for the type of engine the plug is going to be used in. Too large a gap and the spark will be weak. Too small and the spark might jump across the gap too early. Generally speaking, the factory-set spark plug gap is just fine, but if you're running an older engine, or a highly tuned engine, then you need to pay attention to the gap. Feeler gauges are used to measure the gap, and a gapping tool is used to bend the outer electrode so that the gap is correct. Heat ranges. Something that is often overlooked in spark plugs is their heat rating or heat range. The term "heat range" refers to the relative temperature of the tip of the spark plug when its working. The hot and cold classifications often cause confusion because a 'hot' spark plug is normally used in a 'cold' (low horsepower) engine and vice versa. The term actually refers to the thermal characteristics of the plug itself, specifically its ability to dissipate heat into the cooling system. A cold plug can get rid of heat very quickly and should be used in engines that run hot and lean. A hot plug takes longer to cool down and should be used in lower compression engines where heat needs to be retained to prevent combustion byproduct buildup.

How does the fuel-air mix happen? Magic?
You keep seeing me talk about fuel-air mix or fuel-air charge on this page, but I thought it wise to explain how this
http://www.carbibles.com/fuel_engine_bible.html (10 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

happens because it is pretty fundamental to the operation of internal combustion engines. The fuel and air are mixed in one of two main ways. The old-school method is to use a carburettor, whilst the newtech approach is to use fuel injectors. The basic purpose is the same though, and that is to mix the fuel and air together in proportions that keep the engine running. Too little fuel and the engine runs 'lean' which makes it run hot. Too much fuel and it runs 'rich' which conversely makes the engine run cooler. Running rich can also result in fouled up spark plugs, flooded engines and stalling, not to mention wasting fuel. Finding the right balance normally involves about 10 milligrams of petrol for each combustion stroke.

Carburettors
Advantages : analogue and very predictable fuelling behaviour, simple and inexpensive to build and maintain. Disadvantages : carburettor icing in the venturi, imprecise fuel metering, float chambers don't work well if they're not the right way up.

How they work.
A carburettor is basically a shaped tube. The shape of the tube is designed to swirl the incoming air and generate a vacuum in a section called the venturi pipe (or just the venturi). In the side of the venturi is a fuel jet which is basically a tiny hole connected to the float chamber via a pipe. It's normally made of brass and has a miniscule hole in the end of it which determines the flow of fuel through it. In more complex carburettors, this is an adjustable needle valve where a screw on the outside of the carburettor can screw a needle in and out of the valve to give some tuning control over the fuel flow. The fuel is pulled through the jet by the vacuum created in the venturi. At the bottom of the tube is a throttle plate or throttle butterfly which is basically a flat circular plate that pivots along its centreline. It is connected mechanically to the accelerator pedal or twist-grip throttle via the throttle cable. The more you push on the accelerator or twist open the throttle, the more the throttle butterfly opens. This allows more air in which creates more vacuum, which draws more fuel through the fuel jet and gives a larger fuel-air charge to the cylinder, resulting in acceleration. When the throttle is closed, the throttle butterfly in the carburettor is also closed. This means the engine is trying to suck fuel-air mix and generating a vacuum behind the butterfly valve so the regular fuel jet won't work. To allow the engine to idle without shutting off completely, a second fuel jet known as the idle valve is screwed into the venturi downwind of the throttle butterfly. This allows just enough fuel to get into the cylinders to keep the engine ticking over.

Float and diaphragm chambers.
To make sure a carburettor has a good, constant supply of fuel to be sucked through the fuel jets, it has a float chamber or float bowl. This is a reservoir of petrol that is constantly topped up from the fuel tank. Petrol goes through an inline filter and a strainer to make sure it's clean of contaminants and is then deposited into the float chamber. A sealed plastic box is pivotted at one end and floats on top of the fuel. Believe it or not, this is called the float. A simple lever connects to the float and controls a valve on the fuel intake line. As the fuel drops in the float chamber, the float drops with it which opens the valve and allows more fuel in. As the level goes up, the float goes up and the valve is restricted. This means that the level in the float chamber is kept constant no matter how much fuel the carburettor is demanding through the fuel jets. The quicker the level tries to drop, the more the intake valve is opened and the more petrol comes in to keep the fuel level up. This is why carburettors don't work too well when they're tipped over - the float chamber leaks or empties out resulting in a fuel spill - something you don't get with injectors. To combat this, another type of chamber is used where carburettors can't be guaranteed to be upright (like in chainsaws). These use diaphragm chambers instead. The principle is more or less the same though. The chamber is full of fuel and has a rubber diaphragm across the top of it with the other side exposed to ambient air pressure. As the fuel level drops in the chamber, the outside air pressure forces the
http://www.carbibles.com/fuel_engine_bible.html (11 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

diaphragm down. Because it's connected to an intake valve in the same way that the float is in a float chamber, as the diaphragm is sucked inwards, it opens the intake valve and more fuel is let in to replenish the chamber. Diaphragm chambers are normally spill-proof.

Carb icing.
One of the problems with the spinning, compressing, vacuum-generating properties of the venturi is that it cools the air in the process. Whilst this is good for the engine (colder air is denser and burns better in a fuel-air mix), in humid environments, especially cool, humid environments, it can result in carburettor icing. When this happens, water vapour in the air freezes as it cools and sticks to the inside of the venturi. This can result in the opening becoming restricted or cut off completely. When carbs ice up, engines stop. In aircraft engines, there is a control in the cockpit called "carb heat" which either uses electrical heating elements to heat up the venturi to prevent icing, or reroutes hot air from around the exhausts back into the carburettor intakes. In cars, we don't have "carb heat" but instead there's normally a heat shield over the exhaust manifold connected via a pipe to a temperature-controlled valve at the air filter. When its cold, the valve is open and the air filter draws warm air from over the exhaust manifold and feeds it into the carburettor. As the temperature warms up, the valve closes and the carburettor gets cooler air because the risk of icing has reduced. The symptoms of carb icing are pretty easy to diagnose. First, your engine bogs down at high throttle then it loses power and ultimately could stall completely. You'll stop on the side of the road and wait a couple of minutes, then the engine will start and run normally. This is because with the engine off, the heat from the engine starts to warm up the carbs and melts the ice so that when you try to start it up again, everything is fine.

Complexity for the sake of it.
As car engines evolved, carburettors had to evolve to cope with the various demands. It's not unusual to find fivecircuit carburettors which have become so complex that they're a nightmare to design, build and maintain. That flies in the face of one of the carburettor's advantages, which used to be that they were simple. Why five circuits? The main circuit is the one which provides day-to-day running capability. It's augmented by accelerator and load (or enrichment) circuits which can vary the fuelling to accomodate sudden acceleration or the need for more power (like driving uphill). The accelerator circuit also adds a second butterfly valve in most cases which only opens at 70% throttle or more. Then there's the choke circuit designed to provide extra fuel with the throttles closed when the engine is cold, allowing it to start, and finally the idle circuit which does the same thing but when the engine is warm, to keep it going. On top of all of this, with the introduction of stricter emissions requirements came catalytic converters, and these expensive boxes of rare metals just don't work well unless the fuel-air ratio is very carefully controlled. And that's something carburettors just couldn't keep up with. Small wonder then that this mechanical tomfoolery gave way to fuel injection......

Fuel injection
Advantages : precise and variable fuel metering, better fuel efficiency and better emissions. Disadvantages : Fairly complex engineering that isn't very user-friendly. Binary on/off functionality at low throttles, which is especially noticable on motorbikes where the throttle becomes 'snatchy' and it becomes hard to ride smoothly at low speed.

How it works.
Compared to carburettors, fuel injectors themselves are incredibly simple. They are basically electromechanically operated needle valves. The image on the right shows a cutaway of a representative fuel injector. When a current is passed through the injector electromagnetic coil, the valve opens and the fuel pressure forces petrol through the spray tip and out of the diffuser nozzle, atomising it as it does so. When current is removed, the combination of a spring and fuel back-pressure causes the needle valve to close. This gives an audible 'tick' noise when it happens, which is why even a quiet fuel-injected engine has a soft but rapid tick-tick-tick-tick noise as the injectors fire. This on-off cycle time is known as the pulse width and varying the pulse width determines how much fuel can flow through the injectors. When you ask for more throttle either via the accelerator pedal or twist-grip (on a motorbike) you're opening a butterfly valve similar to the one in a carburettor. This lets more air into the intake system and the position of the throttle is measured with a potentiometer. The engine control unit (ECU) gets a reading from this potentiometer and "sees" that you've
http://www.carbibles.com/fuel_engine_bible.html (12 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

opened the throttle. In response the ECU increases the injector pulse width to allow more fuel to be sprayed by the injectors. Downwind of the throttle body is a mass airflow sensor. This is normally a heated wire. The more air that flows past it, the quicker it disappates heat and the more current it needs to remain warm. The ECU can continually measure this current to determine if the fuel-air mix is correct and it can adjust the fuel flow through the injectors accordingly. On top of this, the ECU also looks at data coming from the oxygen (lambda) sensors in the exhaust. These tell the ECU how much oxygen is in the exhaust so it can automatically adjust for rich- or lean-running.

Different types of injector systems.
When fuel-injection was first introduced, it was fairly simple and used a single injector in the throttle body. Basically it was a carburettor-derivative but instead of having the induction vacuum suck fuel into the venturi, an injector forced fuel into the airflow. This was known as throttle-body fuel-injection, or single-point fuel-injection. As engine design advanced, the single-point system was phased out and replaced with multi-point or multi-port fuel-injection. In this design, there is one injector for each cylinder, normally screwed into the intake manifold and aimed right at the intake valve. Because fuel is only sprayed when the intake valve is open, this systems provides more accurate fuel-metering and a quicker throttle response. Typically, multi-point injection systems have one more injector for cold-starting which sprays extra fuel into the intake manifold upstream of the regular injectors, to provide a richer fuel-air mix for cold starting. A coolant temperature sensor feeds information back to the ECU to determine when this extra injector should be used. As you would expect though, technology marches on with no regard to home mechanics, and the latest technology is direct injection, also known as GDI (gasoline direct injection). This is similar to multi-point injection only the injectors are moved into the combustion chambers themselves rather than the intake manifold. This is nearly identical to the direct injection system used in diesel engines. Essentially, the intake valve only allows air into the combustion chamber and the fuel is sprayed in directly through a high-pressure, heat-resistant injector. The fuel and air mix inside the combustion chamber itself due to the positions of the intake valve, injector tip and top of the piston crown. The piston crown in these engines is normally designed to create a swirling vortex to help mix the fuel and air before combustion, as well as having a cavity in it for ultra-lean-burn conditions (see picture to the left). The ECU controls the amount of fuel injected based on the airflow into the engine and demand, and will operate a direct injection engine in one of three modes: Full power mode is basically foot-tothe-floor driving. The fuel-air ratio is made richer and the injectors spray the fuel in during the piston intake stroke. In stoichiometric mode the fuel-air ratio is leaned off a little. The fuel is still sprayed in during the piston intake stroke but the burn is a lot cleaner and the ECU chooses this mode when the load on the engine is slightly higher than normal, for example during acceleration from a stop. Finally, when you're cruising with very little engine load, for example when you're on wide-open motorway with no traffic (I know that's hard to imagine when you live in England), the ECU will choose an ultra lean mode. In this mode, the fuel is injected later on in the 4-stroke cycle - as the piston is moving up its compression stroke. This forces the fuel-air charge right up next to the tip of the spark plug for the best burn conditions and the combustion itself takes place partly in the cylinder and partly in the shaped piston crown mentioned previously.

ECU maps.
http://www.carbibles.com/fuel_engine_bible.html (13 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

The ECU receives a wide number of sensor readings from all over the engine. Built into the ECU is a fuelling and ignition map which is basically a gigantic table of numbers. It's like a lookup table that the ECU uses to determine injector pulse width, spark timing (and on some engines, the variable valve timing). So the ECU receives a set of values from all its sensors, which it then looks up in the fuelling and ignition map. At the point where all these numbers coincide, there is final number which the ECU then uses to set the injector pulse width. These are the manufacturer's "blessed" fuelling routines, and elsewhere on this page, there's a section dealing with chipping and remapping, whereby aftermarket tuners can alter these mapping tables to make the engine behave differently.

Valves and valve mechanisms.
If you've got this far down the page, hopefully you understand that the valves are what let the fuel-air mixture into the cylinder, and let the exhaust out. Seems simple enough, but there are some interesting differences in the various types of valve mechanism.

Spring-return valves.
Spring return valves are about the most commonly-used and most basic type of valvetrain in engines today. Their operation is simplicity itself and there are only really three variations of the same style. The basic premise here is that the spinning camshaft operates the valves by pushing them open, and valve return springs force them closed. The cam lobes either operate directly on the top of the valve itself, or in some cases, on a rocker arm which pivots and pushes on the top of the valve. The three variations of this type of valve-train are based on the combination of rocker arms (or not) and the position of the camshaft. The most basic type has the camshaft at the top of the engine with the cam lobes operating directly on the tops of the valves. The second more complex type still has the camshaft at the top of the engine, but the cam lobes operate rocker arms, which in turn pivot and operate on the tops of the valves. With some of these designs, the rocker arm is pivoted in the middle (as shown below) and with other designed, it's pivoted at one end and the cam lobe operates on it at the midpoint. Think of a fat bloke bouncing in the middle of a diving board whilst the tip of the board hits a swimmer on the head and you'll get the general idea. The third type which you'll find in some motorcycle engines and many boxer engines are pushrod-activated valves. The camshaft is actually directly geared off the crank at the bottom of the engine and the cam lobes push on pushrods which run up the sides of the engine. The top of the pushrod then pushes on a rocker arm, which finally pivots and operates on the top of the valve. The image here shows the three derivatives in their most basic form so you can see the differences between them. Note that the pushrod type shows the camshaft in the wrong place simply for the purpose of getting it into the image. In reality the camshaft in this system is right at the bottom of the engine near the crank. The rocker arms shown here are also called fingers, or followers depending on who you talk to.

http://www.carbibles.com/fuel_engine_bible.html (14 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

Tappet Valves
Tappet valves aren't really a unique type of valve but a derivative of spring-return valves. For the most part, the direct spring return valve described above wouldn't act directly on the top of the valve itself, but rather on an oil-filled tappet. The tappet is basically an upside-down bucket that covers the top of the valve stem and contains the spring. It's normally filled with oil through a small hole when the engine is pressurised. The purpose of tappets is two-fold. The oil in them helps quiet down the valvetrain noise, and the top of the tappet gives a more uniform surface for the cam lobe to work on. From a maintenance point of view, tappets are the items which wear and are a lot easier to swap out than entire valve assemblies. The image on the left shows a simple tappet valve assembly. I've rendered the tappet slightly transparent so you can see the return spring inside.

Desmodromic Valves
Desmodromic valve systems are unique to Ducati motorbikes. From the Ducati website: The word 'desmodromic' is derived from two Greek roots, desmos (controlled, linked) and dromos (course, track). It refers to the exclusive valve control system used in Ducati engines: both valve movements (opening and closing) are 'operated." Classy, but what does it mean. Well in both the above systems, the closure mechanism on the valve relies on mechanical springs or hydraulics. There's nothing to actually force the valve to close. With the Ducati Desmodromic system, the
http://www.carbibles.com/fuel_engine_bible.html (15 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

camshaft has two lobes per valve, and the only spring is there to take up the slack in the closing system. That's right; Ducati valves are forced closed by the camshaft. The marketing people will tell you it's one of the reasons Ducati motorbike engines have been able to rev much higher than their Japanese counterparts. The idea is that with springs especially, once you get to a certain speed, you're bound by the metallurgy of the spring - it can no longer expand to full length in the time between cylinder strokes and so you get 'valve float' where the valve never truly closes. With Desmodromic valves, that never happens because a second closing rocker arm hooks under the top of the valve stem and jams it upwards to force the valve closed. In fact, the stroke length, rods, and pistons all play their part in valve timing and maximum engine speed - it's not just the springs and valve float. This is why F1 cars use such a small stroke and pneumatic valves springs. In truth, both systems, spring or Desmodromic only work well up to a limit. Newer Japanese bikes have engines that can rev to the same limit as a Ducati just using spring-return valves. You can see the basic layout of a desmodromic valve on the right. As the cam spins, the opening lobe hits the upper rocker arm which pivots and pushes the valve down and open. As the cam continues to spin, the closing lobe hits the lower rocker arm which pivots and hooks the valve back up, closing it. The red return spring is merely there to hold the valve closed for the next cycle and doesn't provide any springing force to the closing mechanism. This is a fairly simple layout for the purposes of illustration. The real engines have Desmo-due and Desmo-quattro valve systems in them where pairs of valves are opened and closed together via the same mechanism.

Quattrovalvole, 16v and the other monikers you'll find on the back of a car.
In the 80's, the buzzword was 16-valve. If you had a 16-valve engine you were happening. You were the dogs bollocks, the cat's meouw. In Italy, your engine was a quattrovalvole. So what the heck does all this mean? Well it's really, really simple. "Traditional" 4-cylinder in-line engines have two valves per cylinder - one intake and one exhaust. In a 16V engine, you have four per cylinder - two intake and two exhaust. (4 valves) x (4 cylinders) = 16 valves, or 16V. It follows that a 20V engine has 20 valves - 5 per cylinder. Normally three intake and two exhaust. Unless you've got a 5cylinder Audi or Volvo in which case you've still got 4 valves per cylinder. If you're in America, the thing to have now is 32V a 32 valve engine. Basically it's a V-8 with 4 valves per cylinder. See - it's all just basic maths. And what do all these extra valves get you apart from a lot more damage if they ever go wrong? A better breathing engine. More fuel-air mix in, quicker exhaust. When you get further down the page (and if your wife / husband hasn't come and complained to you about spending so damn long reading this stuff so late at night), you'll find some more information on why this is A Good Thing.

"Clean" diesels? Toyota's D-Cat and DPNR
Old-school diesel engines used to sound like tractors when you started them on a cold morning, and they used to spew particulates out of the exhaust to the point where the back of the car went black. Newer generation diesels start much less noisily but for the most part still have some issues with particulates in the exhaust. Toyota claim to have solved this with their D-Cat and DPNR system. D-Cat stands for Diesel Clean Advanced Technology and DPNR stands for Diesel Particulate NOx Reduction. The operating principle is fairly sound. D-Cat is an advanced computer-controlled system for cleaning diesel exhaust gasses which relies on the DPNR catalyser. This is a combination of particle filters and normal gas-reduction catalysing metals that remove particulates, sulphur dioxide (SO2) and nitrogen dioxide (NO2) from the exhaust gasses. A sensor measures can tell when these filters are nearly full at which point a fifth diesel-injector sprays a little fuel directly into the exhaust system. Combined with the exhaust gas recirculation system, this results in all the collected pollutants being burned off, cleaning the filter in the process. DPNR requires ultra-low sulfur diesel (ULSD) to work properly. This all sounds very good but this system was launched on the D-4D engined 2.0litre Toyota Avensis, and very soon afterwards, the complaints started to come in. Notably, Dutch car magazine AutoWeek (issue 42 / 2006) exposed the problem when their DPNR-equipped Avensis started driving around with a huge cloud of white smoke pouring out of the exhaust. They weren't the only ones to have this problem. Hundreds of complaints have been filed in Germany and other European countries for the same thing. The problem is that the D-Cat/DPNR system needs to 'regenerate' as described above. The particulate and gas filters are cleaned via a combustion mechanism in the exhaust, but this only happens at speeds below 160km/h (99mph), and takes about 20 minutes each time. In Germany especially, where they still have sections of unlimited-speed autobahns, people have been driving well over that speed for miles on end, then stopping and turning the car off, only to repeat the cycle twice a day during their commute. When this happens, the DPNR system never gets time to regenerate normally and the particle filters become clogged. When this happens, the
http://www.carbibles.com/fuel_engine_bible.html (16 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

DPNR system forces a clean cycle to happen and the combustion results in white smoke as there are too many pollutants trying to be burned off at the same time. And not just a little white smoke. In the AutoWeek test, they thought their Avensis was on fire it was trailing so much smoke. Toyota has promised to sort this problem out with an improved version of D-Cat, and will only be fitting it to the higher-spec 2.2litre engine. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Hybrid Engines.
You've no doubt heard of hybrid cars by now, most likely the Toyota Prius. More manufacturers are jumping on the hybrid bandwagon, but just what is a hybrid vehicle? Simply put, it's a vehicle that uses a combination of two technologies to drive it. The most common hybrids are petrol-electric, like the Prius. Hybrid petrol-electric cars use a normal petrol engine, just like you'd find in any other car, but in in addition, there is a high-torque electric motor. The motor draws its power from a bunch of car batteries stored either in the floorpan of the car (for a low centre of gravity) or in the rear (for convenience). Both the petrol engine and the electric motor are connected to an onboard computer system which has been programmed by men in white coats to work as efficiently as possible. Hybrid engines typically have four modes of operation: Pure electric. This is where the electric motor does all the work. It is engaged through the automatic gearbox to the driveshafts and as you use the accelerator, you're basically varying the voltage being sent to the motor. The petrol engine remains off in this mode so you're driving entirely on electric power. Electric assist. In this mode, the petrol engine is running as normal but the electric motor is providing input to the gearbox at the same time. Remember in the section above (on tuning) I talked about reducing the load on the engine to make it more efficient? Well using the electric motor like this reduces the load on the petrol engine so much that it becomes highly efficient. This is where the hybrid gets its name from - you're using a hybrid drive of petrol and electric power to move the car forwards. In electric-assist mode, the petrol engine is turned off when you come to a stop, so you don't waste petrol idling. When you start to move, the electric motor gets you going whilst the petrol engine is restarted and brought online again. Clever, eh? Pure petrol. In this mode, a hybrid vehicle works just like any other car on the road. The electric motor is disengaged and the petrol engine does all the work. Regenerative. Regenerative mode is what happens as you begin to slow down. Rather than just using the brakes to slow you down, when the computer detects decelleration, it re-engages the electric motor to the drivetrain but rather than feeding power to it, it allows the motor to induce drag in the drivetrain, behaving like a brake. As it does this, the motor actually generates electricity and the computer routes this excess power back to the battery pack to help recharge it. Most hybrids have an energy display screen mounted either in the instrument cluster or in the centre console. This is a small LCD which gives you, the driver, information about what mode you're driving in, and where the power is going. Again, the most recognisable and famous of these displays to date is that from the Toyota Prius (see right). The only real problem with these displays is the fascination they provide to the novice hybrid driver. Watching the animations spin around and the energy arrows scroll here and there as you drive is certainly informative but not really conducive to safe driving. One benefit however is the constantly-updated gas-mileage chart. Many Prius owners report that this spurs them to attempt to get videogame-like high scores in their cars, driving them in such a fashion as to get the highest recorded mpg from their cars. If nothing else, the energy display affects most drivers in terms of educating them as to how their driving style directly impacts their gas-mileage. The rendering below shows the basic layout of a petrol-electric hybrid vehicle. The red components are the electric drive components. The computer is represented by the orange box and the control and data connections to the computer are represented by the green lines.

http://www.carbibles.com/fuel_engine_bible.html (17 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

Plug-in hybrids
It's been said that the reason the all-electric car failed in America is because if people forgot to plug it in overnight, they couldn't drive it the next day. The real reason had more to do with the politics of Big Oil, the California clean air act and GM's unwillingness to promote electric vehicles. Regular petrol-electric hybrids are an excellent choice for people wanting to be more frugal in their gas mileage, but the all-electric mode will only run for a couple of miles before the battery pack is completely drained. In fact, in the US, the Prius has been hobbled by the removal of the all-electric mode completely at the behest of Big Oil. The ideal solution to the pure-electric problem, and the petrol-electric problem is to have a plug-in hybrid. Essentially the idea is very simple. You drive the car as you would normally but you plug it in overnight. And extra set of deep-cycle marine batteries is charged up and can be used to drive in pure electric mode the following day. If the batteries run down, the car reverts to the behaviour of a normal petrol-electric hybrid. If you forget to plug it in overnight, again it behaves like a normal petrol-electric hybrid. In other words, if you choose to plug it in overnight, you buy yourself 30 or 40 miles of driving without using a single drop of petrol. If you forget, no biggie - you can still drive. Famously, CalCars have converted a regular Prius to be a 100mpg+ vehicle with their plug-in conversion. How is this possible? Well the average commuter typically doesn't drive more than 30 miles a day. With the plug-in conversion, that entire distance is covered on pure electric mode, with the petrol engine only kicking in on a low charge or when it's needed for a burst of acceleration. Because the petrol engine is used so rarely, by the time you fill up, you can easily have covered more than 100 miles on a single gallon of petrol. CalCars will turn any hybrid into a plugin for you, for a price.
http://www.carbibles.com/fuel_engine_bible.html (18 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

Diesel-electric hybrids
Another type of hybrid is the diesel-electric. There are at the time of writing, no production vehicles using this technology, but essentially it works just like a diesel-electric train. The small diesel engine is directly connected to a generator. The generator produces electricity on-demand, which is fed to wheel motors (electric motors built into the wheels) to drive the vehicle forwards.

The cost of hybrids
Because hybrid engine technology is still relatively new, it cost you more to buy a hybrid car than the equivalent petrolengined car. Some countries, cities and states have incentives to do this, like energy grants, or paying the price difference. Ultimately, if you're willing to write-off the initial extra cost, owning a hybrid is definitely cheaper. If you include the extra cost up front and factor it across the lifetime of the vehicle, you'd need to own a hybrid for about 7 years covering about 15,000 miles a year to break even, given the rising cost of petrol compared to the mpg savings of operating the car. If you choose to go the plug-in hybrid route, you'll be paying even more for a company like CalCars to convert your car for you, but again, over the lifetime of ownership, you can probably recoup the cost within 5 years.

Renting hybrids
At the time of writing (July 2007), Hertz have started to offer hybrids as an option for rental. Some Hertz locations allow you to specify the exact vehicle you want when you rent. There is of course a price premium, but for example if you were to rent from Hertz in England, because the cost of petrol over there is so prohibitively expensive, renting a hybrid will save you money as soon as you go over the 250 mile mark. Up to 250 miles, it's cheaper to rent a regular compact vehicle and fill it with petrol. Over 250 miles, the extra cost of the hybrid is negated by the fuel-saving and you're on your way to a cheaper overall rental.

Engine Cooling Systems
It stands to reason that if you fill a metal engine with fuel and air hundreds of times a second and make it explode, the whole thing is going to get pretty hot. To stop it all from melting into a fused lump of steel and aluminium, all engines have some method of keeping them cool.

Air cooling
Picture credit: Ducati

You don't see this much on car engines at all now. The most famous cars it was used on were rear-engined boxers like the original VW Beetle, Karmann Ghia, and Porsche Roadsters. It is still used a lot on motorbike engines because it's a very simple method of cooling. For air cooling to work, you need two things - fins (lots of them) and good airflow. An air-cooled engine is normally easy to spot because of the fins built into the outside of the cylinders. The idea is simple - the fins act as heat sinks, getting hot with the engine but transferring the heat to the air as the air passes through and between them. Air-cooled engines don't work particularly well in long, hot traffic jams though, because obviously there's very little air passing over the fins. They are good in the winter when the air is coldest, but that illustrates a weak spot in the whole design. Air cooled engines can't regulate the overall temperature of the cylinder heads and engine, so the temperature tends to swing up and down depending on engine load, air temperature and forward speed. A famous problem with aircooling is associated with V-twin motorcycles. Because the rear cylinder is tucked in the frame behind the front cylinder, its supply of cool, uninterrupted air is extremely limited and so in these designs, the rear cylinder tends to run extremely hot compared to the front. The image on the right is ©Ducati and shows the engine from the Monster 695 motorbike. It's a good example of modern air-cooled design and you can see the fins on the engine are all angled towards the direction of travel so the air can flow through them freely.
http://www.carbibles.com/fuel_engine_bible.html (19 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

Oil cooling
To some extent, all engines have oil-cooling. It's one of the functions of the engine oil - to transfer heat away from the moving parts and back to the sump where fins on the outside of the sump can help transfer that heat out into the air. But for some engines, the oil system itself is designed to be a more efficient cooling system. BMW 'R' motorbikes are known for this (their nickname is 'oilheads'). As the oil moves around the engine, at some points it's directed through cooling passageways close to the cylinder bores to pick up heat. From there it goes to an oil radiator placed out in the airflow to disperse the heat into the air before returning into the core of the engine. Actually, in the case of the 'R' motorbikes, they're air- and oil-cooled as they have the air-cooling fins on the cylinders too. For a quick primer on how the radiator itself works, read on....

Water cooling
This is by far and away the most common method of cooling and engine down. With water cooling, a coolant mixture is pumped around pipes and passageways inside the engine separate to the oil, before passing out to a radiator. The radiator itself is made of metal, and it forces the coolant to flow through long passageways each of which have lots of metal fins attached to the outside giving a huge surface area. The coolant transfers its heat into the metal of the radiator, which in turn transfers the heat into the surround air through the fins - essentially just like the air-cooled engine fins. The coolant itself is normally a mixture of distilled water and an antifreeze component. The water needs to be distilled because if you just use tap water, all the minerals in it will deposit on the inside of the cooling system and mess it up. The antifreeze is in the mix, obviously to stop the liquid from freezing in cold weather. If it froze up, you'd have no cooling at all and the engine would overheat and weld itself together in a matter of minutes. The antifreeze mix normally also has other chemicals in it for corrosion resistance too and when mixed correctly it raises the boiling point of water, so even in the warmer months of the year, a cooling system always needs a water / antifreeze mix in it. The coolant system in a typical car is under pressure once the engine is running, as a byproduct of the water pump and the expansion that water undergoes as it heats up. Because of the coolant mixture, the water in the cooling system can get over 100°C without boiling which is why it's never a good idea to open the radiator cap immediately after you've turned the engine off. If you do, a superheated mixture of steam and coolant will spray out and you'll spend some quality time in a burns unit. The complexities of water cooling. Water cooling is the most common method of cooling and engine down, but it's also the most complicated. For example you don't want the coolant flowing through the radiator as soon as you start the engine. If it did, the engine would take a long time to come up to operating temperature which causes issues with the emissions systems, the drivability of the engine and the comfort of the passengers. In truly cold weather, most water cooling systems are so efficient that if the coolant flowed through the radiator at startup, the engine would literally never get warm. So this is where the thermostat comes in to play. The thermostat is a small device that normally sits in the system in-line to the radiator. It is a spring-loaded valve actuated by a bimetallic spring. In layman's terms, the hotter it gets, the wider open the valve is. When you start the engine, the thermostat is cold and so it's closed. This redirects the flow of coolant back into the engine and bypasses the radiator completely but because the cabin heater radiator is on a separate circuit, the coolant is allowed to flow through it. It has a much smaller surface area and its cooling effect is nowhere near as great. This allows the engine to build up heat quite quickly. If you look at the first of the two diagrams on the right, you can see the representation of the coolant flow in a cold engine. As the coolant heats up, the thermostat begins to open and the coolant is allowed to pass out to the radiator where it dumps heat out into the air before returning to the engine block. Once the engine is fully hot, the coolant is at operating temperature and the thermostat is permanently open, redirecting almost all the coolant flow through the radiator. If you look at the second of the two diagrams on the right, you can see the representation of the coolant flow in a cold engine. It's the action of the thermostat that allows a water-cooled engine to better regulate the heat in the engine block. Unlike an air-cooled engine, the thermostat can dynamically alter the flow of coolant depending on engine load and air temperature to maintain an even temperature.
http://www.carbibles.com/fuel_engine_bible.html (20 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

The radiator fan. In the good old days, car radiators had belt-driven fans that spun behind the radiator as fast as the engine was spinning. The fan is there to draw the warm air away from the back of the radiator to help it to work efficiently. The only problem with the old way of doing it was that the fan ran all the time the engine was running, and stopped when the engine stopped. This meant that the radiator was having air drawn through it at the same rate in freezing cold conditions as it was on a hot day, and when you parked the car, the radiator basically cooked because it had no airflow while it was cooling down. So nowadays, the radiator fan is electric and is activated by a temperature sensor in the coolant. When the temperature gets above a certain level, the fan comes on and because it's electric, this can happen even once you've stopped the engine. This is why sometimes on a hot day, you can park up, turn off, and hear the radiator fan still going. It's also the reason there are big stickers around it in the engine bay because if you park and open the hood to go and start messing with something, the fan might still come on and neatly separate you from your fingers. The cabin heater. Most water-cooled car engines actually have a second, smaller radiator that the coolant is allowed to flow through all the time for in-car heating. It's a small heat-exchanger in the air vent system. When you select warm air with the heater controls, you will either be allowing the coolant to flow through that radiator via an inline valve in the cooling system (the old way of doing it) or moving a flap to allow the warm air already coming off that radiator to mix in with the cold air from outside. It's all these combinations and permutations of plumbing in a water-cooled engine that make it so relatively complex. The rendering below shows the basic elements a water-cooled engine.

http://www.carbibles.com/fuel_engine_bible.html (21 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Fuel and Engine Bible Page 1 of 3

Why is good engine cooling important? Case Study : the BMC Mini Minor
The importance of overall engine design and cooling system design and efficiency is very well illustrated by the fate that befell the original British Motor Corporation Mini Minor. The following contribution is by Rodney Brown - a reader of this site. In the Morris Mini, the water pump, fan and radiator block were mounted in the same position as they were on the same 948cc engine which was concurrently being used in the more conventional fore & aft engine layout of the Morris Minor 1000 saloon. Both cars were designed by Alec Issegonis, and this was just post-war; England was basically bust, so make do and mend was the order of the day. It took a genius like Alec to make a fore & aft power train work transversely, by folding beneath itself to fit in a very tight space. The Mini had to be kept small to keep development, production and ownership costs down. Because of all this, whilst the cooling fan and radiator were still where you would expect to find them - at one end of the block, they now closely abutted the nearside front inner wheel arch because the normally fore & aft engine was now turned 90 degrees so it faced across the car. The arch inner flitch panel had suitable slots punched in it and a close fitting cowl enclosed the fan blades on the inner face. Good radiator cooling was possible as the engine was mounted on a sub frame which also carried the suspension components, leaving only a small shock absorber to pass in front of (and obstruct) the slots. The problem was that the Mini's front grille was large - as big an area as the original radiator, but now with no radiator actually behind it - that was on the end of the engine. Without something in the way, it offered little resistence to the flow of cold air onto the engine, (now placed sideways) close behind the grille, with just enough room to take off the distributor cap. (Early on before the cap was covered by a protective boot and plug shrouds fitted, rain would drive through the grille onto the distributor and HT lead plug connections stopping the engine.) The carburettor and inlet manifold shared the space between the engine and the bulkhead with the exhaust manifold (which only just missed the bulkhead). Therefore when the car was in motion, the whole of the side of the block facing the open grille was bathed in a 30 - 60 mph icy blast whilst the opposite side was baked by convection/radiation/ conduction from an ill ventilated exhaust manifold. This is where the problem lay. The side of the piston bores closes to the front of the car remained relatively stable but on the side facing the rear bulkhead, where all the heat built up, it caused the piston bores to expand. So circular piston bores were cold on one side and hot on the other causing uneven distortion. The main effect of this was a poor fit of the piston rings which increased oil consumption, and more disastrously, enabled blow-by for unburnt fuel and combustion gasses which in turn pressurised the sump and gearbox. Remember that space-saving folded design, where the gearbox was folded under the engine? You've got it: the engine oil was also the gearbox oil. The sump/gearbox was not vented initially, but like the engine block above it, was cooled by an icy blast on one side and baked on the other! The consequences for the then-current SAE30 single-weight oils were that the oil was essentially useless after 3,000 miles. This rose to 6,000 miles with the advent of the multi grade oils, and it's interesting to note that the development of these oils in England was prompted by the pressing need to solve the problems posed by the Mini.

Page 1 ------ Page 2 ------ Page 3

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/fuel_engine_bible.html (22 of 22) [2/6/2008 7:12:43 AM]

Car Bibles : The Motorbike Suspension Bible

The motorbike suspension bible. Everything you need to know about motorbike suspension including shocks, forks, springs, different types of suspension, all the technologies involved, DIY bike maintenance and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

This site originally started out as being just for cars, but as I also ride motorbikes, I felt I had to include information for the bikers out there too. Here then is the Suspension Bible : Motorcycle edition. Oh - a little note - the reason I switch back and forth between motorbike and motorcycle is simply an internet thing. I'm trying to make the page more friendly to search engines for people looking for both words : motorbike and motorcycle. That's all.....

A little background.
Motorbikes, or motorcycles if you're American, have a similarly varied selection of suspension systems as cars. On bikes, of course, you only have two wheels, so bike suspension systems tend to be a little more highly engineered because there is more at stake. By far the most common setup now is the single rear coilover shock system with either a regular double swingarm or a single-sided swingarm. At the front, telescopic forks are still the most prevalent. It's surprising that there's still a large number of cruisers out there that are 'hardtail' bikes - bikes where there is no suspension at the back. The wheel is simply axled straight on to the frame. This is a throwback to the very first motorbikes which were basically bicycles with an engine strapped to them. (In the 1920s, motorbike suspension consisted of the springs in the saddle and the air in the tyres.)

Motorbike suspension geometry 101.
Before you dive into the murky world of technical terms which litter the rest of this page, it's worth knowing up front
http://www.carbibles.com/suspension_bible_bikes.html (1 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

what some of them mean in relation to the way motorbike suspension is set up. This little diagram, then, explains the basic terminology you'll come across.

Sports bikes typically have less rake which means less less trail. Less trail means less stability, which means a quickersteering bike. This makes these bikes a lot less stable to ride in a straight line, but a lot more flickable in the corners. Conversely, cruisers, choppers and customs, have much more rake. More rake means more trail, which means more stability, which makes the bike harder to turn. This is why Harley Davidsons are typically a bitch to get around a corner. However, bikes with more rake work better in a straight line, which is why bikes like the Honda Goldwing and BMW LT series have more rake - they're designed to be long-distance cruisers. It's worth noting that when I talk about more and less rake, it can be within 5° For example the difference between a flickable Yamaha R1 race bike and a BMW K1200LT cruiser is 24° and 26.8°

Anti-Dive forks.
One of the drawbacks of telescopic forks on a motorbike is their tendency to compress under braking, making the bike 'dive' forwards. This is due mostly to the steering geometry of the average motorbike. When you brake, you're slowing the forward motion of yourself and the motorbike. That forward force has to go somewhere, and that somewhere is the front suspension. Because the telescopic forks are at an angle to the frame, and consequently at an angle to the braking force, some of that forward force gets sent directly down the forks. Think back to your school physics. Force transmitted at an angle is equal to the main force multiplied by the cosine of the angle. Remember the rake on a motorbike is calculated from vertical. So the angle we want is actually 90° minus the rake - the complement of the angle. Conveniently, because sine and cosine are the inverse of each other, the cosine of one angle is the same as the sine of its complement. So for a bike with a rake angle of 25°, we can either use the cosine of its complement (65°) or the sine of the rake angle itself. Look at the diagram on the right; if the rake angle of our bike is 25°, then the force down the leg of the forks is (braking force) x sin(rake angle). For the sake of getting a number, lets use a ridiculously low
http://www.carbibles.com/suspension_bible_bikes.html (2 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

braking force of 1 newton. That makes our calculation (1) x sin(25) which is 0.4226, or 42.26%. So 42% of the forward force generated while braking travels down the fork legs into the springs and fork oil. To put a real world number on it, lets say you weigh 100kg, and your bike weighs 165kg. Force = (mass)x (acceleration). Jam on the brakes and you could easily generate a deceleration of just under 1G in an emergency lets say 9m/s². In that case, Force = 265Kg x 9m/s² which is 2385N. If 42% of that zips down the fork legs, your springs and fork oil are suddenly dealing with around 1000N - about 100Kg of force. In short : you have just transferred your entire body weight into the forks, which is why they dive. Honda fired the first shot in the anti-dive war in 1969 with the introduction of its TRAC system (Torque Reactive Anti-Dive Control), but it wasn't until the eighties that it became more mainstream. Anti-dive systems were typically linked to the brake hydraulic system, and is remembered best on the Kawasaki GPZ900R where it was introduced under the moniker AVDS Automatic Variable Damping System. AVDS was a supplemental hydraulic cylinder mounted on the front of the fork legs which was connected to both the brake lines and the hydraulic fluid inside the telescopic forks. The idea was that as you applied the brakes, this unit would use the pressure in the brake line against a plunger to close a control valve. This valve restriced the flow of fork oil and thus stiffened the suspension. Stiffer suspension meant less dive. Anti-dive units mostly featured a dial adjuster on them, normally at the base. This was a way of affecting how much the anti-dive plunger moved, which meant the rider could make the anti-dive more or less severe. It all sounded good in principle but a lot of riders took a dislike to it because of its behaviour on bumpy roads. If you went to brake on a bumpy surface, the front suspension stiffened up and it became less like riding a motorbike and more like falling down stairs as all the road bumps and deformities were transmitted up the now-stiffened suspension into the frame of the bike, and consequently, the rider. The control valve would often stick closed resulting in permanently stiff suspension, which in turn would result in frequently blown-out oil seals. These "features" of anti-dive systems have since been ironed out and they tend to work maintenance-free now.

TRAC
The Honda TRAC system differs somewhat from the ADVS-style units. Honda maintain that hydraulic systems have two basic drawbacks. First, the additional brake-line plumbing and increased brake-lever ratios can produce a spongy feeling at the brake lever. Second, those systems are either on or off - there's no modulation of antidive effect. To get around these problems, TRAC is instead activated through the torque reaction of the brake caliper itself. This makes it completely independent of the hydraulics in the brake system. It works because one of the two front brake calipers is hinged behind the fork leg on a pivoting link, rather than being solidly attached. When you apply the brakes, the pads grip the spinning disc and this tries to drag the brake caliper around with it. The caliper pivots on the link and presses against the anti-dive activating valve which is built directly into the fork leg. From then on it, it works just like the Yamaha and Suzuki systems, restricting the flow of fork oil and stiffening the suspension. The advantage of the Honda system (they say) is that the harder you brake, the more pressure the pivoting caliper puts on the control valve, and the stiffer the suspension gets. One important difference with TRAC is its ability to deal with the bumpy road surfaces which the other systems had a problem with. The TRAC valve is a floating piston held in place by a spring. This means that if you hit a bump, the sharp and sudden increase in the pressure of the fork oil can override the anti-dive valve and force oil through the valve as if it were not applied. This means that TRAC can respond to bumpy roads whilst braking. Clever eh?

Headshaking, tankslapping and steering dampers.
As I mentioned above, if the rake a telescopic fork is set just right, you get a bike which has very quick, precise steering, but becomes fundamentally unstable at low speed. This isn't normally an issue because sharp steering is found mostly on sports bikes, which tend to travel pretty quick. The problem comes when you hit a sufficiently large bump. The front suspension compresses, the wheelbase of the bike gets shorter and suddenly, what was on the cusp of driveability becomes totally unstable. The front wheel will tilt to one side or another and then the suspension returns to its normal length. As it does this, it sets up a standing-wave in the chassis of the bike which, because of the gyroscopic
http://www.carbibles.com/suspension_bible_bikes.html (3 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

forces generated by the front wheel, forces the steering over the other way. Now the suspension geometry and gyroscopic force of the spinning wheel together try to straighten the front wheel again. At this point, the bike is in a headshaker - the head of the bike is being shaken back and forth by a rapidly oscillating front wheel. There are ways and means out of this, but if you don't tackle it quickly, things will rapidly go downhill. The headshaker will get more and more violent because now, the wheel starts to slam back and forth from one side to the other. The handlebars will get ripped out of your hands and the steering will go from lock to lock very quickly, slapping the handlebars against the tank of the bike - hence tankslapper. The inevitable outcome of this is normally a highside where the bike will throw you off sideways and upwards. Once you're off, the suspension unloads, the bike settles down, and momentum will take its course as the bike drives off in a straight line without you. This is the reason for steering dampers, and one of the reasons the Suzuki TL 1000S was recalled within weeks of being put in the showrooms - it went into vicious tankslappers without any provocation. Steering dampers, therefore, are A Good Thing if you are going to be racing or owning a bike with suspect handling. They come in two basic forms - linear and rotary. Linear dampers are literally a long cylinder with a clamp on it and a hydraulic ram with another clamp. One end gets attached to the front forks of the bike, the other to the frame. They look like mini shock absorbers and are designed to be virtually unnoticable under normal circumstances (in terms of steering stiffness) but if you get into a headshaker, the rapid vibration can quickly be cancelled out by the damper. On the right here, the top image shows a linear damper attached lower down the forks, and to the frame. The second image shows one mounted across the steering head, attached to the tank and the top yoke. The third image, at the bottom, shows a rotary damper. These are still pretty new at the time of writing, and are normally not available as aftermarket items. (There are some around but what I'm saying is that they typically are designed into the bike from the factory). Rotary dampers sit at the top of the head bearing, either above or below the top yoke, and use either a rubber friction bearing or a hydraulic system. The outer part of the damper is attached to the frame, and the inner part has a splined hole through which the steering head shaft passes. The rubber or hydraulic system sits between the inner and outer sections so that if the bike gets into a headshaker, the rapid oscillation of the steering head shaft causes the splined internal part of the damper to try to spin from side to side. The outer part is solidly attached to the frame and the friction medium in between the two damps down the oscillation. Or to put it more simply, stick your left forefinger out and grasp it with your right hand so as to make a fist. Now twist your left hand and voila - rotary steering damper 101.

Motorbike suspension - front end.
Today's modern telescopic fork front suspension systems are basically the current evolution of something called a 'girder fork'. This was one of the earliest attempts to control the front wheel of a motorcycle but it has one serious disadvantage : as it works through its limits of movement, the effective wheelbase of the motorbike continually changes. Hit a bump, the front wheel moves up and back relative to the frame, and the wheelbase is shortened. Shorter wheelbase means less stability at speed, which is one of the reasons that if you're unlucky enough, you can get into a tank-slapper on almost any modern motorbike. Check back shortly for a breakdown of the different types of front-end suspension. In the meantime, feast your eyes on :

Motorbike suspension - back end.

http://www.carbibles.com/suspension_bible_bikes.html (4 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

Twin-shock, regular swingarm
The classic motorcycle suspension system. An H-shaped swingarm is pivoted at the front to the motorbike frame. On either side there are basic coilover units which provide the suspension. The shocks are inside the coilover units. This is about as basic as you can get on a motorbike and has been around for as long as the motorbike itself. This style of suspension began to fall out of favour in the 80's due to weight considerations and the availability of newer, stronger materials. It was also not a particularly robust design by modern considerations. It all got a bit bendy and flexible under extreme riding conditions, and the only way to make it stronger was to add more metal, which added more unsprung weight, which reduced the efficiency of the suspension.

Monoshock, older style, regular swingarm
In 1977, the first monoshock system appeared to niche markets and racers. It has actually been around in one form or another since the 1930's, but it was only in the early 80's that monoshocks started to appear on production bikes. Monoshock is actually a Yamaha trademark, but it has become synonymous with the design in the same way as people in the UK refer to vacuum cleaners as hoovers. (The Honda version is called Pro-Link). The premise was that manufacturers could save some weight by redesigning the rear suspension and removing one of the coilover units. Monoshocks are still coilovers, but there's only one and it's mounted centrally to the swingarm. On earlier models, the rear swingarm was a sort of basket with a linkage at the top-front. The monoshock sat nearly horizontal in the bike.

http://www.carbibles.com/suspension_bible_bikes.html (5 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

.

Monoshock, newer style, regular swingarm
On the current monoshock designs, there is now a complex linkage at the bottom end which joins the coilover to the swingarm itself, and its important to lube the joints in these linkages regularly. They are very exposed to the elements when riding. The linkage adds leverage to the suspension plus it allows the coilover to be mounted more vertically. Ever in need of less weight (and hence more speed), those clever engineers who devised this variation were able to remove the 'basket' part of the swingarm, and revert to the traditional "H" shaped arm, only with a bit more welding here and there and stronger materials. Hover your mouse over the image to show a closeup detail of the linkage. You can also download a small Quicktime movie (245kb) in a popup window of this linkage in action. You'll need Apple Quicktime 7 for it to display properly as I have used the new H.264 codec for quality.

Monoshock, single-sided swingarm
The ultimate evolution of the monoshock design is the single-sided swingarm. These are super-strong, super-lightweight swingarms like you might find on a VFR800. The advantage of a single-sided system is that the wheel can quickly be taken out and replaced. Not really a huge advantage for you or I fiddling with our bikes at the weekend, but for Moto-GP style racing, it does make a huge difference for the pit crew. Single-sided swingarms need to be pretty heavily engineered because they bear the all the stresses from the rear axle offset to one side. With the traditional double-beam swingarm, the design needs to have longitudinal stiffness to stop it from bending. With the single-sided design, it needs to also have torsional stiffness to stop it from twisting under the offset load. As a result, single-sided swingarms are typically a lot larger and have a huge amount of cross-bracing inside them.

One shock or two? The frothy subject of frappuccino damper oil.
In the good old days, motorbikes had two shock absorbers on the rear of the bike, as shown at the top of this section. As suspension evolved, the dual rear shocks were replaced with a single unit, but
http://www.carbibles.com/suspension_bible_bikes.html (6 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

the question is why? The answer, it turns out, is pretty simple. In a dual-shock system, the suspension units are typically attached very close to the rear axle. This means that as the suspension compresses and expands, the shock absorber pistons are travelling in a stroke which is nearly the same as the full deflection of the swingarm. Hitting a large bump might deflect the rear axle upwards by 10cm and back, resulting in the same 10cm stroke in the shocks. Do this a lot and the shock absorber piston begins to behave like the plunger in one of those natty little cafetières or milkfrothers - it agitates the damper oil so much and so frequently that the oil begins to heat up and foam or froth. At this point it not only looks like frappuccino foam but it has about the same damping properties too, and thus loses its ability to perform as it should. This is known as fading shock absorbers. Enter the single shock absorber system mounted towards the front of the rear swingarm. The swingarm might still have a lot of travel at the axle, but basic geometry shows you that closer to the pivot, the deflection is much less. This translates into shorter shock absorber movements which in turn means less opportunity for the damper oil to froth. The ultimate evolution of this is the complex link monoshock system (also shown above), where a complex series of levers reduce the shock absorber travel even further. Typically multi-link setups like this also have some amount of variance in them so that they have a different amount of deflection in the first part of the stroke to the that in the second. This means a single shock absorber unit can respond better to changing road surfaces, soaking up the smaller bumps and shocks with ease and comfort without sacrificing the ability to respond to the occasional mountain or pothole. As a side note, you'll notice as you read the section on BMW rear suspension below that the monolever and first-generation paralever had a single shock but it was mounted close to the rear axle. This had all the disadvantages of a dual-shock system without any of the advantages of a singleshock system. For the second-generation paralever, the shock was moved closer to the swingarm pivot, thus bringing the design in-line with the small-deflection idea.

The eBay problem
This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at www.carbibles.com, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to www.carbibles.com to see the full site and find my contact details. And now, back to the meat of the subject.... Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

BMW and their contribution to the world of motorbike suspension.
Bayerische Motoren Werke: those teutonic Germans and their incessant need to be at the pinnacle of engineering excellence. BMW are responsible for a lot of developments in motorbike suspension - not just the quirky ones. The first hydraulically dampened telescopic fork on a production motorcycle (1937), the longitudinal swinging arm ('50s and '60s), and the long-stroke high-comfort telescopic fork (1970). Because of this, I've given them an entire section to try to explain some of their innovations for which we should all be thankful. Well perhaps not all, but those riders who have chosen BMW as their steed of choice will know that their bikes have what could best be described as some pretty funky and unconventional suspension systems. BMW, it seems, are never quite happy with the status quo. Why use an existing design when it could be bettered? Why settle for DVD when you can have Blu-Ray? Just because a particular type of suspension system is favoured by the Japanese, and sold on hundreds of thousands of motorbikes every year doesn't necessarily mean that its the best option. At least not in the eyes of the Germans. BMW have long been known for their ability to cast scorn the accepted way of things, and pursue other, better methods of achieving the same result. Whether their suspension systems for their bikes actually are better or not I suppose is open
http://www.carbibles.com/suspension_bible_bikes.html (7 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

to debate. Having ridden and owned a BMW with telelever suspension, I can't understand why its not used on all bikes. Conversely, bullet bike riders will look at a BMW and see nothing but excess weight. You can be certain of one thing with BMW suspension systems: they're different. Very different. So lets start at the back and work forwards.

Rear monolever.
In 1980, BMW introduced the world to the monolever suspension system on the back end of their R80GS big dirt bike. Little did anyone know at the time that it was a sign of the radical design changes to come. Most BMW bikes, modern ones anyway, have shaft drive, so its a given on a beemer that one side of the rear suspension is going to be pretty beefy because it has to house the driveshaft and ultimately the rear drive. BMW capitalised on this and with the monolever, they created a single-sided suspension system, much like the Yamaha monoshock, but the shock / strut unit was mounted to one side of the bike, rather than in the centre. The driveshaft ran down the inside of the single-sided swingarm and into the rear drive. This design helped eliminate the need for beefier engineering at the front of the swingarm which would have been needed to resist the torsional load of having the wheel mounted to a single-sided swingarm.

Rear paralever, first generation.
In 1987, BMW improved on their design and introduced the paralever suspension system on the back end of the new R100GS, a system which found its way on to their K1 sports bike too. (Note : This is an improvement of a suspension system originally fitted to the Magni Sfida called Parallelogramo. It was also available as a kit for Moto Guzzis in the 80s. Parallelogramo itself is a derivative of a prototype suspension of the same type shown on the MV Agusta 500 in 1950) Paralever uses the same basic principle as monolever but adds a lower control arm to the mix and an extra pivot point between the main swingarm and the rear drive. The effect is that the old pivoting swingarm now becomes part of a skewing parallelogram system - in fact a geometric double wishbone system just like in a car. This added lateral stiffness to the suspension, but it also kept the rear drive at the same orientation relative to the rest of the bike. Because of the extra link at the rear drive, the strut / shock unit was turned over so that it was "the right way up", and it was still mounted to one side of the bike. Because the whole system now acts as a double swingarm, it substantially reduces the change of load response of the driveshaft. Using this type of suspension was also the impetus for BMW to change to using the engine as an integral stressed member of the frame, which allowed the swingarm and suspension components to be bolted directly to it.

http://www.carbibles.com/suspension_bible_bikes.html (8 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

Rear paralever, second generation.
In 1993, the second generation paralever system appeared on the R1100GS. The basic design was the same as the original paralever except that the strut/shock unit was moved away from the side of the bike and on to the centreline, bringing it more in line with the monoshock type system. It also gained a remote preload adjuster and spring plate height adjuster. This new paralever was made of aluminium instead of steel so it was lighter than the original whilst maintaining the strength needed for the singlesided shaft drive system.

Rear paralever, third generation.
Skip forward ten years to 2004 - which tells you how good the paralever II was that its design didn't change in nearly a decade. The third generation paralever appeared in the new R1200GS. This design is similar but at the same time noticably different to its predecessor, and at the time of writing is now the current BMW rear suspension of choice. The control arm was moved above the shaft drive from underneath, and the rear drive was changed to have a hole through the middle of it to save weight. The unsprung weight of the latest generation paralever is considerably lighter than its predecessors. That's not to say that it couldn't still be used as a substantial bludgeoning weapon if you got it off the bike, but in engineering terms, it has slimmed down considerably.

http://www.carbibles.com/suspension_bible_bikes.html (9 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

Front telelever.
In 1993, when paralever II appeared on the R1100GS, BMW also introduced their new telelever front end suspension system. The problem with traditional telescopic fork suspension is that all the forces acting on the front of the bike are transmitted to the handlebars, and thus the rider. Some people think this is A Good Thing - it keeps the rider "informed" as to what is going on. Others argue that it is a necessary evil and that telescopic forks are an unfortunate accident of history (see the section on forks above - it's the same reason we got VHS when Betamax was the better system). BMW fell squarely into the second camp, and developed telelever as a method of separating the braking and suspension forces from the steering force. With telelever, there is now a single strut/shock unit in place of the combined spring/shock functions of telescopic forks. Telelever still has front forks, but their primary function now is to make a stiff frame for the front wheel to sit in, and to allow the rider to steer the bike (which is always useful). The strut/shock unit is connected to a wishbone which itself is connected to the frame of the bike at the back via a yoke, and to the crossmember of the forks at the front using a ball joint. When you hit a bump with telelever, the suspension forces are transmitted through the ball joint, across the wishbone and up through the strut / shock unit into the frame of the bike. One of the biggest advantages of this system is that you don't need to engineer an anti-dive system into the forks. The design of the Telelever effectively reduces fork flex under braking to near zero which in turn reduces dive under braking. Another benefit is that the forces acting on the steering head bearings are dramatically reduced. In fact with telelever, as a rider you have to get used to the concept of braking without the bike diving at the front. It's really quite unique.

.

Front duolever.
Never being satisfied with resting on their laurels, by 2004 BMW decided that telelever was yesterday's news, and introduced duolever on the front of their first inline-four sports tourer - the K1200S. I'm not sure, but I think some of the BMW engineers might have discovered suspension nirvana with this system as they now finally have double-wishbone type suspension both front and rear. Duolever is an evolution of Norman Hossack's double wishbone / parallelogram suspension, which is why its sometimes referred to as Hossack Suspension (see below). The idea itself has been around since Hossack modified a Honda XL500 in 1979. In the early 90's he modified a BMW K100RS, and whilst it never really caught on in England, German engineers understood the idea instantly. Like the rear paralever, its geometrically a double wishbone system. As with telelever, in duolever the pivoting links and springs are not steered. But with duolever, the physical link from the handlebars to the suspension is radically different, involving a hinged link. If you look at the image here, you'll see the front suspension is completely independent of the steering, with the two only being connected by the hinged link up top. (That link is simply used for turning the fork assembly and provides no structural support or strength). Hover your mouse over the image for a close-up of the system. With the combination of paralever III on the rear, and duolever at the front, sitting on and riding a K1200S is unlike riding any other type of motorcycle. Whilst it may technically be the current pinnacle of motorbike suspension design, BMW have created a system which has divided riders into the love/hate camps.

A word from Norman Hossack himself
In early 2006 I was contacted by Norman Hossack himself to discuss some of the pros and cons of motorbike suspension. I asked if he'd like to write a "guest piece" for my page, and he jumped at the opportunity. Without further ado, here is
http://www.carbibles.com/suspension_bible_bikes.html (10 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

his contribution, which explains a lot about the history of Hossack suspension as well as his frustration with the motorbike engineering world at large, especially BMW: I set out to bring some new thinking to motorcycle design. I had left McLaren with a wealth of experience seeing how racing cars developed and how Formula 1 addressed their technical problems. I was only a spectator in the motorcycle industry and had no connections with it and still don't; I don't even ride a bike. I do own the first Hossack BMW (see the picture on the right) but can't ride it where I live because the EPA think German carbon monoxide is worse than American carbon monoxide. Back in the mid 70's, from where I stood, motorcycle design problems were obvious and easily solved. Just improve the rigidity, lower the weight, lower the polar moment, and kill stiction. So I did that and it worked, and it won races and then it won again and again. Job done! No! I didn't count on the inertia and negativism in that industry. Seems perceptions are more difficult to change than the engineering. What has become known as the Hossack suspension system, I chose from a list of about 5 designs options that I had invented. I assessed this one was the one that my meager resources could do justice to. The other would have required expensive tooling and structures and didn't take things that much further forward. I am not talking here about simple material changes; making the same thing from aluminum or carbon fiber does not constitute a new invention. To look at the fundamentals of my design there are some first principal elements to study. 1. Lower weight. A bar bending between fulcrums suffers a pure bending load. However if the load wasn't strictly bending, but straight push and pull, it could carry a load thousands of time higher. This higher value can be exploited with triangulation. Race car wishbones are an excellent example. These little devices can carry thousands of times their own weight and have near total rigidity. Everything on my design is triangulated and with that added strength you have a chance to save weight. 2. If you were able to look down the axis of the steering on my design you would see that the weight was quite close to the pivot axis. This means low polar moment and this is important because most forms of weave are sustained by this mass. The further it is from the axis the greater the chance it can add to weave. 3. Low stiction allows the tyre to ride bumps in with out being bullied by the suspension this is where grip come from. You will commonly hear commentators say 'mechanical grip' in F1 events and that's what I am talking about here. 4. Tellies (telescopic forks) turn brake loads into dive, and dive limits free wheel movement. My system doesn't do that and allows full and free movement even while braking. But more when a tyre is stopped too hard and it loses traction, the energy stored in the front spring of a telescopic system is suddenly released and it punches the tyre further making the chance of regaining traction nearly impossible. Vernon Glasier on HOSSACK1, my first bike, could readily slide the front wheel and still regain traction. So the fundamentals are there for discussion and challenge. But whether I managed to get it right first time with only my meager resources is in question. Though as a comment on my design it is worth noting that Hossack1 won its last championship in 1988 at which point it was 10 years old. Could I have done better? You betcha! I never built a bike with a real race engine and never found funding to do it the way it should have been done. So my attempt to revolutionize motorcycle design was a nonstarter in the environment it was born in and I had to wait nearly quarter a century to see the idea reach production (the K1200S) leaving me out in the cold as patents don't last that long. I wonder when the next manufacturer will take it up and exploit the areas that BMW didn't. Norman Hossack. Illustrations of some of Norman's 1974 / 1975 thinking on the subject of front suspension. These support the triangulation part of his essay above; he never set out to build these items and didn't see them as new thinking in any way:

http://www.carbibles.com/suspension_bible_bikes.html (11 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Motorbike Suspension Bible

For further reading on Norman Hossack and his suspension designs, pop over to Hossack-Design.co.uk.

Upcoming topics and additions.
Be sure to check back with my pages shortly for the following topics and additions :
● ● ● ● ● ● ●

front forks - regular and upside-down remote adjusters cush bearings chain adjusters shaft drive fork seals huggers

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/suspension_bible_bikes.html (12 of 12) [2/6/2008 7:13:08 AM]

Car Bibles : The Car Transmission Bible

The car Transmission Bible, covering everything you need to know about car transmission and maintenance, including different types of transmission, gearbox, clutch, CVT, crash gearboxes, how they work, automatics, differentials, limited-slip differentials, 2wd, 4wd, awd and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Transmission, or gearbox?
That question depends on which side of the Atlantic you're on. To the Europeans, it's a gearbox. To the Americans, it's a transmission. Although to be truthful, the transmission is the entire assembly that sits behind the flywheel and clutch the gearbox is really a subset of the transmission if you want to split hairs. Either way, this page aims to deal with the whole idea of getting the power from your engine to the ground in order to move your car (or bike) forwards.

Manual gearboxes - what, why and how?
From the Fuel & Engine Bible you know that the pistons drive the main crank in your engine so that it spins. Idling, it spins around 900rpm. At speed it can be anything up to 7,500rpm. You can't simply connect a set of wheels to the end of the crank because the speed is too high and too variable, and you'd need to stall the engine every time you wanted to stand still. Instead you need to reduce the revolutions of the crank down to a usable value. This is known as gearing down - the mechanical process of using interlocking gears to reduce the number of revolutions of something that is spinning.

A quick primer on how gears work
In this case I'm talking about gears meaning 'toothed wheel' as oppose to gears as in 'my car has 5 gears'. A gear (or cog, or sprocket) in its most basic form is a flat circular object that has teeth cut into the edge of it. The most basic type of gear is called a spur gear, and it has straight-cut teeth, where the angle of the teeth is parallel to the axis of the gear. Wider
http://www.carbibles.com/transmission_bible.html (1 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

gears and those that are cut for smoother meshing are often cut with the teeth at an angle, and these are called helical gears. Because of the angle of cut, helical gear teeth have a much more gradual engagement with each other, and as such they operate a lot more smoothly and quietly than spur gears. Gearboxes for cars and motorbikes almost always use helical gears because of this. A side effect of helical gears is that if the teeth are cut at the correct angle - 45 degrees a pair of gears can be meshed together perpendicular to each other. This is a useful method of changing the direction of movement or thrust in a mechanical system. Another method would be to use bevel gears.

Spur gears

Helical gears

The number of teeth cut into the edge of a gear determines its scalar relative to other gears in a mechanical system. For example, if you mesh together a 20-tooth gear and a 10-tooth gear, then drive the 20-tooth gear for one rotation, it will cause the 10-tooth gear to turn twice. In this case, the larger gear is the input gear. Each tooth on the input gear meshes with one tooth on the output gear. There are 20 teeth on the input gear and only 10 on the output gear. It follows then that for one rotation of the input gear, the output gear will turn twice. This creates a gear ratio of 20 teeth to 10 20:10 or 2:1. This is known as gearing up. Gearing down is exactly the same only the input gear is now the one with the least number of teeth. The output gear is the larger one and now, for every turn of the input gear, the output gear turns half a revolution. In this case it becomes a gear ratio of 10:20, or 1:2. By meshing many gears together of different sizes, you can create a mechanical system to gear up or gear down the number of rotations very quickly. As a final example, imagine an input gear with 20 teeth, a secondary gear with 40 teeth and a final gear with 50 teeth. From the input gear to the secondary gear, the ratio is 1:2 - half. From the second gear to the final gear, the ratio is 4:5 - four fifths. The total gear ratio for this system is (1/2) * (4/5) which works out to be 1/2.5, or 0.4. ie. for one turn of the input gear, the output gear turns 0.4 times. Collections of helical gears in a gearbox are what give the gearing down of the speed of the engine crank to the final speed of the output shaft from the gearbox. The table below shows some example gear ratios for a 5-speed manual gearbox (in this case a Subaru Impreza).
RPM of gearbox output shaft when the engine is at 3000rpm 947 1594 2314 3086

Gear 1st 2nd 3rd 4th http://www.carbibles.com/transmission_bible.html (2 of 39) [2/6/2008 7:13:45 AM]

Ratio 3.166:1 1.882:1 1.296:1 0.972:1

Car Bibles : The Car Transmission Bible 5th 0.738:1 4065

Final drive - calculating speed from gearbox ratios. It's important to note that in almost all vehicles there is also a final reduction gear. This is also called a final drive or a rear- or front-axle gear reduction and it's done in the differential with a small pinion gear and a large ring gear (see the section on differentials lower down the page). In the Subaru example above, it is 4.444:1. This is the final reduction from the output shaft of the gearbox to the driveshafts coming out of the differential to the wheels. So using the example above, in 5th gear, at 3000rpm, the gearbox output shaft spins at 4065rpm. This goes through a 4.444:1 reduction in the differential to give a wheel driveshaft rotation of 914rpm. For a Subaru, assume a wheel and tyre combo of 205/55R16 giving a circumference of 1.985m or 6.512ft (see The Wheel & Tyre Bible). Each minute, the wheel spins 914 times meaning it moves the car (914 x 6.512ft) = 5951ft along the ground, or 1.127 miles. In an hour, that's (60minutes x 1.127miles) = 67.62. In other words, knowing the gearbox ratios and tyre sizes, you can figure out that at 3000rpm, this car will be doing 67mph in 5th gear.

Making those gears work together to make a gearbox
If you look at the image below you'll see a the internals of a generic gearbox. You can see the helical gears meshing with each other. The lower shaft in this image is called the layshaft - it's the one connected to the clutch - the one driven directly by the engine. The output shaft is the upper shaft in this image. To the uneducated eye, this looks like a mechanical nightmare. Once you get done with this section, you'll be able to look at this image and say with some authority, "Ah yes, that's a 5-speed gearbox".

http://www.carbibles.com/transmission_bible.html (3 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

So how can you tell? Well look at the output shaft. You can see 5 helical gears and 3 sets of selector forks. At the most basic level, that tells you this is a 5-speed box (note that my example has no reverse gear) But how does it work? It's actually a lot simpler than most people think although after reading the following explanation you might be in need of a brain massage. With the clutch engaged (see the section on clutches below), the layshaft is always turning. All the helical gears on the layshaft are permanently attached to it so they all turn at the same rate. They mesh with a series of gears on the output shaft that are mounted on sliprings so they actually spin around the output shaft without turning it. Look closely at the selector forks; you'll see they are slipped around a series of collars with teeth on the inside. Those are the dog gears and the teeth are the dog teeth. The dog gears are mounted to the output shaft on a splined section which allows them to slide back and forth. When you move the gear stick, a series of mechanical pushrod connections move the various selector forks, sliding the dog gears back and forth. In the image below, I've rendered a close-up of the area between third and fourth gear.

When the gearstick is moved to select fourth gear, the selector fork slides backwards. This slides the dog gear backwards on the splined shaft and the dog teeth engage with the teeth on the front of the helical fourth gear. This locks it to the dog gear which itself is locked to the output shaft with the splines. When the clutch is let out and the engine drives the layhshaft, all the gears turn as before but now the second helical gear is locked to the output shaft and voila - fourth gear. Grinding gears. In the above example, to engage fourth gear, the dog gear is disengaged from the third helical gear and slides backwards to engage with the fourth helical gear. This is why you need a clutch and it's also the cause of the grinding noise from a gearbox when someone is cocking up their gearchange. The common misconception is that this grinding noise is the teeth of the gears grinding together. It isn't. Rather it's the sound of the teeth on the dog gears skipping across the dog teeth of the helical output gears and not managing to engage properly. This typically happens when the clutch is let out too soon and the gearbox is attempting to engage at the same time as it's trying to drive.
http://www.carbibles.com/transmission_bible.html (4 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Doesn't work. In older cars, it's the reason you needed to do something called double-clutching. Double-clutching, or double-de-clutching (I've heard it called both) was a process that needed to happen on older gearboxes to avoid grinding the gears. First, you'd press the clutch to take the pressure off the dog teeth and allow the gear selector forks and dog gears to slide into neutral, away from the engaged helical gear. With the clutch pedal released, you'd 'blip' the engine to bring the revs up to the speed needed to engage the next gear, clutch-in and move the gear stick to slide the selector forks and dog gear to engage with the next helical gear. The synchromesh - why you don't need to double-clutch. Synchros, synchro gears and synchromeshes - they're all basically the same thing. A synchro is a device that allows the dog gear to come up to a speed matching the helical gear before the dog teeth attempt to engage. In this way, you don't need to 'blip' the throttle and double-clutch to change gears because the synchro does the job of matching the speeds of the various gearbox components for you. To the right is a colour-coded cutaway part of my example gearbox. The green cone-shaped area is the syncho collar. It's attached to the red dog gear and slides with it. As it approaches the helical gear, it makes friction contact with the conical hole. The more contact it makes, the more it matches the rotation of the free-spinning helical gear to the speed of the output shaft before the teeth engage (because the helical gear is meshed with the gear on the layshaft, and the clutch is disengaged.)

What about reverse?
Reverse gear is normally an extension of everything you've learned above but with one extra gear involved. Typically, there will be three gears that mesh together at one point in the gearbox instead of the customary two. There will be a gear each on the layshaft and output shaft, but there will be a small gear in between them called the idler gear. The inclusion of this extra mini gear causes the last helical gear on the output shaft to spin in the opposite direction to all the others. The principle of engaging reverse is the same as for any other gear - a dog gear is slid into place with a selector fork. Because the reverse gear is spinning in the opposite direction, when you let the clutch out, the gearbox output shaft spins the other way in reverse. Simple. The image on the left here shows the

same gearbox as above modified to have a reverse gear.

Before the gearbox - the clutch
http://www.carbibles.com/transmission_bible.html (5 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

So now you have a basic idea of how gearing works there's a second item in your transmission that you need to understand - the clutch. The clutch is what enables you to change gears, and sit at traffic lights without stopping the engine. You need a clutch because your engine is running all the time which means the crank is spinning all the time. You need someway to disconnect this constantly-spinning crank from the gearbox, both to allow you to stand still as well as to allow you to change gears. The clutch is composed of three basic elements; the flywheel, the pressure plate and the clutch plate(s). The flywheel is attached to the end of the main crank and the clutch plates are attached to the gearbox layshaft using a spline. You'll need to look at my diagrams to understand the next bit because there are some other items involved in the basic operation of a clutch. (I've rendered the clutch cover in cutaway in the first image so you can the inner components.) So here we go.

In the diagram above, the clutch cover is bolted to the flywheel so it turns with the flywheel. The diaphragm springs are connected to the inside of the clutch cover with a bolt/pivot arrangement that allows them to pivot about the attachment bolt. The ends of the diaphragm springs are hooked under the lip of the pressure plate. So as the engine turns, the flywheel, clutch cover, diaphragm springs and pressure plate are all spinning together. The clutch pedal is connected either mechanically or hydraulically to a fork mechanism which loops around the throwout bearing. When you press on the clutch, the fork pushes on the throw-out bearing and it slides along the layshaft putting pressure on the innermost edges of the diaphragm springs. These in turn pivot on their pivot points against the inside of the clutch cover, pulling the pressure plate away from the back of the clutch plates. This release of pressure allows the clutch plates to disengage from the flywheel. The flywheel keeps spinning on the end of the engine crank but it no longer drives the gearbox because the clutch plates aren't pressed up against it. As you start to release the clutch pedal, pressure is released on the throw-out bearing and the diaphragm springs begin to push the pressure plate back against the back of the clutch plates, in turn pushing them against the flywheel again. Springs inside the clutch plate absorb the initial shock of the clutch touching the flywheel and as you take your foot off the clutch pedal completely, the clutch is firmly pressed against it. The friction material on the clutch plate is what grips
http://www.carbibles.com/transmission_bible.html (6 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

the back of the flywheel and causes the input shaft of the gearbox to spin at the same speed. Burning your clutch You might have heard people using the term 'burning your clutch'. This is when you hold the clutch pedal in a position such that the clutch plate is not totally engaged against the back of the flywheel. At this point, the flywheel is spinning and brushing past the friction material which heats it up in much the same was as brake pads heat up when pressed against a spinning brake rotor (see the Brake Bible). Do this for long enough and you'll smell it because you're burning off the friction material. This can also happen unintentionally if you rest your foot on the clutch pedal in the course of normal driving. That slight pressure can be just enough to release the diaphragm spring enough for the clutch to occasionally lose grip and burn. A slipping clutch The other term you might have heard is a 'slipping clutch'. This is a clutch that has a mechanical problem. Either the diaphragm spring has weakened and can't apply enough pressure, or more likely the friction material is wearing down on the clutch plates. In either case, the clutch is not properly engaging against the flywheel and under heavy load, like accelerating in a high gear or up a hill, the clutch will disengage slightly and spin at a different rate to the flywheel. You'll feel this as a loss of power, or you'll see it as the revs in the engine go up but you don't accelerate. Do this for long enough and you'll end up with the above - a burned out clutch. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Motorcycle 'basket' clutches
It's worth spending a moment here to talk about basket clutches as found on some Yamaha motorbikes. Even though the basic principle is the same (sandwiching friction-bearing clutch plates against a flywheel), the design is totally different. If nothing else, a quick description of basket clutches will show you that there's more than one way to decouple the a spinning crank from a gearbox. Basket clutches need to be compact to fit in a motorbike frame so they can't have a lot of depth to them. They also need to be readily accessible for mechanics to be able to service them with the minimum amount of fuss, something that's near impossible with regular car clutches. A basket clutch has a splined clutch boss bolted to the shaft coming from the engine crank with strong springs. Metal pressure plates slide on to this shaft, in alternating sequence with friction material clutch plates. The clutch plates are splined around the outside edge, where they fit into slots in an outer basket the clutch housing. The clutch housing is bolted on to the layshaft which runs back through the middle of the whole mechanism and into gearbox. Clever, but as usual, not much use without a picture, so here you go.

http://www.carbibles.com/transmission_bible.html (7 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

In operation, a basket clutch is simplicity itself. A throw-out bearing slides around the outside of the layshaft and when you pull the clutch lever, the throw-out bearing pushes against the clutch boss. The clutch boss compresses the clutch springs and removes pressure from the whole assembly. The friction plates now spin freely in between the pressure plates. When you let the clutch out, the springs pull the clutch boss in again and it re-asserts the pressure on the system, crushing the friction and pressure plates together so they grip. And there you have a second type of clutch. You should now feel proud that with all your newfound (and somewhat geeky) understanding of clutches, you can go about your business safe in the knowledge that you sort of understand how all this spinning, geared-and-splined witchcraft works.

Sequential gearboxes - what, why and how?
If you've ever watched motorsports you'll have noticed that the drivers don't have an "H" gate for their gearstick. They either jam the stick back and forth or use paddle-shifters behind the steering wheel. The paddle-shifters do the same job as the gearstick movement in this case, only using electronics to move the shifter. So what's going on in a sequential gearbox? Actually it's quite simple. A sequential gearbox is just like a manual gearbox but the selector system is different. The manual gearbox example at the top of the page showed a series of selector forks which were moved by the physical position of the gearstick. In a sequential box, those selector forks are connected to a single shaft that has corkscrew-type grooves in it. The collar that fits around this selection shaft has a ballbearing in it which sits in a recess in the collar as well as in one of the corkscrew grooves. When the gearstick is moved forwards or backwards, the selector shaft is mechanically turned by some number of degrees. That twisting motion rotates the corkscrew groove which in turn interacts with the ballbearings and the selector fork collars, forcing them to slide back and forth. Each click of the gearstick rotates the shaft another number of degrees and all the selector forks change position in one go.

http://www.carbibles.com/transmission_bible.html (8 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

That's why it's called a sequential gearbox - the gears are always selected in sequence. You can't jump from first to third, you have to go via second. Often, sequential gearboxes have a "double-click for neutral" option and when you do this, it disengages the clutch and rotates the selector shaft back around to the neutral position, just before first gear. So why design and use a sequential gearbox? Well for a start it's a simpler design than a fully-manual gearbox with less moving parts. For racing drivers it makes for much quicker gearchanges - bang the gearstick and you're up a gear nearly instantly. If you want to see how the corkscrew groove interacts with the selector collars this animation is worth watching. It's a Quicktime movie encoded with the H.264 Codec so you'll need Quicktime 7. Trivia note : TipTronic type gearboxes are not sequential. See the section below for an explanation of why. One final point on sequential boxes - if you've ridden a geared motorbike in the last 50 years or so, you've used a sequential gearbox. Most bikes are 1-down, 5-up with neutral in between first and second gear. That little gear selector pedal that you click up and down with your left foot is simply linked to a ratchet system that ratchets the selector shaft around to pick the relevant gear.

Automatic gearboxes - what, why and how?
If you're reading this in America, there's a fair chance that everything above this point in the page was totally useless to you because you don't "drive stick", you drive an automatic. Automatic gearboxes are a totally different beast. For a start they don't have a clutch pedal. For that matter they don't have a clutch at all; they have a torque converter, but we'll get on to that later. If you took an automatic gearbox apart (and for the love of all that is Holy, please don't), you'd see an enormous collection of mechanical parts all jammed into an impossibly small space. Taking centre stage would be the planetary gearset. Not to be confused with planetary drive, a hyperspace system we've only seen on the Sci Fi channel, the planetary gearset is nowhere near as exciting. In a manual gearbox, the dog gears lock and unlock different sets of helical gears to the output shaft in order to give the various gear ratios. In an automatic gearbox, the planetary gearset produces all the different gear ratios in one go and with only one set of gears. Ok so maybe it is pretty cool, but know this - an automatic gearbox is several orders of magnitude more complicated than a manual gearbox. Read on and you'll begin to understand why
http://www.carbibles.com/transmission_bible.html (9 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

getting an automatic gearbox overhauled costs so damned much.

A quick primer on how planetary gearsets work
Any planetary gearset has three main components. The sun gear, the planet gears (and their carrier) and the ring gear. Any one of these three components can be locked in place, but more importantly, any one can be the input or the output drive. Locking any two of them at the same time will always produce a 1:1 gear ratio. So how the hell does that work? One set of gears for every ratio you need? The work of the Devil? Time to get the old brain massager out again. For this example I'll talk about a planetary gearset with a ring gear that has 75 teeth and a sun gear that has 25 teeth. The following table shows how sending the input to one set of gear and locking another set can give a wide variety of gear ratios.
Input Sun Planet Carrier Sun Ouput Planet Carrier Ring Ring Locked gears Ring Sun Planet Carrier Calculation 1+(Ring/Sun) 1/(1+(Sun/Ring)) -Ring/Sun Resulting ratio 4:1 0.75:1 -3:1 (ie. reverse)

So that table basically has one reverse and two forward gears. Need more gears? Add more planetary gearsets with different numbers of teeth and link them together. Make the ouptut of one become the input of another and you can start to multiply up the number of gears available to you. The image below shows an example planetary gearset with the planet carrier in cutaway.

Compound planetary gearsets In reality, automatic gearboxes typically use one or more compound planetary gearsets instead of chaining regular gearsets together. They look just like a regular planetary gearset from the outside, but inside there are two sun gears and two sets of intermeshing planet gears. There is still only one ring gear though. With a single compound gearset, the number of ratios available increases to 4 forward ratios and one reverse. The image
http://www.carbibles.com/transmission_bible.html (10 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

below shows an example compound planetary gearset again with the planet carrier in cutaway. In my example, the planet gears are arranged as inner and outer planets. The inner ones are shorter and only engage the small sun gear and the outer planet gears. They in turn engage the larger sun gear at the bottom and the outermost ring gear. Another configuration would be to have the two sets of planet gears next to each other but slightly staggered so that only one set meshes with the ring gear. Would you believe there are people paid to come up with this stuff? Makes you wonder if you shouldn't just accept that an automatic gearbox simply works and that you don't want to know why.

I could now go on to explain to you how all the different ratios get selected but if I did, I'd lose most readers at this point and all the typing and fine imagery in the rest of the page would go to waste. For the sake of a working example, I will explain the first two gears though. Looking at the image below, When first gear is engaged, the smaller sun gear (green) is driven from the torque converter. The planet carrier (red) tries to spin the opposite direction but because of a one-way clutch system, it locks in place which forces the ring gear (blue) to turn instead. The ring gear becomes the output from the gearbox in this case and there you have first gear. The catch is that because of the design of the compound gearset, the direction of rotation of the output shaft ought to be opposite to that of the input shaft, but it isn't. This is because the first set of planet gears engages the second set and it's the second set that turns the ring gear. Doing this reverses the direction of rotation, thus making it now the same as the input shaft. Moving swiftly along, when second gear is engaged the input is again the small sun gear but this time the ring gear is held in place by a band and the output becomes the planet carrier.

http://www.carbibles.com/transmission_bible.html (11 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Locking planetary gearset components
If you've got this far, congratulations, you're doing better than I did the first time I had automatics explained to me. You might now be wondering how the clutches and bands I've mentioned above actually work. Bands are literally that - they're a band wrapped around the outside of the ring gear and when tightened, they lock the ring gear in place. Bands are actuated by a lever or pivot connected to a small hydraulic piston in the gearbox housing. The image below shows how a band might work in the example I've been building up. The actuator piston actually sits in a small cylinder inside the hydraulic distributor (see later) which is built into the gearbox case. You can see the band wraps around the ring gear and when the piston is pushed down, it tightens the band and clamps the ring gear into place, locking it to the gearbox case.

http://www.carbibles.com/transmission_bible.html (12 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

The clutches are a little more complex and are used to perform functions such as locking the sun gears to the turbine or input shaft. Automatic transmission clutches are a lot like the motorbike basket clutches mentioned higher up the page. They consist of a series of pressure and friction plates with splines on the inside and outside. These are compressed by hydraulic fluid fed through channels in the various shafts to a clutch piston. Clutch springs make sure the clutch piston releases when hydraulic pressure is reduced. The example below shows how a clutch system might work to lock the ring gear to the output shaft.

http://www.carbibles.com/transmission_bible.html (13 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

The automatic gearbox hydraulic system - how it changes gears.
You've got the idea by now that hydraulics are used a lot in an automatic gearbox. They're used to pressurise the piston plate for the clutches and they're used to move the band-activation pistons up and down. In the good old days, the routing of the hydraulic fluid in the system was controlled by mechanical shift valves linked to the throttle valve on one side and the governor (see later) on the other. Those days are on the way out now and generally speaking, when you move the gear stick, you're doing nothing more than giving an input to the engine management system or engine control unit (ECU) indicating what gear you'd like to be in. The ECU then looks at engine speed, speed across the ground, current gearbox configuration and position of the gear selector and decides what the best action is. It signals solenoid shift valves inside the hydraulic system to open and close appropriately and the gearbox then changes gears as necessary. But how does the gearbox know to go up gears when you're speeding up, and down when you're slowing down? Well there's a device called the governor attached to the output shaft of the gearbox. It's a centrifugal sensor connected into the hydraulic circuit. The faster you're going, the faster the governer spins and the more open the valve in it becomes. That in turn allows the pressure of the hydraulic circuit to rise, which then applies more pressure to different components, pistons and clutch activators and lets the gearbox shift up at the right speeds. Again, in modern cars, all this information is fed through the ECU which also takes another input from a throttle sensor or more usually a vacuum modulator. These devices allow the ECU to know how hard the engine is working - something else that's critical to how the gearbox operates. It's these inputs that can sense the sudden need for more power so that when you stuff the accelerator to the floor, the gearbox can downshift. The ECU sees a relatively sedate output shaft speed from the governor but a sudden and dramatic increase in vacuum pressure in the engine intake manifold. This is the key to dump the gearbox down a gear to get more power and quick. Limiting gear selection. Most gearbox selectors have a '1' and '2' position. When you select one of these positions you're inhibitting the gearbox's ability to pick any gear higher than that. In a mechanical system it locks off certain portions of the hydraulic system physically so the gearbox simply cannot provide hydraulic pressure to the selector components. In a modern electronic gearbox, again you're simply telling the ECU "don't select anything higher than this". The ECU will then simply not ever send commands to open the solenoid valves to activate higher gears. The pump. It's probably no surprise to you that all this hydraulic trickery needs some sort of pressure to work and that
http://www.carbibles.com/transmission_bible.html (14 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

comes from the hydraulic pump. This is normally located in the cover of the gearbox housing itself and it draws fluid from the gearbox sump to feed the gearbox hydraulic system, the fluid cooler (basically a small radiator) and the torque converter. The pump itself is a typically a rotary displacement pump that uses the difference in pressure between the spinning centre lobe and the outer housing to suck fluid in on one side and expel it on the other. For the uninitiated or the morbidly curious, the image below shows a highly simplified example of the rats nest of hydraulic routes in a gearbox housing. The hydraulic lines are effectively cast in the metal because doing it with rubber hoses and clamps would be so complicated and take up so much space that it would be uneconomical and unreliable to do in mass production.

Park it!
So after the long and complicated slog through all that stuff above, are you ready for something simple? Ok, here we go. "P" - the park position on an automatic gear selector. If you've ever engaged park right before you've actually stopped, you'll have heard a clicking sound followed by a thud as the gearbox locks and the car rocks forwards. The mechanism that does this is so disturbingly simple it's almost not worth rendering a picture for. Ready? How about notches on the outside of the clutch housing and a single or pair of spring-loaded catches? Seriously. The image below shows the basic idea behind the park mechanism in an automatic. When you put the gearbox in 'P' for park, the catches are deployed and they fit into the notches on the outside of the clutch housing. Simple.

http://www.carbibles.com/transmission_bible.html (15 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Torque Converters
Just like a manual gearbox, an automatic gearbox needs a method of decoupling the constantly-spinning engine from the gearbox components. To do this it uses a torque converter which is a viscous fluid coupling (because it's full of hydraulic fluid). A torque converter consists of three basic elements. The impeller, the turbine and the stator. The impeller is attached to the torque converter housing which itself is attached to the engine flywheel. The impeller is basically a centrifugal pump. As the flywheel spins, so does the impeller and the vanes take the fluid from the central part of the torque converter and fling it to the outside creating a pumping action. The fluid then circulates around the outer edge of the torque converter and back into the turbine. The turbine is basically the opposite of the impeller - it's like a ships's propeller in that the fluid passing through it causes it to spin. The turbine is connected to the input shaft of the gearbox via a splined shaft so as the turbine spins, so does the input shaft to the gearbox. The fluid passes through the turbine from the outside towards the inside. Finally, as the fluid reaches the central core, it passes through the stator which is designed to help redirect the flow into the inner vanes of the impeller. (Without the stator, the whole system would be a lot less efficient) With this mechanism, the fluid is constantly being circulated. In the image below I've rendered the various parts of an example torque converter taken apart so you can see the internal construction.

http://www.carbibles.com/transmission_bible.html (16 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

When the engine is idling, the fluid is pumping around without a lot of force and the amount of torque on the turbine is minimal. As you accelerate, the impeller speeds up and creates larger forces on the turbine which in turn spins more quickly and with more torque. Because it's connected to the input shaft of the gearbox, this feeds more rotational speed and torque into the gearbox and the car starts to move forwards. It's because of this viscous liquid coupling that automatic gearboxes have a certain amount of 'slop' in them - the engine can rev up and down without the car actually changing speed too much. It's also the reason automatics are less fuel efficient because the torque converter uses up energy from the engine simply in its design by spinning the hydraulic fluid. In the image below I've rendered a cutaway of an assembled torque converter. The shaky yellow arrow is my attempt to show the basic circulation path of the fluid inside as it is pumped from the impeller (red) through the turbine (blue) and back through the stator (green).

http://www.carbibles.com/transmission_bible.html (17 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

For sportier vehicles or those with specialised needs, some torque converters include a hydraulic clutch. Once the car is moving and in top gear, the clutch engages and locks the turbine to the impeller. Once that happens, the whole torque converter spins as one and the viscous coupling becomes redundant - effectively the gearbox now behaves like a manual because the engine flywheel is connected directly to the gearbox input shaft. By locking all the components together, it makes the car as fuel efficient as a manual when in top gear because the energy that was being used up in the viscous coupling is no longer required. It also means instantaneous throttle response you push the accelerator and the car accelerates instantly just as with a manual. But why is it called a torque converter? Very simply, because it has the ability to multiply the torque from the engine 2 or 3 times in certain conditions. Basically, from a standing start, when the engine is spinning far faster than the gearbox, the whole design allows the torque from the flywheel to be multiplied. As the car gets up to speed, the multiplication factor drops until it becomes 1x once everything is in motion and the impeller and turbine are moving at almost the same speed. Doing it yourself. In true Blue Peter fashion, you can demonstrate the principle behind a torque converter at home. Get a large bucket or bowl and a cordless drill with a paint-stirrer. Fill the bucket with water and put some bits of paper around the outside of the bucket, floating on the water. Stuff the paint stirrer in the middle and pull the trigger on the drill. To start with, the paint stirrer is spinning way faster than the water in the bucket, and the bits of paper will barely be moving. As the water in the bowl begins to speed up its circulation, the bits of paper will being circulating the bucket at speed. Eventually the water in the bowl will be circulating at almost the same speed as the paint stirrer is turning. (At this point your wife/husband will probably also be complaining that it's going all over the kitchen/bathroom - you've been warned) It's that "almost" that shows the inefficiency in a
http://www.carbibles.com/transmission_bible.html (18 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

torque converter - the fluid can never spin at exactly the same speed and thus it can never impart the exact same torque and motion into the turbine. Now imagine that the bucket or bowl has vanes around the inside of it. As the water is circulating, it's going to be applying force to those vanes and given a slippery enough surface, your bucket or bowl will eventually start to spin. Voila. The drill and the paint stirrer are the input from the engine and the spinning bucket or salad bowl is the output to the gearbox. The other way to do this is to take two desk fans and turn one on and point it at the other. Eventually the second fan will start to spin because of the air being forced past it by the first fan. This uses the same principle but with moving air instead of water and it's nowhere near as much fun to watch

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

TipTronic® Gearboxes
If you've owned a VW or Audi in the last few years it might have come with a TipTronic® gearbox. To you, the driver, it looks like a regular automatic gearbox but with with an H-gate for the gearshift. In normal operation, you use the gearbox just like an automatic, putting it in 'D' for Drive and just letting it go about its business. But if you click the gearstick over into the H-gate it becomes a discrete automatic, meaning you can then click it fowards and backwards like a sequential gearchange. In this mode you are basically telling the gearbox when you want it to shift rather than allowing it to shift for you. When you click it forwards for example, you're indicating a desire to go up a gear. The ECU looks at the engine speed, road speed, torque and load and if all the planets align, it shifts up by activating the relevant solenoid valves in the automatic hydraulic system. Most TipTronic® designs do have a certain amount of idiot-proofing though, and if you try to rev the tits off the engine in first, it will override you and automatically shift up to second to save the engine. These types of gearboxes often have steering-wheel shifters either as buttons or triggers on the steering wheel (like the Mazda MX-5) or paddle-shifters. TipTronic® is actually a design from Porsche and they simply license it to other vendors, typically German manufacturers. Because it was one of the first designs to come to the mass market, this type of discrete automatic automatic gearbox is now often referred to as TipTronic® even if it isn't one of the VW/Audi/Porsche ones. Here's a non-comprehensive list of some of the manufacturers and their TipTronic® type shifts: Acura: Sequential SportShift. Audi: Tiptronic, Multitronic (CVT). BMW: Steptronic. Chrysler/Dodge: AutoStick. Citroën: Sensodrive. Ford (Australia): Sequential Sports Shift. Honda: iShift, S-matic, MultiMatic. Hyundai: Shiftronic, HMatic. Infiniti: Manual Shift Mode. Jaguar: Bosch® Mechatronic. Lexus: E-Shift. Mazda: Sport AT. Mercedes-Benz: TouchShift. MG-Rover: Steptronic. Mitsubishi: INVECS, INVECS II, Sportronic, Tiptronic. Nissan: Tiptronic. Vauxhall/ Opel: Easytronic. Peugeot: 2Tronic. Pontiac: TAPshift. Saab : Sentronic. Subaru: Sportshift (system developed and name used under license from Prodrive Ltd.). Smart : Softip. Volkswagen : Tiptronic. Volvo: Geartronic

Semi-automatic Gearboxes
Despite the name, these are actually an advanced type of manual gearbox. It's better to refer to them clutchless manual gearboxes because that more accurately describes what they are. Semi-automatics do not use planetary gearsets and torque converters; they use layshafts, output shafts, clutches and selector forks just like a manual. They come in three flavours, all of which have the same internal mechanisms. Two of those use the familiar paddle-shifters or updown gearstick for changing gears. (This begins to explain why you cannot simply look at a gearstick or paddle-shifter and tell what the gearbox is. Up/down gearsticks or paddleshifters can both control sequential manual, clutchless manual or TipTronic® type gearboxes.) The third type has a pure manual gearstick. None of the three types have a clutch pedal though so how do they work? Well in the case of the first type, when you click the gearstick up or down, or press one of the paddleshifters, a hydromechanical system disengages the clutch and then moves the gearbox selector forks into the position for the next gear before re-engaging the clutch. Because the system takes inputs from load- and torquehttp://www.carbibles.com/transmission_bible.html (19 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

sensors as well as road speed, throttle position and engine demand sensors, and because it's all computer controlled, it can shift more quickly and more smoothly that you or I ever could. The third type uses the same hydromechanical system underneath but has additional sensors coupled to the gearstick. With this type, the action of moving the gearstick out of the gate for one of the gears (for example pulling it back from first) passes a hall effect sensor which tells the clutch to disengage. When you push the gearstick into the gate for the new gear, another hall effect sensor detects the final position of the gearstick and tells the clutch to re-engage. Effectively it's identical to driving a manual car only without a clutch pedal. Clutchless manual gearboxes have appeared under many different names such as Saxomat and Olymat (Fiat 1800, Saab 93, some BMWs and Opels).

DSG / DCT Gearboxes - what, why and how?
How does this sound? A manual gearbox that's always in two gears at the same time. Sounds impossible, right? Scroll back up to the top of the page and look at how a manual gearbox works - how can this happen? Enter stage left the dual clutch transmission (DCT) or direct-shift gearbox (DSG). Two different names for essentially the same design. The most famous / common of these currently is the DSG as fitted to the Audi TT and some of the newer VW Golfs. The DSG is licensed technology from BorgWarner, which despite sounding like a horrible accident between a Star Trek character and a large movie studio, is an automotive parts supplier known until this point for its automatic gearboxes. The principle is really simple even if the engineering is really complex. The idea is that when you're going up through the gears, increasing in speed, one clutch has the current gear engaged and a second clutch has the next gear up preengaged ready to use in the blink of an eye. Technically, that's not even true because a DSG can shift gears in 8 milliseconds. At 400 milliseconds it takes you 50 times longer than that to blink. That in essence is the key benefit to the DSG - blisteringly fast gearchanges. Plus, because one clutch engages as the other one disengages, the time that the gearbox is not driven under power is minimised. So how does this work? Well a DSG gearbox has one layshaft like a normal gearbox, but two output shafts that mesh to a third shaft which goes to the differential. One output shaft has 1st, 3rd and 5th gears on it whilst the other has 2nd, 4th and 6th. The layshaft is actually two shafts one inside the other connected to two concentric 4-plate basket-type clutches at the end. In first gear, one clutch is engaged and the central layshaft is connected to the engine. Selector forks have the first dog-gear engaged with the first helical gear and the car is moving forwards. At the same time though, on the second output shaft, the second dog gear is already engaged with the second helical gear. Because the outer clutch on the layshaft is disengaged though, there is nothing driving this second gear and the outer layshaft is simply spinning freely. At the point when the gearbox needs to shift up, it simply engages the second clutch at the same moment it disengages the first and the outer layshaft is now being driven from the engine. Because second gear was already engaged there is literally no delay in shifting so the gearchange is near instantaneous. Once in second gear, the inner layshaft is now freewheeling as the selector forks engage third gear on the first output shaft and so on and so forth. The three images below show my typical manual gearbox example modified into a 5-speed DSG. In this first image, first gear is engaged and second gear is pre-selected. The transmission of power from the engine to the output shaft is shown with the green components. The dual clutch (shown in cutaway) has engaged the inner set of friction plates which are connected to the outer layshaft. The first dog-gear is engaged with the first helical gear.

http://www.carbibles.com/transmission_bible.html (20 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

In this second image, second gear is selected and third gear is pre-selected. Again, the transmission of power is shown with the green components. This time the dual clutch has engaged the outer set of friction plates that are connected to the inner layshaft. The second dog-gear was already engaged with the second helical gear and so is now driving the output shaft.

http://www.carbibles.com/transmission_bible.html (21 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

This final image shows a cutaway of a simplified dual-clutch, dual-layshaft so you can see how the friction plates, layshaft and gears all relate to each other. The green inner layshaft has the drive gears for second and fourth whilst the outer red layshaft has drive gears for first, third and fifth. The grey clutch housing contains all the springs and hydraulics used to engage the various clutch plates, although they're not rendered in this view.

http://www.carbibles.com/transmission_bible.html (22 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

CVT (continuously variable transmission) - what, why and how?
As they say in some circles, it's all downhill from here. Seriously. If you got your head around DSGs and automatic boxes, the rest of this page is going to be a veritable walk in the park, starting with the CVT - continuously variable transmission. CVTs are based on simplicity rather than complexity. Gone are the nightmare of spinning, whirling, intermeshing gears, cluches, clamps, bands, friction plates etc etc ad nauseum. Instead, the CVT essentially has three moving parts. No seriously. Read on. If you live in the Netherlands, you're intimately familiar with the CVT - every brommer has one. For those unfortunate enough to have never lived there, a brommer is a small moped - typically less than 50cc in capacity. They're all twostroke engines and they are uniquely identifiable from their sound - a constant pitched engine. No revving up and down, just a long, continous high-pitched drone, like bees on crack. It's a gorgeous sound. As a matter of fact, the Dutch car company DAF introduced the first CVT in a car way back in 1958. Today, you can find CVTs on modern Vespas and other scooters, including superscooters like the Suzuki Burgman. In 2005 CVTs really moved into the mainstream when Nissan introduced the "no shift shock" gearbox into their cars and SUVs. This followed a somewhat faltering start from Ford in 2004 who, frankly, botched the launch of their CVT so badly that barely anyone remembers it. So what the hell makes it so attractive to the automotive and motorcycling markets? Well apart from the simplicity, it has one extremely sound engineering principle : get the engine to peak torque and keep it there whilst infinitely varying the transmission. That way the engine is always performing at peak capacity. No changing gears, no revving up and down the rev range, and as Nissan so aptly put it - no shift shock. Interesting factoid : CVT's were banned from Formula 1 in 1994 because they were making the cars too fast...

Two pulleys and a belt. It really is that simple.
So how does this magical CVT work? Simply. Very simply. The most basic CVT has two variable pulleys and a steel-core rubber belt. One pulley is connected to the flywheel and the other to the gearbox output shaft. A belt loops around
http://www.carbibles.com/transmission_bible.html (23 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

between the two. On simple scooter-type CVTs, the pulleys change geometry simply by rotational forces - the faster the engine pulley spins, the more it closes up and the faster the output pulley spins, the more it opens out. In automotive applications, the geometry of the pulley is governed by a hydraulic piston connected to the ECU. The pulley itself is basically a splined shaft with a pair of sliding conical wedges on it. The closer the wedges are together, the larger the radius 'loop' the belt has to make to get around them. The further they are apart, the smaller the radius 'loop' the belt has to make. Based on the principles established right at the top of the page when I was talking about intermeshing gears, if the flywheel pulley has a small radius and the output pulley has a large radius, then the transmission is essentially in low gear. As the car gets up to speed, the two pulleys are adjusted together so that they present an infintely changing series of radii to the belt which ends up with the flywheel pulley having the largest radius and the output pulley having the smallest. On then to the pictures. This first image shows the basic layout of a pulley-based CVT with the two sliding pulleys and the drive belt. This is the equivalent of 'low gear' - the drive pulley spins two or three times for each rotation of the output pulley. It's the equivalent of a small gear meshing with a large gear in a regular manual gearbox.

This image shows the same system in 'high gear'. The drive pulley has closed up forcing the drive belt to travel a larger radius. At the same time, the output pulley has pulled apart giving a smaller radius. The result is that for each turn of the drive pulley, the output pulley now spins two or three times. It's the equivalent of a large gear meshing with a small gear in a regular manual gearbox. The difference here is that to get from the low gear to the high gear, the infinite adjustment of the position of the pulleys basically means an infinite number of gears with no point where the drive is ever disconnected from the output. Sweet.

http://www.carbibles.com/transmission_bible.html (24 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Toroidal CVT
As good as a belt-driven CVT is, the weak link is the belt. If it gets damaged in any way, the transmission becomes useless. Another solution then is the toroidal CVT which is equally as simple in operation but has parts which are less prone to wear than the belt-drive type. With a toroidal CVT, both the input and output shafts are sculpted metal discs that face each other. In between are two rollers that free-wheel on their x-axis, making contact with both discs. The position of the rollers is controlled hydraulically and they pivot in their z-axis around a common centre so that wherever they are in their rotation, the rollers always touch the discs. Because the position of contact changes on the discs, the relative rotation of each disc changes. The image below shows a toroidal CVT in low gear. The input shaft is on the left. As it spins, the rollers make contact on the surface of it in the area I've shaded red. This spins both rollers on their x-axes, and because they both touch the output disc, it is spun in turn. The contact area on the surface of the output disc scribes a much larger circle - again rendered in red. Going back to the most basic stuff you learned at the top of the page, this is the equivalent of a small gear driving a large gear - the gearbox is effectively in low gear.

http://www.carbibles.com/transmission_bible.html (25 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

For a toroidal CVT to increase the output shaft speed, both the rollers are pivotted slowly about their y-axes. As they do this, their point of contact on the input and output discs changes in an infinitely smooth, continous motion. Effectively, the radius of the path on the input disc gets larger and larger as the radius of the path on the output disc gets smaller and smaller. This creates and infinite number of gear ratios until 'top gear' is reached when the rollers are in the opposite position to where they started. Now you can see the equivalent of a large gear driving a small gear - the gearbox is effectively in high gear.

http://www.carbibles.com/transmission_bible.html (26 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

This type of infinitely adjustable toroidal CVT can be stacked up end-to-end to provide other gearing options, and is essentially how the system in the 2007 Nissan CVT gearboxes works. This last image shows a double-toroidal Nissan-type CVT configuration.

http://www.carbibles.com/transmission_bible.html (27 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Differentials - they're why you can turn corners
With one or two exceptions, every car has a differential. This was a great surprise to an insurance adjuster I spoke to a few years back when he came to process a claim. He eloquently informed me that my claim was being rejected because my car didn't have a differential to replace. In the following few paragraphs you'll learn why that loss adjuster was talking bollocks. So how best to begin to talk about differentials? I suppose to start with you need to understand a very simple concept to do with circles. When you make a car go around a corner, the outer wheels travel further than the inner wheels. Have a look at the diagram below to see what I'm talking about.

http://www.carbibles.com/transmission_bible.html (28 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

The first thing you'll notice is that the rear wheels take a different path to the front wheels, but the other thing to notice is that because the car's wheels are describing different radius arcs, the further away from the centrepoint of the arc, the larger the distance that gets travelled. In car terms, that means the outer wheels need to turn more times than the inner ones every time you go around a corner, because they're describing a larger arc. The brighter ones amongst you will now have figured out that if the outer and inner wheels were joined together with a solid axle, one of them could not turn more times than the other - they'd have to turn at the same rate. That, dear reader, is the crux of the matter. Differentials basically allow two wheels on the same axle to turn at different rates. (As well as allowing the wheels on the same axle to turn at different rates, the differential also acts as the final gear reduction in the driveline.)

Is there a differential on each axle?
That depends. On a two-wheel-drive car, no. Only the driven axle needs a differential. The undriven wheels are not connected to each other so the differential is a moot point. For four-wheel-drive or all-wheel-drive vehicles, then yes, both the front and rear axles will have differentials because they are both driven axles. Technically, a differential is a torquesplitter - it splits the input torque two ways to two output shafts, each of which can turn at a different rate. For full-time all-wheel-drive, there is often a third differential in the driveline from the front to the rear of the vehicle, to allow the entire front and rear axles to spin at different speeds to each other. The difference between the various drive systems is illustrated later on this page in the section on 2WD, 4WD and AWD.

Open Differentials
We'll deal with open differentials first because they're the easiest to explain, they're the most common, and they supply the same amount of torque to each output. Open differentials have a few essential components, illustrated below. The input pinion gear is the gear that is driven from the drivetrain - typically the output shaft from the transmission. It drives the ring gear which, being larger, is what gives that final gear reduction I mentioned. Attached to the ring gear is the cage, containing two captive pinion gears that are intermeshed with the two output pinion gears, one connected to each axle. The captive pinions are free to rotate how they wish.

http://www.carbibles.com/transmission_bible.html (29 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

As the input pinion spins, it meshes with the ring gear. The ring gear spins, spinning the cage and the two captive pinions. When the vehicle is travelling in a straight line, neither drive pinion is trying to spin any differently from the other, so the captive pinions don't spin and the turning of the ring gear is translated directly to both drive pinions. These are connected to the driveshafts to the wheels, so effectively, the ring gear spins the wheels at the same speed that it is turning. When the vehicle starts to turn a corner, one of the wheels is going to want to spin more quickly than the other. At this point, the captive pinions come into play, allowing the two drive pinions to spin at slightly different speeds whilst still transmitting torque to them. Clever. You can tell if your vehicle's differential is working properly by jacking the driven axle up off the ground and spinning one wheel. When you do, because the gearbox is stationary, it holds the ring gear solid, the captive pinions spin in opposite directions, and the other wheel on the axle spins the other way around. This also explains why a two-wheel-drive vehicle can get into trouble when one wheel has less friction with the ground than the other. The open differential cannot compensate for this. If one drive pinion is held solid compared to the other, then all the input gets redirected to the drive pinion that has the least resistance. This is why when you gun a two-wheel-drive car with one wheel on ice and the other on the road, the wheel on the ice spins and the wheel on the road doesn't. You don't go anywhere because all the engine power is directed to the wheel with least resistance - the one on the ice. Imagine the same scenario on a four-wheel-drive vehicle that has open differentials on the front and rear. If you're offroading in such a vehicle and get it into a situation where one front wheel and one rear wheel are off the ground, you're stuck. The differentials will spin the airborne wheels and send no torque to the ones on the ground. That leads us nicely on to the next topic :

Limited-slip differentials
http://www.carbibles.com/transmission_bible.html (30 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Sometimes known by the "positraction" moniker, the simplest form of limited-slip differential is designed to combat the scenario outlined above. Physically there's not a lot of difference in the design of a limited-slip differential. It still has all the components of an open differential but there is two crucial extra elements. The first are spring pressure plates which are a pair of springs and pressure plates nestled in the cage between the two drive pinions. These push the drive pinions outwards where the second extra element comes into play - clutch packs. The backside of the drive pinions have friction material on them which presses against clutch plates built into the cage. This means that the clutch is always going to try to behave as if the car was moving in a straight line by attempting to make both output pinions spin at the same speed as the ring gear and cage. However, when a car with a limited-slip differential goes into a corner, there are enough forces at play that the drive pinions begin to slip against the clutch material, thus allowing them to turn at different speeds again. The stiffness of the spring pack coupled with the friction of the clutch pack together determine the amount of torque required to overcome the clutch. So lets go back to our hapless driver stuck with one wheel on the ice and another on the road. With a limited-slip differential, because of the spring- and clutch-packs, even though one wheel is on the ice, the differential is going to attempt to spin both drive pinions at the same speed. With low engine revs and steady throttle control, the wheel on the road will get enough spin to move the vehicle forwards. If the engine is revved hard though, it can still generate sufficient torque to overcome the clutch pack and once again, only the wheel on the ice will spin. To get around this, it's a good idea to try to pull away in second gear - that gives the limited-slip differential a chance to do its job. The render below shows the generic open differential from above modified to be a limited-slip differential.

Torsen differentials
http://www.carbibles.com/transmission_bible.html (31 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Torsen differentials are a derivative of open differentials. They derive their name from their function - Torque-Sensing. When the torque going to both outputs is the same, a Torsen differential essentially works just like an open differential. The change comes when the torque going to each output begins to change, for example as a result of a slippery road surface under one wheel. When this happens, what's known as an Invex gear train (inside the differential) begins to bind together. The Invex gear train is designed with a torque bias ratio in mind that determines the ratio of torque that it can split between the outputs as the geartrain begins to bind together. A 3:1 Torsen differential, for example, can deliver three times the torque to the output that has more traction. The downside of this is that if one output suddenly ends up with no traction at all, the differential won't be able to supply any torque to the other output. Using the 3:1 example, one output can have up to three times the torque than the other. If one output has zero traction, then three times zero is zero, so the other output also gets no torque. That's a gross simplification of how the system works too. If you're really interested, Torsen Traction have some good engineering articles on their website. Torsen differentials are normally used in-line between the front and rear drives for performance all-wheel-drive vehicles, to split the torque between the front and rear axles, rather than the left and right wheels.

How does a Torsen 'sense' torque?
The Invex geartrain is essentially a set of helical-cut gears that all mesh together and torque-sensing is actually a bit of a misnomer. The Torsen differential is an entirely mechanical affair with no clutches, hydraulics, actuators or sensors. It doesn't really 'sense' anything. If you look at the rendering above, you can see the Invex gears mesh with the helical
http://www.carbibles.com/transmission_bible.html (32 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

drive pinions. At the ends of the Invex gears are regular-cut gears that mesh with each other. So in this example, looking at the top pair of Invex gears; the left gear meshes it's helical-cut part with the helical left drive pinion, and it meshes it's regular-cut part with the right Invex gear. That gear in turn meshes its helical-cut part with the right helical drive pinion. It's this interconnectivity that allows the Torsen to work like an open differential when the torque is even, but as a torque-sensing unit when its not. Where the helical cuts mesh together (shown in close-up in the rendering on the right), there's a certain amount of friction inherent in that design. The angle of the helical spiral used to create the gears determines the amount of force required to make them turn. The shallower the pitch of the spiral, the more force required, and hence the more torque required to turn two meshed gears. That's the clever part then - the spiral pitch. The precise spiral pitch angle determines the torque bias ratio. The whole system works on simple high-school physics. Remember the experiment where you had two blocks of wood with sloped cuts and you had to determine the downward force required to make the top block slide along the slope of the bottom block? It's the same principle. The steeper the slope, the less force required to make the block slip. With helical gears, the steeper the pitch of the spiral, the less torque required to make them mesh together.

Locking differentials
Locking differentials are another derivative of open differentials but with an electronic, pnuematic or hydraulic actuation system that locks the two drive pinions together as if they were a solid axle. This is for use in serious off-roading, where a vehicle will spend a lot of time with one wheel per axle in the air. By locking the differential, it behaves like a solid axle and both wheels are spun together.

The exceptions that prove the rule
Remember I said that there were a couple of exceptions? A good example of a vehicle with no differential would be a NASCAR or Indy car racer. To save weight, those cars have no differential. "Ah yes," I hear you say, "but they go around corners so they must have differentials!". Well - yes, and no. With the exception of street courses, NASCAR and Indy car racers always turn left, and this is Good News for the engineers. When you know that a vehicle is always going to be turning one direction, you can make the outer tyres physically larger than the inner ones. This gives them a greater circumference, and that in turn means that for every turn of the axle, the outer tyre is going to try to travel further than the inner one - precisely what you need in a corner. For the straights, these racers live with the scrubbing that happens when the tyres tyre to travel different distances because 90% of the time they are cornering.

AWD couplings
Viscous couplings
Viscous coupling aren't really a type of differential but they're worth mentioning because they're used a lot in all-wheel drive vehicles. Lower end AWD vehicles are actually mostly 2-wheel drive vehicles (see the article below for all the differences) until the front wheels begin to slip. When that happens, they become all-wheel-drive through the use of a viscous coupling. In it's most simple form, it's essentially identical to the torque converter found in an automatic gearbox. For a full description of how that works, see torque converters up above.

Hydraulic clutch couplings
Again, not really a differential, but another type of device used in AWD cars to engage the rear differential. With these types of coupling, the front and rear differentials drive hydraulic pumps - normally filled with oil. Any difference in the speed of the two pumps causes a pressure imbalance in the system that activates a clutch pack in-line to the rear differential to
http://www.carbibles.com/transmission_bible.html (33 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

engage it. So again, when the front wheels spin faster than the rear (meaning slip), the clutch pack is engaged and the rear differential comes into play. These types of coupling typically also have braking and thermal overrides so that if the gearbox oil in the rear differential becomes too hot, or the car is braking, the clutch pack can be overridden and disengaged (without this, ABS-equipped vehicles would not be able to sense all four wheels correctly under braking). Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

2WD, 4WD, AWD
Ok so in the last couple of pages you've now seen a lot of references to 2WD (two-wheel drive), 4WD (four-wheel drive) and AWD (all-wheel drive). Time to explain the differences.

2WD - two-wheel drive
This is by far the most common type of drivetrain in any car today. The engine drives the gearbox which sends its output to an open differential either on the front or rear axle, which in turn drives those wheels. If one of the driven wheels comes off the ground, or gets on a slippery surface like ice, the car gets stuck because all the torque is being sent to that wheel whilst the other three sit there helpless.

4WD - four-wheel drive
Also known as part-time all-wheel drive, this system has an open differential on the front and rear axle and a transfer case on the output from the gearbox. Typically 4WD is normally driving the rear axle with the front axle only coming into play in 4WD mode. The transfer case is the device that splits the torque between the front and rear axles. It typically has some sort of selectable internal differential or viscous coupling to allow the front and rear drives to turn at different speeds if need be. Some trucks and SUVs have a selector with 2H, 4H and 4L on it - it looks like a second gear shift. This is actually controlling how the front and rear outputs of the transfer case get locked together. In 2H mode (2-wheel drive, high), it essentially disconnects the front output completely and only drives the rear axle. In 4H mode (4-wheel drive, high), it engages the front output via the viscous coupling so that the axles can turn at different speeds, and now sends torque
http://www.carbibles.com/transmission_bible.html (34 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

to both open differentials. In 4L mode (4-wheel drive, low) it engages a second set of reduction gears and locks the front and rear axles together so they must spin at the same speed. This would be bad for on-road driving because it does not allow any difference in speed between the front and rear wheels, so you'd often get dragging and slipping which would make the car essentially unsafe to drive. However, locking everything together like this and reducing the gear ratio makes perfect sense for off-roading, which is why it's an option. However, with open differentials, it's still entirely possible to get stuck with a 4WD vehicle. If you're off-roading and the front-left and rear-right wheels both leave the ground together (for example), then the torque will all be sent to those wheels and they'll spin helplessly in the air. Locking, limited-slip or Torsen differentials solve this but add weight, complexity and cost to the system. Locking hubs On older 4WD systems, the front wheels could only be engaged to the transfer case by locking hubs. Essentially the transfer case was always sending torque to the front driveshaft and had no viscous coupling. To get into 4WD mode, the driver had to stop and get out, and lock the front wheels to the axles so they could be driven. In newer 4WD systems, the lockable hubs are still present on some models, but are designed more for mechanical sympathy and fuel economy than anything else. With the hubs onlocked, the whole front part of the drive system isn't being dragged along for the ride, which causes mechanical wear and a drop in fuel economy.

AWD - all-wheel drive type 1
Finally, all-wheel drive or full-time 4WD. Found mostly on sportier cars, but also on some SUVs, there are two types of AWD, both designed to try to overcome the problems with 4WD. The simplest form has two open differentials - one on each axle - and a viscous coupling between. The engine drives the gearbox which drives two output shafts. One goes to the front open differential and the other goes to the viscous coupling, the output of which is connected to the rear open differential. Under normal conditions, this type of AWD system functions exactly like a 2WD car, driving only the front axle (unlike a 4WD which normally drives the rear axle). Lower end Subarus and some of the Honda trucks use this system. The front wheels turn at a certain rate, and the rear wheels are dragged along for the ride. Both halves of the viscous coupling are spinning at the same speed so no torque is sent to the rear axle. If the front wheels begin to slip and spin, the input to the front of the viscous coupling begins to spin faster than the rear and because of its torqueconverter-like design, this causes the rear output to want to speed up. At this point, the drivetrain is now transferring torque to the rear axle and the car starts to function in AWD mode. Actally, AWD is a bit of a misnomer at this point, because unless the car has limited-slip differentials front and rear, it's still only really driving two wheels in this mode - the one on the front and the one on the rear axles that have the most traction. That leads us nicely on to.....

http://www.carbibles.com/transmission_bible.html (35 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

AWD - all-wheel drive type 2
This is the other type of AWD found on higher-end Subarus, rally cars, expensive sports sedans and such. Very similar to the type 1 AWD, it replaces the viscous coupling with a Torsen differential, and replaces the open differentials front and rear with either Torsen or limited-slip differentials. This is the only true all-wheel-drive system because it will always drive all four wheels. It's also bloody expensive and it saps gas-mileage because of all the extra drag induced in the driveline. But then if you're into performance off-roading, gas-mileage really isn't your primary concern.

FWD, RWD, FE, ME, RE
http://www.carbibles.com/transmission_bible.html (36 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Not to be confused with the descriptions aboe, these acronyms determine the engine location and driven axle(s) on a car. FWD = front-wheel drive. RWD = rear-wheel drive. FE = front engine. ME = mid engine. RE = rear engine. The position of the engine, being the heaviest part of the car, affects how the car handles. Most vehicles are frontengined, front-wheel drive (FE-FWD) with the engine, gearbox and differential all clustered together in one place.

BMWs and other higher-end vehicles are front-engined, rear-wheel drive (FE-RWD) with a propshaft going from the gearbox and engine at the front to the differential at the rear.

http://www.carbibles.com/transmission_bible.html (37 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Sports cars like the Toyota MR2 and the McLaren F1 are mid-engined. Putting the engine as close to the middle of the car as possible gives the best possible front-to-rear weight distribution and gives predictable, even handling. Mid-engined cars are typically rear-wheel drive (ME-RWD).

Finally, rear-engined vehicles such as most Porsches and the original VW Beetle have the engine, gearbox and differential all clustered at the rear of the car and are typically rear-wheel drive (RE-RWD). The downside of this is that when cornering, with that much weight at the back of the vehicle, it can behave like a pendulum and induce chronic oversteer in corners.

http://www.carbibles.com/transmission_bible.html (38 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Transmission Bible

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/transmission_bible.html (39 of 39) [2/6/2008 7:13:45 AM]

Car Bibles : The Car Steering Bible

The car steering Bible, covering everything you need to know about car steering, rack and pinions, power steering, passive and active 4-wheel steering, tilt-and-slide steering wheels and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Steering : essential to driving
Elsewhere on this site you can learn about all the other stuff that makes a car go and stop, so this page is where you'll learn about how it goes around corners. More specifically, how the various steering mechanisms work. Like most things in a car, the concept of steering is simple - you turn the steering wheel, the front wheels turn accordingly, and the car changes direction. How that happens though is not quite so simple. Well - it used to be back in the days when cars were called horseless carriages, but nowadays, not so much.

Basic steering components
99% of the world's car steering systems are made up of the same three or four components. The steering wheel, which connects to the steering system, which connects to the track rod, which connects to the tie rods, which connect to the steering arms. The steering system can be one of several designs, which we'll go into further down the page, but all the designs essentially move the track rod left-to-right across the car. The tie rods connect to the ends of the track rod with ball and socket joints, and then to the ends of the steering arms, also with ball and socket joints. The purpose of the tie rods is to allow suspension movement as well as an element of adjustability in the steering geometry. The tie rod lengths can normally be changed to achieve these different geometries.

http://www.carbibles.com/steering_bible.html (1 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

The Ackermann Angle : your wheels don't point the same direction.
In the simplest form of steering, both the front wheels always point in the same direction. You turn the wheel, they both point the same way and around the corner you go. Except that by doing this, you end up with tyres scrubbing, loss of grip and a vehicle that 'crabs' around the corner. So why is this? Well, it's the same thing you need to take into consideration when looking at transmissions. When a car goes around a corner, the outside wheels travel further than the inside wheels. In the case of a transmission, it's why you need a differential (see the Transmission Bible), but in the case of steering, it's why you need the front wheels to actually point in different directions. This is the diagram from the Transmission Bible. You can see the inside wheels travel around a circle with a smaller radius (r2) than the outside wheels (r1):

http://www.carbibles.com/steering_bible.html (2 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

In order for that to happen without causing undue stress to the front wheels and tyres, they must point at slightly different angles to the centreline of the car. The following diagram shows the same thing only zoomed in to show the relative angles of the tyres to the car. It's all to do with the geometry of circles:

This difference of angle is achieved with a relatively simple arrangement of steering components to create a paralellogram geometry with one of the parallel sides shorter than the other. Once this is achieved, the wheels point at different angles as the steering geometry is moved. Most vehicles now don't use 'pure' Ackermann steering geometry because it doesn't take some of the dynamic and compliant effects of steering and suspension into account, but some derivative of this is used in almost all steering systems:

http://www.carbibles.com/steering_bible.html (3 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Why 'Ackermann'?
This particular technology was first introduced in 1758 by Erasmus Darwin, father of Charles Darwin, in a paper entitled "Erasmus Darwin's improved design for steering carriages--and cars". It was never patented though until 1817 when Rudolph Ackermann patented it in London, and that's the name that stuck.

Steering ratios
Every vehicle has a steering ratio inherent in the design. If it didn't you'd never be able to turn the wheels. Steering ratio gives mechanical advantage to the driver, allowing you to turn the tyres with the weight of the whole car sitting on them, but more importantly, it means you don't have to turn the steering wheel a ridiculous number of times to get the wheels to move. Steering ratio is the ratio of the number of degrees turned at the steering wheel vs. the number of degrees the front wheels are deflected. So for example, if you turn the steering wheel 20° and the front wheels only turn 1°, that gives a steering ratio of 20:1. For most modern cars, the steering ratio is between 12:1 and 20:1. This, coupled with the maximum angle of deflection of the wheels gives the lock-to-lock turns for the steering wheel. For example, if a car has a steering ratio of 18:1 and the front wheels have a maximum deflection of 25°, then at 25°, the steering wheel has turned 25°x18, which is 450°. That's only to one side, so the entire steering goes from -25° to plus 25° giving a lock-to-lock angle at the steering wheel of 900°, or 2.5 turns (900° / 360). This works the other way around too of course. If you know the lock-to-lock turns and the steering ratio, you can figure out
http://www.carbibles.com/steering_bible.html (4 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

the wheel deflection. For example if a car is advertised as having a 16:1 steering ratio and 3 turns lock-to-lock, then the steering wheel can turn 1.5x360° (540°) each way. At a ratio of 16:1 that means the front wheels deflect by 33.75° each way. For racing cars, the steering ratio is normally much larger than for passenger cars as the racing drivers need to get fuller deflection into the steering as quickly as possible.

Turning circles
The turning circle of a car is the diameter of the circle described by the outside wheels when turning on full lock. There is no hard and fast forumla to calculate the turning circle but you can get close by using this: turning circle radius = (track/2) + (wheelbase/sin(average steer angle)) The numbers required to calculate the turning circle explain why a classic black London taxi has a tiny 8m turning circle to allow it to do U-turns in the narrow London streets. In this case, the wheelbase and track aren't radically different to any other car, but the average steering angle is huge. For comparison, a typical passenger car turning circle is normally between 11m and 13m with SUV turning circles going out as much as 15m to 17m. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Steering System designs : Pitman arm types
There really are only two basic categories of steering system today; those that have pitman arms with a steering 'box' and those that don't. Older cars and some current trucks use pitman arms, so for the sake of completeness, I've documented some common types. Newer cars and unibody light-duty trucks typically all use some derivative of rack and pinion steering. Pitman arm mechanisms have a steering 'box' where the shaft from the steering wheel comes in and a lever arm comes out - the pitman arm. This pitman arm is linked to the track rod or centre link, which is supported by idler arms. The tie rods connect to the track rod. There are a large number of variations of the actual mechanical linkage from direct-link where the pitman arm is connected directly to the track rod, to compound linkages where it is connected to one end of the steering system or the track rod via other rods. The example below shows a compound link.

http://www.carbibles.com/steering_bible.html (5 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Most of the steering box mechanisms that drive the pitman arm have a 'dead spot' in the centre of the steering where you can turn the steering wheel a slight amount before the front wheels start to turn. This slack can normally be adjusted with a screw mechanism but it can't ever be eliminated. The traditional advantage of these systems is that they give bigger mechanical advantage and thus work well on heavier vehicles. With the advent of power steering, that has become a moot point and the steering system design is now more to do with mechanical design, price and weight. The following are the four basic types of steering box used in pitman arm systems.

Worm and sector
In this type of steering box, the end of the shaft from the steering wheel has a worm gear attached to it. It meshes directly with a sector gear (so called because it's a section of a full gear wheel). When the steering wheel is turned, the shaft turns the worm gear, and the sector gear pivots around its axis as its teeth are moved along the worm gear. The sector gear is mounted on the cross shaft which passes through the steering box and out the bottom where it is splined, and the the pitman arm is attached to the splines. When the sector gear turns, it turns the cross shaft, which turns the pitman arm, giving the output motion that is fed into the mechanical linkage on the track rod. The following diagram shows the active components that are present inside the worm and sector steering box. The box itself is sealed and filled with grease.

http://www.carbibles.com/steering_bible.html (6 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Worm and roller
The worm and roller steering box is similar in design to the worm and sector box. The difference here is that instead of having a sector gear that meshes with the worm gear, there is a roller instead. The roller is mounted on a roller bearing shaft and is held captive on the end of the cross shaft. As the worm gear turns, the roller is forced to move along it but because it is held captive on the cross shaft, it twists the cross shaft. Typically in these designs, the worm gear is actually an hourglass shape so that it is wider at the ends. Without the hourglass shape, the roller might disengage from it at the extents of its travel.

http://www.carbibles.com/steering_bible.html (7 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Worm and nut or recirculating ball
This is by far the most common type of steering box for pitman arm systems. In a recirculating ball steering box, the worm drive has many more turns on it with a finer pitch. A box or nut is clamped over the worm drive that contains dozens of ball bearings. These loop around the worm drive and then out into a recirculating channel within the nut where they are fed back into the worm drive again. Hence recirculating. As the steering wheel is turned, the worm drive turns and forces the ball bearings to press against the channel inside the nut. This forces the nut to move along the worm drive. The nut itself has a couple of gear teeth cast into the outside of it and these mesh with the teeth on a sector gear which is attached to the cross shaft just like in the worm and sector mechanism. This system has much less free play or slack in it than the other designs, hence why it's used the most. The example below shows a recirculating ball mechanism with the nut shown in cutaway so you can see the ball bearings and the recirculation channel.

http://www.carbibles.com/steering_bible.html (8 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Cam and lever
Cam and lever steering boxes are very similar to worm and sector steering boxes. The worm drive is known as a cam and has a much shallower pitch and the sector gear is replaced with two studs that sit in the cam channels. As the worm gear is turned, the studs slide along the cam channels which forces the cross shaft to rotate, turning the pitman arm. One of the design features of this style is that it turns the cross shaft 90° to the normal so it exits through the side of the steering box instead of the bottom. This can result in a very compact design when necessary.

http://www.carbibles.com/steering_bible.html (9 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Steering System designs : Rack and pinion
This is by far the most common type of steering you'll find in any car today due to it's relative simplicity and low cost. Rack and pinion systems give a much better feel for the driver, and there isn't the slop or slack associated with steering box pitman arm type systems. The downside is that unlike those systems, rack and pinion designs have no adjustability in them, so once they wear beyond a certain mechanical tolerance, they need replacing completely. This is rare though. In a rack and pinion system, the track rod is replaced with the steering rack which is a long, toothed bar with the tie rods attached to each end. On the end of the steering shaft there is a simple pinion gear that meshes with the rack. When you turn the steering wheel, the pinion gear turns, and moves the rack from left to right. Changing the size of the pinion gear alters the steering ratio. It really is that simple. The diagram below shows an example rack and pinion system as well as a close-up cutaway of the steering rack itself.

http://www.carbibles.com/steering_bible.html (10 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

http://www.carbibles.com/steering_bible.html (11 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Variable-ratio rack and pinion steering
This is a simple variation on the above design. All the components are the same, and it all works the same except that the spacing of the teeth on the rack varies depending on how close to the centre of the rack they are. In the middle, the teeth are spaced close together to give good, quick-reacting steering for the first few degrees. As the teeth get further away from the centre, they increase in spacing slightly so that the steering becomes less sensitive at steeper angles. Simple.

Topics still to come in late 2007 & early 2008
Hydraulic and electronic power steering Speed-sensitive power steering 4-wheel steering - passive and active Drive-by-wire steering Tilt / slide steering wheels and collapsible steering columns
http://www.carbibles.com/steering_bible.html (12 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : The Car Steering Bible

Oversteer and understeer

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/steering_bible.html (13 of 13) [2/6/2008 7:14:02 AM]

Car Bibles : Product Reviews

The car Bibles product review page, covering in-depth reviews of motoring accessories from pressure gauges and pumps to fuel economy devices, traffic light changers and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Welcome
This page is where I am collecting product reviews for all manner of motoring accessories from fuel economy devices to footpumps. The products are reviewed in date order and cover all aspects of motoring and motorcycling. If you have a motoring accessory you'd like me to review, contact me at the Email me page and we'll talk.

'Wearable' action / sports camcorders
There's a new breed of camcorder coming to the market - self-contained flash memory camcorders. Two of them tout their product as 'sports' or 'action' camcorders. The idea is simple enough - a compact, self-contained unit with a lens, CCD, microphone, memory card slot, some batteries and a set of rudimentary controls. I review the two contenders here.

GoPro Hero Digital Sports Camcorder
Tested January 2008 Website: www.goprocamera.com
Billed as a waterproof digital camera for sport, the Digital Hero
http://www.carbibles.com/productreviews.html (1 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

was launched at the SEMA show in Vegas last in 2007. It comes in three flavours - wrist camera, helmet camera and motorsports camera. The three units are actually all the same - the difference is in the mounting kits that they come with. The wrist camera comes with a velcro wrist strap. The helmet cam comes with various helmet mounting options and the motorsports cam comes with a bunch of stick-on mounts and a suction cup mount. What differentiates the GoPro from the ATC-2K is the form factor (it looks like a mini digital camera) and the fact that it comes in a shockproof, bombproof, waterproof housing. To test it, I went skiing with it, and then used the suction cup mount to video footage from my motorbike. You can see samples of the bike test later in the review. Higher resolution, more fps. One of the things I noted about the ATC-2K below is that the sensor is a 320x240 sensor that upscales to 640x480 for the video. The GoPro runs a 512x384 panel at 30fps so you get about 50% more resolution and double the framerate. Because of this, a 2Gb SD card will hold about 55 minutes of video with the GoPro compared to over an hour with the ATC-2K. Playback, menus and transferring the data. The GoPro comes with a hybrid connection cable with an ultra mini proprietary plug on one end and a USB, audio and video connector on the other end. Plug it in to a PC and it shows up as a removable disk drive full of AVI and JPG files. It's USB 1.0 so transferring the data takes a while. Plug it into an AV input on your TV and you get to see the results played back instantly. The on-screen menu is a little cumbersome, as with the ATC-2K below, but it does a reasonable job given the camera only has two buttons. The buttons are located on the front and the top of the camera. The front one is on/off and mode selection. The top one is shutter and mode entry. So to flip through the menu options on the built-in LCD screen, click the button on the front. To select an option, click the button on the top and so on. The LCD is actually upside down, which is a bit odd, but the camera was originally designed to be wrist-mounted, and once you understand that, it sort of makes sense. The various menu options allow you to output video at 50 or 60hz, NTSC or PAL, and to set up things like auto power off, remember previous shooting mode, and upside down mode. In upside down mode, you can mount the camera upside down and the video will be flipped so it's the right way up. Neat. Mounting options and that case. There are a bazillion mounting options for the GoPro depending on the kit you buy. They also offer accessory kits for around $40 a piece which give you even more options. The Motorsports version I review here comes with a grab-bag of flat and curved mounting plates (for flat surfaces, or slightly curved surfaces like a helmet), thumbscrew connectors to join the various mounting arms together and a suction cup mount for window and car or bike bodywork. One thing to note. The supplied mounting plates come with double-sided 3M VHB tape. VHB means Very High Bond. Do not - I repeat do not stick one of these somewhere where you might regret it - like on to a painted surface. It will not come off without destroying the mounting surface. VHB tape is bloody strong and it's an inspired choice for a camera mount. For the trivia buff, VHB tape is 10 times stronger than rivets in a like-for-like bonding strength test. (Discovery channel clip about testing VHB tape). The clear plastic case that you fit the camera into looks quite well constructed too, with a lever-action clasp on top to hold the back plate shut, compressing a sealing o-ring to keep water and dirt out.

http://www.carbibles.com/productreviews.html (2 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

Stills, video and sound. The GoPro takes 3MP still photos - pretty reasonable ones - and it can be set to do single-shot, three-in-a-row, or time-lapse one shot every 5 seconds. Obviously it also shoots video with sound. There is a menu option on the camera to set the audio sensitivity of the microphone to high or low. In low mode, it's tuned to engine sounds. In high mode, it's less muffled and designed for less noisy environments. In my test, I forgot to set it to high mode when skiing, which made the sound very muffled. On the motorbike, in low mode, it picks up the sound of the engine beautifully. It's only marred by the fact that on my bike it also picked up a lot of electrical interference from the alternator or one of the spark plugs. It manifests itself as a constant buzzing on the soundtrack. Bummer. When the weather warms up, I'll try it again mounted with a little RF screen around the camera to try to isolate it from the electrical noise to see if I can get better results. The video does suffer the same vertical 'wah wah' type effect as the ATC-2K below, but it's nowhere near as pronounced and it takes a good sized bump in the road to make it noticable. I think the extra framerate helps this out, plus the resulting video does give more of a sense of speed. This example shows some clips from my road test. The black thing on the left of the video is my GPS mount which was in the way.

http://www.carbibles.com/productreviews.html (3 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

Heed the battery warning! One of the slips of paper that comes with the GoPro, there's quite a strong recommendation that you don't use alkaline batteries in it. The current drain of the GoPro is a lot more than the ATC-2K below, because the CCD is larger, and in cold weather, alkaline batteries just don't cut it. I tested the GoPro with alkaline and the recommended Lithium batteries. On a 4°C (40°F) day in January, attached to my motorbike, the alkaline batteries died in 7 minutes. They went from 1.65v new, to 1.37v after 7 minutes. That's below the power threshold for the GoPro and it just shut down. Doing the same test with Lithium batteries revealed a voltage drop from 1.75v new to 1.66v after 50 minutes of filming. With the lithium batteries, 30 minutes of filming was done skiing in -3°C (28°F) temperatures. Okay so that's down there in terms of filming temperatures, but the GoPro is billed as a sports camcorder and it does lay claim to being useful for skiing and snowboarding. So my recommendation : Lithium batteries, or rechargeable NiMh (nickel metal hydride) batteries are what you want. A couple of items missing from the manual. There are a couple of details missing from the instruction sheet which are worth knowing with the GoPro. (1) Even if the camera is set to 'remember' the previous mode it was in, if you connect it to a PC via USB to pull the videos and photos off, the next time you turn the camera on it defaults to single image photo mode again. If you use this camera, you need to double-check the shooting mode after a USB connection. (2) To connect via USB, plug the USB into the camera when it's turned on, then connect it to the PC. If you plug it in first and then turn it on, you'll get a generic device failure message and the camera won't be properly recognised. These are minor irritations but nothing to cry about. Once you've come across these issues once, you tend to remember next time.

Conclusion : A worthy contender
In a like-for-like test, I'd have to go with the GoPro over the ATC-2K. I found it easier to use and a lot easier to line up when using a helmet mounting option. The video seems clearer, the sound is a little better and it takes 3MP stills too which is
http://www.carbibles.com/productreviews.html (4 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

a bonus. The video still has distortion when used on a vibrating surface, like a motorbike, but I think that's an inherent issue with this type of device. Short of a vibration-isolating platform, or in-camera vibration cancelling, I'm not sure there's anything you can do about it. But compared to the ATC-2K, I found the effect much less pronounced in the GoPro.

ATC-2K / ATC2000 ActionCam
Tested October 2007 Website: www.oregonscientific.com
Second up is the ATC-2K; a followon to the ATC1000 - also a 'wearable' sports camcorder. Unlike the GoPro, the ATC-2K has a tube form factor with the lens at the front and the batteries and connectors at the back, with the LCD and buttons on the top. To test it, I attached it to a friend's motorbike handlebars using the supplied mounting kit, and got him to shoot some video of me during a motorcycle trip in late 2007. You can see the video later in the review. Like the GoPro, the ATC-2K has a small amount of memory built-in, but it's so small you'll want the 2Gb SD card again. The camera comes with a rubber helmet strap, a quick-release bracket, a handlebar clamp, a USB cable and an A/ V cable. The helmet strap allows a lot of wobble once the camera is mounted, because there's no permanent mount like there is with the GoPro. Plus the camera is quite hefty so once it's perched in it's quick release bracket, there's a lot of mass to wobble about and stress the rubber strap. The controls are pretty simple again - on/off and record/stop. The rear cap is a waterproof, o-ring sealed affair that you screw off to get at the batteries, SD card slot, USB and A/V connectors. The spec for this camera is video at 640x480 but the results look like they're 320x240 upscaled in the camera. An examination of the resulting video files shows they're running at 15 frames per second which is OK, but not stellar. The lower sized LCD panel and lower framerate do mean you can get more video on to a 2Gb card than the GoPro though. Playback and connectivity. The easiest way to get the videos out of the ATC-2K is to attach it to a PC using the supplied USB cable. Once connected, it shows up as a removable disk drive and you can just copy the videos over to the PC and play them back. Unlike the GoPro, it doesn't seem as sensitive to the connection and power on/off order. There is an option to use an A/V cable to connect it to a TV for direct playback. This works reasonably well but the on-screen navigation is again a little cumbersome and basic. But then again, the camera only has three buttons on it so there's a limit to how much functionality you can achieve with those limits. No viewfinder. As with the GoPro, there is no screen to preview what the camera is looking at. The real problem here is that there's not even a viewfinder to give you some idea. This leads to a certain amount of guesswork when mounting the camera because you're never entirely sure what it's looking at. For a motorbike or car, it's not so difficult - point it level and straight and you're pretty much set. For using it on a helmet though, the results are considerably harder to predict. I did shoot some skiing footage in January 2008 but after three attempts, each time I ended up shooting the sky or the tip of one of my skis because I just couldn't get the alignment right. So that's a definite drawback for the ATC-2K.
http://www.carbibles.com/productreviews.html (5 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

Recessed lens - hard to keep clean. In the ATC-2K, the lens is recessed quite noticably into the unit itself. When skiing, this recess filled with snow very quickly, but I didn't realise until I got home and played back an hour of fog. When using it on the motorbike, we got dead bugs stuck in the recess frequently and because of the design, it's bloody difficult to get them out and to clean the lens cover. Can you shout that again? I have a real issue with the audio on the ATC-2K - it's almost none-existant. The example video here has a nice engine and wind sound to it, but when you take the ATC-2K in to a quiet environment, like skiing, or filming from inside a vehicle, the audio is imperceptible on playback. I tried videoing a narrated commute home one day, and all I got was the rattling panel in the front of my dashboard. My entire narration was there, but I had to crank the volume up to 11 to hear it, by which point, the rattling panel sound was like Concorde crashing into my house. Unlike the GoPro, there is no audio sensitivity option so it's loud, or nothing. On the plus side, the ATC-2K doesn't seem to be as sensitive to electrical interference noise, so my noisy alternator might not be a problem with this camera. Video distortion. Finally, and perhaps most annoyingly, he ATC-2K has no vibration or shockproofing. When used on the motorbike which had high frequency vibration coming through the handlebars, the ATC-2K suffered from a terrible vertical 'wah wah' picture distortion. You can see it in the example video. The picture constantly stretches and squashes vertically, and it seems to lose framerate too. You'd never know it from the video, but we were doing well over 80mph on that road yet on the video, with the missing frames and picture distortion, it looks like we were out for a 30mph afternoon ride. The GoPro has the same issue but it's markedly less apparent. This is the sample ATC-2K video:

Better battery performance. One area the ATC-2K does win out over the GoPro is battery performance. Because the power requirements for the smaller LCD panel are less, it does better in cold weather shooting. In my test, with alkaline batteries, the ATC-2K got about 18 minutes of shooting to the GoPro's 7 minutes. The voltage drop was about the same: 1.65v down to 1.35v in 4°C (40°F) weather. Again, once replaced with lithium batteries, you'd probably run out of memory card space before battery life became an issue.

Conclusion - the not-so-action cam.
I've given this product two to three stars because if you use it for basic videography, it's not bad. However, if you use it for what it's advertised for - sports and action videography, it's not really up to snuff. The image distortion in motorsports is really irritating and the recessed lens design is just plain bad. The audio pickup is dodgy unless you're shouting or videoing something suitably noisy. I suspect these wrinkles will be ironed out in due course with later designs, but for now, I'd give this a miss.

http://www.carbibles.com/productreviews.html (6 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

Comparison
GoPro Hero
Video resolution Form factor Memory card Video in minutes Waterproof Shockproof? Batteries Price when tested 512x384 native 30fps native Rectangular mini cam Up to 2Gb SD card 56 mins / 2Gb 30m / 100ft Yes 2 x AAA US$139 / US$169 / US$179 depending on version

ATC-2K
320x240 upscaled to 640x480 15fps with frame-doubling to 30fps Tubular 'bullet' Up to 2Gb SD card 70 mins / 2Gb 3m / 10ft Yes 2 x AA US$129 with free 2Gb SD card

FFT Fuel Treatment
Tested July 17th 2007 to October 19th 2007 Website: www.fftfuelsaver.com and futurefueltechnologies.com
With the ever-rising price of petrol, I've been getting a lot of email asking me to look into another of the miracle fuel additives that claims to increase your gas mileage. The basic claim from FFT is that adding 30ml (1oz) of their product to every 38 litres (10 gallons) of petrol will give you a 10-20% increase in fuel economy and a drop in CO2 and NOx emissions. I will be testing the mileage claims. The emission claims are a little curious given that the material safety data sheet (MSDS) for this product lists CO2 as one of the main byproducts of its combustion. In order to do this test, I collected a year's worth of gas-mileage information for my Honda Element. I've been collating the results at greenhybrid.com which allows me to enter the number of gallons per fill-up vs. the recorded mileage on the odometer. I've been careful to use the same pump at the same gas station in order to eliminate differences in the sensitivity of the pumping and cutoff systems. Each fill-up has been to the point where the pump automatically shuts off. A fully annotated record of my gas mileage is available at the greenhybrid.com website by following this link: Honda Element gas mileage. By hovering over any of the [more] links on that page, you can see comments relating to that particular fill-up.

The product
The product comes in a dispensing bottle and looks like a medium-strong tea. It has a slight lemon smell to it. According to the MSDS, the main hazardous (read: useful) ingredients in FFT are as follows:
● ●

t-butyl perbenzoate (t-BP) - An explosive oxidising agent. (t-butyl perbenzoate data sheet) Lupersol DDM-9 - Methyl ethyl ketone peroxide - an explosive oxidising agent that undergoes selfaccelerating decomposition, exploding at 230°F. This one is sensitive to sunlight and is incompatible with natural and

http://www.carbibles.com/productreviews.html (7 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

●

synthetic rubbers and chemical accelerators. At 200ppm this would appear to be the main component. (DDM-9 data sheet) d-limonene - a highly flammable and combustible peroxide compound. Also sensitive to light and can oxidise in air. Interestingly this is listed as being incompatible with other strong oxidising agents. It's what gives FFT the slight lemon smell. (d-limonene data sheet)

Essentially then, FFT Gasoline Additive would appear to be an oxidising agent or an oxygenating reagent. These are substances that, while not essentially combustible on their own, may, by yielding oxygen, cause, or contribute to, the combustion of another material. In other words, this stuff ought to make regular petrol burn better by adding oxygen to it during the combustion process.

Conclusion : don't waste your money

At the beginning of this test, the overall gas-mileage for my Element was 19.8mpg after 8,213 miles. You can see variations in the graph above based on weather and trip types but the mean average is normally just below that 20mpg line. That's a one-year cycle of everyday driving including road trips, short in-town commuting, and mountain driving during the ski season. The first tank with FFT is the first arrow on the above graph - you can see it dropped off from 18.9mpg to 16.4mpg instantly. The test ended at the second arrow on the above graph, at which point you can see the consistency of readings appears to come back. After a three month road test, in all driving conditions, following the instructions to the letter on the FFT product packaging, my fuel economy dropped from an average 19.8mpg down to 19.0mpg. The previously reasonably steady mpg readings went all over the map from very high to very low - all the consistency went away. That's a real car, in real everyday use, commuting to and from work in traffic, with road trips, shopping trips, one, two and four people in the car essentially what you and I do everyday to our cars.

BrightCar mileage tracking software
Tested March 2007 Website: www.brightcar.com
Hot on the heels of GasDandy (below) I was sent a copy of BrightCar for review. This is another vehicle mileage tracker, but it has more complexity to it than GasDandy. BrightCar should be considered more of a car maintenance tracker than just a simple mileage tracker. The major difference between it and GasDandy is that BrightCar has an available online database of over 10,000 vehicle service plans. So

how does it work? Setup is pretty simple and only takes a few minutes. Once the software is installed it prompts you for your vehicle information, year first, then make, then model and options. An initial quirk I noticed straight away is that on first starting, BrightCar expands to full screen. On a 2560x1600 monitor that's quite a smack in the face especially as most of the intial screen is whitespace while you set up the first vehicle. But once you make your selection, it connects to the BrightCar servers and downloads a vehicle service plan specific to your car (you can check on their website first to make sure they have one) then you can resize the window however you like and it's persistent between sessions. The service plans that get downloads are quite, quite comprehensive. When you dig into the details, it gives you everything from the timing of simple oil changes right down to when the track-rod ends need greasing and the window tracks need a lube. Because of this, BrightCar is not so much for the casual mileage tracker - more for the driver who's serious about
http://www.carbibles.com/productreviews.html (8 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

keeping their car in tip top condition. The interface is nice to use with the main 'home' page showing a user-definable graph as well as any services due. Entering petrol stops is fairly straightforward and you can put all the usual stuff in there - odometer reading or tripmeter reading, petrol station, price etc. On the home page there's a print function that prints out some basic info on your vehicle. A separate print icon prints out the mileage graph. One of the plus points about BrightCar is that they seem to be very receptive of customer feedback. The initial version I was sent for review had a couple of ridiculous bugs in it and a particularly annoying mpg graph that stuffed everything close together and overlaid the whole graph with mpg figures. It made it near impossible to read. I mentioned this to their customer support and in the service release that came out a couple of weeks later, they'd modified the mpg graph to have a more laid-back appeal to it, with the mpg figures appearing for any given point when you hover the mouse over it. In this day and age of get-it-done-now-and-bugger-the-customer, it's nice to come across a company who still takes the time to listen to its customers.

Summary
BrightCar or GasDandy? I'd say if you're a casual driver who'd like to keep track of basic cost and gas mileage, either would do - probably GasDandy simply on price though - BrightCar is $39.95. That being said, if you're serious about tracking full vehicle maintenance and all the other miscellaneous expenses to boot, then BrightCar might be more the piece of software for you. It costs more but then it's more feature-rich. QED. Fortunately, both offer trials from their site so you can try before you buy. One last thing with BrightCar - it worked perfectly at home on my DSL connection but at my office where we have firewalls and proxy servers, it had a bit of a panic attack trying to reach the BrightCar servers. I think it was our proxy server that was messing it up.

Special offer
If you're interested in a license for BrightCar, carbibles.com has negotiated a 20%-off deal. Click on the coupon on the right to get the deal. When you click through to their "buy now" page, you'll see the discount applied to the total cost.

GasDandy mileage tracking software
Tested February 2007

http://www.carbibles.com/productreviews.html (9 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

Website: www.gasdandy.com
If you've read my fuel & engine bible, you'll know I use an online mileage-tracking service from GreenHybrid.com. When I was looking around for a way to track my mileage, there were a few bits of software here and there but none of them quite did what I wanted. In February 2007 I discovered GasDandy. The idea is really simple: track your mileage and fuel costs and have the software generate small reports for you. The software is free to try (available from the GasDandy website) and the trial version allows 5 sets of data to be entered. The full piece of software is $14.95. In use, GasDandy is pretty easy. You set it up with a couple of named data items typically your car(s) and/or motorbike(s). Then, each time you start it, you can choose one of your vehicles and enter in some basic information from your most recent fill up. This includes how much the petrol cost you, the mileage (total odometer reading) and the number of gallons of petrol used. Note that there is a metric version available from the website too if you want to work in litres and kilometres. My only bone of contention here is that it insists you enter the total odometer reading. A lot of car nuts track their mileage using the trip meter. It would have been nice for GasDandy to allow total odometer or most recent trip meter reading. Because of that I took one star off my review rating. Because GasDandy is tracking your mileage, you can enter in oil-change intervals and tyre rotation dates and it will remind you when its time to get an oil change or a tyre rotation, which is a neat feature. It also allows you to keep track of any mileage driven for business along with notes to remind yourself about the what, where and why of the business trips. Finally, GasDandy allows you to print out basic reports and generate graphs. The graphing function is a nice touch as it shows the overall average mpg for your vehicle and colour-codes the graph nodes green or red depending on whether that tank was above or below average, respectively.

Summary.
GasDandy is a simple (ie. not bloated), inexpensive piece of software that will help you keep track of mileage. The interface could do with some eye-candy - it has a distinct 90's feel to it - and like I said, it would be nice to be able to put trip-mileage as well as total mileage, but apart from that, I like it. The screenshots below show the main mileage interface, and the graph screen.

Signal Sorcerer traffic light changer
http://www.carbibles.com/productreviews.html (10 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

Tested September 2006 Website: www.signalsorcerer.com
There are plenty of devices and gizmos out there designed to entice the impatient driver with the allure of forcing traffic lights to be green in their favour. They fall into two categories. In the first and illegal category, there are devices like infra red blasters and emergency vehicle transmitters. These both work on the same principle - either an infrared or a radio signal is sent out from the vehicle. Traffic lights at the next junction will receive the signal and force the current cycle to drop into emergency mode where all the lights are changed to red except for those for the approaching vehicle. System designers assume these vehicles to be emergency vehicles, and facilitating their progress by stopping all traffic at a junction is A Good Thing. But not all devices are on emergency vehicles; they've started to find their way into the consumer world. They're expensive, they're illegal and expect to go to jail if you're caught with one. Fortunately for all of us, the Signal Sorcerer falls into the second, legal category of traffic-light changers. To understand how the Signal Sorcerer works, you need to understand how traffic lights work. Generally speaking, they are either controlled from a central control centre, or more often, local control boxes (the little grey box at every junction). Depending on the time of day, the lights will operate in a fixed pattern designed to allow the maximum flow of traffic. For the lessused paths through the junction, inductive loops are buried in the road. These are loops with a weak electric current in them which generate a magnetic field. When a car passes over them, the field is disturbed and the traffic lights "know" a vehicle is now waiting in that lane. Typically, this is a left-turn lane, or if you're in England, a right-turn lane. When the traffic lights detect the presence of a vehicle, the cycle changes to allow a green light for that lane, thus allowing you, the hapless driver, to turn across the junction. The principle is sound, and it works really well. Sort of. To paraphrase George Orwell, "All vehicles are created equal but some are more equal than others". You see the problem is that inductive loops work exceptionally well when hulking great chunks of steel drive over them. Like cars built in the 80's, trucks, buses and so on. Even today, the buzzing, noisy lump of pollution in the front of a car (the engine) has enough steel in it for these inductive loops to work. The problem is motorbikes and ultra-modern sports cars, and to some extent, newer sedans. There's a lot of aluminium in these things now and less and less steel. This is especially true on motorbikes - essentially a collection of plastic, carbon fibre and aluminium. This presents a problem. The traffic light's inductive loop often doesn't pick up motorbikes. I ride a motorbike, I know. There are some junctions around where I live that never detect my bike. I have to sit there like an idiot staring at a red light waiting for a car to come along behind me and trip the cycle of lights. Worse, if it's late and there is no other traffic around, I have to shoot a red light, or do a bizarre series of right turns and u-turns to get where I want to be. It's bloody ridiculous, and anyone who rides a motorbike will bear me out on these experiences. So it was with keen interest that I received a Signal Sorcerer for review. Their website is flashy and has tantalising claims about all your greenlight dreams coming true for $20. I read up on the device and the theory seemed sound enough so I decided to give it a go. Basically, the Signal Sorcerer is a really strong magnet housed in a weatherproof plastic case. The idea is simple. If you attach it to the bottom of your vehicle - in my case my motorbike - and drive over an inductive loop, the strong magnetic field is enough to disrupt the inductive loop into registering your presence. Sort of like Darth Vader and the old "sensing Luke" trick, only with magnets. The idea, then, is that it gives you the presence that your bike is missing, and so rather than sitting there waiting at the endless red light, you'll trip the system and a green light will be forthcoming in due course. And on you go. The packaging is pretty simple - a plastic tube with a paper instructional insert, the magnet, two alcohol swabs and a ziptie. The instructions are straightforward; clean the area where you're going to put the Signal Sorcerer with the alcohol swabs, peel off the protective backing from the sticky stuff and stick it in place. The zip-tie is there for added security to back up the sticky stuff. The idea is sound, and on most motorbikes I can imagine it works well. The ideal place to stick this thing is on a lower frame rail, as close to the road as possible. My problem was that my bike has skidplates on the bottom - aluminium ones at that. The magnet had nothing to stick to so I was reliant on the sticky stuff to hold it in place. No matter, I cleaned off the only place I had available - the bottom of the centrestand - peeled off the protective backing and stuck the unit in place. I secured it with two zip-ties just to be sure. You can see it nestled under my centrestand, stuck to the skidplate in this photo:

http://www.carbibles.com/productreviews.html (11 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

The road test At the risk of boring you stupid, I'll mention one junction that's my favourite for staring at a red light. This will mean nothing to you unless you live in Salt Lake City and own a motorbike, but westbound Bangerter Highway turning left on to southbound Redwood road. I have gone through that left turn light on red more times than I can remember. Without fail, it never sees my bike. Seemed to me to be the best place to give the Signal Sorcerer its first test. I cruised to a stop at the front of the line with no traffic behind me and waited to s.....what the? A green arrow? Fumble the clutch, crunch, stall the bike. It was so unexpected I muffed it. One quick recovery later and I was off. Well that was an excellent start. I looped around and back and did it again. Again, a green arrow as the cycle came up. Wow! The rest of my roadtest was basically much the same. I found all the lights that never normally see me, and they all tripped their cycles and gave me a green light in due course. I was duly impressed. I did my road test more of less in the dead of night to ensure I was the only vehicle around. That way I wasn't ever in a situation where a car came up behind me and tripped the light sequence. What Signal Sorcerer won't do. If you buy one of these expecting to cruise up to a red light and have it magically turn green, you'll be disappointed. That's not what it does. It merely ensures your vehicle is seen by the traffic light inductive loop, so that the signal order will be tripped to include your lane in the next cycle. Where Signal Sorcerer won't work. Not all traffic lights use inductive loops to detect traffic. Some work on reflected light detection and others are simply run off timers with no way of influencing them. You'll know if you've found a timerdriven light. You'll be sitting at a totally empty junction in the dead of night for 5 minutes at a red light with no other traffic. The picture on the right shows a typical inductive loop setup - they're buried in the road surface and the cuts are filled in with hot tar giving a tell-tale rectangle or circle 'drawn' on the road on the runup to the lights.

Conclusion - it works.
If you've had problems with your motorbike or lightweight sports car, or even your sedan not being detected by inductive loop traffic light systems, this certainly seems to do the trick. Don't buy one expecting miracles, but go in with the knowledge that you'll stand a far better chance of being an 'equal' at the traffic light grand prix next time.

FFI mpg caps magic fuel pill
Tested September 2006
A work colleague of mine is a believer in the oil industry conspiracy theory, i.e. they keep anything from going to mass market that would dramatically save oil and give us, the consumers, better fuel economy in our vehicles. Since he was going to purchase a package of the magic FFI fuel pills, I volunteered to split the cost with him on the understanding that we could use his car as the guineau pig and that we could document the results for my site. I suspected I'd just wasted
http://www.carbibles.com/productreviews.html (12 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

some lunch money but for the sake of adding more value to my site, I figured it was worth it. My colleague's commuting car is a 1995 Volvo 850 Turbo, automatic with 257,000 miles on the clock. It has an on board average fuel consumption display in mpg that can be reset to zero to begin an averaging run. The engine was at operating temperature before each trial. We first did a base line run between his house and our office - about 16 miles each way - with cruise control set to either 70mph or 75mph. The route has an HOV lane on the freeway so maintaining these speeds is easy for the sake of testing. The results are tabulated below.

mpg
33.6 29.4 30.6 31.4 30.6 29.4 33.6 30.6 30.6 31.4

Distance in miles
32 16 16 16 16 16 16 16 64 16

Cruise setting in mph
75 75 70 70 70 75 75 70 70 70

Running avg mpg = 31.12 Next we did the same sequence of drives, but with the FFI fuel pill in the tank.

mpg
28.3 29.0 30.5 27.3 29.0 29.0 27.3 28.0 29.4 28.6

Distance in miles
32 32 32 32 64 32 16 16 32 32

Cruise setting in mph
75 70 70 75 75 70 70 70 75 75

Running avg mpg = 28.64 If we group the results by speed, into 70mph and 75mph groupings, this is what it looks like.
● ● ● ●

For For For For

the the the the

pre pill 70mph speed the average is 30.86mpg post pill 70mph speed the average is 28.76mpg pre pill 75mph speed the average is 31.5mpg post pill 75mph speed the average is 28.52mpg

Conclusion. On average, with the pill in the tank, we saw a drop in fuel economy by about 2mpg. There was no perceivable increase in acceleration or the ability to perform at-speed overtaking maneuvers. This pill is another scam.
http://www.carbibles.com/productreviews.html (13 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

Don't bother with it.

The raging debate.
As well as a response from FFI (see below), my review has garnered comments from other people who've tried this product out. Out of the many emails I've had, this is one of the most interesting: I just want to comment on the MPG Caps from Fuel Freedom International. I tested the caps for 5 months in 4 vehicles, 2 Camrys a 2002 & 2004, a Toyota Tundra 2005 truck & a 1973 VW Beetle. I saw a decrease in mpg in all vehicles and gave up after testing over 20,000 miles total. Some people claim that it works, but you cannot prove it by me. In addition, I gave out pills to others who found either no improvement or also lost mpg. I was a distributor for them but obviously I am no longer...I do not want to promote something that only works for a few.

Followup - calling their bluff?
A couple of weeks after posting my review, I was contacted by an FFI representative who didn't think I'd been fair by trying their product out in an older car. He suggested I re-performed the test at their expense in a newer vehicle. I offered up my (at the time) 2000 mile Honda Element and gave them an address to send the product to for testing. Thanks to a natty little 'count up' javascript, I can tell you that it's now been 511 days since then and I've yet to see anything. The original order for the product for the original test took only three days to get here. Have I called their bluff?

TomTom Go 510 GPS Navigator
Tested August 2006
By 2006, GPS navigation devices have come a long way since their earliest incarnation, and I decided to research the available models. I settled on a TomTom Go 510 device, despite some of the published problems people have been having with it. More on those later though. The TTG510 is the lower-spec version of the TTG910. In Europe, the model is known as the TTG710 simply because it comes with a different map set. Whereas the TTG910 has an 20Gb internal hard drive and can display pictures, play MP3s and speak the actual road names, the TTG510 is a base model without the frills that stores its maps on SD cards. The operation of the 510, 710 and 910 versions is identical in their user interface. In America, the TTG510 is supplied with a 1Gb SD card with all of America, Canada, and oddly, Guam on it. My test was during a business trip to Nebraska which was a good test for two reasons. Firstly, I'd never been to Nebraska before so had no idea of any locations. Secondly, in the summer, when I went, the temperature was a hot 35°C outside but more importantly, the humidity was at about 85%. Going between this environment and airconditioned cars and buildings was a great test of the durability of the TTG unit and it didn't once suffer from humidity or condensation-related problems. So what about the unit itself? Well it's a nifty little widescreen device with a touch-screen interface. It comes well-packed with a charger/docking station for your computer, a 12v adapter and suction cup mount for the car and a little carrying pouch. The pouch is nicely designed because it has a stiffened side where the screen goes to further protect the screen from sharp objects poking through the pouch itself. One design flaw of the TTG becomes apparent as soon as you use the pouch though - the position and design of the power switch is exactly where you'd hold the device to put it in and out of the pouch. Three times I've accidentally turned it on as I've put it away only to find it warm and with dead batteries next time I've come to use it. D'oh! For a $599 GPS navigator, you'd think they'd have done a better job! The computer charger/docking station works just fine and if you buy one of these, I recommend using the included backup software. TomTom do not provide source maps for the TTG510 on a CD or DVD - the only place they exist is on the SD card. Because TomTom maps need to be activated on the device they're being used on, if you end up with a corrupted card or worse, you won't have any way to re-install the maps or activate them at the TomTom website. You've been warned. In-use, the device is simplicity itself. It has a SiRFStar III GPS receiver in it which locks on quickly once it's done it once. For example once it's located you, if you turn the unit off and then turn it on again the next day near the same place, it locks on within about 20 seconds. If you fly somewhere else and then turn it on, it's last "known" set of satellite locations
http://www.carbibles.com/productreviews.html (14 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

is wrong so it takes longer to relocate itself. The GPS receiver is pretty good and worked remarkably well indoors - previously a no-no for GPS receivers. Entering a destination is a breeze, either by giving it a street address, a point of interest (POI) or a street intersection. It calculates the route very quickly and you're ready to go. (You have the choice when planning the route of fastest, shortest distance, avoid motorways etc - plenty of options.) You can navigate through a traditional 2D map, but the 3D display is by far and away the best way to do it. It gives a display which is far more intuitive to read because it resembles the road layout you can see through your windscreen. The LCD screen on the TTG510 is brighter than that of the older models and is covered with a glare-resistant coating which makes it totally useable in bright sunlight - something of a novelty for an LCD device. One point to note : the TomTom screen is also readable through polarised glasses - something I've had problems with on the Garmin units before. As you drive, a user-selectable voice (in plenty of different languages and variations) tells you where to go. Some of the nomenclature takes a little while to get used to, for example "Ahead, turn left" doesn't mean "take the next left", but rather "be prepared to turn left somewhere up ahead". When you get to the actual turn, the instruction is simply "In 100 metres, turn left" followed by "Turn left". (It's worth noting that the TTG910 - the high-end version - has text-to-speech ability built-in so it will attempt to pronounce the name of the road too. For example "Turn left into Acacia Avenue".). Whilst en-route, the TTG will recalculate almost instantly if you take a wrong turn or miss a turn, and you also have the ability to tell it to avoid certain parts of the route entirely, for example if a road is undergoing construction. The menu system of the TTG is really easy to use and has a nice up-to-date feel to it. There are two modes - basic and extremely verbose. In basic mode, a lot of the less well-used options are simply hidden away from you but when you activate the "show all options" option, you end up with screen after screen after screen of things to twiddle, tweak, poke and tune. Some seem a bit odd when you first look at them, but after using the device for a while, you'll begin to understand why there are so many options. One of the best ones is the ability to change the mapping colours. If you don't like the ones shipped as default, there is a choice of five or six alternatives, plus three or four alternative "night mode" mapping colours. The night mode is a neat feature in itself - the TTG510 has a light sensor on it and when it gets dark, the maps all switch to low-intensity, low-contrast maps so as not to blind you when driving at night. A neat touch. The Point Of Interest (POI) capability is neat - basically shops, restaurants, cash machines etc all reside in the POI database. This is where the TTG loses a little of its shine because being a European company (Dutch, actually), the POI database for America is a little out-of-date. The major items are all there, but for example, the hotel we were driving to from the airport had its old name in the TTG POI database. You can download POIs from the internet from all manner of things from fishing spots and speed camera locations up to user-created databases of all the locations of a particular hotel chain. You can also input your own POI using the TTG510 either from where you are right now, or by browsing the map in 'offline' mode. Something else which has been moaned about on various internet forums is the mapping database for America. A lot of people have complained that it's massively out of date. For new developments and roads, it might be. TomTom use the TeleAtlas database which is better at European mapping but in my tests I was using long-established routes and roads and it didn't miss a beat. (Garmin use the Navteq maps which are great in America but suffer the same mapping complaints in Europe as TeleAtlas do in America) And so to the suction cup mount. Well what can I say that hasn't been said a thousand times on a thousand forums all over the internet. Actually, for the most part, I've not had a problem with it. My stock factory item holds my TTG510 well enough and has yet to fall off the windscreen or suffer the droop problem so many people have complained about. So from my experience, it's not so bad, but that's just me. To be safe, I've taken TomTom up on their current offer of free replacement mounts for those with the older mount in the box. The new one has a better ball-and-socket joint to attempt to counter the droop problem, and a little nubbin on the back to help prevent the rocking / power disconnection problem some people have reported. I'll not go into it in depth here, just simply give you a Google link to check out. Google search for 'TomTom 910 windshield mount' So why did I give this little unit only 4 out of 5 stars. Well I took off 1 star for a combination of the following - the reported mount problems, the dated POI database, and the power button location and design. Apart from that, I love the thing. It got us everywhere we needed to be, on time and without getting lost, in a city I've never driven in before.

http://www.carbibles.com/productreviews.html (15 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

PressurePro TPMS
Tested August 2006
I had a chance to get 'hands on' with the PressurePro system in August 2006. The system is composed of two parts - the sensors themselves and the in-vehicle reporting unit. The sensors retail for arouns $50 each and the reporting unit runs about $200 so for a regular passenger car you'd be looking at a $400 shell-out. PressurePro sell mainly to the trucking and RV markets right now, and the unit I had to test was, as you can see from the photos, an RV unit. PressurePro have struck deals with a couple of RV manufacturers who are equipping their vehicles with the PressurePro system and connecting it to the RV central display / monitoring device via RS232 connections. The sensors themselves are quite large and weigh in at about 14 grams. If you were going to fit these to your vehicle, I'd recommend you get your wheels and tyres balanced afterwards just to be safe. With the system powered on, the display initially reads "No Sensor" for each position on the vehicle. In my test, the unit was an RV system and capable of monitoring 16 tyres. I set it up so the front two sensors were set as the front two wheels on the RV, and the rear two were set up as the trailing tyres on the towed vehicle. Using the up and down arrow keys, you select the appropriate position for the sensor you're going to install, and screw the sensor on to the valve stem. After about 4 seconds, the display changes from "No sensor" to a numerical display of the tyre pressure. That becomes the baseline pressure for that sensor. It will trip warning when the pressure drops 12.5% below the baseline, and again at 25% below the baseline. Setting up the sensors and the in-car unit was a snap and for the test, my vehicle was a rental car. As it happened, within 6 miles of leaving the rental counter, the PressurePro system beeped and the right-front LED started flashing on the display unit. It turns out the rubber in the valve stem had perished and was leaking and the sensor detected the drop in tyre pressure and alerted me, exactly as it should. Frankly it was a far better test than I'd been planning. My idea had been to drive around for a while, the stop and unscrew a sensor, thus giving it a zero reading. I did this anyway, and it took around 4 second from unscrewing the sensor to the in-car unit alerting me to a problem and flashing "00" on the display. That seems like a long time in a static test, but in reality, it's no time at all if you're driving. The car version of the display unit looks similar to the RV version I had to test only it doesn't have the RV graphic on it, and the F/B button is missing. On the RV versions, that button can be used to temporarily disable the readings from either the front or back vehicle. For example if you were to unhitch the towed vehicle, you'd only want the unit to look for readings from the front vehicle. If you didn't, when you got more than a couple of metres away, all four readings from the towed vehicle would error with zero readings because they'd be out of range. Speaking of 'out of range', the little aerial on the top of the display unit can be removed and replaced with a 35ft coax extension with another aerial at the far end. For particularly long RVs or trailers, this allows you to place the receiver antenna further back along the vehicle to ensure a strong signal from all sensors. So what do I make of this system? Well from model year 2007 onwards, all SUV and truck class vehicles in America must have a tyre pressure alerting system. These systems must alert the driver when any tyre drops 25% below its target pressure. The systems can be as simple as a flashing "there's something wrong" light up to elaborate systems like the PressurePro which show the tyre in question and give you a pressure reading. So my take on it is this; if you're buying a new vehicle and it comes with one of these systems, you can probably pass. But if you've already got a vehicle and you want an aftermarket system, this seems as good as any. The nice thing is it requires no technical knowledge or electrical or bodywork modifications to fit. It ultimately comes down to two things : relative cost, and percieved safety. $400 for a system like this on a passenger vehicle might seem expensive compared to the cost of fitting out a $100,000 RV with the same system. But as Ford proved with the exploding tyres problem on their Explorer, your perceived safety will evaporate very quickly when a tyre blows out at speed. As a plus, because of the design of the PressurePro, it is 100% portable - you can take it from vehicle to vehicle so it could easily be a one-time expense that you can take with you
http://www.carbibles.com/productreviews.html (16 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

as you go through your vehicles. Is it worth $400 to you to fit a system like this before you get into trouble? Or do you want to take it in the bank account in the event of an accident? The PressurePro system, like all TPMS systems, is ultimately like car insurance. It's a pain in the arse to pay for it up front because you might never need it. But if you have an accident and don't have insurance, then $400 seems really cheap in comparison. If you're strict with yourself and check your pressures regularly, then you probably don't really need a TPMS system. But as with so many products, here they're catering for human frailty, because in reality, how many drivers (who aren't car nuts) ever check their tyre pressures?

Michelin Digital Tyre Pressure Gauge
Tested July 2006
This is part of Michelin's new line of automotive products which came out in 2006. Given that they've been in the business of selling tyres for ages, it seems like the question surrounding their new product line is "What took you so long?". This review goes hand-in-hand with the new digital tyre inflator below. At the time of writing, this new pressure gauge cost $19.99 from motoring parts stores. It comes in a vacuum-wrap plastic display box with a small window in it for people to 'check out' the display by pushing the button. My first piece of advice - get one from the back of the rack. The front one will likely have been hammered by ham-fisted patrons for weeks if not months before you get to it. The gauge itself is nicely built and quite weighty. It's made of what feels like billet aluminium with rubber inserts for grip. The inserts are a particularly sticky compound so if you put it down on the garage floor, it will come up covered in muck. It comes with an expanding neoprene pouch that contains the instructions, and an adapter for certain types of bicycle valve. The adapter is a small brass unit which has no place to store it in the pouch other than loose, and when you do, it can scratch the silver finish on the pressure gauge. The instructions are pretty simple and once you've used the unit once, you'll likely not need them again. It comes with three batteries pre-installed and has an error of +/- 1psi up to 50psi. It's really easy to use. Click the button and the LCD display lights up blue with black digits, and the collar around the nozzle lights up a similar blue - a nice feature if you're in a dark corner. Click the button to cycle through three pressure units - PSI, Bar and kPa. Slot the nozzle on to your tyre valve for a couple of seconds, pull it off and take a reading. Simple. The nozzle itself has a snug collar in it so it's easy to locate on the valve stem, and helps prevent you from accidentally letting air out of your tyres whilst taking a measurement. After 90 seconds of inactivity, the unit shuts off. Apart from the lack of place to put the brass adapter and the super sticky rubber inserts, it's a nice gauge to use. I removed half a star from my rating for the lack of storage for the brass adapter and the over-sticky rubber inserts, and another half because it's nearly impossible to use this gauge on motorbike tyres due to its design. The shape of the handle is great for testing car tyres but the angle it needs to attach to the valve stem means it interferes with spokes or brake discs on motorbikes. I tested it against the digital inflator, as well as an old stick-type pressure gauge and a quality analogue gauge which I
http://www.carbibles.com/productreviews.html (17 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

have calibrated every 6 months. At 40psi, the stick gauge reads 39psi and Michelin's digital pressure gauge reads 40.5psi so its well within tolerance, and it matches the inflator tested below.

Michelin Digital Tyre Inflator
Tested July 2006
This is also part of Michelin's new line of automotive products which came out in 2006. I tested this in conjunction with their new pressure gauge, above. At the time of writing, this inflator cost $29.99 from motoring parts stores. It comes in a medium quality cardboard box and will likely have been opened and looked over a few times before you get to it. It has a long power lead with a 12v adaptor on the end which stores neatly underneath the unit, and a good-quality rubber hose with a clip-on style valve adapter on the end of it. The hose wraps around the outside of the unit when not in use. Underneath there are recesses containing a couple of adapters for footballs and bicycle tyres. The instructions are a 4-page booklet. The instructions themselves take up about 2 line inches and are reproduced on a label on the bottom of the inflator. The rest of the booklet is consumed with (basically unnecessary) warnings and notices. The top of the unit has an on/off rocker switch at the bottom, and three buttons at the top surrounding a digital display. The top button has an 'R' on it. This is the reset button - hold it down for three seconds and it resets the device to zero. It doesn't mention this in the booklet and if you do this whilst the inflator is connected to your tyre, it will recalibrate the gauge to believe the current tyre pressure is zero. Be warned! The other two buttons are a '+' and '-'. In use, you plug the unit in to a 12v supply and the display lights up blue with black LCD figures. Press the 'R' button to cycle through the pressure units, same as the gauge reviewed above. Use the '+' and '-' buttons to set the desired pressure, starting at 30psi and working up, and once you're done, the display resets to zero. Attach the clipon nozzle to your valve stem and the display reads your current tyre pressure. If its below the pressure you tapped in to the inflator, when you turn the inflator on, it will start pumping up the tyre until it reaches your desired pressure, then cut off. The first unit I had didn't cut off though - it must have been a dud because it just kept on going. The second unit worked just fine. Don't be alarmed if you're watching the display and it goes up to 1psi above your chosen pressure; once the pump cuts off, it will read correctly. I think the pulsing of the pump causes the reading to be too high whilst it's running. This doesn't seem to affect the cutoff feature though. The noise when the unit is inflating is pretty loud. I guess they're using an RS540 electric motor attached to a meaty oneway valve, and if you leave it on the floor, it will vibrate around and 'walk' off to the extend of the rubber hose if you let it. Something weird happens with this unit though - both my test units had the same issue so I think it's a design 'feature'. Once it gets hot, the unit can over-read by as much as 10psi. This means that if you leave it to inflate something, it will underinflate it by up to 10psi. I noticed this first when I took the nozzle off the fourth test tyre and connected to nothing, it read 2psi. I reset the unit and it zero'd out and after a moment, went back up to 2psi. Then 5psi. I let it cool off for 5 minutes or so, and it read zero again. There is a warning in the booklet about letting it cool off for 10 minutes after any 'inflation activity' and I guess this is why. You need to be careful then - if you do all four tyres in one go, by the time you get to the last one, you could be off by as much as 10psi. For that reason I took half a star off my rating, with another half removed for the inability to deflate overpressurised tyres. You have to do that by hand then re-check the pressure. I finally took another half a star off for the initial dud unit. In this day and age, it ought to be possible to buy something like this that works first time. I tested it against the digital pressure gauge, as well as an old stick-type pressure gauge and a quality analogue gauge which I have calibrated every 6 months. At 40psi, the stick gauge reads 39psi and Michelin's digital inflator reads 40.5psi so its well within tolerance, and it matches the pressure gauge tested above.

The Tornado Fuel Saver
Tested March 2006
The Tornado is in a class of device marketed through scare tactics and confusion. It is marketed under many names including Vortec Cyclone, Vortex, HiClone and Tornado.. With climbing gas prices, the manufacturers of such devices will attempt to lure you in with promises of better fuel economy, more power, less engine wear and so on and so forth.
http://www.carbibles.com/productreviews.html (18 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Product Reviews

The Tornado comes in a pretty shabby cardboard box along with an instruction / installation sheet. The Tornado itself is made of fairly lightweight pressed steel or aluminium and has some sharp edges on it. Fitting it was pretty easy; unclip the cold-air intake, pop in the Tornado, clip it back together and away you go. The test vehicle was a completely stock 2001 Subaru Impreza RS. The vehicle regularly returns 25.9mpg on the freeway. I tested the Tornado on a trip to Vegas and back - a 900 mile round-trip, as well as week's worth of testing around town on the daily commute. I filled up the vehicle at the usual gas stops from the usual pumps. We do the Vegas trip a couple of times a year so I have a good set of data points for how the Subaru performs. I calculated our fuel efficiency based on reported mileage on the odometer vs. reported gallons in the tank (from the pumps) which is the same technique I use every time I do this. On the way down to Vegas, our gas mileage dropped to 22mpg and on the way back it was about 21.5mpg. The average for this trip was 21.75mpg, down from the usual 25.9mpg. Around town, the Subaru normally manages 21.9mpg. After a week's use with the Tornado, my average gas mileage was 21.8mpg - near enough the same. Conclusion? On long motorway hauls, the Tornado absolutely does not help. In my test it actually made the gas mileage worse, which in the days of $3/gallon petrol is nothing to be laughed at. Around town it made a negligible difference. I'd say Don't was your money on this thing except I managed to flog mine on e-bay so evidently people are still buying them. Note: I was so underwhelmed by the results that I didn't bother dyno testing the vehicle to see if the claims of improved power were true or not.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/productreviews.html (19 of 19) [2/6/2008 7:14:27 AM]

Car Bibles : Basic Car Maintenance Tips

Car maintenance tips, from the carbibles.com website. Basic car maintenance tips for the motoring enthusiast.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Basic Car Maintenance Tips
Throughout the rest of this website you'll find in-depth articles describing in intricate detail how everything automotive works. On this page, I've simplified all that knowledge into a series of basic car maintenance tips, subdivided by category. Some tips have simple explanations right here whilst others link back to the articles in the rest of the site. If you can't find what you're looking for, try the search button at the end of the top menu. If you still can't find what you're looking for, or have a suggestion for something else I should cover, contact me using the contact button on the top menu bar.

Wheels and tyres
Rotate your tyres!
Every 5,000 miles or 8,000km, rotate your tyres. Tyre rotation.

http://www.carbibles.com/maintenancetips.html (1 of 7) [2/6/2008 7:14:44 AM]

Car Bibles : Basic Car Maintenance Tips

Clean brake dust off regularly
Brake dust contains all sorts of nasty stuff. If you leave it too long, the combination of road grime, moisture and heat from your brakes will bake it on to your wheels. Brake dust normally clings to wheels with static electricity so a damp sponge and clean cold water is the best way to get it off.

Check your tyre pressures
Check your tyre pressures regularly - once a week is ideal. Bad tyre pressures can affect fuel economy, handling and comfort. It's easy to do and there is no excuse not to. Checking your tyre pressure.

Check your tread depth
Bald, slick tyres might be good for motor racing but they're no good on the road. Most tyres come with tread wear bars built into them now - find one, examine it and if your tread is too low, replace your tyres. Four new tyres might seem expensive but they're cheaper than a fine or an accident. Tread wear bars.

Engine
Check your belts
At the front of your engine there will be a series of rubber drive belts that loop around various pulleys, driving everything from the alternator to the a/c compressor. Rubber perishes, more so in extreme conditions like those found in an operating engine bay. Get your timing belt and accessory drive belt checked every 25,000 miles, preferably replacing it every 50,000 miles. See the Fuel and Engine bible for information on interference engines and why checking your timing belts is a necessity, not a luxury: Interference engines

Fuel Economy
Check your tyre pressures regularly - once a week is ideal. Bad tyre pressures can affect fuel economy very noticeably. Checking your tyre pressures It's easy to do and there is no excuse not to.

Checking your oil level
This is something everyone can do - it's quick and easy and it'll tell you if your engine needs oil. If the oil is too high or too low, it can cause trouble for your engine. To check the oil, park on level ground and wait until the engine has cooled down after driving, then locate the dipstick. Pull it out and wipe it clean, then push it all the way back in until the top of it is seated properly in the dip tube again. Wait a moment then pull it out again. Check the level of the oil. If it's between the high and low marks, you're fine. (If it's too low, add a little.) The high and low marks can be denoted by two dots, an "H"
http://www.carbibles.com/maintenancetips.html (2 of 7) [2/6/2008 7:14:44 AM]

Car Bibles : Basic Car Maintenance Tips

and "L" or a shaded area on the dipstick. The photos below show a Honda dipstick which has the two dots. Why not just read the level first time around? The first time you pull the dipstick out, it will have oil all over it and it will be difficult to tell where the level is. That's why you need to wipe it on a rag to get a clean dipstick, then dip it back into the oil to get Checking your oil level. a good reading. More information on why you should check your oil level is here

Checking your coolant level
Again, something everyone can do. The coolant is the other thing your engine cannot go without. Every engine is different but if you check your handbook you should find where the coolant reservoir is. It will normally be bolted to one side of the engine bay or the other, and be a white semi-transparent bottle. Wait until your engine is cool and take a look at it the outside should have 'low' and 'high' markings on it and the level of coolant inside should be between the two. Do not take the radiator cap off to check coolant levels. If the coolant system is still hot then it is still Engine cooling systems. under pressure and the pressure release will burn you. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Fuel / gas
Will higher octane or premium fuel give me better gas mileage and/or more power?
No. Sportier cars have higher compression engines which generate more power and require higher octane fuel to prevent detonation. That's where the myth of "premium = more power" came from. If your handbook says "regular", use regular. See octane and power for more information.

Electrical
Disconnecting and reconnecting your battery
If you're going to do any work on your car involving the electrical system, disconnect the battery first. To do this, loosen the connector for the negative/ground terminal first, and wiggle the terminal cap off. Use a wire-tie or similar to tie the cable back out of the way. If you need to take the battery out, you can now take off the positive connector. Why negative then positive? If you disconnect the positive side of the battery first, the negative side is still connected to the entire car. If you drop a tool and it lands on the positive battery terminal
http://www.carbibles.com/maintenancetips.html (3 of 7) [2/6/2008 7:14:44 AM]

Car Bibles : Basic Car Maintenance Tips

and touches anything else on the car, you'll have an electrical short. By disconnecting the negative first, you're cutting off the return path for the current. Now, if a tool drops on to either of the battery terminals, it doesn't matter if it touches part of the chassis or not - there's no continuous path for the electrical current. Reconnecting your battery. Connect the positive terminal first, and the negative second - the reverse of removal, and for the same reasons. When you slip the negative connector on, there will be a spark as it gets close and makes contact with the negative battery terminal. Don't be afraid of this it's nothing to worry about. Make sure the terminal caps are done up nice and tight.

Check your battery terminals
Most modern cars run on a 12 volt negative ground electrical system. If your battery terminals or contacts aren't clean, you're making it more difficult for the current to pass around the electrical system. Remove the terminal caps as described above and clean each contact post with a wire brush to get a nice clean metal contact surface. Do the same to the terminal caps, then reattach them as described above.

Lights
One indicator or blinker is flashing faster than the other
When you indicate one way and the blinker flashes quicker than when you indicate the other way, it means one of the bulbs has blown. An auto parts store will be able to tell you what sort of bulb you need to replace it with and your manual should show you how to get at the indicator bulbs - they're different on every car.

http://www.carbibles.com/maintenancetips.html (4 of 7) [2/6/2008 7:14:44 AM]

Car Bibles : Basic Car Maintenance Tips

Don't touch the glass when changing headlight bulbs
Most headlight bulbs now are filled with halogen and have special coatings on the outside of the glass. If you pick the bulb up by the glass with your fingers, you will leave trace amounts of oil and grease on the glass. When the bulb is used, that area of the glass will get hotter than the rest and it will eventually cause the bulb to crack. When changing headlight bulbs, only hold the metal bulb holder at the base, or make sure you're wearing rubber surgical / mechanic's gloves (clean ones) if you're touching the glass.

Dash / instrument warning lights
The check engine light.
Every new car now comes with OBD-II - On Board Diagnostics 2. This is a fault-registering system connected to sensors all over the car, engine, fuel and emissions system. When the check engine light comes on, it can mean many things. There are something like 4,000 unique OBD2 codes that can be stored. Handheld OBD2 diagnostic tools can be plugged in to the OBD2 port which is normally under the dash on the driver's side. These tools can read out the fault code and/or reset the system to contain no codes. Codes are split into two categories - historical/inactive, and active. The historical codes are lists of things that have been detected in the past but are no longer an issue, whilst the active codes are things that are a problem right now. Codes are subdivided into B-codes (body), C-codes (chassis) and the biggest list of all - P-codes (powertrain). P0440 OBD-II code. This is the most common code you'll find and it's the first thing you should check. P0440 is the code for Evaporative Emission Control System Malfunction which covers a multitude of sins. The one thing it covers that you can check is your gas cap (petrol cap). Most new cars have a pressurised fuel system and vapour recovery loop. If you've filled up with petrol and not twisted the gas cap until it clicks, you've not sealed the fuel system. It won't pressurise and the OBD2 system will log a P0440 code. In fact, on a lot of cars, that code is so common they'll actually have some way of telling you to check the gas cap. In the Honda Element, for example, if a P0440 code is logged, the dash scrolls "CHECK GAS CAP" across the odometer display. So if you get a check engine light, check the gas cap first and see if the light goes off. Note : even if the light does go off, the code will likely still be stored in the OBD system and will show up next time it is checked. It wasn't the gas cap. If tightening the gas cap didn't do it, you'll need to find someone with an OBD2 diagnostics tool or reader. Some garages will charge you just for plugging the device in and reading the code for you. If they do, walk away. They're ripping you off because there are a lot of places that will do it for free - find one. In America specifically, the Schuck's chain do free diagnostics checks (Checker, Kragen, Murray's, Advance). In the UK I'm not sure who does - if you know, drop me a line. The alternative, if you're into maintaining your own vehicles, is to buy a reader and do it yourself.

The service engine light / Maint Reqd light.
This might indicate "Service", "Service Engine" or "Maint Reqd". It's an indicator that you're getting close to a scheduled maintenance interval. On some cars it's as simple as counting miles before it comes on, whilst on others it maps engine temperatures, oil temperatures, air temperatures and other indicators of probable stress to tell you when it might be time for new oil or a service. In most cars this can be overridden or reset by you, the owner. Your handbook will tell you if this is the case. If you take your car for a service, the garage should reset it for you. Typically this light will come on when you start your car, and then turn off again as part of the self-check. If it stays on for 10 seconds then turns off, it normally means you're within 500 miles of needing a service. If it flashes for 10 seconds, it normally means you've exceeded a recommended service interval.

http://www.carbibles.com/maintenancetips.html (5 of 7) [2/6/2008 7:14:44 AM]

Car Bibles : Basic Car Maintenance Tips

The electrical fault light.
This warning light is different in every car but normally it looks like a picture of a battery, similar to the picture on the left here. You'll see it come on and go off when you start your engine as part of the car's self-test, but if this light comes on and stays on, it means the electrical charging system is no longer working properly. Think of it like a cellphone battery. If the cellphone is plugged into the charger, you can use it indefinitely, but when you disconnect it from the charger, there's a limited amount of time before your battery runs out. It's exactly the same in your car, only bigger. Every car has an alternator - the charger - and a 12v battery used to supply power to the electrical system. If the alternator becomes faulty or the drive belt to it snaps, then it will not be able to do its job. The longer you drive, the more your car will use up the remaining juice in the battery and eventually the engine will die. This almost always requires a new or refurbished alternator.

Brake warning light 1
Most cars nowadays have a brake warning light on the dash. Its purpose is to alert you that something is wrong in the braking system somewhere. If it comes on, check your owner's manual to find out its meaning. Unlike the single-purpose ABS warning light, the brake warning light doesn't have a standard meaning; it could be used for multiple purposes. For example, the same light may be used to show that the hand brake (parking brake for the Americans amongst you) is on. If that's the case and you're driving, you ought to have noticed the smell of burning brake dust by now. The light can also indicate that the fluid in the master cylinder is low. Each manufacturer has a different use and standard for this light. Which is nice. Because it would be such a drag if the same indicator meant the same thing in every vehicle.

Brake warning light 2
If you've got an ABS-equipped car, you also have a second light - the ABS light. If it comes on, get it seen to as soon as possible. It means the ABS computer has diagnosed that something is amiss in the system. It could be something as simple as dirt in one of the sensors, or something as costly as an entire ABS unit replacement. Either way, if that light is on, then you, my friend, have got 1970's brakes. It's important to note that this light normally comes on when you start the car and then switches off a few seconds later. If it stays on, blinks, throbs, flashes or in any other way draws your attention to itself, take note. It's not doing it just to please itself.

Coolant warning light
This is normally the coolant level warning light. If this comes on it means that the level of coolant in your radiator is low and needs topping up. DO NOT OPEN THE RADIATOR CAP WHEN THE ENGINE IS HOT! The coolant system is pressurised and it could easily release pressure and spray you with boiling coolant. Do it when the engine is cold. Top up the system with either a pre-mixed coolant bought from a shop, or with distilled water. Don't use tap water - the mineral deposits in it boil out in the cooling system and calcium gets depositted around the inside of the radiator making it less efficient (which will eventually cause it to fail). It's always best to use pre-mixed coolant, or to mix your own rather than using neat water. The coolant mixture behaves as an antifreeze in winter as well as a corrosion-inhibitor to stop your engine rusting from the inside out.

Oil warning light
Typically this light will come on if your oil pressure is too low. Low oil pressure is serious and if you continue to drive with this light on, eventually your engine will die. Low oil pressure can be caused by a failed oil pump, a blocked oil filter or strainer in the sump, or by low oil levels - for example if your engine is burning oil. Either way, you need to get it fixed, and fast. Low oil pressure is A Bad Thing and your engine won't thank you for leaving this problem untreated.

Links
http://www.carbibles.com/maintenancetips.html (6 of 7) [2/6/2008 7:14:44 AM]

Car Bibles : Basic Car Maintenance Tips

All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/maintenancetips.html (7 of 7) [2/6/2008 7:14:44 AM]

The Car Maintenance Bibles : What's new?

CarBibles.com - the official home of the Car Maintenance Bibles Covering everything you need to know about, wheels, tyres or tires, engine oil or motor oil, suspension (including springs and shock absorbers), brakes (disc brakes and drum brakes) and general car maintenance.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Many visitors to my site come back from time to time looking for new information. This page is simply a changelog of additions, edits and modifications to the Car Bibles, along with links to the relevant parts. This changelog was started in June 2006, so obviously there won't be anything further back than that.

Special offers
Rochford Tyres has an excellent fitment guide page where they list a ton of combinations and permutations of wheels and tyres for all the popular makes and models. The guide is designed to give you an idea of wheel and tyre sizes that will keep you close to spec for rolling radius. Use the 'Alloy Wheel Search' box at the top-left of their site. As an added bonus, at the checkout to get 5% off! Sweet! if you decide to buy anything from them, use the If you're interested in a license for the BrightCar software reviewed on my reviews page, carbibles.com has negotiated a 20%-off deal. Click on the coupon on the left to get the deal. When you click through to their "buy now" page, you'll see the discount applied to the total cost.

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

2008
http://www.carbibles.com/whatsnew.html (1 of 6) [2/6/2008 7:14:55 AM]

The Car Maintenance Bibles : What's new?

February 1st 2008 FREE STUFF! A New competition launched today. Win a GoPro Motorsports camcorder. January 21st 2008 Product Reviews : Re-wrote the review of the ATC2K action/sports camcorder, and added a review of the GoPro Hero motorsports camcorder. January 21st 2008 Tyre & Bible : Added info about ultra high speed tyre size notations. January 16th 2008 Fuel & Engine Bible : Minor edit - changed tense of article about EPA 2008 figures. January 10th 2008 Product Reviews : Added a review (with video) of the ATC2K action/sports camcorder, and concluded the test of the FFT fuel treatment. January 3rd 2008 Fuel & Engine Bible : Added a video of in-cylinder combustion cycle. January 2nd 2008 Fuel & Engine Bible : Added a Schlieren photo of a spark plug spark to illustrate the idea of keying your spark plugs.

2007
December 5th 2007 and variable stiffness anti-roll bars. Suspension Bible : Added a section on transverse leaf springs. November 23rd 2007 NEW SECTION: Started work on a new page : The Steering Bible November 18th 2007 Speeding facts: Added a lot more information on the facts vs. the fiction about speeding and tidied up the whole page. November 14th 2007 Brake Bible: Added info on BMW's brake drying system and some other new technologies. November 12th 2007 Wheel & Tyre Bible: Added a note about the DOT age code on spare tyres. October 25th 2007 Suspension Bible : Added a section on air suspension. October 25th 2007 Fuel & Engine Bible : Added information about checking ignition timing. October 18th 2007 Fuel & Engine Bible : Added information about the Fifth Gear Octane Booster test. October 17th 2007 Fuel & Engine Bible : Added information on direct-injection as it applies to petrol engines (gasoline direct injection - GDI). October 8th 2007 Wheel & Tyre Bible : Added a section on tyre reviews. September 24th 2007 Fuel & Engine Bible : Added a case study on why cooling and engine design is important. September 16th 2007 The Tyre Bible : Added some more info and new photos on Porsche N-rated tyres. September 11th 2007 Wheel & Tyre Bible : Re-wrote the section on nitrogen inflation. September 10th 2007 Basic Maintenance Tips : Added oil and coolant warning light descriptions. August 28th 2007 Suspension Bible : Miscellaneous corrections to the article on hydropneumatic suspension. August 20th 2007 Like the site? Help Chris buy a bike. The total is up to $485 so far. August 11th 2007 Transmission Bible : Completed the article on differentials and AWD couplings. August 9th 2007 Brake Bible : Re-wrote the section on master brake cylinders and added some info on cross-linked brakes. August 8th 2007
http://www.carbibles.com/whatsnew.html (2 of 6) [2/6/2008 7:14:55 AM]

The Car Maintenance Bibles : What's new?

Brake Bible : Added some more info on brake squeal. Suspension Bible : Rendered new images for suspension bushes and anti-roll bars. July 29th 2007 Transmission Bible : Started the article on differentials. Still need to write about Torsen and Viscous couplings. July 28th 2007 Fuel & Engine Bible : Split this article into 3 pages - it was getting too long for a single page. Page 1 Page 2 Page 3 Wheel & Tyre Bible : Split this article into 2 pages - it was getting too long for a single page. Page 1 Page 2 July 27th 2007 Fuel & Engine Bible : Added a new section on fuel filters. July 25th 2007 Basic Car Maintenance Tips : Added a new page on basic car maintenance. July 24th 2007 Fuel & Engine Bible : Added a new section on cooling systems. July 23rd 2007 Like the site? Help Chris buy a bike. July 20th 2007 Product Reviews : Started a long-term test of the FFT Fuel Additive. July 18th 2007 Wheel & Tyre Bible : Added info on vintage radial load letter sizing. July 15th 2007 Brake Bible : Completely re-wrote the section on antilock brakes. Added a new page separating the facts from the fiction about speeding (in relation to ABS). July 14th 2007 Wheel & Tyre Bible : Added a calculator to figure out the differences in offsets between wheel sizes. July 11th 2007 Fuel & Engine Bible : Added a new section on hybrid engines. July 10th 2007 Wheel & Tyre Bible : Added info on nitrogen inflation. July 9th 2007 Wheel & Tyre Bible : Added a case study illustrating the process of changing wheels and tyres. July 8th 2007 Fuel & Engine Bible : Expanded the section on power-to-weight ratio. July 3rd 2007 Wheel & Tyre Bible : Added some blurb about tyre rotation. July 2nd 2007 Fuel & Engine Bible : Added some information on reducing the electrical load on your engine to give more horsepower. July 1st 2007 Brake Bible : Added some info about collision warning systems and brake-assist. June 6th 2007 Engine Oil Bible : Added some new info on not using car engine oils in motorcycle engines. May 29th 2007 Wheel & Tyre Bible : Added some blurb about the new Goodyear Wrangler 'SilentArmor' tyre. May 16th 2007 Engine Oil Bible : Added a writeup of the Moroso engine pre-luber. May 8th 2007 Carbibles.com has partnered with justanswer.com to provide a paid Q&A for unique technical questions which will be answered by licensed/certified experts. May 7th 2007 Wheel & Tyre Bible : Added another imperial tyre calculator and description for LT-style light truck tyres. May 1st 2007 Brake Bible : Clarified angular force with respect to braking and larger brake rotors. April 30th 2007 Wheel & Tyre Bible : Clarified PCD on wheels and added some blurb about spigot size. Added a new diagram to illustrate the two. April 16th 2007 Fuel & Engine Bible : Added some information on hydrogen vehicles. April 11th 2007 Wheel & Tyre Bible : Added a graphic representation to the tyre size calculator so you can compare the relative size of your old and new tyres.
http://www.carbibles.com/whatsnew.html (3 of 6) [2/6/2008 7:14:55 AM]

The Car Maintenance Bibles : What's new?

April 10th 2007 Wheel & Tyre Bible : Added some clarification on wheel dimensions, PCD, inset, outset and offset. April 4th 2007 Product Reviews : Added a 20% off coupon for readers who would like to buy BrightCar mileage-tracking software. April 2nd 2007 Suspension Bible : Added some more info on de Dion tube rear suspension. March 30th 2007 Fuel & Engine Bible : Added some more info on turbos. March 2nd 2007 Product Reviews : Reviewed BrightCar mileage-tracking software. March 1st 2007 Tyre Bible: Clarified the section on wheel inset and outset with a new diagram. February 20th 2007 NEW SECTION. I've unveiled the first part of the new Transmission Bible. The second part will follow shortly. February 19th 2007 Tyre Bible: Added info on Goodyear's new Eagle Responsedge tyre. February 7th 2007 The Tyre Bible : Added a section on Porsche N-rated tyres. February 4th 2007 FREE STUFF! Seriously. New competition page. Win stuff I've reviewed. February 2nd 2007 Product Reviews : Reviewed GasDandy mileage-tracking software. February 1st 2007 Engine Oil Bible : Added a case study about oil sludge in a Saab 9 5 Aero. January 2nd 2007 Brake Bible : Added a new section on handbrakes. January 22nd 2007 Added a new menu style to the Tyre Bible. I'm experimenting with this drop-down system. Please take a look and drop me a line to let me know if you like it, and that it worked ok. It's going to cost me to buy the full version so I'd like to be sure before I go ahead and roll it out to the whole site. January 17th 2007 Tyre Bible : Re-jigged all the wording about run-flat tyres, added a calculator to convert Michelin PAX tyre sizes to standard notation, and added some info about PAX asymmetric beads. January 4th 2007 Brake Bible : Added a new section on the Siemens electric wedge brake (EWB). January 2nd 2007 Brake Bible : Added a new section on handbrakes.

2006
November 18th 2006 Fuel & Engine Bible : Added a new section on LPG / LNG / Autogas. December 9th 2006 Suspension Bible : added info on the OnCamber variable camber steering system. November 27th 2006 Fuel & Engine Bible : 10 tons of water to refine 1 ton of grain for E85. November 14th 2006 Fuel & Engine Bible : Refined some of the wording about E85. November 6th 2006 Fuel & Engine Bible : Added a new section on fuel-air mixing, carburettors and fuel injection. November 5th 2006 Brake Bible : Added some trivia on the history of disc brakes. Fuel & Engine Bible : Added some updated info on chipping and remapping. Fuel & Engine Bible : Added some info on the Toyota D-Cat and DPNR clean diesel system. Engine Oil Bible : Added some info on the dangers of over-filling an engine with oil. October 21st 2006 Suspension Bible : Added a new section on de Dion tube rear suspension and Rover 2000 MacPhersonhttp://www.carbibles.com/whatsnew.html (4 of 6) [2/6/2008 7:14:55 AM]

The Car Maintenance Bibles : What's new?

derivative suspension. and October 10th 2006 Fuel & Engine Bible : Added a new section on exhaust wraps. October 5th 2006 Fuel & Engine Bible : Added a new section on valvetrain types and engine layouts. and October 3rd 2006 Bike Suspension Bible : Added some info on the reasons for monoshocks vs. dual shocks. October 1st 2006 Brake Bible : Correct words and diagrams relating to mechanical advantage Rendered a new image and changed the text describing radially mounted brake calipers September 28th 2006 Engine Oil Bible : Added some info on phosphorus. September 27th 2006 Product reviews : Added a review of the Signal Sorcerer traffic light changer. September 13th 2006 Wheel & Tyre Bible : Added a section about "correct" tyre pressures. September 12th 2006 Wheel & Tyre Bible : Clarified the types of passenger car tyres. September 7th 2006 Fuel & Engine Bible : Added a section on MPG Caps and other fuel-saving pills. Product Reviews: Added a review of MPG Caps fuel-saving pills. September 6th 2006 Engine Oil Bible : Added a section on oil extractors. August 28th 2006 Fuel & Engine Bible : Added a section on gas-mileage and why American cars will never meet EPA estimates. August 18th 2006 General : Managed to secure a 5% discount for anyone who shops at Rochford Tyres in the UK. Fuel & Engine Bible : Added a section on E85 ethanol. August 16th 2006 Engine Oil Bible : Added a mini section on not using diesel engine oils in a petrol engine. Fuel & Engine Bible : Added a section on 4-stroke and 2-stroke diesel engines. August 11th 2006 Fuel & Engine Bible : Added some reader comments on hydrogen generators. August 8th 2006 Fuel & Engine Bible : Added information on spark plugs and keying spark plugs for better combustion efficiency. August 7th 2006 Product Reviews : Added a test of the PressurePro TPMS. July 31st 2006 August 4th 2006 Fuel & Engine Bible : Added information about torque, bhp and horsepower. July 31st 2006 Added a product reviews page for motoring accessories. July 27th 2006 Wheel & Tyre Bible : Added new information on the PressurePro TPMS. July 24th 2006 Suspension Bible : Added some information links for Hydragas suspension. Fuel & Engine Bible : Another email about the Electronic Engine Ionizer. Fuel & Engine Bible : Up-to-date information on the voltage stabilizer aftermarket accessory. July 20th 2006 Wheel & Tyre Bible : Expanded information on minimum legal tread depth and why it's not safe. July 19th 2006 Added a feedback page for general comments on the site. July 17th 2006 Fuel & Engine Bible : Clarified one of my comments on 12v electrical systems and fuel economy. FAQ : Clarified the policy of linking to and/or copying from this site. July 13th 2006 Suspension Bible : Added a new section on magneto-rheological suspension as fitted to the new Audi TT. July 11th 2006 Engine Oil Bible : Ammended status of 'SJ' oil classification.
http://www.carbibles.com/whatsnew.html (5 of 6) [2/6/2008 7:14:55 AM]

and

The Car Maintenance Bibles : What's new?

Suspension Bible : Deleted invalid links and added two new ones for further reference on Citroën suspension systems. July 9th 2006 Wheel & Tyre Bible : Modified caster / camber image to include direction of travel. July 1st 2006 Wheel & Tyre Bible : Added some extra values to the tyre size calculator. June 21st 2006 Wheel & Tyre Bible : Added new information about tyre tread wear indicators and hydroplaning. June 11th 2006 Fuel & Engine Bible : Added new information about grounding kits and voltage stabilisers.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/whatsnew.html (6 of 6) [2/6/2008 7:14:55 AM]

The Engine Oil Bible : Additives

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

The not-so-clever classic oil additives
IMPORTANT NOTE TO COMPANIES AND lawyers: If you find I've got something in here which you think is out of place, please email me first. I'm not in the business of misrepresenting people. I'm trying to present a fair and balanced website, free of advertising and sponsorship. Frankly, I don't have the money for a lawsuit, so a gentle email from the relevant department will work wonders. For those of you who've already discovered this for yourselves, both I and my bank thank you for not wading in with the big guns.

Happiness is ..... an engine treated with mineral oil filled with food colouring????
To illustrate the whole point about additives, consider this. In the manufacture of synthetic oils, once the synthetic polyol ester bases are created, anti-wear additives such as zinc dithiophosphates (essentially combinations of zinc, phosphorous, and sulphour molecules) are added. These combinations are extremely effective as anti-oxidant, anti-wear, anticorrosion inhibitors. Now look at the contents of some of the after-market additives. Wow! Zinc, phosphorous and sulphour! Imagine that. Those aftermarket additives are actually exactly what your oil manufacturer has put in already. Consider further that some oil companies actually make a point of telling you not to use aftermarket additives with their oils. So if these additives are so brilliant, why do the companies always seem to end up in trouble? Well - misleading advertising and non-active "active" ingredients claim a lot of victims. Read on...... Note : you can search for the FTC's rulings on any engine additive by using their search page and searching their 'news releases' for the product you're interested in - most of them are in there, which should tell you something.....

Slick 50 in $20M lawsuit, loses to FTC.
http://www.carbibles.com/additives.html (1 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

Blue Corral, the manufacturers of the Slick 50 engine oil additive, have been banned by the Federal Trade Commission from making claims about reduced engine wear, increased fuel economy and lower running temperatures in it's advertising in America. The Federal Commission found the company's claims of increased performance and reduced wear were unsubstantiated, and Blue Corral has agreed to pay upwards of $20M in damages to affected customers. Source: Max Power magazine, March 1998. Click here to see all the FTC Reports pertaining to Slick50.

DuraLube challenged by Car&Driver, loses to FTC.
The manufacturers of the DuraLube engine additive were dealt a smack in the face by a Car & Driver Magazine report into their product. C&D tried the same tests as Consumer Reports did on ProLong, and had similar results, but in a much quicker time. The C&D engines treated with DuraLube lasted a staggering 11 seconds without oil. You do the math. The Federal Trade Commission dealt with it..... Click here to see all the FTC Reports pertaining to Duralube.

MotorUp loses to FTC for deceptive advertising claims.
In an ongoing campaign targeting ads that tout motor oil additives with deceptive claims that they reduce engine wear or extend engine life compared to motor oil alone, the FTC has charged the seller of Motor Up Engine Treatment with making unsubstantiated and deceptive advertising claims, in violation of federal laws. Motor Up Corporation and its principal, Kyle Burns, face an administrative trial.
Click here to see all the FTC Reports pertaining to MotorUp.

The magnet-on-your-fuel-line boys
FuelMax loses to FTC for deceptive advertising claims.
The marketers of the Super FuelMAX automotive fuel-line magnet, advertised as providing dramatic fuel-saving and emissions-reducing benefits, have agreed to settle Federal Trade Commission charges that their claims were unsubstantiated. These guys claimed that sticking a pair of magnets around your fuel line would increase your gas mileage by 27% whilst reducing harmful pollutants by 42%. The one slight flaw in their plan? There's nothing in fuel that can be affected by magnets...... The FTC alleged that the manufacturers did not possess or rely on reasonable substantiation for the claims they made. The complaint also alleged that the manufacturers falsely represented that tests performed at a certified EPA laboratory prove that Super FuelMAX performed to the above figures. Finally, the FTC charged that ads for Super FuelMAX featuring a testimonial from Alexander Elnekaveh endorsing the product did not reflect Elnekaveh's actual experience with the product or the typical or ordinary experience of members of the public who use the product. Therefore, the FTC complaint said, the representations concerning the testimonial were false or misleading.
Click here to read the FTC Report on the FTC vs. FuelMax. Click here to see all the FTC Reports pertaining to FuelMax.

The additives that fought back
ZMax wins against an FTC settlement for misleading advertising.
The Federal Trade Commission filed suit in a U. S. District Court that sought to halt false and misleading advertising for zMax auto additives and which asked the court to order refunds to consumers who bought the products. The agency
http://www.carbibles.com/additives.html (2 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

alleged that enhanced performance claims for the product were unsubstantiated, that tests cited to support performance claims actually demonstrated that motor oil treated with zMax produced more than twice as much bearing corrosion than motor oil alone, and that the three different products - an engine additive, a fuel line additive and a transmission additive - were all actually mineral oil tinted with food colouring.. Well on 20th March 2003, Speedway Motorsports Inc. (TRK) and Oil-Chem Research Corp., the manufacturers of zMax, announced that they had settled their dispute with the FTC. The Concord, North Carolina-based Speedway said that the dispute was concerning the advertising of zMAX Power System. Marylaurel E. Wilks, VP and general counsel said, "We at Speedway Motorsports are very pleased that the staff of the Federal Trade Commission has specifically confirmed that Oil-Chem can continue to make the following claims in its advertising and promotion of zMAX:".
● ● ● ● ● ● ●

●

zMAX soaks into metal, zMAX reduces friction, zMAX increases horsepower, zMAX dissipates engine heat, zMAX helps to improve or restore gas mileage and reduce emissions in older cars, by virtue of reducing engine deposits, zMAX helps to maintain gas mileage and emissions in newer cars, by virtue of reducing engine deposits, zMAX helps to reduce engine wear on engine valve-stems and guides and piston rings and skirts, by virtue of reducing engine deposits, zMAX helps to extend engine life, by virtue of reducing engine deposits.

Here's the kicker (from their website): "Oil-Chem and SMI have not admitted any liability in this litigation. However, in order to avoid the significant expense and time involved in the litigation, the FTC, Oil-Chem and SMI have agreed to end the litigation by the signing of an order, which, in summary, states: (a) Oil-Chem and SMI do not admit any liability and continue to deny any liability; (b) The FTC has issued its compliance letter (which confirms that enforcement is not merited for the eight specified claims); (c) Oil-Chem and SMI will not make advertising claims which are not properly substantiated; and (d) Oil-Chem and SMI will offer a refund of up to $1 million, in the aggregate, to certain purchasers of zMAX, who bought zMAX before January 31, 2001."
Click Click Click Click here here here here to to to to read the original FTC Report on the FTC vs. ZMax. read the somewhat fuzzy final ruling in this case. go to zMax's own site and read the settlement blurb. see all the FTC Reports pertaining to zMax.

Click here to see the FTC court order (PDF file). The first 17 pages are the original Court Order with all stipulations, pages 18-20 show the letter from the Oil-Chem Research and Speedway Motorsports, Inc attorneys (12/23/2002) to Elaine D. Kolish (an Associate Director at the FTC) outlining the "Claims" Zmax intended to make from that date forward, and in anticipation of the FTC Court Order. Page 21 is the response from Ms. Kolish (12/26/2002) to those attorneys that accepts their information as, "accurate and complete," and that it will continue in that manner assuming our test information is maintained as such (which it has,) in addition to the provision that, "no defendant violates the terms of the order."

It should be noted that the FTC is a Federal Government Commission that must maintain an extreme level of integrity, and therefore remain impartial on all matters. As a result, they cannot be seen even remotely as endorsing any product, company or entity over another. Even after all of the negative press that was generated during this litigation, (and is still available for view on various websites), the FTC is not allowed to produce a letter that endorses a product or company regardless of the outcome of that litigation. What they were able to do was allow "side letters" (the followup communications with Oil-Chem Research and Speedway Motorsports, Inc attorneys) to be posted along with the court order, the latter of which is confusing for any non-legal professional to read if it is not viewed along with these other letters.

ProLong challenged by Consumer Reports. FTC investigates, upholds CR claims, then ultimately allows ProLong to continue marketing.
The manufacturers of the ProLong engine additive were dealt a smack in the face by a Consumer Reports Magazine report into their product. CR attempted to reproduce the "no oil" test where all the oil was drained out of an engine which had been treated with ProLong, and then the engine was run. CR managed
http://www.carbibles.com/additives.html (3 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

a maximum of 13 seconds running out of each of two engine before they seized up, welding the pistons to the barrels. The case was brought to a Federal Commision for prosecution for false advertising claims. You can subscribe to the online version of Consumer Reports here for a minimal fee, and read all about it in their October 1998 features. Source: Consumer Reports, October 1998. The FTC ultimately settled it's investigation with Prolong, without fines of any kind. After 18 months of testing the FTC indicated that Prolong is exactly what they say it is. Further, the FTC has approved Prolong's new advertising statement, currently in print in Car and Driver, as "The World's Most Powerful Oil". Click here to see all the FTC reports pertaining to ProLong.

But what about Henry "Smokey" Yunick?
I get a fair number of emails from people who put a lot of stock in what the late Henry Yunick had to say about ProLong because he was a respected mechanic and car designer. The sad fact of the matter is that his endorsement of ProLong was paid for by them with financial enticements, air fares, NASCAR hard cards, uniforms and other expenses, as documented in their SEC 10K filing. SEC ProLong 10K filing re. Smokey Yunick. Because of the ProLong financial interest in Yunick, his views were not impartial and he was essentially paid to promote ProLong, for better or for worse. So whilst he was an excellent designer and mechanic, you can't really take his point of view on ProLong seriously because he was no longer independent.

ADDITIVES AND TURBO ENGINES - READ CAREFULLY
There are certain brands of additives that make the claim that they'll "stop engine smoking" amongst other things. Now the way these work as I understand it, is by having some form of resin in solution form in the oil. The idea is that where the cylinder bores have become scored over years of use, oil is squirting past the piston rings and into the combustion chamber where it is being burned, hence the smokey engine. This resin makes the oil slightly thicker which helps it to seal those tiny scores whilst still lubricating the cylinder bores. The problem comes when this resin solution gets extremely hot - it turns hard. With most turbo systems, the bearings on the turbo get extremely hot, and the way around this is to use the engine oil to lube the bearings whilst at the same time transporting the heat away from them. When the additive finds its way into the turbo bearings, it can solidify and seize the turbo. Now feel free to correct me if I'm wrong there. I've heard this from five different people now although I've not experienced it myself (I don't use additives, period). It seems that none of the additive manufacturers put any warnings about this on their products which leads me to believe that either (a) I'm wrong, or (b) they don't want you to know about this problem. I'd appreciate any further info or corrections on this subject from any of my readers if they have any.

The squeaky-clean new boys on the block?
Since the initial euphoria over oil additives died down, and with ongoing proceedings against some of the most wellknown household names, there's a clutch of new additive manufacturers starting to appear. A lot of them are using something called Boron CLS Bond®. This is based on the intricate crystal lattice structure of hydrated boron molecules. That lattice structure allows the layers of hydrated boron particles to slide virtually friction-free over each other, like the playing cards in a fresh deck, while retaining strength. The ultrafine particles of hydrated boron reach into every metal crevice, lubricating with super-slipperiness as they chemically bond with the host material. This all sounds well and good, but I'm not a chemist so I can't comment. What does worry me a little is that the chemical starts out as Boric Acid and has to react with air and water to get its chemical reaction going. But what do I know? A lot of the manufacturers are claiming things like Reduces engine wear by 80%. Sounds familiar doesn't it? Well, like I said, I don't know enough about this to claim otherwise, so if you have any direct experience of one of the following, I'd like to hear about it so I can pad my pages with more informative information. Each graphic links to the website of the manufacturer or distributor of the product in question. I've linked a couple of Word documents here if you want to read up more on the claims. The first is a basic rundown of what CLS Bond is and the other is a list of people claimed to be using or testing the product. Tech document. People using or testing. Dean Brubaker, the president of this organisation, actually contacted me directly to ask if I'd consider giving them some space on my site. Fair play. Again I
http://www.carbibles.com/additives.html (4 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

can't comment one way or another on Motorbond - I've not used it myself. Their site is very comprehensive and it does have a fair amount of technical data to backup their claims. Interestingly, they also have technical data and products for marine engines. These things undergo a different type of stress to car engines - normally more - and so promoting a product for marine use is a good indicator that Motorbond should have done their research well. So if you have used Motorbond's products, please let me know. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

My personal views on additives:
Apart from the fact that all the additive manufacturers have been in trouble in the past, and most of them have lost their cases (see above): My views on engine oil additives are this: the oil companies spend hundreds of millions on research and development in order to make their oils suitable for use in car engines. A standard off-the-shelf engine oil is already stuffed with a cocktail of additives put there by the oil company (see above). By contrast, additive companies spend a couple of million on R&D and an equal amount in PR and advertising to claim that their product (and only their product) will enhance the life of your engine. You're adding an unapproved additive to an already additive-full oil. Spot the problem? The current trend is the "90% of your engine wear happens at startup" advertising ploy. This fact is absolutely true, but as it happens, it's less to to with "grinding engine parts" and more to do with combustion. When the combustion gases burn, they form acids which are highly corrosive when their vapours condense. These acids collect in the upper cylinder areas where their temperature is raised above their dew point. The acids condense and etch the cylinder walls and piston rings. In reality, this accounts for over 85% of engine wear, the other 15% being down to abrasion. So the adverts are nearly right - most of the engine wear does happen at startup, and it is because of a lack of oil, but it isn't because the oil isn't coating moving parts - it's because it's not transporting these acidic gases away. Having said that, if you start the engine and let it idle for 15 seconds or so before moving off, you can probably add another 100,000 miles to your engine's life without one bottle of additive. This warms the oil up a tad and makes sure it's in all the most vital areas before you start putting a strain on the engine. Most handbooks tell you not to let the engine warm up before driving off (they're referring to the acid corrosion mentioned above), but they mean don't let it reach working temperature. If, however, you insist on starting up and belting off down the road, think of this next time: it takes an average engine around 3 minutes of average driving for the exhaust manifold to reach 300°C. If you blast off and run around at full throttle, right from the word go, that process takes a little under a minute. Think about it - from outside air temperature to 300°C in a minute - what exactly is that doing to the metal in your manifold? Ask anyone who's ever owned an original Audi Quattro - they'll tell you exactly what happens. I'm not saying that these companies are having us all on, heaven knows there are plenty of statements from companies and private individuals who have reportedly reaped the benefits of these products. But in my experience, it's simply not worth the huge risk of putting the additive in there.

Another perspective:
I received this email from Albert Clark who has, it seems, had first-hand experience of one of the additive products: I kept hearing about such a product and found a store going out of business that was practically giving it away. I put a quart in two cars: An MGB and a Chevy 305 V-8. The MGB went 20 miles before a ring stuck causing it to start throwing oil everywhere. A mechanic then messed up when putting new pistons on the old rods and shortly after rebuild a piston froze and threw a rod bearing that ruined the crank, etc. The Chevy started using a quart every 25 miles immediately after the product was used. I drained it and refilled immediately, but it took engine flush and about 4 oil changes over 2000 miles before oil usage was reduced to a quart every 400 miles. It was using a quart every 800 miles before that. I ended up putting another 60,000 miles for a total of 180,000 miles before rebuild. I will never recommend such a product to anyone.
http://www.carbibles.com/additives.html (5 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

The moral? If you're going to care for your engine, do it properly, not in half-measures, and it will look after you for as many miles as you care to drive.

Your opinion.
TM "Chris, you misguided fool! You're talking out of your ass! I've used SuperHappySlippyOil and it's been great!" Does this seem like something you want to say? Well there are so many new products coming out on the market now in the additive arena that I don't have time to keep up with them. Things like Z-Max, for example. So here's your chance to have your say. Once I've gathered enough opinions, I'll be adding a new page with people's real world experiences of various products. What do I want you to do? Well - just send me an email with a short tale about your experiences, good or bad, with any engine additive or additive system. Include things like ProLong, DuraLube, Z-Max - anything you like. Make sure you include pertinent information such as your car or truck model and year, engine type, mileage etc. Once people read the experiences of others, it will make for a far more useful section on this page than just my personal opinion.

On to your comments:
Product : Motor Up (USA) Vehicle : 2.2 FI Mazda 285,000kms. Chris. My cold start 'death rattle' disappeared after about 700kms. Compression presures all about 140psi, and engine so quiet people comment. Used with Castrol Magnatec 10W 40 for 3-4 changes (added a bottle at each change) and now using Pennzoil 15W 50 semi-synthetic for summer months. Changing to full synthetic Penrite 5W 60 when it's released in a month or so. Regards...Stephen Murray. Product : Slick 50 (USA) Vehicle : 1989 Civic Si. I bought a brand new Civic Si in '89 and soon after used Slick 50. I did notice a significant difference in performance, smoothness and acceleration, sorry to say. I don't know if it was doing damage, but I repeated the application after about 30k with the same results. I was driving courier and put about 75000 mi on the engine in 1.5 yrs. I also used nothing but synthetic oil for most of that period, changing oil/filter every 2500mi or so (about 2 weeks). The car was running almost like new by the time I was no longer in possession of the car with the aforementioned mileage. Now I know you are going to say that's because of the frequent changes, but I have to say again with each application of Slick 50, there was a significant difference for at least a while after application, which made me believe it was doing something positive. G Wood - Canada (had the car through one cold Canadian winter) Product : Slick 50, ProLong, Duralube (USA) Vehicle : 1979 Pontiac Grand Prix. I have used Slick 50, Duralube and currently use Prolong in my car. My car a 1979 Pontiac Grand Prix with a 301 V8 engine in it, I bought back in Dec. 1990 and it had 163,000 miles on it when I bought it and retired it with 850,000 PLUS miles on it. I used Slick 50 in it. I then heard about Duralube and switched to it, then when I heard about the Viper running around the desert race track being driven by one of the Unser's I immediately switched to Prolong and used it for years. I am not sure exactly how many years I have used Prolong, but I do believe that I would not have be able to go 850,000 PLUS without some type of additive like the one's listed above that I have both tried and currently use. I recently retired my 1979 Pontiac and was so impressed with Prolong that when I bought my recent car 1993 Pontiac Grand Prix I had the oil changed to Mobil 1 5w-30 synthetic and even put Prolong in it not too long after I bought the car. Oh, one other thing I have used infrequently is the STP Oil Treatment. My grandpa always used it so I did too, but I didn't use it regularly like I did the above products I talked about. V.F. Product : Duralube (USA) Vehicle : 1995 Mercury Sable. I just wanted to share a couple of my experiences with the Duralube products.I currently own a 1995 Mercury Sable with 260,000 miles on it.I drive it 70 miles daily to and from work.The tach still reads at the same rpms that it did when it had 3000 miles on it and it still performs great.I have used Duralube at every oil change with Valvoline 5w30.My
http://www.carbibles.com/additives.html (6 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

previous vehicle was a 1985 Dodge 600.This vehicle developed a leak in the power steering at the rack.IT grew progressively worse until it was leaking a quart of fluid a day.I purchased a bottle of Duralube transmission treatment and poured it into the power steering resoivor.That same day the leak stopped and the car was driven for four more years without ever leaking or adding power steering fluid again. T.M. Product : Slick 50 Vehicle : Heavy construction vehicles. Hey there, thought I would let you know about an experience that I had with Slick 50. I work for a heavy construction company that owns a very large amount of construction equipment such as backhoes, excavators, bulldozers, front-end loaders and some VERY LARGE cranes. Since some of these pieces of equipment have price tags in excess of $500,000 US Dollars we have a very keen interest in keeping everything running all day every day with the least amount of fuel burned. To help us do this we regularly send oil samples in for analysis to let us know what is going on in those pricey engines. In doing this we can often fix something before it breaks, pretty cool huh? Well anyway, I bought 5 gallons of Slick 50 and installed it in a few of these money pits after changing the oil and filters. I let the equipment rack up about 100 hours on the hour meter and took an oil sample. Guess what I found! All the wear metals found in the oil sample were exactly the same as before my little test began (except for one which lost a turbocharger). Now, if Slick 50 was supposed to make my engines, hydraulic systems and gear drives last longer, why did they wear out at the same rate as before? Hmmmm...... My engines already last a long time. You know why? I take care of them! T.B. Product : ProLong Vehicle : 1989 VW Jetta. Hi there. I just wanted to share my experience of Prolong with you. I was very sceptical of these products until one day in 2002 when I had bought a 1989 VW Jetta with over 100,000 miles on the clock. I thought I would try Prolong out as it didn't matter if it wrecked the car as it only cost me £200. Before I put the Prolong in the gearbox made a whining noise and fuel consumption was 29.87MPG. I added the fuel, gearbox and engine additives to the car. The gearbox was less noisy, the engine temperature was lower and the fuel consumption went up to 41.4MPG. Now this product may or may not be good long term in a car, I don't know yet. But it is certainly worth adding to an old banger as you will save money just on the fuel consumption. The money I saved in fuel paid for my next banger. The Jetta was pensioned off due to rust not engine problems :-) Hell if it does die, throw it away and buy a new one for less than the price of a pair of trainers. Rob Moore (not 100% convinced but still experimenting) Product : Restore Vehicle : '86 Chevy Suburban diesel. Being a skeptic on additives and TV hype i finally gave in a tried an additive called "RESTORE" in my 86 chevy suburban diesel. At about 140,000 miles it started smoking profusely on cool morning start up. mechanics told me it was incomplete combustion in the cylinders that were losing compression. One can of this stuff and about 100 or so miles for it to do its thing, ta daa smoking stopped. then i tried it in my 305 chevy, (100,000 plus miles on the clock) smoother idle, much improved performance (not the kind like when you wash and wax it) i recommend this in anything that has high miles, just gets a little more life out of a tired engine. PS: the suburban had 240,000 mi when I traded it in. Bob Piper. Product : Morey's Oil Stabiliser Vehicle : 1973 Fiat Station wagon. In 1993 we purchased a 1973 Fiat station wagon with a 1438cc pushrod engine. As we were bringing it home, my husband, a longtime Fiat mechanic, heard a slight rattle in the bottom end. His first thought was to pull the oil pan and change rod bearings, but decided to see what would happen with Morey's Oil Stabilizer (a petroleum product, not a Teflon or other chemical whoopdedoo), and we have been using it in this car ever since. The rattle went away and the engine ran fine for four years, until the radiator fan motor failed and the engine overheated. We overhauled it and that time, and after breaking it in, have continued to add the Morey's at each oil change. We are still driving it, it has more than 150,000 miles on it, and the engine runs quiet. Linden Malki. Product : Duralube Vehicle : 1988 Ford Escort. I had a 1988 Ford Escort that went all the way to 232,000 miles with DuraLube. Yes, the oil-seal rings leaked to begin with, but the product isn't designed to deal with that. It got 25 mi./g. until creamed from behind at a freeway on-ramp. I
http://www.carbibles.com/additives.html (7 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

believe DuraLube did a lot to extend its engine life and efficiency. Oil seemed to blacken much less once I started using DuraLube (at each oil change, which I do myself), so apparently it does reduce friction above what the oil alone will. Helge Skjeveland. Product : Duralube Vehicle : Various. I used Duralube in a 10 year old AMC Spirit and it instantly developed a carbon knock. So beware - the detergents did a number on it. Secondly, I used a veriety of Teflon products on my 1985 Plymouth Voyager with Castrol Syntec oil but at deep oil change intervals - and it blew smoke after 140,000. Conclusion? Teflon and oil filters on deep change intervals don't mix. I think you can't skip the additives when discussing longetivity.. Rob Green. Product : Restore Vehicle : '83 Pontiac Grand Prix. A few years back, I had a 1983 Pontiac Grand Prix. I got it with around 43K miles on it. At around 90K or so, the engine died, stranding me 70 miles from home. I had done carbuerator work about a year and a half before, and rebuilt the carb 3/4 of a year before; it just seemed like the car had endemic problems, and had finally had it. The mechanic gave me a horror story, and I ended up getting a new car. In order to get the thing sold, I tried Restore on the advice of a mechanic. Lo and behold, the thing started and was able to run reasonably under it's own power. I sold it for $400 or so. It may not have been the Restore, and I don't know what happened afterwards, but it seemed to work. I certainly had nothing to lose. C Coccio. Product : Redline Oil Vehicle : Various. .......One small point I wish to make is that for a number of years I have used RedlineOil which in my experience is the mount Everest of lubricants (Engine, Transmission, Differentials, Fuel additives et al) and is designed so the same engine lubricant runs in my non-turbo petrol engine car, diesel turbo engine 4*4 and 1000cc motorcycle. As an enthusiast of cars, trucks, bikes, boats et al for many years, thanks to redlineoil, my lube worries are thankfully a solved problem and I run it in everything from an SL through to a generator. Please DO NOT mistake this as preaching, merely the fact that I like to help like minded enthusiasts. I hope you will enjoy the same benefits as I do. (To clarify, Redline Oil produce independently verifiable minimum compromise lubricants [Engine, Transmission, Trans-axle] in addition to additives.) Keith Banks. Product : Amsoil Vehicle : Various. Back around 1982, I used Amsoil for a year, then switched to MobilOne because the price was better. My 2.5 L Pontiac engine used almost no oil until (at 102,000 miles) a spark plug failed and dropped ceramic into the combustion chamber. Long story about that... I switched to Castrol in my new car and had good luck with it for years after that. One day I got a wild hair and decided to give Pennsoil Semi Synthetic a try. It turned my engine brown inside! I switched to Amsoil for another try. The main reason is that they advertise you can go 25,000 miles or 12 months between oil changes, as long as you change the filter half way through and use their superduty filters. It makes financial sense over changing regular oil 3 or 4 times a year. I also think it makes good mechanical sense, but you have to have faith in their formulation and use very high efficiency filters (Mobil-1 and PureOne are about equal in efficiency, but less capacity, from what I have read). If you're a mechanic at heart, it is really hard to accept the idea that oil can go that long without a change. But I think Amsoil has done their homework on this. I became an Amsoil "preferred customer" for $20 a year; which means I save about 20% on my purchases, and I can buy their lubrication courses intended for dealers. These courses are a little rough in some places but have a lot of good info in them. If you get a hankering to read more than you ever wanted to know about lubrication, they might be a good investment. Jacques Morrise. Product : STP Leak Prevention Vehicle : 1994 Geo Prizm w/185.6k miles. Regular oil changes w/Mobil 1 since I acquired it at 55k miles. Vehicle developed a major leak out rear seal and was losing
http://www.carbibles.com/additives.html (8 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

1 quart per 100 miles on a recent trip. STP leak prevention additive staunched the flow long enough for me to return with family to my home town and drive around for two weeks looking for a new car. I do not use an additive on a regular basis but this one did help keep things together long enough to get me through a tight spot. G.N. Product : Bi-Tron Engine Formulation Vehicle : VW Golf. After using the oil additive in my VW diesel rabbit, the compression was so bad that it wouldn't start anymore in the cold weather and the engine ran away by itself on the highway, meaning the blow by was so bad that the oil fumes got sucked into the intake manifold and powered the engine like a rocked with the key off. Only way to kill the process was use the brakes and cover the intake air to the air filter quick before the motor came undone, happened twice - cure was to hone cylinders and insall new rings, avoid Bi Tron of course, then it ran like a top for 5 years. Denis Casserly. Product : DuraLube Vehicle : '74 ford van 302 v8 I drove to pheonix in my 72 ford van and was experienceing extreme heat to the motor and a hard time on the mountain passes. When we got to Phoenix it stayed hot - the gauge was pegged before we could even find the mother inlaws house. I stopped at Autozone and got Duralube just to try to make it to our destination I put the Duralube in right there at the Autozone. We pulled out of the parking lot went about three blocks stopped at a light and I noticed the heat gauge had gone down about 25%. The light changed and I pushed on the throttle as normal and the tires spun for about three feet. It ran great and all the mountains on the way home from Phoenix to Utah became hills 80 mph plus over the top no over heating.The van was still running great two more years then I sold it to a friend of mine. More than 200k miles as far as I know that thing is probably still running somewhere. S.S.. Product : Slick50 Vehicle : '87 Chevy S-10 I am another satisfied Slick 50 user. I have used it in numerous vehicles, however one in particular sold me on the product. I was driving as a courier and had an 87 Chevy S-10 with a 2.8 liter V6 (not the most durable engine by any standard) I was at around 125,000 miles when I began burning around 1 qt of oil every 3k miles. I changed the oil with slick 50. Not only did the oil consumption stop, but my mileage went up around 3 mpg. I was driving 250-400 miles a day depending on my routes so it was easy to note the immediate difference. I was skeptical before using and am a loyal convinced customer since seeing those results. BTW the truck went to 225,000 miles when I sold it with no more oil burned and no repairs except a fuel pump. Dominic C Product : ProLong Vehicle : '91 Jeep Cherokee 4 litre six cylinder I saw the Prolong oil additive commercials on TV, where they drove a Viper, along with other cars, with no oil pan or filter, for extended time periods with no oil. I didn't believe them. However, I subscribed to Circle Track (racing technology) magazine, which did an interview with the legendary Smokey Yunick, a recognized automotive engineer/ genius. Smokey had seen the same commercials and considered them, to quote the article, "BS", and he proceeded to test the Prolong additive thoroughly, and much to his surprise, discovered it worked as advertised. He had even recommended it to race car teams, including top Nascar teams, who he consulted for. So I bought some, put it in my wifes 1991 Jeep Cherokee, 4.0 liter inline six cylinder engine. Have you ever heard an engine lose oil pressure? I have. The first thing you notice is the camshaft lifters clattering as they collapse from zero oil pressure. One day I came home from work as my wife was pulling into the driveway. First thing I noticed was all the lifters clattering noisily. I knew what that meant: no oil pressure. Sure enough, it turned out that the oil filter base O rings had failed and it developed a massive oil leak, dumping 5 quarts of the six quart capacity out of the engine. For four days she had driven a 30 mile roundtrip route to work and back, plus various side errands, with zero oil pressure. I replaced the O rings, added five quarts, started up the engine....it ran perfectly normal. In fact the oil mileage went up from 750 MPQ it had been getting to 1500 MPQ, not bad for an engine with 120,000 miles on it. So that sold me on Prolong. Smokey Yunick said it worked, and it did, as advertised. In my case, it had been in the oil for a couple of months, prior to the major oil loss problem. Yunick said in his tests, once plated onto metal, it had to be worn off, it couldn't be wiped, washed, or otherwise removed. Another thing Smokey said, was that a Prolong treated engine would not seize up from overheating, thus protecting the engine until parts start melting, such as exhaust valves and spark plugs. That's one reason he recommended it to Nascar race teams. He gave an example of a short track race car with Prolong additive in it, breaking a water pump belt at the start of a
http://www.carbibles.com/additives.html (9 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

50 lap race (1/2 mile race track). The engine got very hot, with no damage to it. C.D. Editor's note : Smokey Yunick did endorse ProLong but he was paid to so his view was neither independent nor impartial. See the ProLong 10k filing for information on his remuneration package to promote their product. Product : Restore Engine Oil Treatment Vehicle : 1980 Honda Accord w/ 100k miles I drove my 1980 Accord from about 90,000 miles on. It was 12 years old when I bought it and ran until I drove it into the ground years later. I used Restore in the engine oil and got noticeable, dramatic improvements in horsepower and gas mileage. What I didn't expect was to have Restore save my manual transmission... Somewhere around 100k, the 5speed manual transmission started making a horrible low-pitched grinding noise whenever it was in gear. The noise was loud and unsettling and got louder with higher speed... I knew it was probably a bearing and it wasn't worth getting a $700 tranny job on a $300 car. So, in a last-ditch effort to squeeze a little more life out of the poor thing, I added a small (4-cylinder sized) can of Restore to the manual transmission oil... I was ASTOUNDED when - in about 300 miles - the grinding noise started to fade. After a month and about 500 miles, it was COMPLETELY GONE! I never heard another peep out of the transmission! I wouldn't recommend this to anyone unless they have no other options (I looked, and Restore does not recommend their product in manual transmissions), but Restore did completely fix a worn-out, dying manual transmission in a 16-year-old Honda. If it can do that, think of what it can do for worn rings and mainshaft bearings. Chris N

Your Opinion: A Ford Engineer contacts carbibles.com about additives
In 2006 I was contacted by a Ford engineer who has worked for them for 24 years. These views do not necessarily represent Ford, but it makes an interesting read nevertheless. Some of the things in your site are true like the pure baloney that additive companies put out. I have been with Ford for 24 years in research and development for their power train division. I have forgotten more lube problems than 90% of so-called mechanics will ever know. I like the way some mechanics make statements like they're some sort of God without being able to back them up. All that mallarkey in some of the feedback above claiming 800,000 miles on a gas engine are laughable. There is so much that goes into producing engine oil that dumping "magic" additives into it is just criminal. The quality of most addatives is questionable at best. Whilst the names may be similar, the quality is not. Additives are blended at the proper rate, heat and in the proper proportions by the manufactures of their particular product. Crude supplies are not all the same quality and the additives have to be adjusted for the quality of the base stock being used by each particular company, per batch. Dumping your own personal stuff will more than likely be way inferior to what the oil manufacturer uses. The chemicals will normally differ from the manufacturers blend, and can cancel each other out to the point where there will be no anti-wear properties left in the product. (This is one reason it's not wise to mix oils from different manufacturers together). Changing the oil from say Mobil to Shell and then to Pennzoil will have a negative effect on your engine from conflicting chemicals. Buy an oil that you may like and STICK TO THAT COMPANY'S product. What you may get away with when using Shell may cause instant havoc with Valvoline. The major oil companies work closely with the auto manufacturers so that bearing material, seal material, roller bearings, ball bearings, and all other moving parts are not adversely affected by the oil products. This is especially true for automatic transmissions. DO NOT USE SOMETHING OTHER THAN WHAT IS SPECIFIED BY THE CAR MAKER FOR YOUR AUTOMATIC TRANSMISSION. Nothing in your site mentions surface finish of the journals, cylinder walls, lobing of the crank journals, or a whole host of mechanical reasons for engine life or engine early death regardless of what oil you use. Nobody has mentioned how wear is affected by hotrodding the vehicle. I can ruin any engine and oil combination that you want to give me in a few hours or less. I can wreck a transmission in 15 minutes. What about user abuse and manufacturing defects? Grinding a crankshaft in the wrong direction of rotation will eat up the bearings in 5 to 10 minutes. Quality control during manufacturing is the key to long engine life along with following oiland filter-change intervals as laid out by the manufacturer in your handbook that comes with the car (that nobody reads). From Ford's perspective, they test Mobil way more than other brand. I pushed using Mobil synthetics for transmission use to eliminate low speed hot oil low pressure and the opposite problem of high speed high pressure and cold oil drag at any speed. More power is lost from pumping torque than from bearing and piston drag. Trying to keep oil pressure up to spec when hot requires a larger pump and more R.P.M. and when things are cold the pump has very high torque and most of the oil flow is going thru the pressure relief valve back into the oil pan. Wasted horsepower; it lowers gas mileage by 20 to 30% If it takes only 12 to 15 horsepower to move the average car 60mph. and the engine plus the transmission are using 2 to 3 extra horsepower each due to high oil drag (being too thick) you can see how the C.A.F.E. ratings would not be favorable
http://www.carbibles.com/additives.html (10 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

for Ford if we did not use synthetics. Engines on new Fords come with semi-synthetics and the dealerships only use this oil. Full synthetics are still better but cost more. Conclusion: Read, learn, and use your brain.

What about Ionically Charge Oil Particles? Enter Castrol Magantec.
Pardon? Sounds like something out of Star Trek doesn't it? Well there's an increasing trend in the industry now to try something a little different. It seems that a couple of the big players are now experimenting with charge oil molecules which attract themselves to engine parts with no other additives. The idea is, to simplify it, magnetic oil. The oil sticks to the engine parts when the engine is turned off, and is theoretically still there, ready to protect, when you next turn the engine on. The first big player on the scene with this was Burmah Castrol with their Castrol Magnatec oil. Theoretically, this type of product is a far safer bet than an additive, and so far I've heard nothing but glowing reports about it. But just stop and think for a moment - why have these companies now decided to go this route? Are they admitting that the older additives with suspended solids in them were perhaps not such a miracle after all? Truly magnetic? A U.S. Coast Guard Machinery Technician recently emailed me with some interesting observations. If you know enough about chemistry, you'll know that oil is a non-ionic compound which is one of the properties that precludes it from mixing readily with water (which is an ionic compound). What does this mean? It means that the ionization potential for oil is nil. No ionization potential = no magnetism. Chemists may be able to synthesize an ionic compound that replicates the characteristics of oil such as viscosity, surface tension, etc, but then would it really be an oil? Still reading? Okay - it gets even more complicated then: The real reason oil and water do not mix has everything to do with their polar strength. This has to do with whether the electrons are equally shared or not. Water is a highly polar substance, the oxygen atom somewhat steals the electrons from the hydrogen atoms, giving it a partial negative charge. Because of this, and the way an water molecule is shaped, the water molecules attract strongly to each other, much like magnets. Still with me? Oil, on the other hand, is a weakly polar substance because the electrons are mostly evenly "shared". Because of this, the water molecules attract each other more strongly than they attract oil particles. The reason that they do not visibly mix is because the water-water attraction is stronger than the water-oil attraction, so the water-water attraction must be broken in favor for a weaker attraction costing energy that isn't there. Thus, most oil molecules do not mix with the water. Hey - you're still reading so far, so obviously you wanted to know. I'll continue: The oil could have a polymer additive (since oil manufacturers DO add stuff to their oil), which might work, since polymers can have ionizing polar groups on them. You can thank reader Kenny for that last little bit of weird science.... July 2004 Update Interestingly, Castrol Magnatec was NOT available in the U.S. until July 2004. A reader of my site called two national Castrol distributors and they told him that Castrol's equivalent is the Syntec line but they couldn't confirm that it was the same as the Magnatec. They really doubted that they were the same, as the GTX is a different formula than Syntec. An email to Castrol's website confirmed this suspicion but they wouldn't explain why Magnatec was only available overseas. If you go to www.castrol.com and then www.castrolusa.com you will notice the product descriptions don't even read close to being the same thing. Confusing as usual with any big corporation - there's no straight answer. Then in July 2004, Castrol started advertising Castrol GTX Startup. It's basically the same thing as Magnatec, but with a different name. Another email to Castrol resulted in a brief phone conversation with them. I asked why they'd waited so long to bring the same product out in North America when it had been available in Europe for at least 6 years previously. There was no good answer. Now the product is available in the US, I expect the volume of emails on this subject to double :-) April 2007 Update In a reversal of fortune, Castrol has now pulled the GTX StartUp product from all the shelves apparently in all countries. They've not replaced it with anything which shows you how fickle the advertising and marketing arms are. People are less sensisitve to the idea of wear on startup, so it seems Castrol have pulled their niche product. Return to where you were on the Engine Oil Bible page.
http://www.carbibles.com/additives.html (11 of 12) [2/6/2008 7:15:13 AM]

The Engine Oil Bible : Additives

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/additives.html (12 of 12) [2/6/2008 7:15:13 AM]

Car Bibles : Help Chris buy his next bike

Help chris get the money together for his next motorbike.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

Like the site? Help Chris buy a bike
If you like what you've found on my site, if you think you've gained some knowledge or found what you came looking for, please help me out. The internet is free - sure - and this site is free too - I'm not making anyone pay for the information. I'm also not spamming people by collecting email addresses. I'm just trying to do the right thing by sharing my knowledge. So what we have here then is a shameless whoring of my site to ask you, dear reader, for some cash. Not a lot - $5 or $10 will be just fine. Originally I was asking for some cash to help cover the shortfall between the trade-in value of my old BMW R1150GS and the new Triumph Tiger - the object of my desire. At this point then, I have to give an enormous 'thank you' to all those who got me to the first $1000, at which point I couldn't wait any longer, bought the bike and financed the rest of the cost. So now I'm continuing to ask for small donations from many people that I'm hoping will continue to help me pay for the bike. I'm being totally honest with you here; I could give you a line about it being for a noble cause like cancer research or something but you and I both know you'd never believe that. So the bread and butter of it is that I'm asking you for a little money in return for a great website. Here's the object of my desire parked on Hell's Backbone in Utah after the first long ride. I still owe $5000 on the bike but for a day of riding around this area, I forgot all about the hideous debt....

http://www.carbibles.com/donate.html (1 of 3) [2/6/2008 7:15:21 AM]

Car Bibles : Help Chris buy his next bike

Help Chris buy a bike started on July 23rd 2007

Target: $6000. Current donations: $1791

http://www.carbibles.com/donate.html (2 of 3) [2/6/2008 7:15:21 AM]

Car Bibles : Help Chris buy his next bike

$5 Thank you to : Mike and the crew, Srinivasan, Joe, Owen, Ken, Carl, 'troublemaker', Mark, Seth, Harold, Jacob, Jamie, Andrej, Dan, Stephen, PJ, Glenn, Peter, PDG, Phil, Silvio, John, Patrick, Sorin, Jave, Tom, Stuart, Pat, Scott,KG, Michael, Chris, Emmanuel, Cerni, Steve, Veerraju, Pedro, Frank, Mr.H, Alex, Seth, Will, Sheila, Rich, Jun, Malcolm, Volker, Kwet, Tim, Neal, Paul, Bert, Bruce, Marcus, Ian, Ian, Gennady, Richard, Bence, Chris, Bill, Anthony, Chieh-Hwa, Jocelyn, Robert, Megan, Anthony... $10 Thank you to : Rosemary, David, Anthony, David, Brian, (Have you met)Ted?, Stuart, Ben, Clement, Matt, Denis, Michael, Weerwolf, Derek, Peter, Mark J, Joshua, Andrew, Tim, KM, Mike, Phil, "The Main Objective", Jerry, Peter, Charles, Neil, U.K.O.L., Benjamin, Michael, Hans, Jay, Alex, Jonathan, Alec, Louis, Paolo, Gary, Glyn, Ivan, Liberty, Chris, Harry, Matthew, Tim.. $more Thank you to : Anonymous, Ken O, Emmanuel, Mohamed, Mario, Mr.G, Matt, Brian, Harry, Mr. E.P, David, Sarro, Robin, Roman, Edward, Daniel, Mark, Daryl, David, 911Design, Garrett, Michael, Nicholas, Russell, Artin, William...

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/donate.html (3 of 3) [2/6/2008 7:15:21 AM]

Chris's Motorbike Page

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

Why I Ride.
Why not? Essentially, I ride because it's fun, and because in Europe at least, you can slice through traffic like it's not there. I currently live in America and the traffic laws are a little different, so most of my commuting is done in a car now. The bike has become a pleasure tool, used in the evenings and weekends when I want to, rather than when I have to. I did 7 years commuting 120 miles a day around London in all weathers on a bike so I've done my 'hard man' bit. Nothing sharpens the senses like tussling with blind drivers in freezing rain at 7am on the M25. Been there. Done that. Don't need to do it again.

What I Ride.

http://www.carbibles.com/bikes.html (1 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

The almost pornographic 2007 Triumph Tiger 1050. I made the fatal mistake of test-riding one of these whilst I still had my BMW R1150GS. Six weeks later, a scorched yellow Tiger was mine, along with a buttload of debt. This picture was taken on route 72 in Utah. Google Earth placemark For the curious, here's my trusty steeds going back to 1988 - the earliest photo I have of one. Not that I like Big Trailies or anything.

Yamaha DT80. This was my introduction to riding. I went through one piston on this bike - I still have it in my office. It was a loud little bumble-bee of a two-stroke bike.

http://www.carbibles.com/bikes.html (2 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

Yamaha DT125. Bigger and better. Louder, faster. Still small. Great bike.

Yamaha TDR250. The idiot-proof hooligan tool. Based on the race-bred TZR250, this was a wheelie machine. I used this bastard on the motorways every day and it was well scary. It has the typical two-stroke powerband where all the power arrives at 5000rpm and dies off at 5500rpm. Amazing bike.

Yamaha XTZ660 Tenere. My first 4-stroke bike. A big-single - one cylinder, 660cc. A thumper of a bike, great for riding with a passenger but with possibly the least comfortable seat, ever.

Honda XRV750 Africa Twin. Think Tim Taylor. More power! Arf arf arf! This was a fantastic bike. If I could get one here in America, I'd buy another one in a heartbeat. It did 120 miles a day for 18 months without a single problem. W-a-y better build quality than the Yamaha's I'd owned and supremely comfortable.

http://www.carbibles.com/bikes.html (3 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

BMW R1150GS. The über-moto. I lusted after this for years. Went all over America with me until a sad day in 2007 when I sold it to a Canadian, who then promptly rode it 1100 miles non-stop back to Alberta. Go figure.

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

When I Don't Ride - when the bike is in the shop.
The Beemer is barely ever unrideable. In fact its only been off the road for repairs once and that was a factory recall. However in January 2005 it was off the road for some engine maintenance - head de-coking, honing cylinder bores, cleaning pistons, new rings etc. I felt the need to give a plug to a new BMW mechanic in my area who did the work. So if you're cruising through Utah and find yourself in need of some BMW help, try Motorcycle Repair & Rendezvous. They're just off the side of I-15 at 7200S in Salt Lake City. Easy to get to if you're passing through. They have a full line of clothing and accessories, and most importantly, are run by a couple of friends of mine who are certified BMW mechanics. Perhaps most importantly they have coffee and doughnuts.... This is a link to their website. Google Earth placemark.

What I Dislike about fair-weather bikers.
These are the guys who buy a 15-grand plastic crotch rocket, and then put 800 miles a year on it because they only bring it out when it's sunny and dry. They're afraid of getting any rain on their carefully spit-polished Akrapovic exhaust and luminous pink headlamp cover. Now before I get under everyone's skin, let's make a quick distinction here. I've got no problem with the people who own these overpowered monsters and ride them so well that they're inconspicuous (ie. most of us). My bone of contention is with the dickheads who buy these bikes as a fashion accessory to go with their Armani suits and Rolex watches. They'll buy an insanely fast litre bike, some race-replica leathers and a Doohan helmet, and assume that this means they can ride like Rossi. They then wonder what went wrong when they drive under a truck/into a car/into a tree/up a kerb/over a roundabout etc etc etc. You know the types. They have no regard for any other road users, other motorcyclists included. They shoot the gap at 80mph in stationary traffic, overtake on blind bends, scare the crap out of car drivers and give the rest of us a bad image. The media love an easy target, and these guys give them the target they need. The result is that the rest of us all get tarred with the same brush. So if you're a stockbroking yuppie who's bought himself a nice toy, do us all a favour and sell it would you? We don't need your types around. There's a good chap.

Helmets vs. 'invincible' bikers.
Living in America now, it amazes me how many states don't have helmet laws. It amazes me even more that one of the states did have a helmet law, but repealed it in 2003 because of complaints that it was infringing on people's civil liberties and their rights to 'freedom'. Some riders believe they're invicible, some think that because they ride slow-andstraight cruisers, any crash will be mild. All of these people are simply wrong. It's pretty obvious to anyone on a bike that you're very vulnerable in any crash. If you want to have a nervous moment, next time you overtake a semi, slow down and take a quick look at the wheels and driveshafts spinning next to you..... Proper clothing isn't really an option when riding a bike - it's a necessity. It has nothing to do with your freedom,
http://www.carbibles.com/bikes.html (4 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

and everything to do with giving you a fighting chance when you come off. Some people's self-preservation instinct is functioning so badly that their brains don't even have the common sense to wear a helmet to protect the very skull that contains them. Face it - any crash over about 15mph and you're going to hurt if you don't have protective gear on. Any crash involving another vehicle and it will be much worse. (Bear in mind that over 60% of motorcycle crashes are caused by a car or SUV driver.)

Flip flops, sandals, T-shirts, O.R. scrubs - apparently these two future bodybag occupants are too stupid to be breathing, let alone riding a bike.

Every weekend I see guys on sports bikes charging along the freeways. But occasionally, I see something truly ridiculous. For example, a guy riding in shorts, flip-flops, and a t-shirt. No helmet, no gloves, no armour or padding. Exactly what does this guy think is going to happen to him when he comes off? Does he think he'll never come off? If that's the case, he's more dangerous that he thinks. Does he somehow think he'll be thrown clear? Great - what happens when he lands? Does he think it will all happen in a nice controlled fashion so he can control how he falls and what happens in the crash?.....For the uninitiated, then, here is: The anatomy of a motorbike crash You see the car pull out from the side road as you're approaching. You didn't leave enough safety sphere around you so it looks like a crash is inevitable. You check behind you, and grab a fistful of brake lever and clutch. You stomp on the rear brake and the back wheel locks. The bike starts to skid sideways as the rear end comes out. Because the wheels have stopped, the gyroscopic stabilising effect has gone and the bike is now top-heavy. You're getting closer to the car and he's now seen you and has stopped instead of pulling out of the way - a crash is now certain. The bike starts to go down and then the tyres dig-in and the bike highsides you. You're about 60° to your original direction of travel now and you're flipped over so you're now lying on the ground skidding head-first towards the car with the bike on top of you. Your bike boots are stopping your foot from being crushed and the padding in your jacket and pants is rapidly shredding sacrificing itself for your skin. Your head bounces off the road and the shock stuns you and makes you dizzy. Disoriented, you put a hand out and your glove starts to burn as the leather and padding rubs away on the road surface. You're almost upon the car now and in the last moments, you crumple like a rag-doll and slam into the side of the car head-first with the bike on top of you. The change in speed causes the momentum of the bike to flip up into the side of the car. You still have one leg over the saddle so this forces you to do the splits and flicks that leg off into the car door. As everything comes to rest, the bike falls back on your foot and the crash is over. Of course, that all happened in slightly under a second, and what you remember is sky-ground-sky-ground-skyground-car........I'll leave you to re-write that paragraph from the point-of-view of someone wearing no helmet and no protective gear, crashing on a motorway at 130km/h. The anatomy of the same crash from your passenger's point of view if you have one. You see the car pull out from the side road as you're approaching. Your rider looks over his shoulder, and grabs a fistful of brake lever and clutch. He stomps on the rear brake and the back wheel locks. The bike starts to skid sideways as the rear end comes out and you start to shift on the pillion seat. Because the wheels have stopped, the gyroscopic stabilising effect has gone and the bike is now top-heavy. You're getting closer to the car and he's now seen you and has stopped
http://www.carbibles.com/bikes.html (5 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

instead of pulling out of the way - a crash is now certain. The bike starts to go down and then the tyres dig-in and the bike highsides you. You're catapulted up in the air like a cat on a trampoline. As you spin end-over-end, you see your rider pinned under the bike skidding head-first towards the car. As you start to descend from your parabolic flight, you see the see your rider crumple up like a rag doll and slam into the side of the car head-first. The change in speed causes the momentum of the bike to flip up into the side of the car. As you plummet towards the resulting melee, you see the rider still has one leg over the saddle. As everything below you comes to a rest, you land head-first on a wrecked bike and car combo and the rider's trapped foot catches you in the stomach. You decellerate at about 40G and come to rest on the wreckage, and the crash is over.

This little scene took all of 2 seconds to set up. Note the non-bike boots that came off and the blood from the head-ground (no helmet) interface...

What about the lawyer option?. Yes? What about it? Came off your bike and you've got a lawyer suing the motorist great. Money isn't going to reverse brain damage. It won't heal road-rash. It doesn't cure incurable stupidity. Ok so don't go the whole leather biker thing if you don't want, but use some common sense. Why the protective gear? Well... Helmet Protects your noggin from splitting open like a ripe watermelon. Boots Proper bike boots have a heavy steel shank in them. If you wear trainers, then when the bike keels over and lands on your foot during a crash, the sole of the trainer crushes and the bike mangles your foot against the road. With a steel shank in there, it provides a rigid sole that resists crushing. Gloves Look at your knuckles and the palm of your hand. Now scrape the palm of your hand with a pair of scissors, and run your knuckles along a brick wall. Hurts doesn't it? Do it over 15mph on a rough road and you'll understand the reason for gloves. Back-protector Ever felt how close your spine is to the skin - no muscles or padding there is there? Armoured jackets and pants Denim - great fashion accessory, lousy tear-resistance as indicated by the speed at which you can ruin a $100 pair of Levis by falling over and scuffing the knees. Armour and padding in pants and jackets cushions your knees, thighs, shoulders and elbows - all parts of your body that will interface very quickly with the ground when you come off. Ok so what do you wear, Chris?
http://www.carbibles.com/bikes.html (6 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

An armoured jacket with a separate hard armoured back protector underneath, armoured riding pants armoured gloves, leather boots with steel shanks and a Shoei helmet:

"It'll never happen to me" You keep thinking that, then look at this picture and imagine its you. Blind car driver, red light. For the sake of your own protection, wear proper gear. The only thing this picture is missing is the driver's white cane sticking out of the window (see below).

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

http://www.carbibles.com/bikes.html (7 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

An email from a non-motorcyclist.
I received this email on March 12th 2000, and it explains a great deal about why car-only driver behave the way they do. Read it and weep. I've published the guy's name at the bottom and his email address. If you feel he's a dick, go ahead and spam him. Note - I've pretty much left the grammar and spelling as it was... Having read your atricle on motorbikes I must strongly disagree that they are cool as they are hazards and should be banned. Firstly most accidents with severe injuries and death are motorbikers. Secondly today during a 4 miles trip to and from a local football ground where I work I was nearly killed twice by two motorbikers traveling behide car coming towards me and then overtaking in dangerous place causing myself to brake hard to avoid them. May I also remind you that if bikers hit care the car will have a dent while the biker is in a wooden box. In my opinion the motorcycle is ok on holiday but in the uk stupid idea unless you're on a proper track. Also I have noticed that bikers have the beam on all the time firstly this is against the law and secondly it means the driver will probably be so annoyed that he will brake later knowing the car has four brakes and four wheels or tyres while the biker has two and will be launched over the car and then probably then be driven over cartainly not to drive again. - Miles Stinger This guy has clearly missed the boat completely. He's right about the number of fatalities of course, but has completely missed the fact that over 60% of all motorbike accidents are caused by, and directly attributable to car drivers. His last statement was what made me publish this email and his name. This guy gets his kicks from brake-testing trailing motorcyclists in an effort to try and kill them. Can I say "TWAT" and get away with it? Of course I can - it's my site! More to the point, the freedom of information that the web gives means I can let you all know his email address so you can spam/flame/emailbomb him, or otherwise pass on your thoughts on this grade-A asshole. Its: miler@miler. screaming.net I feel I ought to also point out a couple of flaws in Miles' comments, just in case there are any non-motorbike aware motorists out there. 1. Metre-for-metre, most bikes can haul up way quicker than a car. 2. If Miles tells us that in most car-bike accidents, the biker ends up in a wooden box whilst the car is only dented, then why does he think he was nearly killed twice in a 4 mile trip? 3. He's going to hate this one : all new bikes delivered in the UK have their lights permanently wired on now - you can't turn them off. Just some food for thought.

Good grief - another email from a non-motorcyclist.
I received this email on July 21st 2003, and it seems to have been written by a distant relative of Miles Stinger. It seems we're all "fat loser gaylords" who are antisocial and cause accidents. Emails like this are the reason for my rant about car drivers below.... I'm sure you're far too busy to be troubled with trifling emails from idiot car drivers like me, but... The picture of "what a car driver sees" is of course the view from his back mirror (cf. the picture of "what a biker sees", which is his view from the front). It is completely insane to suggest that a biker has better road-vision than a car driver. Furthermore: 1. That bikes are hard to see is not the fault of car drivers. Many more people want to drive cars than want to drive motorbikes, in both the UK and US. The percentage of bikes that get into accidents that harm car drivers is far higher than the percentage of cars that get into accidents that harm other car drivers. Therefore (and for other reasons as well, of course) biking is selfish and anti-social. 2. As far as speed limits are concerned, bikers break the law, all the time. All of them. And by a far greater margin than car drivers ever do. As far as I can tell, bikers, aside from a bit of muttering about 'bad apples', think that they are
http://www.carbibles.com/bikes.html (8 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

good enough riders to do this safely. Statistics show otherwise. Moreover, parliament has seen fit to set a speed limit which applies to skilled motorcyclists as well as mere car drivers, so you should stick to it. No car driver should ever have to take precautions against a biker coming round the corner at 150mph. 3. Almost all bikers are ugly. The only way you lot can look cool is by putting on a full-body costume and a helmet that covers your face. If you didn't we'd all be able to laugh at what a bunch of fat loser gaylords you are. The overall tone of your website gives the impression that you are a complete cunt. So fuck off. Andy Naylor.

Apparently the lunatics are on the radio too.
In January 2006, a popular San Francisco-area radio host (Woody, of 105.3) made some seriously anti-motorcycling comments in his morning broadcast. Woody told his listeners "One of my pet-peeves is people on motorcycles who think they don't have to wait in traffic like everybody else... Nothing would make me happier than to watch somebody, and I've actually seen this happen, somebody open a door and take you out as you are trying to squeeze through..." Well, "Woody", it's not that we don't think we have to wait in traffic - we don't have to wait in traffic - we've had the common sense to try to solve the problem of traffic congestion by using a motorbike so we can take up less road space and get where we want to go on time. You are the idiot for sitting in your cage every day complaining and suggesting that other drivers try to murder motorcyclists. Because the premeditation you suggest means it wouldn't be manslaughter...... Motorcycle Daily have the full story online.

Don't antagonise the car drivers - check your headlight.
One thing that I get emailed about a lot is car drivers hating motorbikes with badly-adjusted headlights. On the one hand, riding with your lights on makes you more visible, and you could argue a badly-adjusted headlight that dazzles the other drivers is sure to attract their attention. But don't antagonise them - if your low beam is all squiffy and it's pissing car drivers off, you're not helping your image as a motorbike rider. So do yourself a favour and check your headlight aim once in a while. It gives the car drivers one less thing to be irritated about...

My rant about car-only drivers.
Know your enemy. I ride a motorbike and I try to put to the back of my mind one simple truth : people who have never ridden a motorbike are totally blind to them. The picture on the right (© TWO magazine) is not an exaggeration. That's exactly how every car driver who's never ridden a motorbike should be considered. If you're a car-only driver and you've got this far, you're probably now stuck in a mental debate about how arrogant I am and how offensive that comment is because it doesn't apply to you. Don't try to analyse it - you're confused, and wrong. This does apply to you. No - stop debating it because you don't understand. You ride around in a 2-ton mobile entertainment complex and you can't see anything further ahead than your own windscreen. As I stated above, over 60% of bike accidents are caused by car drivers. The Booth report, published in 1989, assessed nearly 10,000 motorcycle accidents. It concluded that nearly two-thirds (62%) of motorcycle accidents were primarily caused by the other road user. The report found that two-thirds of motorcycle accidents where the driver was at fault were due to the driver failing to anticipate the action of the motorcyclist or failing to see the motorcyclist. Motorcyclists don't tend to just fall off their bikes for no reason. Now I know this will come as news to some of you, but it's true - we're actually pretty good at staying on our bikes until you fools put metal boxes in our way. I used to ride in England - 120 miles a day commuting to and from work along three of the busiest roads in the country; the M23, M25 and A23. I've learned, just like every other motorcyclist learns, that there's really nothing we can do that will educate
http://www.carbibles.com/bikes.html (9 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

you car drivers into seeing us. I've had people look right at me, and (still looking me right in the eye), pull out into the road. In the UK, it's called SMIDSY - Sorry Mate, I Didn't See You. This is normally what comes out of the mouth of a car driver once you're lying on the road with a broken limb and a written-off motorbike. And it's also the one response most likely to result in a violent lashing out from the motorcyclist. It's pretty obvious you didn't see him - he's lying under your bloody car! I tried all sorts of things to make myself more conspicuous - flashing lights, luminous strips, loud exhaust, bright clothes. Nothing works. We riders simply have to understand that as a bike rider, we will not be seen by the majority of car drivers. Not only do we have to understand that, but we have to deal with it. It's one of the reasons I love bikes like the Triumph Tiger - I'm up so high up that I can see what is happening way further ahead than most car drivers (and sportsbike riders for that matter). I've been riding since 1987 - 2 years in Holland, 12 years in the UK, and the rest of the time in the US. The attitude of car drivers is the same everywhere - they look, but they don't see. Making eye contact with these people is a myth too - remember they look, but don't see. The responsibility then rests with us motorcyclists to ride according to the abject incompetence of car drivers. Most of them don't understand that they are accountable for their behaviour and actions, and most of them have their two A's mixed up - Ability and Ambition. The bottom line? As a motorcyclist, I'd be just as safe riding a black motorbike wearing black leathers at night with the lights off - because most car drivers will still see the same thing - empty road. So if you drive a car, and don't ride a bike, and you've read this far, just think about this little rant the next time you go out in your car. See how many motorbikes you can spot if you actually look for them - you'll be surprised and shocked at how blinkered you normally are. USE YOUR EYES!

What the average motorcyclist sees when riding

http://www.carbibles.com/bikes.html (10 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

What the average motorist sees when driving

What's actually there

http://www.carbibles.com/bikes.html (11 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

How a motorists sees the same scene

Threat perception and the average motorist.
The average motorist, when assessing a traffic scene, prioritises things mentally based on threat perception. They don't know they're doing it, but it turns out that a tall, thin object, like a motorbike, is percieved as less of a threat than a short, fat object, like a car. There's some talk of the position of lights on a motorbike helping out this mental awareness. If you put bright lights further apart than normal - say on outriggers - a motorbike will be percieved as more of a threat, and thus register higher in the motorist's scene analysis. This is all very well, but how does the average motorist's brain deal with the threat perception of a hot cup of Starbucks and a cellphone first thing in the morning. Apparently, clamping a phone to their ear and drinking coffee while driving is also not perceived as a threat, whilst most motorists consider a motorcyclist threatening to look at (leathers, helmet etc - oooooooohhh. Scary....) Yet the same motorcyclist actually on a bike registers so low that the average motorist will look straight through them. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Chris's tips for car-only drivers
(Because clearly millions of you need to be told)
Eyes You have two of these, normally located in the front of your head. Use them. Don't just look, but see what's going on. You might spot someone else on the road other than you. I know that comes as a surprise, but there are other people entitled to share the same road space with you. Here's something else - get them tested. In the UK, a 2003 study found that 1 in 7 drivers who didn't think they needed glasses had vision so bad that their licenses could have been revoked.

Brain

You should have one of these. Most humans are issued with one as standard. It's used for a lot of things, and is certainly capable of multitasking. When you're using your eyes (see above) to look in your mirrors (see below), use your brain to interpret the information. Very handy. Mirrors The shiny, reflective things in your car. You have at least one, and most modern cars have three. Interestingly, they're not for putting your makeup on, or adjusting your hair. They are in fact to help you use your eyes to see what's behind you without the horrible inconvenience of actually turning your head. Look in them occasionally, you'll be surprised at what you see.

http://www.carbibles.com/bikes.html (12 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

Indicators You know those pretty little orange lights that light up the corners of your car? I hate to tell you, but they're not decorative elements put there by the designers on a whim. They actually have a purpose. For the 99.999% of us who can't read your thoughts, those are indicator lights, for you to use to indicate to us what you intend to do. They're operated by a stalk on the steering column - you should try them some time. Oh, and when you do, make sure you use them before actually turning. Like I said, most of the rest of us have trouble reading your mind. Steering wheel The big circular thing you hold on to when driving. Apparently, not many of you realise that if you turn this, your car will drift from lane to lane. Most often, you also haven't grasped the basic use of the indicators (see above) so the result is that you'll change lanes, probably surprising yourself, and certainly surprising everyone behind you because you didn't tell us you were going to do it. By the way, when you do this, that grating, scraping, crashing sound from the back of the car isn't "ordinary car noises" - it means you've hit someone. Brakes Now this is a complicated one. The middle pedal in your manual car, or the left pedal in your automatic, is there to slow you down, and even stop you. I mention this because it seems that when you've committed to a bonehead maneuver, and see the motorbike at the last minute, not many of you realise that pushing this pedal will make you stop. Often, if you stop, it will avoid the accident. You don't have to run into us you know - your car will stop if instructed to do so. I think the problem is that in order to use the brakes, you also need to engage your eyes and your brain at the same time, and for most of you, that does seem to cause some trouble. Cellphone Throw the fucking thing away. You can't drive on a good day. Now you're trying to drive while clamping a cellphone to your ear and holding a conversation? I know I said the brain was multitasking, but you know that you can't do all this at the same time. Just throw it away. You're not that important, really - you aren't. And believe me, your phonecall isn't so important that you have to endanger everyone else on the road to take it. "Sorry, I didn't see you" This is the phrase that your brain will be desperately trying to get you to say, when you realise that your eyes didn't see the motorbike you just hit because you didn't use your mirrors, brakes or indicators appropriately, and were having an unimportant, inconsequential conversation on your cellphone. You'll step out of the car and find the motorcyclist and you'll be so desperately wanting to say this phrase that you'll not be able to hold back. It's worth knowing that if you do utter these five words to an injured motorcyclist, you are likely to be punched and kicked and otherwise generally assaulted because these are not words that we like to hear. You say "sorry, I didn't see you". What we hear is "I'm a blind fucking moron and my brain doesn't work". These five words are only marginally less offensive than "Are you okay?" Crash helmet This is not so much of a tip as a public information service. Now that you've run the motorcyclist down, and pissed him off by telling him you didn't see him, and asking if he's okay, your next course of action will typically be to try to take his crash helmet off. No, no no no no no no no no a thousand times no. Use your brain. You just nearly killed the guy and now you want to remove the one item of protective gear that might be holding his head together after you swatted him with your Buick? Are you totally deranged? No - don't answer that. If you've got this far into the accident, we all know the answer. You're blind, and stupid. We don't need to add deranged to the list.

Proof.
I don't have to ride very long to see shitty car driving. So much so that I can put a camera on my bike, ride for 5 minutes, and video stuff like this. Note the sequence of events: my lights go green and I pull away. On the right, the BMW driver cruises through his red light without stopping, looks right at me then turns on to the road I'm on. The best bit - he didn't stay in his own lane, but changed lanes mid corner and ended up in my lane in front of me. In the US, he's just broken two laws - 1 - he didn't stop at the red light before turning right, and 2 - he changed lanes in an intersection. So why did I pass him on the inside? Because frankly I've given up with drivers like this. I see no point in pandering to their appalling driving by being inconvenienced by their arrogance and selfishness. I'm sure the BMW driver is wondering why I gave him the finger when I went past him too - he undoubtedly didn't see me, and has no idea he did anything wrong. So take note Idaho plate EGT 4519 - this is for you because you didn't use your eyes, your brain or your mirrors:

http://www.carbibles.com/bikes.html (13 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

Bike Links.
More will be added as I find ones worth being here (ie. not crap!). For now though: RideDrive UK advanced training Advanced motorcycle training UK Adventure Rider BMW Forums

KillBoy - photographs on the Dragon

BMW Motorcycle Club's

BMW Motorcycle Club's
© WebRing Inc.

Prev | Ring Hub | Join | Rate| Next >>

Search

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.
http://www.carbibles.com/bikes.html (14 of 15) [2/6/2008 7:15:44 AM]

Chris's Motorbike Page

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/bikes.html (15 of 15) [2/6/2008 7:15:44 AM]

Car Bibles : The Car Suspension Bible

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

Got lost in my site? Can't find what you're looking for ? Google search the site using the box below and hopefully you'll find what you're looking for.

Search
Web www.carbibles.com

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/search.html [2/6/2008 7:15:50 AM]

Car Bibles : Competitions

The car Bibles competition page. Win free stuff.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

You lucky people. This is your chance to win stuff absolutely free. Gratis. No cost. Occasionally I get promotional items for review as well as for giveaways. This page is where I literally give the stuff away. No, seriously. "So what's the catch?" I hear you ask yourself. Should you expect to get spam offering millions in Nigerian cash for giving me your email address? Or a L@@K MUST BUY NOW stock offers? Erm. No. Here's how it works. When the competitions are running, simply enter the one or ones you want and that's it. Your email addresses aren't stored, given away or sold. Once the competition is over, the email addresses vanish into my recycle bin and that's it. So go crazy, people.

How the winners are picked
Once a competition closes, I use a highly scientific method of picking the winner from all the correct entries. I print out all the correct entries on a piece of paper and give it to our cat who loves to chew on paper. Where she first bites or claws the paper is where the winner is chosen - you're the lucky winner if she chews through your name first. I call it the cat-o-matic. Scientific testing by overpaid people in white lab coats has proven this method to be extremely random if not a little dangerous for me when I try to retrieve the paper before she shreds it out of existence. IMPORTANT: If you don't put your proper email address here, I won't be able to notify you if you've won. Sounds obvious, but you'd be surprised......

Current competition - GoPro Motorsports Camcorder kit. CLOSING DATE SUNDAY MARCH 9th 2008

http://www.carbibles.com/competitions.html (1 of 3) [2/6/2008 7:16:02 AM]

Car Bibles : Competitions

This is your chance to win a brand new GoPro Motorsports Hero sports camcorder. Take a look at the video clip in the review of the GoPro Hero digital sports camcorder. On the freeze-frame at the beginning of the video, I'm at a very specific location on the face of the planet. There is enough information in the entire video clip for you to be able to find out where that was. Using Google Earth, create a placemark where you think I was at the beginning of that clip and send it to me. Because I had a GPS on the bike at the time, I know the precise location to within 2ft / 60cm. The winner will be the person who's placemark is closest to that GPS location. In the event that there are multiple people who's placemarks are all within the same distance, the Cat-o-matic will be used to determine the winner. Only one entry per person will be accepted.

Important:
I apologise to all my worldwide readers but this competition is only open to residents of the US and UK. This is due to shipping cost restrictions. Ready? Then email me your Google Earth kml or kmz placemark file. Please also let me know if you're in the US or the UK. I will contact the winner for a full mailing address on March 9th 2008.

Submit your answer to the GasDandy competition

-->

Previous competitions & winners
GasDandy - February 2007
The winners are Jasmin Jandric, Harry Bergfelds, Marq Holmes, Hai Nam Nguyen and Eric Neville. Winners have been contacted by email. The question was According to the GreenHybrid.com information in the Fuel & Engine Bible, what is the current average mpg of my Honda Element?. The answer was 19.3mpg

Signal Sorcerer - February 2007
http://www.carbibles.com/competitions.html (2 of 3) [2/6/2008 7:16:02 AM]

Car Bibles : Competitions

The winner is Eddie Brennan who has been contacted by email. The question was What is the colour and exact engine capacity of my R1150GS motorbike?. The answer was Silver / 1130cc (from my Bike Bit page)

BrightCar software - March 2007
The winner is Jason Copland who has been contacted by email. The question was According to the information in the Fuel & Engine Bible, what is the average highway speed that the EPA choose to perform their gas-mileage tests?. The answer was 49mph.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/competitions.html (3 of 3) [2/6/2008 7:16:02 AM]

Car Bibles : Sludge - a case study

The engine oil Bibles, covering everything you need to know about engine or motor oil including viscosity, friction reducers, additives, oil types, sludge, SAE and API classifications and ratings, what all the codes and markings mean, how your engine oil works, how to keep your engine running at peak fitness and much mode.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

A Case Study
I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

In January 2007 I was contacted by a reader (Mike) with a curious problem. As he described it, "small 'flakes' on the dipstick....that disappeared when rubbed between my fingers". Not entirely sure what to expect, I asked if he could take a photo and email it to me, which he did:

We figured out pretty quickly that Mike was seeing sludge on his dipstick. This was a dilemma because he'd only just
http://www.carbibles.com/sludge_casestudy.html (1 of 4) [2/6/2008 7:16:19 AM]

Car Bibles : Sludge - a case study

bought the car - a Saab 9 5 Aero with 42,000 miles on it. At this point Mike had one of three options open to him. First, take the car back. Second, let his dealer take it to their regular mechanic and let them sort it out. And finally, get Mike to take it to his own mechanic who he trusted, but that would absolve the dealer from any further responsibility to damage caused by this situation. Whatever happened, the sump would need to be dropped and the engine would need flushing. I recommended that Mike go with option 2 and that he go along camera-in-hand to document what the dealer mechanic found. For those of you with a Saab, this is what can happen when you succumb to sludge. Click on the pictures for larger (1600x1200) versions:

http://www.carbibles.com/sludge_casestudy.html (2 of 4) [2/6/2008 7:16:19 AM]

Car Bibles : Sludge - a case study

http://www.carbibles.com/sludge_casestudy.html (3 of 4) [2/6/2008 7:16:19 AM]

Car Bibles : Sludge - a case study

The second image shows the most worrisome aspect of sludge in this case. The oil pickup that dips into the sump is covered with a mesh strainer - not unusual. The sludge has peppered the strainer with little clumps and reduced its capacity to pick up oil. This can lead to a starved oil pump which in turn would normally lead to reduced oil pressure and capacity in the upper part of the engine. The end result of that is usually a seized engine - where the metal parts rub together with no lubrication and basically weld themselves together. Mike's Saab 9 5 Aero is now sludge-free, and hopefully will stay like that with regular, decent oil changes. At least the problem was caught early and resolved. If you want a true horror story, you need look no further than this page to see what happens when sludge isn't caught early on.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/sludge_casestudy.html (4 of 4) [2/6/2008 7:16:19 AM]

Castrol Service Bulletin

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Castrol Canada Inc.
Technical Service Bulletin #229
January, 1996

CD OBSOLETE JANUARY 1, 1996
The oil industry is dynamic. Specifications and test methodology are constantly being created or revised. For example, within the last two years, the system by which motor oils are approved was totally revamped (API SH) and new oil standards and their associated symbols (ILSAC GF-1) were added to the mix of existing specifications. Once again, a change has taken place in the industry and Castrol has responded. The API Performance Category CD has become obsolete as of January 1, 1996. Oil marketers can no longer use the CD category designation inside the API donut. In fact, Caterpillar, the sponsor of the test which defines CD performance, no longer provides the hardware necessary to run the test. Caterpillar is now committed to sponsoring the test associated with one of the new diesel performance categories, API CF. CF will be a category for off-road, indirect injected, heavy duty trucks. API CD has served an important purpose. This performance category has long been recognized as providing additional thermal stability to passenger car motor oils. CD performance in these oils provided greater control of deposits and protections against obsolescence of API CD. The industry has established a more precise test (the Thermo-oxidation Engine Oil Simulations Test or TEOST) pertinent to passenger car and light truck high temperature deposits. This new test is part of current and future passenger car lubricant specifications. Chrysler incorporated this test into its service fill engine oil specification back in 1991. The next generation of ILSAC specifications (GF-2) also include this test. Castrol now markets passenger car motor oils WITHOUT the API CD designation. These new Castrol formulations have been evaluated in the new industry standard. All Castrol formulations exceed current and future requirements for this measurement of thermal stability. The deletion of API CD will in no way compromise the maximum protection which consumers receive from GTX. We have and always will provide maximum protection against viscosity and thermal breakdown. Passenger cars and light trucks which call for API SG/CD or SH/CD can confidently continue to use Castrol GTX. This applies to gasoline, diesel and turbocharged engines. For those diesel passenger cars and trucks which call for API CD, API CF-4 or API CG-4, Castrol RX Super 15W-40 is recommended. Castrol RX Super 15W-40 can offer improved deposit control and wear protections for these special diesel applications.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

http://www.carbibles.com/castrol.html (1 of 2) [2/6/2008 7:16:37 AM]

Castrol Service Bulletin These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/castrol.html (2 of 2) [2/6/2008 7:16:37 AM]

The Engine Oil Bible

The Engine Oil Bible - viscosity.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Eeeewwww! Sticky!
When you see 10W50 oil, you know (from reading my pages) that the '10' and the '50' refer to viscosity of the oil at different temperatures. But what do those numbers actually mean? Well, they're called 'Saybolt Seconds' and are measured using a Viscometer. There are three different types of viscometer though, and they all look like something you'd find on the set of a Flash Gordon episode. ("must....kill.....flash.....gordon........") First up we have the Redwood Viscometer, also known as the Standard British viscometer. Redwood Seconds refer to the number of seconds required for 50ml of the oil to flow out of the device at a predefined temperature. The instrument is available in two sizes: Redwood type-I and type-II. When the flow time exceeds 2,000 sec, the type-II must be used. I wouldn't recommend putting 10W2000 in your car though .... In true VHS vs. Betamax fashion, the industry can never settle on one standard, so there's also the Engler Viscometer. This measures in Engler Degrees, rather than Redwood Seconds, and is preferred by the rest of Europe. On the Engler Viscometer, the reading is the time (in seconds) required for 200ml of the oil to flow through the device at a predefined temperature. The conversion of Engler degrees to absolute units requires an appropriate table, a degree in rocket science and an intricate knowlege of fluid dynamics. Alternatively, an oil page written by a garage hack will do the trick. To wit: For liquids having a viscosity of 100 centistokes or more the Engler degree is roughly equal to 7.6 centistokes. So for kinematic viscosity, the formula is: kinematic viscosity in centistokes (cSt) = Ct where C is the calibration constant of the particular viscometer and t is the observed time of flow. The value computed by this formula is reported in centistokes, units of kinematic viscosity. I don't expect you to understand that - frankly I don't but it looks good when I put the information on the site, so if you're going to email me about anything, please don't ask about Engler degrees..... Finally, in the category of "America" = "The World", there's what is affectionately referred to as Saybolt Viscosity seconds the term I used at the top of the page. For the Saybolt Viscometer, the amount of oil to be measured is 60ml. There's two types of Saybolt Viscometer, as with the Redwood system. Type-I is called the Furol Viscometer, Type-II is called the Universal Viscometer. "Furol" is a made-up word based on "Fuel and Road Oil" - ie. that's what's used to test the oil you put in your car. The Universal Viscometer is used for other industrial lubricants and oils, and has largely been superceded by kinematic viscosity methods - those performed using the type-I system. You'll notice for all of the above, they measure time for a predetermined temperature. Under these classifications, the winter grades of 5W, 10W and 20W are determined by the oils' viscosity at 0° Fahrenheit (-18°C), while grades 20,30, 40 and 50 are determined by its viscosity at 212° Fahrenheit (100°C). Those are the predetermined temperatures.
http://www.carbibles.com/viscosity.html (1 of 3) [2/6/2008 7:16:54 AM]

Viscous, actually.

The Engine Oil Bible

On to the results, then.
Saybolt viscosities are reported as the number of elapsed seconds indicated by the timer. For Saybolt Universal viscosities, the units are Saybolt Seconds Universal (SSU), and for Saybolt Furol viscosities, the units are Saybolt Seconds Furol (SSF). For a given oil, the Saybolt Universal value will run about 10 times as high as the Saybolt Furol value at the same temperature. Redwood and Engler viscosities are also based on the time of flow and are reported as "Redwood seconds" or "Engler degrees," as the case may be. In all instances, the test temperature is reported along with the corresponding viscosity. In case you're at all inclined, here's some sample values for common oil ratings.
Viscosity equivalents at 212°F - summer ratings Kinematic Saybolt Universal Redwood Engler (Centistokes) (Seconds) (Seconds) (Degrees) 1.8 2.7 4.2 5.8 7.4 8.9 10.3 32 35 40 45 50 55 60 30.8 32.2 36.2 40.6 44.9 49.1 53.5 1.14 1.18 1.32 1.46 1.60 1.75 1.88

What about 0W oils then?
Good question. Given that you can't have 50ml, 60ml or 200ml of oil flowing through any size hole in zero seconds, what on earth does the 0W rating denote? Well it's a special case denoting a difference in the 'pour point' of the oil. Most 5W oils have a pour point at -40°F (-40°C) The base oil is the same in 0W40, but it's pour point has been lowered even further - sometimes to as much as -50°F (-46°C) Pour point is 5°F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. This measurement is especially important for oils used in the winter. A lot of manufacturers tend to quote pumping temperature rather than pour point. Pumping temperature is the temperature at which the oil will pump around the engine and maintain adequate oil pressure. This is typically 20°F above the pour point - ie. 25°F above the point at which the oil is basically a gel. So 0W oils don't flow through a viscometer in zero seconds - they rate at 5 seconds like a 5W oil, but they will be pourable at a much lower temperature. The bottom line then is that if you think your car is ever likely to see a cold morning in the -45°F (-43°C) range, you should be considering 0W40 oil. If not, 5W40 will do. Note that at -45°F, you'll probably have more to worry about than your engine oil - like your radiator fluid, brittle tyres, frozen locks, permafrost on the windscreen etc. etc.etc.......

Now I'm all confused. Can you simplify all that for me?
Sure. Here's a three-line table to give you an idea where typical engine oils are used:
Oil type Typically used in.... 5W-30 Cooler climates, like Sweden or Canada

10W-40 Temperate climates, like England 15W-50 Hot climates, like Italy, Spain, Egypt

http://www.carbibles.com/viscosity.html (2 of 3) [2/6/2008 7:16:54 AM]

The Engine Oil Bible

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/viscosity.html (3 of 3) [2/6/2008 7:16:54 AM]

Car Bibles : The Engine Oil Bible

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

Snake Oil! Is That Additive Really A Negative?
Article by Fred Rau. ROAD RIDER/August 1992/Pg 15 This article is reproduced without permission but is nevertheless all © ROAD RIDER magazine.
I don't believe in, nor deny the comments made here, I'm simply reproducing it for informative purposes.Bear in mind this information is well out of date now, but still makes interesting reading.

Information for this article was compiled from reports and studies by the University of Nevada Desert Research Center, DuPont Chemical Company, Avco Lycoming (aircraft engine manufacturers), North Dakota State University, Briggs and Stratton (engine manufacturers), the University of Utah Engineering Experiment Station, California State Polytechnic College and the National Aeronautics and Space Administration's Lewis Research Center. Road Rider does not claim to have all the answers. Nor do we care to presume to tell you what to do. We have simply tried to provide you with all the information we were able to dredge up on this subject, in hopes it will help you in making your own, informed decision.

You Can't Tell The Players Without A Program
On starting this project, we set out to find as many different oil additives as we could buy. That turned out to be a mistake. There were simply too many avail able! At the very first auto parts store we visited, there were over two dozen different brand names available. By the end of the day, we had identified over 40 different oil additives for sale
http://www.carbibles.com/snakeoil.html (1 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

and realized we needed to rethink our strategy. First of all, we found that if we checked the fine print on the packages, quite a number of the additives came from the same manufacturer. Also, we began to notice that the additives could be separated into basic "groups" that seemed to carry approximately the same ingredients and the same promises. In the end, we divided our additives into four basic groups and purchased at least three brands from three different manufacturers for each group. We defined our four groups this way: 1. Products that seemed to be nothing more than regular 50-rated engine oil (including standard additives) with PTFE (Teflon TM) added. 2. Products that seemed to be nothing more than regular 50-rated engine oil (including standard additives) with zinc dialkyldithiophosphate added. 3. Products containing (as near as we could determine) much the same additives as are already found in most major brands of engine oil, though in different quantities and combinations. 4. Products made up primarily of solvents and/or detergents. There may be some differences in chemical makeup within groups, but that is impossible to tell since the additive manufacturers refuse to list the specific ingredients of their products. We will discuss each group individually.

The PTFE Mystery
Currently, the most common and popular oil additives on the market are those that contain PTFE powders suspended in a regular, over-the-counter type, 50-rated petroleum or synthetic engine oil. PTFE is the common abbreviation used for Polytetrafloeraethylene, more commonly known by the trade name "Teflon," which is a registered trademark of the DuPont Chemical Corporation. Among those oil additives we have identified as containing PTFE are: Slick 50, Liquid Ring, Lubrilon, Microlon, Matrix, Petrolon (same company as Slick 50), QMl, and T-Plus (K-Mart). There are probably many more names in use on many more products using PTFE. We have found that oil additive makers like to market their products under a multitude of "private brand" names. While some of these products may contain other additives in addition to PTFE, all seem to rely on the PTFE as their primary active ingredient and all, without exception, do not list what other ingredients they may contain. Though they have gained rather wide acceptance among the motoring public, oil additives containing PTFE have also garnered their share of critics among experts in the field of lubrication. By far the most damning testimonial against these products originally came from the DuPont Chemical Corporation, inventor of PTFE and holder of the patents and trademarks for Teflon®. In a statement issued about ten years ago, DuPont's Fluoropolymers Division Product Specialist, J.F. Imbalzano said, "Teflon is not useful as an ingredient in oil additives or oils used for internal combustion engines." At the time, DuPont threatened legal action against anyone who used the name Teflon® on any oil product destined for use in an internal combustion engine, and refused to sell its PTFE powders to any one who intended to use them for such purposes. After a flurry of lawsuits from oil additive makers, claiming DuPont could not prove that PTFE was harmful to engines, DuPont was forced to once again begin selling their PTFE to the additive producers. The additive makers like to claim this is some kind of proof that their products work, when in fact it is nothing more than proof that the American legal ethic of innocent until proven guilty is still alive and well. The decision against DuPont involved what is called restraint of trade. You can't refuse to sell a product to someone just because there is a possibility they might use it for a purpose other than what you intended it for. It should be noted that DuPont's official position on the use of PTFE in engine oils remains carefully aloof and noncommittal, for obvious legal reasons. DuPont states that though they sell PTFE to oil additive producers, they have no proof of the validity of the additive makers' claims. They further state that they have no knowledge of any advantage gained through the use of PTFE in engine oil. Fear of potential lawsuits for possible misrepresentation of a product seem to run much higher among those with the most to lose. After DuPont's decision and attempt to halt the use of PTFE in engine oils, several of the oil additive companies simply went elsewhere for their PTFE powders, such as purchasing them in other countries. In some cases, they disguise or hype their PTFE as being something different or special by listing it under one of their own tradenames. That doesn't change the
http://www.carbibles.com/snakeoil.html (2 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

fact that it is still PTFE. In addition, there is some evidence that certain supplies of PTFE powders (from manufacturers other than DuPont) are of a cruder version than the original, made with larger sized flakes that are more likely to settle out in your oil or clog up your filters. One fairly good indication that a product contains this kind of PTFE is if the instructions for its use advise you to shake well before using. It only stands to reason that if the manufacturer knows the solids in his product will settle to the bottom of a container while sitting on a shelf, the same thing is going to happen inside your engine when it is left idle for any period of time. The problem with putting PTFE in your oil, as explained to us by several industry experts, is that PTFE is a solid. The additive makers claim this solid coats the moving parts in an engine (though that is far from being scientifically proven). Slick 50 is currently both the most aggressive advertiser and the most popular seller, with claims of over 14 million treatments sold. However, such solids seem even more inclined to coat non-moving parts, like oil passages and filters. After all, if it can build up under the pressures and friction exerted on a cylinder wall, then it stands to reason it should build up even better in places with low pressures and virtually no friction. This conclusion seems to be borne out by tests on oil additives containing PTFE conducted by the NASA Lewis Research Center, which said in their report, In the types of bearing surface contact we have looked at, we have seen no benefit. In some cases we have seen detrimental effect. The solids in the oil tend to accumulate at inlets and act as a dam, which simply blocks the oil from entering. Instead of helping, it is actually depriving parts of lubricant. Remember, PTFE in oil additives is a suspended solid. Now think about why you have an oil filter on your engine. To remove suspended solids, right? Right. Therefore it would seem to follow that if your oil filter is doing its job, it will collect as much of the PTFE as possible, as quickly as possible. This can result in a clogged oil filter and decreased oil pres sure throughout your engine. In response to our inquiries about this sort of problem, several of the PTFE pushers responded that their particulates were of a sub-micron size, capable of passing through an ordinary oil filter unrestricted. This certainly sounds good, and may in some cases actually be true, but it makes little difference when you know the rest of the story. You see, PTFE has other qualities besides being a friction reducer: It expands radically when exposed to heat. So even if those particles are small enough to pass through your filter when you purchase them, they very well may not be when your engine reaches normal operating temperature. Here again, the' scientific evidence seems to support this, as in tests conducted by researchers at the University of Utah Engineering Experiment Station involving Petrolon additive with PTFE. The Petrolon test report states, There was a pressure drop across the oil filter resulting from possible clogging of small passageways. In addition, oil analysis showed that iron contamination doubled after using the treatment, indicating that engine wear didn't go down - it appeared to shoot up. This particular report was paid for by Petrolon (marketers of Slick 50), and was not all bad news for their products. The tests, conducted on a Chevrolet six-cylinder automobile engine, showed that after treatment with the PTFE additive the test engine's friction was reduced by 13.1 percent. Also, output horsepower increased from 5.3 percent to 8.1 percent, and fuel economy improved from 11.8 percent under light load to 3.8 percent under heavy load. These are the kind of results an aggressive marketing company like Petrolon can really sink their teeth into. If we only reported the results in the last paragraph to you, you'd be inclined to think Slick 50 was indeed a magic engine elixir. What you have to keep in mind is that often times the benefits (like increased horse power and fuel economy) may be out weighed by some serious drawbacks (like the indications of reduced oil pressure and increased wear rate).

The Plot Thickens
Just as we were about to go to press with this article, we were contacted by the public relations firm of Trent and Company, an outfit with a prestigious address in the Empire State Building, New York. They advised us they were working for a company called QMI out of Lakeland, Florida, that was marketing a technological breakthrough product in oil additives. Naturally, we asked them to send us all pertinent information, including any testing and research data. What we got was pretty much what we expected. QMI's oil additive, according to their press release, uses ten times more PTFE resins than its closest competitor. Using the unique SX-6000 formula, they say they are the only company to use aqueous dispersion resin which means the microns (particle sizes) are extensively smaller and can penetrate tight areas.
http://www.carbibles.com/snakeoil.html (3 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

This, they claim, completely eliminates the problem of clogged filters and oil passages. Intrigued by their press release, we set up a telephone interview with their Vice-President of Technical Services, Mr. Owen Heatwole. Mr. Heatwole's name was immediately recognized by us as one that had popped in earlier research of this subject as a former employee of Petrolon, a company whose name seems inextricably linked in some fashion or another with virtually every PTFE-related additive maker in the country. Mr. Heatwole was a charming and persuasive talker with a knack for avoiding direct answers as good as any seasoned politician. His glib pitch for his product was the best we've ever heard, but when dissected and pared down to the verifiable facts, it actually said very little. When we asked about the ingredients in QMI's treatments, we got almost exactly the response we expected. Mr. Heatwole said he would have to avoid discussing specifics about the formula, for proprietary reasons. After telling us that QMI was being used by a major oil company, a nuclear plant owned by a major corporation and a major engine manufacturer, Mr. Heatwole followed up with, Naturally, I can't reveal their names - for proprietary reasons. He further claimed to have extensive testing and research data available from a major laboratory, proving conclusively how effective QMI was. When we asked for the name of the lab, can you guess? Yup, We can't give out that information, for proprietary reasons. What QMI did give us was the typical testimonials, though we must admit theirs came from more recognizable sources than usual. They seem to have won over the likes of both Team Kawasaki and Bobby Unser, who evidently endorse and use QMI in their racing engines. Mr. Heatwole was very proud of the fact that their product was being used in engines that he himself admitted are torn down and completely inspected on a weekly basis. Of course, what he left out is that those same engines are almost totally rebuilt every time they're torn down. So what does that prove in terms of his product reducing wear and promoting engine longevity? Virtually nothing. Mr. Heatwole declined to name the source of QMI's PTFE supply for proprietary reasons. He bragged that their product is sold under many different private labels, but refused to identify those labels for proprietary reasons. When asked about the actual size of the PTFE particles used in QMI, he claimed they were measured as sub-micron in size by a major motor laboratory which he couldn't identify - you guessed it - for proprietary reasons. After about an hour of listening to don't quote me on this, I'll have to deny that if you print it, and I can't reveal that, we asked Mr. Heatwole if there was something we could print. Certainly, he said, Here's a good quote for you: 'The radical growth in technology has overcome the problem areas associated with PTFE in the 1980s' Not bad, we said. Then we asked to whom we might attribute this gem of wisdom. DuPont Chemical, perhaps? Me, said Mr. Heatwole. I said that. QMI's press releases like to quote the Guinness Book Of Records in saying that PTFE is The slickest substance known to man. Far be it from us to take exception to the Guinness Book, but we doubt that PTFE is much slicker than some of the people marketing it. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

The Zinc Question
The latest miracle ingredient in oil additives, attempting to usurp PTFE's cure-all throne, is zinc dialkyldithiophosphate, which we will refer to here after as simply zinc. Purveyors of the new zinc-related products claim they can prove absolute superiority over the PTFE-related products. Naturally, the PTFE crowd claim exactly the same, in reverse. Zinc is contained as part of the standard additive package in virtually every major brand of engine oil sold today, varying from a low volume of 0.10 per cent in brands such as Valvoline All Climate and Chevron l5W-50, to a high volume of 0.20 percent in brands such as Valvoline Race and Pennzoil GT Performance.
http://www.carbibles.com/snakeoil.html (4 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

Organic zinc compounds are used as extreme pressure, anti-wear additives, and are therefore found in larger amounts in oils specifically blended for high-revving, turbocharged or racing applications. The zinc in your oil comes into play only when there is actual metal-to-metal con tact within your engine, which should never occur under normal operating conditions. However, if you race your bike, or occasionally play tag with the redline on the tach, the zinc is your last line of defense. Under extreme conditions, the zinc compounds react with the metal to prevent scuffing, particularly between cylinder bores and piston rings. However - and this is the important part to remember - available research shows that more zinc does not give you more protection, it merely prolongs the protection if the rate of metal-to-metal contact is abnormally high or extended. So unless you plan on spending a couple of hours dragging your knee at Laguna Seca, adding extra zinc compounds to your oil is usually a waste. Also, keep in mind that high zinc content can lead to deposit formation on your valves, and spark plug fouling. Among the products we found containing zinc dialkyldithiophosphate were Mechanics Brand Engine Tune Up, K Mart Super Oil Treatment, and STP Engine Treatment With XEP2. The only reason we can easily identify the additives with the new zinc compounds is that they are required to carry a Federally mandated warning label indicating they contain a hazardous substance. The zinc phosphate they contain is a known eye irritant, capable of inflicting severe harm if it comes in contact with your eyes. If you insist on using one of these products, please wear protective goggles and exercise extreme caution. As we mentioned, organic zinc compounds are already found in virtually every major brand of oil, both automotive and motorcycle. However, in recent years the oil companies voluntarily reduced the amount of zinc content in most of their products after research indicated the zinc was responsible for premature deterioration and damage to catalytic converters. Obviously this situation would not affect 99 percent of all the motorcycles on the road - however, it could have been a factor with the newer BMW converter - equipped bikes. Since the reduction in zinc content was implemented solely for the protection of catalytic converters, it is possible that some motorcycles might benefit from a slight increase in zinc content in their oils. This has been taken into account by at least one oil company, Spectro, which offers 0.02 to 0.03 percent more zinc compounds in its motorcycle oils than in its automotive oils. Since Spectro (Golden 4 brand, in this case) is a synthetic blend lubricant designed for extended drain intervals, this increase seems to be wholly justified. Also, available research indicates that Spectro has, in this case, achieved a sensible balance for extended application without increasing the zinc content to the point that it is likely to cause spark plug fouling or present a threat to converter-equipped BMW models. It would appear that someone at Spectro did their homework.

Increased Standard Additives (More Is Not Necessarily Better)
Though some additives may not contain anything harmful to your engine, and even some things that could be beneficial, most experts still recommend that you avoid their use. The reason for this is that your oil, as purchased from one of the major oil companies, already contains a very extensive additive package. This package is made up of numerous, specific additive components, blended to achieve a specific formula that will meet the requirements of your engine. Usually, at least several of these additives will be synergistic. That is, they react mutually, in groups of two or more, to create an effect that none of them could attain individually. Changing or adding to this formula can upset the balance and negate the protective effect the formula was meant to achieve, even if you are only adding more of something that was already included in the initial package. If it helps, try to think of your oil like a cake recipe. Just because the original recipe calls for two eggs (which makes for a very moist and tasty cake), do you think adding four more eggs is going to make the cake better? Of course not. You're going to upset the carefully calculated balance of ingredients and magnify the effect the eggs have on the recipe to the point that it ruins the entire cake. Adding more of a specific additive already contained in your oil is likely to produce similar results. This information should also be taken into account when adding to the oil already in your bike or when mixing oils for any reason, such as synthetic with petroleum. In these cases, always make sure the oils you are putting together have the same rating (SA, SE, SC, etc.). This tells you their additive packages are basically the same, or at least compatible, and are less likely to upset the balance or counteract each other.
http://www.carbibles.com/snakeoil.html (5 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

Detergents And Solvents
Many of the older, better-known oil treatments on the market do not make claims nearly so lavish as the new upstarts. Old standbys like Bardahl, Rislone and Marvel Mystery Oil, instead offer things like quieter lifters, reduced oil burning and a cleaner engine. Most of these products are made up of solvents and detergents designed to dissolve sludge and carbon deposits inside your engine so they can be flushed or burned out. Wynn's Friction Proofing Oil, for example, is 83 percent kerosene. Other brands use naphthalene, xylene, acetone and isopropanol. Usually, these ingredients will be found in a base of standard mineral oil. In general, these products are designed to do just the opposite of what the PTFE and zinc phosphate additives claim to do. Instead of leaving behind a coating or a plating on your engine surfaces, they are designed to strip away such things. All of these products will strip sludge and deposits out and clean up your engine, particularly if it is an older, abused one. The problem is, unless you have some way of determining just how much is needed to remove your deposits without going any further, such solvents also can strip away the boundary lubrication layer provided by your oil. Overuse of solvents is an easy trap to fall into, and one which can promote harmful metal-to-metal contact within your engine. As a general rule of thumb these products had their place and were at least moderately useful on older automobile and motorcycle engines of the Fifties and Sixties, but are basically unneeded on the more efficient engine designs of the past two decades.

The Infamous No Oil Demo
At at least three major motorcycle rallies this past year, we have witnessed live demonstrations put on to demonstrate the effectiveness of certain oil additives. The demonstrators would have a bench-mounted engine which they would fill with oil and a prescribed dose of their miracle additive. After running the engine for a while they would stop it, drain out the oil and start it up again. Instant magic! The engine would run perfectly well for hours on end, seemingly proving the effectiveness of the additive which had supposedly coated the inside of the engine so well it didn't even need the oil to run. In one case, we saw this done with an actual motorcycle, which would be rid den around the parking lot after having its oil drained. A pretty convincing demonstration - until you know the facts. Since some of these demonstrations were conducted using Briggs and Stratton engines, the Briggs and Stratton Company itself decided to run a similar, but somewhat more scientific, experiment. Taking two brand-new, identical engines straight off their assembly line, they set them up for bench-testing. The only difference was that one had the special additive included with its oil and the other did not. Both were operated for 20 hours before being shut down and having the oil drained from them. Then both were started up again and allowed to run for another 20 straight hours. Neither engine seemed to have any problem performing this minor miracle. After the second 20-hour run, both engines were completely torn down and inspected by the company's engineers. What they found was that both engines suffered from scored crankpin bearings, but the engine treated with the additive also suffered from heavy cylinder bore damage that was not evident on the untreated engine. This points out once again the inherent problem with particulate oil additives: They can cause oil starvation. This is particularly true in the area of piston rings, where there is a critical need for adequate oil flow. In practically all of the reports and studies on oil additives, and particularly those involving suspended solids like PTFE, this has been reported as a major area of engine damage.

The Racing Perspective
Among the most convincing testimonials in favor of oil additives are those that come from professional racers or racing teams. As noted previously, some of the oil additive products actually are capable of producing less engine friction, better gas mileage and higher horsepower out put. In the world of professional racing, the split-second advantage that might be gained from using such a product could be the difference between victory and defeat.
http://www.carbibles.com/snakeoil.html (6 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

Virtually all of the downside or detrimental effects attached to these products are related to extended, long-term usage. For short-life, high-revving, ultra-high performance engines designed to last no longer than one racing season (or in some cases, one single race), the long-term effects of oil additives need not even be considered. Racers also use special high-adhesion tires that give much better traction and control than our normal street tires, but you certainly wouldn't want to go touring on them, since they're designed to wear out in several hundred (or less) miles. Just because certain oil additives may be beneficial in a competitive context is no reason to believe they would be equally beneficial in a touring context.

The Best of The Worst
Not all engine oil additives are as potentially harmful as some of those we have described here. However, the best that can be said of those that have not proved to be harmful is that they haven't been proved to offer any real benefits, either. In some cases, introducing an additive with a compatible package of components to your oil in the right proportion and at the right time can conceivably extend the life of your oil. However, in every case we have studied it proves out that it would actually have been cheaper to simply change the engine oil instead. In addition, recent new evidence has come to light that makes using almost any additive a game of Russian Roulette. Since the additive distributors do not list the ingredients contained within their products, you never know for sure just what you are putting in your engine. Recent tests have shown that even some of the most inoffensive additives contain products which, though harmless in their initial state, convert to hydrofluoric acid when exposed to the temperatures inside a firing cylinder. This acid is formed as part of the exhaust gases, and though it is instantly expelled from your engine and seems to do it no harm, the gases collect inside your exhaust system and eat away at your mufflers from the inside out.

Whatever The Market Will Bear
The pricing of oil additives seems to follow no particular pattern whatsoever. Even among those products that seem to be almost identical, chemically, retail prices covered an extremely wide range. For example: One 32-ounce bottle of Slick 50 (with PTFE) cost us $29.95 at a discount house that listed the retail price as $59.95, while a 32-ounce bottle of T-Plus (which claims to carry twice as much PTFE as the Slick 50) cost us only $15.88. A 32-ounce bottle of STP Engine Treatment (containing what they call XEP2), which they claim they can prove outperforms leading PTFE engine treatments, cost us $17.97. Yet a can of K Mart Super Oil Treatment, which listed the same zinc-derivative ingredient as that listed for the XEP2, cost us a paltry $2.67. Industry experts estimate that the actual cost of producing most oil additives is from one-tenth to one-twentieth of the asking retail price. Certainly no additive manufacturer has come forward with any exotic, high-cost ingredient or list of ingredients to dispute this claim. As an interesting note along with this, back before there was so much competition in the field to drive prices down, Petrolon (Slick 50) was selling their PTFE products for as much as $400 per treatment! The words buyer beware seem to take on very real significance when talking about oil additives.

The Psychological Placebo
You have to wonder, with the volume of evidence accumulating against oil additives, why so many of us still buy them. That's the million-dollar question, and it's just as difficult to answer as why so many of us smoke cigarettes, drink hard liquor or engage in any other number of questionable activities. We know they aren't good for us - but we go ahead and do them anyway. Part of the answer may lie in what some psychiatrists call the psychological placebo effect. Simply put, that means that many of us hunger for that peace of mind that comes with believing we have purchased the absolute best or most protection we can possibly get. Even better, there's that wonderfully smug feeling that comes with thinking we might be a step ahead of the pack, possessing knowledge of something just a bit better than everyone else.
http://www.carbibles.com/snakeoil.html (7 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

Then again, perhaps it comes from an ancient, deep-seated need we all seem to have to believe in magic. There has never been any shortage of unscrupulous types ready to cash in on our willingness to believe that there's some magical mystery potion we can buy to help us lose weight, grow hair, attract the opposite sex or make our engines run longer and better. I doubt that there's a one of us who hasn't fallen for one of these at least once in our lifetimes. We just want it to be true so bad that we can't help ourselves.

Testimonial Hype vs. Scientific Analysis
In general, most producers of oil additives rely on personal testimonials to advertise and promote their products. A typical print advertisement will be one or more letters from a satisfied customer stating something like, 1 have used Brand X in my engine for 2 years and 50,000 miles and it runs smoother and gets better gas mileage than ever before. I love this product and would recommend it to anyone. Such evidence is referred to as anecdotal and is most commonly used to pro mote such things as miracle weight loss diets and astrology. Whenever I see one of these ads I am reminded of a stunt played out several years ago by Allen Funt of Candid Camera that clearly demonstrated the side of human nature that makes such advertising possible. With cameras in full view, fake product demonstrators would offer people passing through a grocery store the opportunity to taste-test a new soft drink. What the victims didn't know was that they were being given a horrendous concoction of castor oil, garlic juice, tabasco sauce and several other foul-tasting ingredients. After taking a nice, big swallow, as instructed by the demonstrators, the unwitting victims provided huge laughs for the audience by desperately trying to conceal their anguish and disgust. Some literally turned away from the cameras and spit the offending potion on the floor. The fascinating part came when about one out of four of the victims would actually turn back to the cameras and proclaim the new drink was Great or Unique or, in several cases, One of the best things I've ever tasted! Go figure. The point is, compiling personal testimonials for a product is one of the easiest things an advertising company can do - and one of the safest, too. You see, as long as they are only expressing some one else's personal opinion, they don't have to prove a thing! It's just an opinion, and needs no basis in fact whatsoever. On the other hand, there has been documented, careful scientific analysis done on numerous oil additives by accredited institutions and researchers. For example: Avco Lycoming, a major manufacturer of aircraft engines, states, We have tried every additive we could find on the market, and they are all worthless. Briggs and Stratton, renowned builders of some of the most durable engines in the world, says in their report on engine oil additives, They do not appear to offer any benefits. North Dakota State University conducted tests on oil additives and said in their report, The theory sounds good - the only problem is that the products simply don't work. And finally, Ed Hackett, chemist at the University of Nevada Desert Research Center, says, Oil additives should not be used. The oil companies have gone to great lengths to develop an additive pack age that meets the vehicle's requirements. If you add anything to this oil you may upset the balance and prevent the oil from performing to specification. Petrolon, Inc., of Houston, Texas, makers of Petrolon and producers of at least a dozen other lubrication products containing PTFE, including Slick 50 and Slick 30 Motorcycle Formula, claim that, Multiple tests by independent laboratories have shown that when properly applied to an automotive engine, Slick 50 Engine Formula reduces wear on engine parts. Test results have shown that Slick 50 treated engines sustained 50 percent less wear than test engines run with premium motor oil alone. Sounds pretty convincing, doesn't it? The problem is, Petrolon and the other oil additive companies that claim scientific evidence from independent laboratories, all refuse to identify the laboratories that conducted the tests or the criteria under which the tests were conducted. They
http://www.carbibles.com/snakeoil.html (8 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

claim they are contractually bound by the laboratories to not reveal their identities. In addition, the claim of 50 percent less wear has never been proven on anything approaching a long-term basis. Typical examples used to support the additive makers' claims involve engines run from 100 to 200 hours after treatment, during which time the amount of wear particles in the oil decreased. While this has proven to be true in some cases, it has also been proven that after 400 to 500 hours of running the test engines invariably reverted to producing just as many wear particles as before treatment, and in some cases, even more. No matter what the additive makers would like you to believe, nothing has been proven to stop normal engine wear. You will note that all of the research facilities quoted in this article are clearly identified. They have no problem with making their findings public. You will also note that virtually all of their findings about oil additives are negative. That's not because we wanted to give a biased report against oil additives - it's because we couldn't find a single laboratory, engine manufacturer or independent research facility who would make a public claim, with their name attached to it, that any of the additives were actually beneficial to an engine. The conclusion seems inescapable. As a final note on advertising hype versus the real world, we saw a television ad the other night for Slick 50 oil additive. The ad encouraged people to buy their product on the basis of the fact that, Over 14 million Americans have tried Slick 50! Great. We're sure you could just as easily say, Over 14 million Americans have smoked cigarettes! -but is that really any reason for you to try it? Of course not, because you've seen the scientific evidence of the harm it can do. The exact same principle applies here. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

In Conclusion
The major oil companies are some of the richest, most powerful and aggressive corporations in world. They own multimillion dollar research facilities manned by some of the best chemical engineers money can hire. It is probably safe to say that any one of them has the capabilities and resources at hand in marketing, distribution, advertising, research and product development equal to 20 times that of any of the independent additive companies. It therefore stands to reason that if any of these additive products were actually capable of improving the capabilities of engine lubricants, the major oil companies would have been able to determine that and to find some way to cash in on it. Yet of all the oil additives we found, none carried the name or endorsement of any of the major oil producers. In addition, all of the major vehicle and engine manufacturers spend millions of dollars each year trying to increase the longevity of their products, and millions more paying off warranty claims when their products fail. Again, it only stands to reason that if they thought any of these additives would increase the life or improve the performance of their engines, they would be actively using and selling them - or at least endorsing their use. Instead, many of them advise against the use of these additives and, in some cases, threaten to void their warranty coverage if such things are found to be used in their products. In any story of this nature, absolute facts are virtually impossible to come by. Opinions abound. Evidence that points one direction or the other is avail able, but has to be carefully ferreted out, and is not always totally reliable or completely verifiable. In this environment, conclusions reached by known, knowledgeable experts in the field must be given a certain amount of weight. Conclusions reached by unknown, unidentifiable sources must be discounted almost totally. That which is left must be weighed, one side against the other, in an attempt to reach a reasonable conclusion. In the case of oil additives, there is a considerable volume of evidence against their effectiveness. This evidence comes from well-known and identifiable expert sources, including independent research laboratories, state universities, major engine manufacturers, and even NASA. Against this rather formidable barrage of scientific research, additive makers offer not much more than their own claims of effectiveness, plus questionable and totally unscientific personal testimonials. Though the purveyors of these products state they have studies from other independent laboratories supporting their claims, they refuse to identify the labs or
http://www.carbibles.com/snakeoil.html (9 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : The Engine Oil Bible

provide copies of the research. The only test results they will share are those from their own testing departments, which must, by their very nature, be taken with a rather large grain of salt. You should also note that the AA (UK Automobile Assosciation) has since also carried out tests on Slick-50 type friction reducers and concluded the same: they generally result in blocked oil filters.

Sidebar: Synthetic Oils
Whenever we talk about oil additives, the subject of synthetic oils inevitably crops up. Actually, the two subjects have very little to do with each other, but since many riders seem to equate additives and synthetics together in their minds, we will take a few lines just to clear the air. Synthetic oils were originally developed for use in gas turbine engines. In most cases they are capable of maintaining their viscosity for longer periods of use and under much greater temperatures and pressures than petroleum products. Commons synthetics used for engine lubrication today are Polyalphaolefin (like Mobil 1) or Dibasic Organic Esters (like AMSOIL). They are fully compatible with conventional oils and can be mixed, providing their ratings match. Probably the best situation is a blend of synthetics and mineral oils, such as Golden Spectro and AGIP Sint 2000. These products seem to offer the best of both worlds in protection and extended service life. They may cost considerably more than standard petroleum products, but they also can be used for much longer periods between oil changes without losing their protective capabilities. Synthetics and synthetic blends offer a wider range of protection than standard petroleum products. However, it should be noted that this extended range of protection reaches into an area of temperatures and pressures virtually impossible to attain inside most motorcycle engines and transmissions. In other words, if you use them, you are buying a sort of overkill protection. It's certainly not going to hurt anything - it's just unnecessary. That is, unless it makes you feel better knowing the extra protection is on board, in which case the added expense may be well justified. As a basic rule of thumb, using the standard engine oil recommended by your bike's manufacturer and changing it about every 3000 miles will afford you all the protection you'll ever need. But if you feel better knowing you have more protection than you need or, if you like the extended service-life feature, there's certainly nothing wrong with using a premium grade synthetic blend lubricant.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/snakeoil.html (10 of 10) [2/6/2008 7:17:21 AM]

Car Bibles : Links

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

The Car Bibles Link Exchange
This is my link exchange. I've placed links here to other sites which you might find useul, all car and automotive-related of course. These are unpaid links provided purely as a service to people looking to carry on to another website with similar content. There are or will be links to chip companies, tyres (or tires), suspension, oil companies, engine tuners etc. Click on the link or banner ad to open a new browser window to the website. Note: The top part of the page is links to smaller companies, fan sites, stuff like that. The bottom part of the page is links to corporate homepages, vendors and suppliers.

Reciprocal links
If you'd like to link back to my site, please either use the banner below and link back to http://www.carbibles.com, or use the following little HTML snippit. Thanks..... <FONT SIZE="-1"><A HREF="http://www.carbibles.com">The car maintenance bibles. Everything you need to know about wheels, tyres, suspension,<BR>brakes and engine oils. Home of the original car maintenance bibles.</A></FONT>

Car Insurance Links (UK)
www.Diamond.co.uk Women's Car Insurance Specialises in cheap car insurance for women www.elephant.co.uk Cheap Car Insurance Provides Cheap Car insurance. Receive an instant quote online www.bell.co.uk Car Insurance Provider of cheap and flexible car insurance and online quotes

General Links

Aftermarket Auto Accessories : Car Accessories and Trucks Accessories.

http://www.carbibles.com/links.html (1 of 5) [2/6/2008 7:18:07 AM]

Car Bibles : Links

The UK's favourite car modifications shop.

Barbari Fabric Leather & Neoprene custom seat covers.

Car Recovery and Nationwide Car Transportation offer a 24 hour breakdown & recovery throughout the UK. If you've got a classic or prestige car, this lot will certainly be better than the AA or RAC because they have a covered / enclosed transporter.

Pulling Power Car Recovery (UK)

A complete guide to the car industry in Pakistan.

View the hottest Drifting Videos - car racing, tuning, and Japanese sports cars for sports car enthusiasts from the ultimate car video network GTChannel.com.

http://www.carbibles.com/links.html (2 of 5) [2/6/2008 7:18:07 AM]

Car Bibles : Links

Car club links
Links to general car clubs, performance cars, modified cars and so on and so forth. Essex Modified Car Club (UK) Cobretti Viper (UK)

Mitsubishi Pajero Owners Club

Corporate / company links : Suspension
Links to various companies that supply car suspension components and/or kits, springs, shocks and related suspension services.

Kinetic Suspension systems TMS Suspension catalogue for BMWs Monroe shock absorbers Suspension Eibach Suspension

Tim Stiles Racing - VW and Audi suspension mods etc Koni Suspension Spax Suspension

Autoshocks.co.uk is a UK outfit that always try to provide what the customer wants even if it means supplying donor units for a one off order. No order is too small or too difficult.

SuperSprings.com is a US company specialising in truck suspension.

Corporate / company links : Engine tuning & mods
Links to various companies that supply tuning and mods for your engine.

Superchips AEM power

Cobb Tuning (Subaru) NoS Nitrous Oxide Systems

http://www.carbibles.com/links.html (3 of 5) [2/6/2008 7:18:07 AM]

Car Bibles : Links

Corporate / company links : Engine oils
Links to the big oil companies. It doesn't matter what you think of the oil tycoons, you need a good engine oil in your car. These sites are the big hitters when it comes to corporate doublespeak.

Mobil Exxon Castrol

Shell Group BP Valvoline

Shell Nederland Chevron Pennzoil

Texaco

Corporate / company links : Brakes
Links to various companies that supply car brake components and/or kits, discs, pads, rotors, springs, clips and other related brake services.

Brembo Goodridge

EBC Brakes AeroTek UK

Raybestos

Corporate / company links : Tyres & wheels
Rochford Tyres has an excellent fitment guide page where they list a ton of combinations and permutations of wheels and tyres for all the popular makes and models. The guide is designed to give you an idea of wheel and tyre sizes that will keep you close to spec for rolling radius. Use the 'Alloy Wheel Search' box at the at top-left of their site. As an added bonus, if you decide to buy anything from them, use the the checkout to get 5% off! Sweet!

BestBuy Tyres is a UK outfit that sell low cost tyres and then have them fitted to your vehicle at your local garage by experts.

Etyres is the UK's first online mobile tyre service. Offering low cost tyres and batteries with free "on your driveway or work place fitting" order online or free phone. Click this link to find out more.

Event Mobile Tyres are a uk based mobile tyre fitting service. We supply and fit all leading brands of car tyres including performance tyres, run flat tyres, van tyres and 4x4 tyres. We replace tyres at your home or work address. All our prices are fully inclusive. Quotations available online.

Kulcha wheels is an alloy wheel distributor and wholesaler in Singapore.

http://www.carbibles.com/links.html (4 of 5) [2/6/2008 7:18:07 AM]

Car Bibles : Links

Merit Tyres: Competitive low prices on tyres, exhausts, alloy wheels and more. Visit the website for information and to download your money saving vouchers to make your next service even cheaper.

Tyretraders is one of the largest independent tyre retailers and wholesalers in the UK. Unlike other UK-based and Pan-European Internet tyre retailers, we have some major plus points:- (1) They have real branches we own, we are not a franchised "virtual" company. (2) They have real stock, not "virtual" stock like some other online retailers. Europe's largest online tire retailer, Delticom AG : www.mytyres.co.uk - the home of low tyre prices for cars, 4x4s and vans www.tires-easy.com - the home of low tire prices for cars, 4x4's and vans

yokahama pirelli firestone bridgestone goodyear dunlop continental michelin BFGoodrich toyo holland tyre tyres online tire rack

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/links.html (5 of 5) [2/6/2008 7:18:07 AM]

Car Bibles : Copyright information.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

This page contains copyright and usage information for the Car Bibles (http://www.carbibles.com).

©Copyright Info
www.chris-longhurst.com and the Car Maintenance Bibles. Designer, Artist, Author: Chris Longhurst

Copyright Information
Copyright ©1994,1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005,2006,2007,2008 Christopher J Longhurst. All Rights Reserved. All the pages within this Internet site ("Site") are the property of Christopher J Longhurst unless otherwise stated. Permission (which may be revoked at any time) is granted to download the material in this Site without alterations and for private and non-commercial use only so long as the following copyright notice is included: Copyright ©1994 - 2008 Christopher J Longhurst. All Rights Reserved.

Prohibitted uses.
No page, text, passage, image or animation from this Site may be used for commercial gain. Uses which are specifically prohibitted include but are not limited to:
●

● ●

Duplicating The Site to recordable, printed or electronic media for re-sale online via personal websites or auction sites such as eBay. Inclusion or duplication of any part of The Site in printed, recordable or electronic format for commercial gain. Reproduction of images or text on another personal or commercial website without explicit written permission from The Author.

Any violation of the above conditions will be responded to expeditiously by The Author and will involve financial penalty.

Specifically permitted uses.
http://www.carbibles.com/copyright.html (1 of 3) [2/6/2008 7:18:23 AM]

Car Bibles : Copyright information.

The following are vendors, re-sellers, educational establishments and publications that are specifically granted rights to use parts of The Site as agreed in communication with The Author:
● ● ● ● ● ●

www.design911.com Practical Classics magazine Classic Cars magazine Sport Compact Car magazine MG Car Club U.K. Cengage Learning Inc.

● ● ● ●

Croatian Automotive E-zine AutoNet. MC Square magazine Dreaming Lego. Club 306.

Service Marks Notice
"The Car Maintenance Bibles", "The Engine Oil Bible", "The Brake Bible", "The Suspension Bible", "The Wheel and Tyre Bible", "The Fuel & Engine Bible", "The Motorbike Suspension Bible", "The Transmission Bible" and the associated logo(s) and design(s) are service marks of Christopher J Longhurst. All other trademarks, service marks and logos used in this Site are the property of their respective owners and are displayed under Fair Use. The display of such trademarks, service marks and logos should be considered reasonable and necessary in light of their use to illustrate the articles contained herein, and neither carbibles.com nor Chris Longhurst make any claim to their ownership.

Acknowledgment
This Site may contain links to other Web sites operated by third parties ("Linked Sites"). You acknowledge that Christopher J Longhurst and his sponsors and/or site providers neither endorse nor is affiliated with the Linked Site and is not responsible for any content that appears on the Linked Site. You also acknowledge that the owner of the Linked Site neither endorses nor is affiliated with Christopher J Longhurst and his sponsors and/or site providers.

Code Of Conduct
You agree to indemnify, defend and hold harmless Christopher J Longhurst and his sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly out of or from (a) your breach of this Agreement, (b) your violation of the Code of Conduct and/or (c) your activities in connection with the Site or Siterelated services.

Privacy Statement
From time to time, in order to improve the usefulness of the information in the Car Maintenance Bibles, this site will send packets of data related to your usage of the site to the ChrisPlex, a heavily guarded, massively parallel server farm. The location of the server farm is known only to Chris (The Author), who carries its GPS coordinates on a 256-bitencrypted smart card locked in a stainless-steel briefcase handcuffed to his right wrist. No personally identifiable information of any kind related to your viewing of this site or any links thereof or any thoughts you might have about this site or where you might be going later will ever be given, sold, bartered, auctioned off, tossed into a late-night poker pot, or otherwise transferred in any way to any untrustworthy third party, ever, we swear.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

http://www.carbibles.com/copyright.html (2 of 3) [2/6/2008 7:18:23 AM]

Car Bibles : Copyright information.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/copyright.html (3 of 3) [2/6/2008 7:18:23 AM]

http://www.carbibles.com/images/multilink2.jpg

http://www.carbibles.com/images/multilink2.jpg [2/6/2008 7:18:30 AM]

The Car Maintenance Bibles FAQ

CarBibles.com - the official home of the Car Maintenance Bibles Covering everything you need to know about, wheels, tyres or tires, engine oil or motor oil, suspension (including springs and shock absorbers), brakes (disc brakes and drum brakes) and general car maintenance.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Linking to or copying from The Car Maintenance Bibles
Can I make a copy of this site for my own site?
No. The Car Maintenance Bibles are licenced under a Creative Commons licence. See the copyright page for more info. Apart from copyright infringement, this site changes very frequently with additions and corrections. If you make a copy, it will instantly be out-of-date. See the change log for an idea of how frequently this site is updated.

Can I link to this site?
Yes. All information about linking can be found on the links page in the Reciprocal Links section at the top.

Wheels and tyres
Can heavier wheels affect my gas mileage (mpg)?
They can, yes. As well as contributing to a heavier vehicle, adding heavier wheels adds to the unsprung weight of the vehicle. This means the engine has to work slightly harder just to turn the wheels themselves, which can rob you of power and/or fuel efficiency. They'd have to be pretty heavy wheels to see a really noticable drop in mpg though.

http://www.carbibles.com/faq.html (1 of 4) [2/6/2008 7:18:53 AM]

The Car Maintenance Bibles FAQ

Brakes
What is ABS?
ABS stands for Antilock Braking System. It's a system designed to sense when the a brake is about to cause a wheel to lockup, and relieve the pressure on that brake automatically to keep the wheel turning. When the wheels are turning, not locked up, you have more control over your car.

My brakes judder when I press on the pedal. What's going on?
It's almost certainly warped rotors that are causing the problem. The first time around, it's always hard to tell what causes it. This sort of thing happens most often if you live in a mountainous area and use the brakes coming down mountain passes instead of relying on the drag from the engine. The other thing that can cause it is corrosion in the brake calipers. If the brake pistons aren't retracting properly into the caliper housings, then they will be binding slightly on the rotor when you're driving. Not enough to make any difference to the handling, but enough to overheat the rotors. The solution is one of two things. You can either get the rotors re-machined where they're placed in a machining tool that shaves off some of the metal around the face of the rotor to make sure both sides are parallel and flat again. The other option is to buy new rotors. Bear in mind that if you have them re-machined, they lose a lot of their heat capacity and its a lot easier to warp them again. It's also a lot easier to make a warped and re-machined rotor fail.

Engine Oils
Should my oil be black when I change it? It's a clear brown when I put it in but 3000 miles later, it's black. Why?
Don't worry about the engine oil turning black. It will lose it's golden-brown colour within a few hundred miles of being put in to the engine. That doesn't mean it's not working. Quite the contrary - it means it is working well. It changes colour as it traps oxidised oil, clots and the flakes of metal that pop off heavily loaded engine parts.

How long will new, bottled engine oil last for?
An unopened container should be good for about 3 years. See the engine oil bible page for full details on this topic.

Is there any way to tell if my current oil is mineral, semi- or fully-synthetic?
The short answer is 'no'. The long answer is 'yes' if you're prepared to extract a sample and send it to a chemical lab for analysis.

Additives
I've heard that Zmax/BoostR/Miracle-Wonder-Oil-O is a fantastic new engine oil additive. Is it really any good?
I don't know. I don't put additives in my oil for reasons outlined in the oil bible. As I don't use them any more, I can't post opinions about them, nor can I libel the companies concerned (these people have lots of clever lawyers). If that new product really is endorsed by Nascar or FIA, then why don't you ever see it on shirts and hats in the pit lane, or on mechanic's workbenches in the garages?
http://www.carbibles.com/faq.html (2 of 4) [2/6/2008 7:18:53 AM]

The Car Maintenance Bibles FAQ

But Chad Richbastard's NASCAR team use Miracle Wonder Oil. Surely that's a good sign?
If I could get my engine rebuilt after only 400 miles of use, then I would endorse just about anything. Hell they could run sawdust in there if they strip it down after every race. Think about it - those engines typically don't do more than 400 or 600 miles. For the average car, that's about a week and half's driving.

Suspension
I want to lower my car - should I buy new springs and shocks, or should I just cut the springs that are in there?
You should buy new springs and/or shocks. If you cut the existing springs, you will compromise their structural integrity. If they then fail at a later date, your insurance won't cover you because of a hack-job done on a critical part of your car.

I've just put sports springs on my car to lower it. Should I put sports shocks on too?
You should ideally buy springs and shocks as a matched set in a kit. When you get sports springs and use stock shocks, the shocks will tend to wear prematurely. They are designed to be a blend of comfortable ride and safe handling. By using shorter springs, the shocks are now overloaded. Getting a kit will mean that the shocks are matched to the length of springs.

Every time I go over a bump, my front suspension bangs / knocks / clonks. Why?
The most likely cause of this is the big rubber bush at the top of the front suspension mounts. If it has perished and worn out, then the top of the suspension is knocking against the inside of the suspension strut tower. Another symptom of this is if you park the car and turn the steering wheel from lock to lock, then move off slowly, there will be a "sproing" type noise as the suspension spring untensions. You should invest in new suspension bushes.

My car used to ride really nice. Now it's got 65,000 miles on it and it seems wallowy - the ride has gone to Hell. How can I solve this?
Most car companies won't tell you this, but shock absorbers and springs are pretty much end-of-life after 60,000 miles of average use. You need to change them. And if you do, then change them all at once. It's dangerous to do just the front, or just the back. Few people understand that shock absorbers make a lot of difference not only to the ride of your car, but the effectiveness of the brakes. With worn shocks, the wheels bounce and skip under braking. With good shocks they don't. Guesstimates as to the difference at 100km/h can be as much as 10 metres difference in braking just because of the shock absorbers.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

http://www.carbibles.com/faq.html (3 of 4) [2/6/2008 7:18:53 AM]

The Car Maintenance Bibles FAQ These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/faq.html (4 of 4) [2/6/2008 7:18:53 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

The wheel and tyre Bible, covering everything you need to know about wheels, tyres or tires, rim sizes, tyre tread, tread depth and tread wear, tyre markings, aquaplaning, wheel balancing, aftermarket wheels, alloys, TPMS tyre pressure monitoring systems and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Page 1 ------ Page 2

Moving on - Wheel measurements.
Okay. If you want to change the wheels on your car, you need to take some things into consideration.
●

●

Number of bolts or studs It goes without saying that you can't fit a 4-bolt wheel onto a 5-bolt wheel hub. Sounds obvious, but people have been known to fork out for an expensive set of wheels only to find they've got the wrong number of mounting holes. Pitch Circle Diameter Right. So you know how many holes there are. Now you need to know the PCD, or Pitch Circle Diameter. This is the diameter of the invisible circle formed by scribing a circle that passes through the centre point of each mounting hole. If

http://www.carbibles.com/tyre_bible_pg2.html (1 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

●

●

you've got the right number of holes, but they're the wrong spacing, again the wheel just won't fit. PCD notation Stud patterns and PCD values are typically listed in this notation : 5x114.42. This means a 5-bolt pattern on an imaginary circle of 114.42mm diameter. Centre spigot size This is a tricky one. The wheel bolts or studs are there to hold the wheel laterally on to the axle, but they're not really designed to take vertical load - ie. they're not designed to take the weight of the car. That's the job of the centre spigot the part of the axle that sticks out and pokes through the hole in the middle of the wheel. It's the load-bearing part of the axle and the wheel, as well as being the assembly that centres the wheel on the axle. For the most part, the centre spigot on aftermarket alloys is much larger than that of the car you want to put them on to. When this happens, the best solution is a spigot locating ring (also called a hub-centric ring) which is essentially a steel or hard plastic doughnut designed to fit snugly on to your axle spigot and into the wheel spigot. The image below shows the PCD (the red ring and mounting hole centrelines) and the spigot size (the blue ring). The spigot hole on an alloy is normally covered up with a centre cap or cover.

●

Inset or outset This is very important. Ignore this and you can end up with all manner of nasty problems. This is the distance in mm between the centre line of the wheel rim, and the line through the fixing face. You can have inset, outset or neither. This determines how the suspension and self-centring steering behave. The most obvious problem that will occur if you get it wrong is that the steering will either become so heavy that you can't turn the car, or so light that you need to spend all your time keeping the bugger in a straight line. More mundane problems through ignoring this measurement can range from wheels that foul parts of the bodywork or suspension, to high-speed judder in the steering because the suspension setup can't handle that particular type of wheel. This figure will be stamped on the wheel somewhere as an ET figure. Inset and outset are subsets of offset and the relationship is this : positive offset = inset. Negative offset = outset. Typically you can get away with 5mm-7mm difference from the vehicle manufacturer specification before you'll run into trouble with the wheels fouling the suspension or bodywork. So for example if your stock wheels have an offset of 42mm and you can only find replacements with a 40mm offset, that 2mm difference ought to OK.

No offset

Inset wheel

Outset wheel

http://www.carbibles.com/tyre_bible_pg2.html (2 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

●

More inset = closer to the suspension? It may sound counterintuitive, but when you increase the inset of a wheel, you decrease the clearance between the inner edge of the wheel and the suspension components. In the example below, the red wheel has a larger inset - ie. the distance from the mounting face to the centreline of the wheel is larger than that of the green wheel. The grey blocks indicate a stylised mounting hub, axle and suspension component. You can see that by increasing the inset (positive offset) of the wheel, it pushes the inner edge of the wheel and tyre closer to the suspension. Conversely, decreasing the inset moves the wheel and tyre closer to the outside of the vehicle where it might scrub and rub against the bodywork and wheel arches. It might help to think of this more in terms of overall offset rather than inset and outset. The most positive the offset, the more the wheel is tucked into the car. The more negative the offset, the more the wheel sticks out.

●

A real example They say a picture is equivalent to a thousand words, so study this one carefully. It's one of the wheels off one of my old cars. Enlarged so you can read it is the wheel information described above. You'll notice it reads "6J x 14 H2 ET45". The "6J x 14" part of that is the size of the wheel rim - in this case it has a depth of 6 inches and a diameter of 14 inches (see the section directly below here on wheel sizes for a more in-depth explanation). The "J" symbolises the shape of the tyre bead profile. (see rim contours below) The "H2" means that this wheel rim is a double hump design (see hump profiles, below). The "ET45" figure below that though symbolises that these wheels have a positive offset of 45mm. In other words, they have an inset of 45mm. In my case, the info is all stamped on the outside face of the wheel which made it nice and easy to photograph and explain for you. On most aftermarket wheels, they don't want to pollute the lines and style of the outside of the wheel with stamped-on information - it's more likely to be found inside the rim, or on one of the inner mounting surfaces.

http://www.carbibles.com/tyre_bible_pg2.html (3 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

The wheel offset calculator
This little javascript will help you to understand the different between your old and new wheel and tyre combination in terms of the offset and how it's going to affect the overall lateral position of the wheel and tyre.
Current wheel/tyre Tyre Section: 215 Wheel offset: New wheel/tyre Tyre Section: 235 Wheel offset:

42 Click to calculate differences

38

Matching your tyres to your wheels.
Okay. This is a biggie so take a break, get a hot cup of Java, relax and then when you think you're ready to handle the complexities of tyre matching, carry on. This diagram should help you to figure out what's going on.

Wheel sizes
Wheel sizes are expressed as WWWxDDD sizes. For example 7x14. A 7x14 wheel is has a rim width of 7 inches, and a rim diameter of 14 inches. The width is usually below the width of the tyre for a good match. So a 185mm tyre would usually be matched to a wheel which is 6 inches wide. (185mm is more like 7 inches, but that's across the entire tyre width, not the bead area where the tyre fits the rim.)

Rolling Radius
The important thing that you need to keep in consideration is rolling radius. This is so devastatingly important that I'll mention it in bold again:rolling radius!. This is the distance in mm from the centre of the wheel to the edge of the tread when it's unladen. If this changes because you've mismatched your new wheels and tyres, then your speedo will lose accuracy and the fuel consumption might go up. The latter reason is because the manufacturer built the engine/ gearbox combo for a specific rolling radius. Mess with this and the whole thing could start to fall down around you. It's worth pointing out that the actual radius the manufacturers use for speedo calculation is the 'dynamic' or the 'laden' radius of the wheel at the recommended inflation pressure and 'normal' loading. Obviously though, this value is entirely dependent on the unladen rolling radius.

J, JJ, K, JK, B, P and D : Tyre bead profiles / rim contour designations.
No, my keyboard letters weren't stuck down when I typed this. The letter that typically sits between the rim width and diameter figures stamped on the wheel, and indicates the physical shape of the wheel where the tyre bead meets it. In the cross-section on the left you can see the area highlighted in red. Like so many topics, the answer as to which letter represents which profile is a long and complicated one. Common wisdom has it that the letter represents the shape. ie. "J" means the bead profile is the shape of the letter "J". Not so, although "J" is the most common profile identifier. 4x4 vehicles often have "JJ" wheels. Jaguar vehicles (especially older ones) have "K" profile wheels. Some of the very old VW Beetles had "P" and "B" profile wheels. Anyway the reason it is an "awkward topic to find definitive data on" is very apparent if
http://www.carbibles.com/tyre_bible_pg2.html (4 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

you've ever looked at Standards Manual of the European Tyre and Rim Technical Organisation. It is extremely hard to follow! There are pages and pages (64 in total) on wheel contours and bead profiles alone, including dimensions for every type of wheel you can think of (and many you can't) with at least a dozen tabled dimensions for each. Casually looking through the manual is enough to send you to sleep. Looking at it with some concentration is enough to make your brain run out of your ears. To try to boil it all down for you, it seems that they divide up the rim into different sections and have various codes to describe the geometry of each area. For example, the "J" code makes up the "Rim Contour" and specifies rim contour dimensions in a single category of rims called "Code 10 to 26 on 5deg. Drop-Centre Rims". To give you some idea of just how complex / anal this process is, I've recreated one such diagram with Photoshop below to try to put you off the scent.

From the tables present in this manual, the difference in dimensions between "J" and "B" rims is mainly due to the shape of the rim flange. This is the part in the above diagram defined by the R radius and B and Pmin parameters. Hence my somewhat simpler description : tyre bead profiles. Note that in my example, the difference between "J" and "B" rims is small but not negligible. This area of rim-to-tire interface is very critical. Very small changes in a tyre's bead profile make large differences in mounting pressures and rim slip. "A" and "D" contour designations come under the category of "Cycles, Motorcycles, and Scooters" but also show up in the "Industrial Vehicles and Lift Trucks" category. Naturally, the contours have completely different geometry for the same designation in two different categories. The "S", "T", "V" and "W" contour designation codes fall into the "Commercial Vehicles, Flat Base Rims" category. The "E", "F", "G" and "H" codes fall into the "Commercial Vehicles, Semi-Drop Centre Rims" category. Are you beginning to see just how complex this all is? I think the best thing for you, dear reader, is a general rule-of-thumb, and it is this : if your wheels are stamped 5J15 and you buy 5K15 tyres, rest assured they absolutely won't fit.

H, H2, FH, CH, EH and EH2 : Hump profiles.
More alphabet soup. So you might have just about understood the bit about bead profiles, but there's another design feature of wheel rims. The 'hump' is actually a bump put on the bead seat (for the bead) to prevent the tire from sliding off the rim while the vehicle is moving. As with rim contours, there are several different designations of hump design and configuration, depending on the number and shape of the humps. For the inquisitive reader, here's a table of the hump designations, and a diagram similar to the one above which displays in nauseating detail just what a hump really is. The eagle-eyed amongst you (or those paying attention) will notice that this diagram is an enlarged view of the area around Pmin in the other ETRO diagram above, because that's typically where the hump is.

http://www.carbibles.com/tyre_bible_pg2.html (5 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Designation
Hump Double Hump Flat Hump Double Flat Hump Combination Hump Extended Hump Extended Hump 2+ Hump Hump

Bead Seat Contour Outside
Hump Normal Flat Hump Hump Extended Hump Extended Hump 2+

Inside
Normal

Marking
H H2 FH FH2 CH EH2 EH2 +

Flat Hump Flat Hump Flat Hump Extended Hump Extended Hump 2+

If you're obsessive-compulsive and absolutely must know everything there is to know about bead profiles, humps and rim flanges, you can check out the ETRTO (European Tyre and Rim Technical Organisation website from where you can purchase their manuals and documents. Go nuts. Meanwhile, the rest of us will move on to the next topic.

Why would I want to change my rims and tyres anyway?
A good question. Styling and performance are the only two reasons. Most cars come with horrible narrow little tyres and 13 inch rims. More recently the manufacturers have come to their senses and started putting decent combinations on factory cars so that's not so much of a problem any more. The first reason is performance. Speed in corners more specifically. If you have larger rims, you get smaller sidewalls on the tyres. And if you have smaller sidewalls, the tyre deforms less under the immense sideways forces involved in cornering.

So how does it all figure out?
Point to note: 1 inch = 25.4mm. You need to know that because tyre/wheel manufacturers insist on mixing mm and inches in their ratings.
http://www.carbibles.com/tyre_bible_pg2.html (6 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Also note that a certain amount of artistic licence is required when calculating these values. The tyre's rolling radius will change the instant you put load on it, and calculating values to fractions of a millimetre just isn't worth it - tyre tread wear will more than see off that sort of accuracy. Lets take an average example: a car with factory fitted 6x14 wheels and 185/65 R14's on them.
● ● ●

Radius of wheel = 7 inches (half the diameter) = 177.8mm Section height = 65% of 185mm = 120.25mm So the rolling radius for this car to maintain is 177.8+120.25=298.05mm

With me so far? Good. Now lets assume I want 15 inch rims which are slightly wider to give me that nice fat look. I'm after a set of 7x15's First we need to determine the ideal width of tyre for my new wider wheels. 7 inches = 177.8mm. The closest standard tyre width to that is actually 205mm so that's what we'll use. (remember the tyre width is larger than the width of the bead fitting.)
● ● ● ● ● ●

Radius of wheel = 7.5 inches (half of 15) = 190.5mm We know that the overall rolling radius must be as close to 298.05mm as possible So the section height must be 298.05mm-190.5mm = 107.55mm Figure out what percentage of 205mm is 107.55mm. In this case it's 52.5% So combine the figures - the new tyre must be 205/50 R15 ....giving a new rolling radius of 293mm - more than close enough.

A tyre size calculator.
Well if all that maths seems a little beyond you, and judging by the volume of e-mails I get on this subject, it might well be, I've made a little Javascript application below to help you out. Select the tyre size you currently have, and then the size you're interested in. Calculate each tyre size and then click on the click to calculate the difference button. It will show you all the rolling radii, circumferences, percentage differences and even speedometer error. Enjoy.
Current wheel/tyre New wheel/tyre R

185 14

/ 65

205 15

/ 50

R

Calculate

Calculate

Current RR: Current circumference:

mm mm

New RR: New circumference:

mm mm

Click to calculate difference

Difference in circumference:

mm or

% mph

So when your speedo reads 70mph, you're actually travelling at

http://www.carbibles.com/tyre_bible_pg2.html (7 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

A Speedometer error means an odometer error too.
It stands to reason that if you change the rolling radius of your wheels and tyres, and the speedometer no longer reads correctly, that your odometer will also gradually become inaccurate. Assume for example that you bought a car brand new and changed the wheels and tyres on day one from 195.65R14 to 205/50R15 - not an uncommon change. By the calculator above, that makes your speedometer over read by 1.7%. Consequently, the registered odometer reading will also be out by the same value. So for example, when you get to 10,000km of driving (in the real world), your odometer will actually read 10,170km. OK so that's not a huge difference but it is one of the reasons why most car dealers have a disclaimer on their secondhand vehicles telling you that they won't guarantee the displayed mileage. ("Clocking" the odometer is the other reason). Odometer errors due to mis-matched tyres and wheels will happen on regular odometers as well as the newer digital ones.

A quick word about motorcycle speedometers.
Veering off-topic for a moment, it's worth pointing out that without exception, all motorbike speedometers are designed to inflate the ego of the rider by at least 5%. In some cases, they are are much as 10% optimistic. ie. the speedometer on a motorbike will always over-read. 100mph? Not likely - you're actually doing closer to 90mph.

Aspect Ratio and Rim / Pan Width.
Aspect ratio is, as you know if you read the bit above, the ratio of the tyre's section height to its section width. The aspect ratio is sometimes referred to as the tyre 'series'. So a 50-series tyre means one with an aspect ratio of 50%. The maths is pretty simple and the resulting figure is stamped on all tyres as part of the sizing information:
Aspect ratio = Section height Section width

The actual dimensions of a tyre are dependent on the rim on which it is mounted. The dimension that changes the most is the tyre's section width; a change of about 0.2" for every 0.5" change in rim width.

http://www.carbibles.com/tyre_bible_pg2.html (8 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

The ratio between the section width and the rim width is pretty important. If the rim width is too narrow, you pinch the tyre in and cause it to balloon more in cross-section. If the rim width is too wide, you run the risk of the tyre ripping away at high speed. For 50-series tyres and above, the rim width is 70% of the tyre's section width, rounded off to the nearest 0.5. For example, a P255/50R16 tyre, has a design section width of 10.04" (255mm = 10.04inces). 70% of 10.04" is 7.028", which rounded to the nearest half inch, is 7". Ideally then, a 255/50R16 tyres should be mounted on a 7x16 rim. For 45-series tyres and below, the rim width is 85% of the tyre's section width, rounded off to the nearest 0.5. For example, a P255/45R17 tyre, still has a design section width of 10.04" (255mm = 10.04inces). But 85% of 10.04" is 8.534", which rounded to the nearest half inch, is 8.5". Ideally then, a 255/45R17 tyre should be mounted on an 8½x17 rim.

An ideal rim-width calculator
Blimey I'm good to you. Can't figure that maths out either? Click away my friend and Chris's Rimwidthulatortm will tell you what you need to know. Obvious disclaimer : the results should be verified with the tyre dealership/manufacturer. Your tyre size: 185 / 65 R 14
Click to calculate rim size

x

up to

x

Too wide or too narrow - does it make a difference?
Given all the information above, you ought to know one last thing. A rim that is too narrow in relation to the tyre width will allow the tyre to distort excessively sideways under fast cornering. On the other hand, unduly wide rims on an ordinary car tend to give rather a harsh ride because the sidewalls have not got enough curvature to make them flex over bumps and potholes. That's why there is a range of rim sizes for each tyre size in my Rimwidthulator above. Put a 185/65R14 tyre on a rim narrower than 5inches or wider than 6.5inches and suffer the consequences.

The Plus One concept
The plus one concept describes the proper sizing up of a wheel and tyre combo without all that spiel I've gone through above. Basically, each time you add 1 inch to the wheel diameter, add 20mm to the tyre width and subtract 10% from the aspect ratio. This compensates nicely for the increases in rim width that generally accompany increases in diameter too. By using a larger diameter wheel with a lower profile tyre it's possible to properly maintain the overall rolling radius, keeping odometer and speedometer changes negligible. By using a tyre with a shorter sidewall, you gain quickness in steering response and better lateral stability. The visual appeal is obvious, most wheels look better than the sidewall of the tyre, so the more wheel and less sidewall there is, the better it looks.

http://www.carbibles.com/tyre_bible_pg2.html (9 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Tyre size table up to 17" wheels
Here, for those of you who can't or won't calculate your tyre size, is a table of equivalent tyres. These all give rolling radii within a few mm of each other and would mostly be acceptable, depending on the wheel rim size you're after.

80 SERIES
135/80 R 13 145/80 R 13 155/80 R 13 165/80 R 13 175/80 R 13 185/80 R 13 http://www.carbibles.com/tyre_bible_pg2.html (10 of 28) [2/6/2008 7:20:08 AM]

75 SERIES
165/75 R 13 175/75 R 14 185/75 R 14 -

70 SERIES
145/70 R 13 155/70 R 13 155/70 R 13 165/70 R 13 175/70 R 13 175/70 R 13 185/70 R 13 165/70 R 14 185/70 R 13 165/70 R 13 175/70 R14 175/70 R 14 185/70 R 14 185/70 R 14 195/70 R 14 -

65 SERIES
165/65 R 13 175/65 R 13 175/65 R 13 165/65 R 14 165/65 R 14 175/65 R 14 175/65 R 14 185/65 R 14 185/65 R 14 195/65 R 14 185/65 R 15 195/65 R 14 185/65 R 15 195/65 R 15

60 SERIES
175/60 R 13 185/60 R 13 175/60 R 14 175/60 R 14 185/60 R 14 195/60 R 14 195/60 R 14 205/60 R 14 205/60 R 14 215/60 R 14 195/60 R 15 215/60 R 14 225/60 R 14 195/60 R 15

55 SERIES
185/55 R 14 195/55 R 14 185/55 R 15 205/55 R 14 185/55 R 15 195/55 R 15 205/55 R15 195/55 R 15 205/55 R 15 205/55 R 16 -

50 SERIES
195/50 R 15 205/50 R 15 195/50 R 16 215/50 R 16 195/50 R 16 205/50 R 16 205/50 R 16 225/50 R 16 205/50 R 17

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

-

-

-

-

205/60 R 15 215/60 R 15

-

-

So that's it then?
Yes - that's it. A little time with a calculator, a pen and some paper will enable to you confidently stride into your local tyre/wheel supplier and state exactly what you want.

A Case study to help you out
Lead by example - that's a good motto. My Case Study will walk you through the entire process of selecting a new set of wheels and tyres so you can get an idea of what is involved.

Oversizing tyres
If you want the fat look but don't want to go bonkers with new wheels, you can oversize the tyres on the rims usually by about 20mm (to be safe). So if your standard tyres are 185/60 R14s, you can oversize them to about 205mm. But make sure you recalculate the percentage value to keep the sidewall height the same.

Fitment guides
Rochford Tyres has an excellent fitment guide page where they list a ton of combinations and permutations of wheels and tyres for all the popular makes and models. The guide is designed to give you an idea of wheel and tyre sizes that will keep you close to spec for rolling radius. Use the 'Alloy Wheel Search' box at the at top-left of their site. As an added bonus, if you decide to buy anything from them, use the the checkout to get 5% off! Sweet! And finally, you might like to check out this little program written by Brian Cassidy,which helps with tyre size calculation. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Fat or thin? The question of contact patches and grip.
If there's one question guaranteed to promote argument and counter argument, it's this : do wide tyres give me better grip? Fat tyres look good. In fact they look stonkingly good. In the dry they are mercilessly full of grip. In the wet, you might want to make sure your insurance is paid up, especially if you're in a rear-wheel-drive car. Contrary to what you might think (and to what I used to think), bigger contact patch does not necessarily mean increased grip. Better yet, fatter tyres do not mean bigger contact patch. Confused? Check it out: Pressure=weight/area. That's about as simple a physics equation as you can get. For the general case of most car tyres travelling on a road, it works pretty well. Let me explain. Let's say you've got some regular tyres, as supplied with your car. They're inflated to 30psi and your car weighs 1500Kg. Roughly speaking, each tyre is taking about a quarter of your car's weight - in this case 375Kg. In metric, 30psi is about 2.11Kg/cm². By that formula, the area of your contact patch is going to be roughly 375 / 2.11 = 177.7cm² (weight divided by pressure) Let's say your standard tyres are 185/65R14 - a good middle-ground, factory-fit tyre. That means the tread width is 18.5cm side to side. So your contact patch with all these variables is going to be about 177.7cm² / 18.5, which is 9.8cm.
http://www.carbibles.com/tyre_bible_pg2.html (11 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Your contact patch is a rectangle 18.5cm across the width of the tyre by 9.8cm front-to-back where it sits 'flat' on the road. Still with me? Great. You've taken your car to the tyre dealer and with the help of my tyre calculator, figured out that you can get some swanky 225/50R15 tyres. You polish up the 15inch rims, get the tyres fitted and drive off. Let's look at the equation again. The weight of your car bearing down on the wheels hasn't changed. The PSI in the tyres is going to be about the same. If those two variables haven't changed, then your contact patch is still going to be the same : 177.7cm² However you now have wider tyres - the tread width is now 22.5cm instead of 18.5cm. The same contact patch but with wider tyres means a narrower contact area front-to-back. In this example, it becomes 177.7cm² / 22.5, which is 7.8cm.

Imagine driving on to a glass road and looking up underneath your tyres. This is the example contact patch (in red) for the situation I explained above. The narrower tyre has a longer, thinner contact patch. The fatter tyre has a shorter, wider contact patch, but the area is the same on both.

And there is your 'eureka' moment. Overall, the area of your contact patch has remained more or less the same. But by putting wider tyres on, the shape of the contact patch has changed. Actually, the contact patch is really a squashed oval rather than a rectangle, but for the sake of simplicity on this site, I've illustrated it as a rectangle - it makes the concept a little easier to understand. So has the penny dropped? I'll assume it has. So now you understand that it makes no difference to the contact patch, this leads us on nicely to the sticky topic of grip. The area of the contact patch does not affect the actual grip of the tyre. The things that do affect grip are the coefficient of friction and the load on the tyre - tyre load sensitivity. Get out your geek-wear because this is going to get even more nauseatingly complicated now.

http://www.carbibles.com/tyre_bible_pg2.html (12 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

The graph up above here shows an example plot of normalised lateral force (in Kg) versus slip angle (in degrees). Slip angle is best described as the difference between the angle of the tyres that you've set by steering, and the direction in which the tyres actually want to travel. Looking at it, you can see that as the load on the tyre is increased, the peak obtainable lateral force also increases but at a decreasing rate. ie. more load doesn't mean infinitely more lateral force - at some point it's going to tail off. At that point you reach the peak of the curve - the slip angle at the maximum lateral force. Rubber friction is broken into two primary components - adhesion and deformation or mechanical keying. Rubber has a natural adhesive property and high elasticity which allows it readily deform and fill the microscopic irregularities on the surface of any road. This has the effect of bonding to various surfaces, which aids in dry weather grip but is diminished in wet road conditions. Look at this next drawing - this depicts the deformation process as the load varies.

As the load is increased the amount of tire deformation also increases. Increasing the load also increases the contact between the tire and road improving adhesion. As the load increases, the rubber penetrates farther into the irregularities, which increases grip but at a diminishing rate. This next little graph shows the change in deformation friction (Fdef) and the deformation coefficient of friction (Cdef) with change in load.
http://www.carbibles.com/tyre_bible_pg2.html (13 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

As far as cars are concerned, any reduction in load usually results in an increase in the coefficient of friction. So for a given load increasing the contact patch area reduces the load per unit area, and effectively increases the coefficient of friction. If this change in coefficient of friction were not true then load transfer would not be an issue. During acceleration grip is reduced partly from the change is suspension geometry and party from the transfer of load from one set of tires to another. Since the coefficient of friction is changing (non-linearly lower for higher loads), the net grip during acceleration is reduced. In other words maximum grip occurs when all four tires are loaded equally. That last paragraph also explains why dynamic setup on your car is pretty important. In reality the contact patch is effectively spinning around your tyre at some horrendous speed. When you brake or corner, load-transfer happens and all the tyres start to behave differently to each other. This is why weight transfer makes such a difference the handling dynamics of the car. Braking for instance; weight moves forward, so load on the front tyres increases. The reverse happens to the rear at the same time, creating a car which can oversteer at the drop of a hat. The Mercedes A-class had this problem when it came out. The load-transfer was all wrong, and a rapid left-right-left on the steering wheel would upset the load so much that the vehicle lost grip in the rear, went sideways, re-acquired grip and rolled over. (That's since been changed.) The Audi TT had a problem too because the load on it's rear wheels wasn't enough to prevent understeer which is why all the new models have that daft little spoiler on the back. If your brain isn't running out of your ears already, then here's a link to where you can find many raging debates that go on in the Subaru forums about this very subject. If you decide to read this, you should bear in mind that Simon de Banke, webmaster of ScoobyNet, is a highly respected expert in vehicle dynamics and handling, and is also an extremely talented rally driver. It's also worth noting that he holds the World Record for driving sideways........... If you decide to fatten up the tyres on your car, another consideration should be clearance with bits of your car. There's no point in getting super-fat tyres if they're going to rub against the inside of your wheel arches. Also, on cars with McPherson strut front suspension, there's a very real possibility that the tyre will foul the steering linkage on the suspension. Check it first!

Caster, camber, alignment and other voodoo.
http://www.carbibles.com/tyre_bible_pg2.html (14 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Alignment
This is the general term used to gloss over the next three points:

Caster
This is the forward (negative) or backwards (positive) tilt of the spindle steering axis. It is what causes your steering to 'self-centre'. Correct caster is almost always positive. Look at a bicycle - the front forks have a quite obvious rearward tilt to the handlebars, and so are giving positive caster. The whole point of it is to give the car (or bike) a noticeable centre point of the steering - a point where it's obvious the car will be going in straight line.

Camber
Camber is the tilt of the top of a wheel inwards or outwards (negative or positive). Proper camber (along with toe and caster) make sure that the tyre tread surface is as flat as possible on the road surface. If your camber is out, you'll get tyre wear. Too much negative camber (wheels tilt inwards) causes tread and tyre wear on the inside edge of the tyre. Consequently, too much positive camber causes wear on the outside edge. Negative camber is what counteracts the tendency of the inside wheel during a turn to lean out from the centre of the vehicle. 0 or Negative camber is almost always desired. Positive camber would create handling problems. The technical reason for this is because when the tyres on the inside of the turn have negative camber, they will tend to
http://www.carbibles.com/tyre_bible_pg2.html (15 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

go toward 0 camber, using the contact patch more efficiently during the turn. If the tyres had positive camber, during a turn, the inside wheels would tend to even more positive camber, compromising the efficiency of the contact patch because the tyre would effectively only be riding on its outer edge.

Toe in & out
'Toe' is the term given to the left-right alignment of the front wheels relative to each other. Toe-in is where the front edge of the wheels are closer together than the rear, and toe-out is the opposite. Toe-in counteracts the tendency for the wheels to toe-out under power, like hard acceleration or at motorway speeds (where toe-in disappears). Toe-out counteracts the tendency for the front wheels to toe-in when turning at motorway speeds. It's all a bit bizarre and contradictory, but it does make a difference. A typical symptom of too much toe-in will be excessive wear and feathering on the outer edges of the tyre tread section. Similarly, too much toe-out will cause the same feathering wear patterns on the inner edges of the tread pattern. A reader of my site emailed me this which is a nice description of toe-in and toe-out. As a front-wheel-drive car pulls itself forwards, the wheels will tend to pivot arount the king-pins, and thus towards the center of the car. To ensure they end up straight ahead, they should sit with a slight toe-out when at rest. A rear-wheel-drive car pushes itself forward, and the front wheels are rotated by friction... thus they will tend to want to trail the king-pins, and therefor will want to splay apart. To ensure that they run parallel when rolling, they should be given some toe-in when at rest. The perfect 4WD car will have neutral pressure on the front wheels, so have neither toe-in or toe-out... however very few companies make the perfect 4WD, so some will have a small amount to toe-in/out, depending on the dominant axle.

Rotating your tyres.
This is the practice of swapping the front and back tyres to even out the wear, not the practice of literally spinning your tyres around (you'd be surprised how often people seem to get confused by this). I used to believe that this wasn't a good idea. Think about it: the tyres begin to wear in a pattern, however good or bad, that matches their position on the car. If you now change them all around, you end up with tyres worn for the rear being placed on the front and vice versa. However, having had this done a few times both on front-wheel drive and all-wheel-drive vehicles during manufacturer services, I' a bit of a convert. I now reckon it actually is A Good Thing. It results in even overall tyre wear. By this, I mean wear in the tread depth. This is a valid point, but if you can't be bothered to buy a new pair of tyres when the old pair wear too much, then you shouldn't be on the road, let alone kidding yourself that putting worn front tyres on the back and partly worn back tyres on the front will cure your problem. So how should you rotate your tyres? It depends on whether you have 2-, 4-, front- or rear-wheel drive, and whether or not you have unidirectional tyres (meaning, those with tread designed only to spin in one direction). With unidirectional tyres, you can swap the front and rear per-side, but not swap them side-to-side. If you do, they'll all end up spinning the wrong way for the tread. Generally speaking you ought to rotate your tyres every 5,000 miles (8,000km) or so, even if they're showing no signs of wear. The following table shows the correct way to rotate your tyres. Front-wheel drive, non-unidirectional tyres Rear-wheel drive, non unidirectional tyres

http://www.carbibles.com/tyre_bible_pg2.html (16 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

4-wheel drive, non-unidirectional tyres

Any unidirectional tyres

http://www.carbibles.com/tyre_bible_pg2.html (17 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Diagnosing problems from tyre wear.
Your tyre wear pattern can tell you a lot about any problems you might be having with the wheel/tyre/suspension geometry setup. The first two signs to look for are over- and under-inflation. These are relatively easy to spot:

http://www.carbibles.com/tyre_bible_pg2.html (18 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Here's a generic fault-finding table for most types of tyre wear:

Problem
Under-inflation Shoulder Wear Both Shoulders wearing faster than the centre of the tread

Cause
Repeated high-speed cornering Improper matching of rims and tyres Tyres haven't been rotated recently Over-inflation Improper matching of rims and tyres Tyres haven't been rotated recently Improper wheel alignment (especially camber) Tyres haven't been rotated recently Faulty suspension, rotating parts or brake parts Dynamic imbalance of tyre/rim assembly Excessive runout of tyre and rim assembly Sudden braking and rapid starting Under inflation Faulty suspension, rotating parts or brake parts Improper wheel alignment Dynamic imbalance of tyre/rim assembly Tyres haven't been rotated recently Under inflation Improper wheel alignment (faulty toe-in) Bent axle beam

Centre Wear The centre of the tread is wearing faster than the shoulders One-sided wear One side of the tyre wearing unusually fast

Spot wear A part (or a few parts) of the circumference of the tread are wearing faster than other parts.

Diagonal wear A part (or a few parts) of the tread are wearing diagonally faster than other parts.

Feather-edged wear The blocks or ribs of the tread are wearing in a feather-edge pattern

Checking your tyres.
http://www.carbibles.com/tyre_bible_pg2.html (19 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

It's amazing that so many people pay such scant attention to their tyres. If you're travelling at 70mph on the motorway, four little 20-square-centimetre pads of rubber are all that sits between you and a potential accident. If you don't take care of your tyres, those contact patches will not be doing their job properly. If you're happy with riding around on worn tyres, that's fine, but don't expect them to be of any help if you get into a sticky situation. The key of course, is to check your tyres regularly. If you're a motorcyclist, do it every night before you lock the bike up. For a car, maybe once a week. You're looking for signs of adverse tyres wear (see the section above). You're looking for splits in the tyre sidewall, or chunks of missing rubber gouged out from when you failed to negotiate that kerb last week. More obvious things to look for are nails sticking out of the tread. Although if you do find something like this, don't pull it out. As long as it's in there, it's sealing the hole. When you pull it out, then you'll get the puncture. That doesn't mean I'm recommending you drive around with a nail in your tyre, but it does mean you can at least get the car to a tyre place to get it pulled out and have the resulting hole plugged. The more you look after your tyres, the more they'll look after you.

Lies, damn lies, and tyre pressure gauges.
Whilst on the subject of checking your tyres, you really ought to check the pressures once every couple of weeks too. Doing this does rather rely on you having, or having access to a working, accurate tyre pressure gauge. If you've got one of those free pencil-type gauges that car dealerships give away free, then I'll pop your bubble right now and tell you it's worth nothing. Same goes for the ones you find on a garage forecourt. Sure they'll fill the tyre with air, but they can be up to 20% out either way. Don't trust them. Only recently - since about 2003 - have I been able to trust digital gauges. Before that they were just junk - I had one which told me that the air in my garage was at 18psi with nothing attached to the valve. That's improved now and current-generation digital gauges are a lot more reliable. One thing to remember with digital gauges is to give them enough time to sample the pressure. If you pop it on and off, the reading will be low. Hold it on the valve cap for a few seconds and watch the display (if you can). Generally speaking you should only trust a decent, branded pressure gauge that you can buy for a small outlay - $30 maybe - and keep it in your glove box. The best types are the ones housed in a brass casing with a radial display on the front and a pressure relief valve. I keep one in the car all the time and it's interesting to see how badly out the other cheaper or free ones are. My local garage forecourt has an in-line pressure gauge which over-reads by about 1.5psi. This means that if you rely on their gauge, your tyres are all 1.5psi short of their recommended inflation pressure. That's pretty bad. My local garage in England used to have one that under-read by nearly 6 psi, meaning everyone's tyres were rock-hard because they were 6psi over-inflated. I've yet to find one that matches my little calibrated gauge. One reader pointed something else out to me. Realistically even a cheap pressure gauge is OK provided it is consistent. This is easy to check by taking three to five readings of the same tyre and confirming they are all the same, then confirming it reads (consistently) more for higher pressure and less for lower pressure. One last note : if you're a motorcyclist, don't carry your pressure gauge in your pocket - if you come off, it will tear great chunks of flesh out of you as you careen down the road....

Tyre pressure and gas-mileage.
http://www.carbibles.com/tyre_bible_pg2.html (20 of 28) [2/6/2008 7:20:08 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

For the first two years of our new life in America, I'd take our Subaru for its service, and it would come back with the tyres pumped up to 40psi. Each time, I'd check the door pillar sticker which informed me that they should be 32psi front and 28psi rear, and let the air out to get to those values. Eventually, seeing odd tyre wear and getting fed up of doing this, I asked one of the mechanics "why do you always over-inflate the tyres?" I got a very long and technical response which basically indicated that Subaru are one of the manufacturers who've never really adjusted their recommended tyre pressures in line with new technology. It seems that the numbers they put in their manuals and door stickers are a little out of date. I'm a bit of a skeptic so I researched this on the Internet in some of the Impreza forums and chat rooms and it turns out to be true. So I pumped up the tyres to 40psi front and rear, as the garage had been doing, and as my research indicated. The result, of course, is a much stiffer ride. But the odd tyre wear has gone, and my gas-mileage has changed from a meagre 15.7mpg (U.S) to a slightly more respectable 20.32 mpg (U.S). That's with mostly stop-start in-town driving. Compare that to the official quoted Subaru figures of 21mpg (city) and 27mpg (freeway) and you'll see that by changing the tyre pressures to not match the manual and door sticker, I've basically achieved their quoted figures. So what does this prove? Well for one it proves that tyre pressure is absolutely linked to your car's economy. I can get an extra 50 miles between fill-ups now. It also proves that it's worth researching things if you think something is a little odd. It does also add weight to the above motto about not trusting forecourt pressure gauges. Imagine if you're underfilling your tyres because of a dodgy pressure gauge - not only is it dangerous, but it's costing you at the pump too.

What's the "correct" tyre pressure?
How long is a piece of string? Seriously though, you'll be more likely to get a sensible answer to the length of a piece of string than you will to the question of tyres pressures. Lets just say a good starting point is the pressure indicated in the owner's manual, or the sticker inside the driver's side door pillar.I say 'starting point' because on every car I've owned, I've ended up deviating from those figures for one reason or another. On my Subaru Impreza, as outlined above, I got much better gas mileage and no difference in tyre wear by increasing my pressures to 40psi. On my Honda Element, I cured the vague handling and outer-tyre-edge wear by increasing the pressures from the manufacturer-recommended 32/34psi front and rear respectively, to 37psi all round. On my Audi Coupe I cured some squirrelly braking problems by increasing the pressure at the front from 32psi to 36psi. On my really old VW Golf, I cured bad fuel economy and vague steering by increasing the pressures all-round to 33psi. So what can you, dear reader, learn from my anecdotes? Not much really. It's pub-science. Ask ten Subaru Impreza owners what they run their tyres at and you'll get ten different answers. It depends on how they drive, what size wheels they have, what type of tyres they have, the required comfort vs. handling levels and so on and so forth. That's why I said the sticker in the door pillar is a good starting point. It's really up to you to search the internet and ask around for information specific to your car.

The Max. Pressure -10% theory.
Every tyre has a maximum inflation pressure stamped on the side somewhere. This is the maximum pressure the tyre can safely achieve under load. It is not the pressure you should inflate them to. Having said this, I've given up using the door pillar sticker as my starting point and instead use the max.pressure-10% theory. According to the wags on many internet forums you can get the best performance by inflating them to 10% less than their recommended maximum pressure (the tyres, not the wags - they already haves inflated egos). It's a vague rule of thumb, and given that every car is different in weight and handling, it's a bit of a sledgehammer approach. But from my experience it does seem to provide a better starting point for adjusting tyre pressures. So to go back to my Subaru Impreza example, the maximum pressure on my Yokohama tyres is 44psi. 10% of that is 4.4, so 44-4.4=39.6psi which is about where I ended up. On my Element, the maximum pressure is 40psi so the 10% rule started me out at 36psi. I added one more to see what happened and it got better. Going up to 38psi and it definitely went off the boil, so for my vehicle and my driving style, 37psi on the Element was the sweet spot. Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Nitrogen inflation
http://www.carbibles.com/tyre_bible_pg2.html (21 of 28) [2/6/2008 7:20:09 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Nitrogen inflation (nitrogen filled tyres) is one of those topics that gets discussed in car circles a lot. Some people swear by it, whilst others consider it to be an expensive rip off. So what's the big idea? Well there are two common theories on this.

Theory 1: nitrogen molecules are larger than oxygen molecules so they won't permeate through the rubber of the tyre like oxygen will, and thus you'll never lose pressure over time due to leakage. The fact is any gas will leak out of a tyre if its at a higher pressure than the ambient pressure outside. The only way to stop it is a non-gas-permeable membrane lining the inside of the tyre. The science bit: Water is about half the size of either nitrogen or oxygen, so it might diffuse out of the tyre faster, but it would have to be much, much faster to make a difference. Tyres can leak 1-2 psi a month at the extreme end of the scale although it's not clear how much of that is by permeation through the rubber, and how much is through microscopic leaks of various sorts. For a racing tyre to lose significant water during its racing lifetime (maybe an hour or so for Formula 1), the permeation rate would have to be hundreds of times faster than oxygen or nitrogen, so that pretty much cancels out the idea that it's the molecule size that makes the difference. Theory 2: Nitrogen means less water vapour. This is more to do with the thermal properties than anything else. Nitrogen is an inert gas; it doesn't combust or oxidise. The process used to compress nitrogen eliminates water vapor and that's the key to this particular theory. When a tyre heats up under normal use, any water vapour inside it also heats up which causes an increase in tyre pressure. By removing water vapor with a pure nitrogen fill, you're basically going to allow the tyre to stay at a more constant pressure irrespective of temperature over the life of the tyre. In other words, your tyre pressures won't change as you drive. The science bit: The van der Waals gas equation provides a good estimate for comparing the expansions of oxygen and nitrogen to water. If you compare moist air (20°C, 80% RH) to nitrogen, you'll find that going up as far as 80°C results in the moist air increasing in pressure by about 0.01 psi less per litre volume than nitrogen. Moist air will increase in pressure by 7.253psi whereas nitrogen will increase in pressure by 7.263psi. Even humid air has only a small amount of water in it (about 2 mole % which means about 2% by volume), so that all puts a bit of a blunt tip on the theory that it's the differences in thermal expansion rates that give nitrogen an advantage. In fact it would seem to suggest that damp air is marginally better than nitrogen. Go figure. So which option is right - smaller molecules, or less water vapour? It would seem neither. A reader of this site had a good thought on the whole nitrogen inflation thing. He wrote: Some racer who did not know the details of chemistry and physics thought that nitrogen would be better because (insert plausible but incorrect science here) and he started using nitrogen. He won some races and word got out that he was using nitrogen in his tires. Well, it is not expensive to use nitrogen in place of air, so pretty soon everyone was doing it. Hey, until I hear a reason that makes good scientific sense, this explanation seems just as good. Nitrogen inflation is nothing new - the aerospace world has been doing it for years in aircraft tyres. Racing teams will also often use nitrogen inflation, but largely out of conveience rather than due to any specific performance benefit, which would tend to fit with the armchair science outlined above. Nitrogen is supplied in pressurised tanks, so no other equipment is needed to inflate the tyres - no compressors or generators or anything. So does it make a difference to drivers in the real world? Well consider this; The air you breathe is already made up of 78% nitrogen. The composition is completed by 21% oxygen and tiny percentages of argon, carbon dioxide, neon, methane, helium, krypton, hydrogen and xenon. The kit that is used to generate nitrogen for road tyres typically only gets
http://www.carbibles.com/tyre_bible_pg2.html (22 of 28) [2/6/2008 7:20:09 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

to about 95% purity. To get close to that in your tyres, you'd need to inflate and deflate them several times to purge any remaining oxygen and even then you're only likely to get about 90% pure nitrogen. So under ideal conditions, you're increasing the nitrogen content of the gas in the tyre from 78% to 90%. Given that nitrogen inflation from the average tyre workshop is a one-shot deal (no purging involved) you're more likely to be driving around with 80% pure nitrogen than 90%. That's a 2% difference from bog standard air. On top of that, nitrogen inflation doesn't make your tyres any less prone to damage from road debris and punctures and such. It doesn't make them any stronger, and if you need to top them up and use a regular garage air-line to do it, you've diluted whatever purity of nitrogen was in the tyres right there. For $30 a tyre for nitrogen inflation, do you think that's worth it? For all the alleged benefits of a nitrogen fill, you'd be far better off finding a tyre change place that has a vapour-elimination system in their air compressor. If they can pump up your tyres with dry air, you'll get about the same benefits as you would with a nitrogen inflation but for free.

TPMS - Tyre (Tire) Pressure Monitor Systems.
For those of you who live in America and are in to cars, you'll no doubt remember the Ford Explorer / Firestone Bridgestone lawsuits of the early 21st century. A particular variety of Firestone tyre, sold as standard on Ford Explorers, had a nasty knack of de-laminating at speed causing high-speed blowouts, which, because the Explorer was an S.U.V, resulted in high-speed rollover accidents. After the smoke cleared, it turned out that the tyres were particularly susceptible to running at low-pressure. Where most tyres could handle this, the Firestones could not, heated up, delaminated and blammo - instant lawsuit.

The NHTSA ruling.
The American National Highways and Transport Safety Association made some sweeping regulatory changes in 2002 because of the Ford Explorer case. Section 13 of the Transportation Recall Enhancement, Accountability and Documentation (TREAD) Act, required the Secretary of Transportation to mandate a warning system in all new vehicles to alert operators when their tires are under inflated. After extensive study, NHTSA determined that a direct tire pressure monitoring system should be installed in all new vehicles. In a "return letter" issued after meetings with the auto industry, the Office of Management and Budget (OMB) demurred, claiming its cost-benefit calculations provided a basis for delaying a requirement for direct systems. The final rule, issued May 2002, would have allowed auto makers to install ineffective TPMS and would have left too many drivers and passengers unaware of dangerously underinflated tires. The full text of the various rulings and judgments, along with a lot more NHTSA information on the subject can be found at this NHSA link.

Indirect TPMS
Indirect TPMS works without actually changing anything in the wheel or tyre. It relies on a component of the ABS system on some cars - the wheel speed sensors. Indirect TPMS reads the wheel speeds from all 4 ABS sensors and compares them. If one wheel is rotating at a different rate to the other three, it means the tyre pressure is different and the onboard computer can warn you that one tyre is low. Indirect systems don't work if you're losing pressure in all four tyres at the same rate because there is no differential between the rotations. Typically losing pressure in all tyres at once is a result of either incredibly bad luck or driving over a police spike strip.

Current / First / Second generation Direct TPMS.
The current generation of direct tyre pressure monitoring systems all work on the same basic principle, but have two distinctly different designs. The idea is that a small sensor/transmitter unit is placed in each wheel, in the airspace inside the tyre. The unit monitors tyre pressure and air temperature, and sends information back to some sort of central console for the driver to see. This is a prime example of trickle-down technology from motor racing. Formula 1 teams have been using this technology for years and now it's coming to consumer vehicles. At its most basic, the system has 4 lights in the cabin and a buzzer or some other sound. When one of the tyre pressure monitors registers over-temperature or under-inflation, the driver is alerted by a sound and a light indicating which tyre has the problem.

http://www.carbibles.com/tyre_bible_pg2.html (23 of 28) [2/6/2008 7:20:09 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Picture credit: SmarTire

Strap-on sensors. The first type of sensor is a strap-on type. It's about the size of your thumb and it clamped to the inside of the wheel rim with a steel radial belt. SmarTire manufacture an aftermarket kit that can be fitted to most vehicles. Typically these sensors weigh in at about 42g (about 1½ ounces) and the load is centred on the wheel rim. Normal wheelbalancing procedures can compensate for these devices. The downside is that you have the potential for the steel strap to fail and start flailing about inside your tyre, and if you do get a flat, the location of the sensor means it will be crushed and destroyed within the first wheel rotation of your tyre going flat. Then again, these devices are there to warn you of weird operating conditions. They cannot predict a blowout.

Picture credit: Autodax

Valve-stem sensors. The second type of sensor is a small block which forms part of the inside of the tyre valve stem. It's a little smaller than the strap-on type and doesn't have the associated steel band to go with it. Autodax are one of the manufacturers of this type of system. This is the type that you can now get on some GM and Subaru vehicles. These sensors are lighter and weigh about 28g (an ounce). Because they are smaller and are part of the valve stem itself, they are mounted to one side of the wheel rim. Again, regular wheel-balancing can account for this weight. The disadvantage of this system is that because of its proximity to the side of the wheel, a ham-fisted tyre-changer can easily destroy the sensor with the machine that is used to take tyres off the rims. Also, when re-fitting the tyres, the tyre bead itself, if not correctly located, can crush the sensor.
http://www.carbibles.com/tyre_bible_pg2.html (24 of 28) [2/6/2008 7:20:09 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

The third type of sensor is perhaps the easiest to use as an add-on item. PressurePro sell a system where the sensors are actually built in to the dust caps that you screw on to your tyre valves. In their system, the in-car monitor ($199 at the time of writing) plugs into the 12v accessory socket so it requires no in-vehicle wiring. The PressurePro sensors send readings to the in-car unit every 7 seconds via wireless RF. The system alerts you if the pressure in any tyre drops 12.5% below its baseline pressure - the pressure the tyre was at when the sensor cap was first screwed on. 12.5% is actually quite a lot. For a passenger car tyre running at 34psi, 12.5% represents a drop of 4.25; psi. Whilst that's definitely into the danger zone - the reason for TPMS in the first place - a drop of 1psi is enough to begin to affect tyre temperature and gas mileage. Note: the PressurePro system doesn't monitor tyre temperature. I've been in contact with one of the engineering types at PressurePro and will be reviewing their system for these pages in August 2006. One concern I had about this system was the construction of their dustcaps themselves. Built wrong, they could cause the one thing they're designed to prevent - tyre deflation. How? In order for the dustcap-monitor to work, it has to hold the valve stem open once it is screwed on (see also The Low Tech Approach below). If the unit should crack or break under duress whilst it is holding the valve stem open, it could lead to tyre deflation. After speaking to a PressurePro rep, he informed me that there are three failsafes built into the dustcap to prevent this from happening, even if the cap itself begins to distort. The caps are tested up to 300°F (148°C) and down to -40°F (-40°c) for distortion and brittle fracture. Each cap costs $50 retail at the time of writing, so judge for yourself if they're likely to be built better than the low tech approach which cost $19 for four. See the product review page for my test of the PressurePro system.

Dust-cap sensors.

Driver displays. As I mentioned above, the driver displays range from the über simple buzzer and light, to items which would look at home on the bridge of the starship Enterprise. In the SmarTire picture above, you can see their sensor has 4 lights on it to the right of the box - an example of the basic system. The Autodax image shows a more complex system which shows actual pressures and temperatures as well. SmarTire have a second generation display available now which shows a graphic representation of the vehicle along with the problem tyre. Their new system can be set to trigger at specific temperatures and inflation pressures. For example it can go off when the tyre gets too hot, when the pressure goes below a set threshold, or the pressure gets a specified amount below the "starting" pressure (eg if it loses 1psi of pressure). This is SmarTire's second-generation display showing some of their operating modes:

http://www.carbibles.com/tyre_bible_pg2.html (25 of 28) [2/6/2008 7:20:09 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Picture credit: SmarTire

The limits of what TPMS can do. All TPMS systems have limits. These are usually around ±1.5 PSI/.1 BAR in pressure accuracy, and ±5.4°F/3°C temperature accuracy. They cannot warn you of an impending blowout. Tyre blowouts are caused by instantaneous failure of the tyre. However they can tell you about the symptoms that lead to blowouts, and that is the primary reason for having TPMS. Tyre failures are usually preceded by long periods of running at lower-than-acceptable pressures - TPMS would warn you about that. When the tyre pressure is low, the sidewall flexes a lot more, generating more heat - TPMS can tell you about that too. Typically, tyre pressure is transmitted as soon as your vehicle starts moving. Pressure data is then transmitted every 46 minutes randomly, although the sensors read tire pressure every 7 seconds. If the new pressure reading differs from the last transmitted pressure by more than 3 PSI/.21 BAR, then the data is transmitted immediately to alert you of a problem. Tyre temperature is also normally transmitted as soon as the vehicle starts moving. As with pressure data, temperature data is then transmitted every 4-6 minutes randomly. Again the sensors will read the temperature more frequently, however the system will only alert you if the temperature exceeds 80°C/176°F. One thing to note is that if you rotate the tyres on your vehicle, you MUST re-program the receiver unit inside otherwise it will think the sensor is on a different wheel. The hidden down-side of current TPMS. TPMS sensors need power to work. All the current sensors use batteries. Whilst these are rated for about 5 years use, or 250,000 miles, the batteries are not replaceable in any system. The manufacturers don't want a battery cover to come loose and start zipping around inside your tyre. For one it is dangerous to the inside of the tyre and for another, if the battery compartment opened, the battery would come out and you'd lose all sensor data for that wheel. As a result, the batteries are built-in to the sealed unit during manufacture. If you get a dead sensor, you need to buy a whole new one. Also, you know what batteries are like in extreme cold and extreme hot - bear that in mind if you regularly park in snow and ice.... Currently, there are no laws mandating manufacture dates to be put on these third-party systems. So if you buy one from a store, it could be brand new, or it could have been sitting on the shelf for a year. You've been warned.

Next-generation TPMS.
Several companies are working on the battery problem for the sensor modules. As I mentioned above, the basic pitfall of all existing systems is that at some point, the battery will wear out, and you'll need a new sensor. There are a few competing, emerging technologies right now trying to tackle the problem of perfecting transmitter-sensors that don't require a battery.. The Pera Piezotag system relies on the inherent properties of piezoelectric materials - that is a material which
http://www.carbibles.com/tyre_bible_pg2.html (26 of 28) [2/6/2008 7:20:09 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

generates current when pressure is applied to it. The inside of a tyre is constantly at pressure so it seems reasonable that a correctly-manufactured piezoelectric wafer could generate enough current to operate the sensor just from the pressure inside the tyre. The ALPS Batteryless TPMS system (licenced from IQ Mobil, a small German R&D company) is similar to an RFID chip in that it gets its power from the radio signal which interrogates it. Current systems, (including the Pera proposal) are classified as "active" transmitter / receiver systems. The sensors transmit signals of their own accord and the in-car receiver picks them up. The ALPS system is a "passive" RFID transceiver system. The sensors remain dormant and un-powered until the in-car transceiver sends a high-power short-range radio signal out which basically carries a "tell me your status" command. The RF power in the radio signal is enough to cause the RFID unit in the sensor to power up, take a reading, transmit it and power down. Clever eh? The downside of this system is that it's likely to be pricey compared to others coming to the market. There are 9 pcbs in their system; one in each wheel, one in each wheel arch and one in the console. Transense Technologies in England are licensing their technology to SmarTire, Michelin and Honeywell. Unlike the Alps system, Transense's system has only one PCB and employs passive surface acoustic wave sensors (piezo-based again) at the inner end of each tyre valve. Their sensors monitor both pressure and temperature. It's worth noting that Transense hold the patent for resonant SAW technology which expires in 2019. Pera were exposed to this technology in the early 90's and have since come out with their own Piezotag system (see above). Coincidence? Michelin has an inductive (125kHz) system for trucks developed for them by TI, Goodyear and Siemens have a similar technology system for passenger cars. Qinetic (formerly DERA / RAE Farnborough) also have an offering.

The low-tech approach.
If all this electronic wizardry seems too much for you, you can always go to the low-tech approach. Valve-cap pressure sensors. These are available over-the-counter at just about any car parts store and are about as simple a device as you can get. You inflate your tyre, and replace the dust cap on the valve with one of these. If it shows green, you're OK. If it shows yellow, your tyres have lost some pressure. If it shows red, your tyres are dangerously underinflated. This system does of course require you to walk around the car and check each time you want to drive off. There are some drawbacks to this system which you should be aware of. For the pressure sensor to read the tyre pressure, it has to depress the valve stem when its screwed on. This means that the tyre valve is no longer the thing keeping the air in your tyre - it's now the seal between this pressure cap and the screw threads. If it's not snug, it will leak slowly and let air out of your tyre. Secondly, there's the question of balance. If you use these screw-on caps, you should get your wheels re-balanced afterwards because it's adding weight to the rim. Third there's the question of durability - it's better for one of these things to come off completely if you hit a pothole because then the valve stem will re-seal. If you crack the pressure cap, you'll let all the air out of the tyre very quickly. And finally, the question of accuracy. Typically these things are very coarse in their readings. A "yellow" signal might not appear until you're 4psi down, and it might not show red until you're as much as 8psi down. Even 1psi can be a problem so 4psi or 8psi is dangerously underinflated.

The ultra-low-tech approach, and why all this money is being spent in the first place.
Drivers are lazy. That is the very simple reason that all these companies are burning off millions in R&D budgets, sales and marketing. If we all checked our tyre pressures once a week using one of the tyre pressure gauges mentioned above,
http://www.carbibles.com/tyre_bible_pg2.html (27 of 28) [2/6/2008 7:20:09 AM]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

we'd know if there was a problem brewing. That is the ultra-low-tech approach. The problem is that 90% of drivers don't ever bother to check their tyres. They either rely on their servicing mechanic or garage to do it for them, or they rely on blind dumb luck. For as long as uneducated people drive around blissfully unaware of the latent danger in their tyres, governments and safety regulators will mandate TPMS. The real question is this : given how unaware some drivers are of their surroundings and their instruments (think of the number of people you see driving with their indicators on on the motorway, or with their fog lights on in bright sunshine) do we really believe that an extra warning light in the vehicle is going to make any difference? Probably not. The key is that if the system was installed, and it worked, and the driver ignored it, then the car, wheel and tyre manufacturers can no longer be held accountable for blowouts and rollovers.

Some TPMS links.
Google Search. Subaru / GM valve-stem info (PDF file). TyreAlert. A US manufacturer of TPMS products. TyreAlert-UK. A UK manufacturer of TPMS products. Action Imports of Australia, dealing with TPMS products.

Page 1 ------ Page 2

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/tyre_bible_pg2.html (28 of 28) [2/6/2008 7:20:09 AM]

The Wheel and Tyre Bible : An Opinion on TwinTyres

The car Bibles product review page, covering in-depth reviews of motoring accessories from pressure gauges and pumps to fuel economy devices, traffic light changers and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

An opinion on Twintyre systems
Here's some first-hand opinions of the TwinTire system from someone who has been using them since the year dot. Take it away Mike from Perth, Australia:
I recall AVON started it off around 20 years ago but since they were the only manufacturer that it probably wasn't quite as widely accepted until Yokohama added theirs. The AVON does however still have a larger range of tyre sizes for twins I think they go down to a 110 width for the 16" - but I'm not certain. The Avon's are OK but a bit too hard compound for my preference. I like the Yokohama; they have a nice soft compound but wear very well indeed. Considering I have them on a Turbo 3Litre straight six they have lasted 65,000km with quite a bit of 'performance driving'. The only negative thing about the Yokohama is that odd 'memory' effect - where the rubber takes a bit longer to forget its standing-shape when you drive off after a long while standing still - especially if they were a bit deflated. In respect of Wheels, there are about 3 styles I've seen in Perth:
● ● ●

The full dish which looks a lot like a normal flat wheel. The mesh which is the cast equivalent that looks a bit like a wired rim. The spoke which has 5 large spokes - a bit like ROH but better styling - that's the type I have.

On the outside of the wheel is raised alloy lettering which reads 'Crimson, Inc'. Further around the side are three letters 'JIL'. The centre hub has a removable black/yellow plastic motif with the lettering 'JJD WHEELS CONCEPT® PRESENTED BY CRIMSON'. Mine have a 40mm offset. When tyres are fully inflated, the gap between them is about 0.25" and the overall width is about 9.5". I used to run equal tyre pressures of 22PSI all round until I discovered you could tweak the performance by making the inside 4 tyres a little higher in pressure by about 5psi or a bit more until you notice the difference and can deal with it. So I used to have the front inside ones at 26psi, the front outside ones at around 20 to 22psi. The rear inside ones at 32psi and the rear outside ones at 26psi. This was my optimum setting for great breaking and plenty of warning when cornering really hard on stiff suspension. I varied the pressure just a bit if/when I noticed a change in wear pattern or if I had to compensate when swapping front to back to even out the wear overall. When I get my car back on the road I want to try 125/90 on the rear with 125/85 on the front. I had to adjust the toe-in so it's not so severe (around 2mm) as the original 15" tyres had far too severe toe-in of around 6mm. The camber and castor should really be made more precise for twins since they track better. There was a little wandering at about 160 to 180km/h but I felt quite safe even up to 240km/h which was the cars limit, although I think I might select a slightly tighter toe-in for those long country trips. My car was one of those that had a bit of slop in the camber area and I think I could have had better tyre wear had this been set properly.

http://www.carbibles.com/ttyreopinion.html (1 of 2) [2/6/2008 7:20:27 AM]

The Wheel and Tyre Bible : An Opinion on TwinTyres

I suppose an automatic toe-in adjustment for speed might prove useful to further improve stability, save tyre wear and reduce fuel consumption - anyone care to comment on this? If so then feel free to email me. The good thing was I never had a problem with a flat stopping me getting anywhere - the flat could usually be pumped up with that sealer stuff and it would be OK. The handling change is noticeable when one of them goes flat but you can keep going for ages - like 500km without any trouble and the flat one is not damaged and can still be used when the puncture is repaired. I wouldn't recommend travelling this sort of distance with a flat, even with twintyres, but it goes to show that they do the job they're supposed to. By having the tyre pressures as I set them up meant I had lots of warning in terms of feel when I pushed it hard into a corner with a very predictable and surprisingly safe drift when they eventuallydid let go. I used to have Pirelli singles on an older car - they were great for road holding but gave virtually no warning when they'd let go - could be quite dangerous if you've never put the car to it's limits. I think it would be worthwhile trying Pirelli's with those tyre pressure settings (if they made the same sizes - that is). It's like anything I suppose, there are lots of people that proclaim their particular selection over others but, I'd likely stick with the twins for the safety at least. Going through puddles at speed on ordinary singles was always a worry - with the twins it's so much safer and precise. My recommendation if you wish to try twin tyres on your own car for any length of time is to have the camber and castor checked as precisely as possible, I'd even have it done when sitting in the drivers seat so the checks account for the included weight of the driver. Otherwise you might find the normal cars settings could be out quite a bit and this will give you premature wear and might even make the stability appear worse. If you can get those camber/castor correction units then thats the best thing as the twin tyres seem to tolerate less negative camber and less toe in as well but, naturally a bit of experimentation can give improved results.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/ttyreopinion.html (2 of 2) [2/6/2008 7:20:27 AM]

Car Bibles : Nanny Cars

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

Nanny Cars : really, really bad vehicle design.
Nanny cars
What's the point? Have people grown so lazy now that they don't know how to turn vehicle headlights on and off. Can we suddenly not work the windscreen wipers? Holy Jebus - it's annoying when you get into a car now and there's bells and chimes for ignition keys, handbrakes, doors, windows, seatbelts etc. etc. Then you're driving along and the car decides it's too dark and puts the lights on. And You Can't Override It! Then it does the same with the windscreen wipers. Drop of rain? Turn on the windscreen wipers so that they screech back and forth across a dry windscreen, ruining the wiper blades and driving the driver insane. Can you turn this function off? Of course not. It's all very helpful. NOT. So if the manufacturers can put all this "useful" gadgetry in a car, why the hell do we have a single "check engine" light? Why don't we have a multi-function display to actually tell us what's wrong with the engine, instead of just "check engine". Despite being the single most complex piece of machinery in the entire car, all it's faults can be summed up with "check engine." Timing off? Check engine. Fuel cap loose? Check engine. Oil-starved engine about to explode? Check engine. Seatbelt undone? Has it's own light! Key in ignition? Has it's own bell! Apparently, it's more important that we have lights to state the bleeding obvious. Just so long as the drivers side window can be made to totally retract with a single button press. God knows it's so stressful to keep your finger on the button for three seconds.

Speaking of headlights...
I've noticed this phenomenon in more and more cars now : the headlight switch has an "off" position, but it doesn't actually turn the lights off. They come on (in the "off" position) as soon as the ignition is turned on. But then they have an "on" and an "auto" position. These are largely the same - if you can't ever turn the lights off, then they're on. And if they come on when the ignition is turned on, then it's automatic. If they're going to take control of the lights away from the driver then why put in redundant controls? It's a waste of time and money. Another area of creeping rot is automatically-locking doors. I don't want my doors locked when I drive off - that's dangerous. It would perhaps (perhaps) be okay if the door automatically unlocked when you came to a stop, but they don't. They lock, and stay locked. What about seatbelts? Have you seen those automatic seatbelt things that some cars have, where the rear mounting point slides forward across the drivers side door when you turn the ignition off? Clearly we're too lazy to put our seatbelts on now too. The only problem with those things is that they're deathtraps. I only had a rental car with one of those things in once, and in the space of getting in and out of the car just twice, it nearly strangled me once, and trapped my left arm twice. The result was probably the opposite of what the manufacturer intended : I disconnected the seatbelt and drove back to Hertz with it dangling from the ceiling.

Power doors.
Do you know it's actually possible to get power doors in luxury cars now? Not power-sliding doors, like you might find on the side of a minivan, but regular driver and passenger doors that can be commanded to swing open, and swing shut with the push of a button. How lazy is that? I bet that function added yet more complex electronics, safety interlocks and wiring, plus probably another 10- to 20kg in weight to the car, and for what? Who the hell is going to be so lazy that they need push-button doors? Well - I guess the same people that are too lazy to slide the doors in their minivans, or open the tailgates by hand. The top-notch minivans all now come with power tailgates and power sliding side doors too. Why? What purpose do these serve? The adverts show us the lady coming out of the supermarket in the rain with her arms loaded with shopping, and the convenience of having the tailgate open when she gets there. The only problem with that, of course, is that if your arms are loaded with shopping, how are you going to manipulate the key fob to press the button to open the tailgate in
http://www.carbibles.com/nannycars.html (1 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Nanny Cars

the first place? Ah. Didn't think of that did they? Think of the extra weight and complexity these systems introduce. It's not just the door-open door-close logic. They have to have safety interlocks in case someone is in the way of the door. Then they need the motors, levers and other mechanical additions to perform these actions. I bet the reason for the portly 110kg weight-gain in the 2005 Grand Caravan is nothing other than the "convenience features" of power doors. That's the equivalent of last year's model constantly having a passenger in it. A heavy one too. Gas mileage goes down, pollution goes up. But hey! You don't have the stress of leaning out to close your own door any more. The car will do it for you. Until it breaks.

ABS.
I read an article in Popular Science in 2004, and one of the comments in it struck a nerve. The author said that (paraphrased) "Drivers are resistant to new technology, but will inevitably get used to it. When ABS was first introduced, a lot of drivers didn't trust it and thought it would actually increase their stopping distance. Now though, even the most hardened critics wouldn't be without it." Obviously I'm not one of those people then. I think ABS is a blight on modern car designs which causes more dangerous driving and more accidents than it prevents. It's also a pain in the arse. For example - try braking gently as you're going down a moderate hill. If you hit a bump in the road, as the wheels rebound from the bump, most ABS systems will interpret that as lockup. When they do, they brake pedal vibrates and you suddenly find yourself stopping a lot more quickly than you'd intended - the car has effectively taken control away from you. This is invariably followed by a horn and the squeal of tyres from behind you as the next car back is presented with a very sudden stop for no reason. Very dangerous. Another example : emergency stops in snow and ice. There's not an ABS system on the market that can make you stop quicker in snow and ice than good old fashioned driver-powered brakes. The reason is simple. When the wheels lockup, they dig-in to the snow or ice and work their way down to the road surface. With ABS, they just skip around, as you sail merrily into the vehicle in front because the ABS just registered all the wheels locked up and took the brakes off. As a final example, take the one they show a lot on TV : the car braking and swerving around the tractor pulling out of a field on a muddy road. This simply doesn't work for the same reason as the snow and ice above - the wheels lockup because they're skating on wet mud. If they stayed locked up, the tyres would dig in and you'd regain control. Instead, the ABS kicks in and takes your brakes off for you. *SLAM*. Right into the side of the supposed tractor. The problem with ABS is that it's a placebo designed to put to rest the fears of the bad drivers. They think that ABS means they can stop in any situation, which is wrong. It makes people more dangerous on the roads because of this false illusion and I reckon more accidents are caused now by people trying to rely on ABS when it really doesn't work in anything but ideal situations. ie. bone dry, billiard-table-smooth road surfaces. I wish there was a way I could disable the ABS on my Subaru. I felt a lot safer in my older vehicles which had a pure mechanical connection from my brake pedal to the brakes. The intervention of ABS in my current car scares me to death every time I have to use the brakes, because I don't trust it to not take control away from me. I shouldn't have to drive around constantly wondering "is the car going to override what I want it to do?"

The hidden gremlin of ABS - what they don't advertise.
If you look at the statistics for crashes, a large percentage of them are "fender benders" - low-speed impacts that only do a little damage and so slow that the vehicle occupants are in no danger. Less than 15mph normally. I'll give you one guess what the typical "minimum activation speed" is for ABS. That's right. Your average ABS system is useless much below 15mph. Seriously. Try it yourself. Find an empty road on a slight downhill grade - even better if its on a dewy morning. Run your car up to about 15mph and jam on the brakes as hard as you can. The car will skid to a stop and the ABS system will remain totally silent. Absolutely true. So ABS doesn't help prevent the accidents which insurance and safety companies tell us are the most common. Go figure.

Bosch's Predictive Cruise Control
From a Bosch press release: The system works by watching what's around the car, as well as keeping its speed constant. It combines the ABS, the electronic stability programme (ESP) and hydraulic brake assist with the radar sensors of Adaptive Cruise Control (ACC), which will in future also be aided by video sensors.
http://www.carbibles.com/nannycars.html (2 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Nanny Cars

Bosch said it will market predictive safety systems in three stages. The first stage will allow the system to build up a preventive brake pressure by aligning the brake pads to the brake discs if the radar sensor identifies a critical situation, not noticed by the driver, thus putting the hydraulic brake assist in a state of "alert". If the driver hits the brake, he produces the fastest possible response with optimal deceleration values and the shortest possible stopping distance. If the critical situation is alleviated or the brakes are not applied, the state of alert is cancelled. The system will go into volume production during 2005. The second generation of Predictive Safety Systems not only alerts the braking system to a critical situation, it also alerts the driver in time to a critical traffic situation and can thus in many cases prevent the accident. To do this, the system may trigger, for example, a short, violent brake jerk. Bosch is planning to start volume production in 2006. The third stage of upgrading the predictive safety system is by recognising that a crash with the car in front is unavoidable. In this case automatic emergency braking is initiated with maximum vehicle deceleration. This reduces the severity of an accident where the driver has not reacted sufficiently or at all to the preceding warnings. In order to detect with certainty that an impact is unavoidable, other sensors, such as video cameras, must support the radar sensors. Am I the only one that this scares the pee out of? It's bad enough that we've all had ABS forced upon us, but this level of computer intervention is just plain dumb. This is again going to make the roads less and less safe as more and more people drive in the mistaken belief that the car will save them from their own stupidity. Of particular worry is this statement: "if the radar sensor identifies a critical situation, not noticed by the driver". This is truly truly scary. How can a piece of electronics decide that a situation is (a) dangerous and (b) not noticed by the driver ? I don't want some arbitrarily programmed computer trying to decide for me if I'm driving too close. And what about the lunatic in the side road? Human eyes are going to see the car and human minds will think "I wonder if he's going to pull out". A computer will see a block of metal on the side of the road. Does this mean that the computer will freak out and apply the brakes when I pass a postbox? A car parked on the side of the road? Hell - a metal drain cover? Worse still is this statement : "To do this, the system may trigger, for example, a short, violent brake jerk". Good God! So now the car is actually going to jam on the brakes without the driver asking for it? What better way to scare the living shit out of a driver than jam on the brakes without warning. Hell if my car did that and I wasn't expecting it, I can almost 100% guarantee I'd have a crash because I'd likely panic thinking "what the hell?" For the Love of God. If drivers really want to be so taken out of the loop when travelling that they're willing to have some computer make decisions for them, get rid of the car and take the damn train or bus instead. In the realm of truly dumb things to put into a vehicle, this has to be right up there at the top of the list.

If you don't live in America, you've probably not had the displeasure of this aberration of motoring kit. OnStar® is one of those creeping forms of technology that serves no real purpose other than to allow GM to be able to tell where you are at any given point in time. The glossy adverts claim that it's a real boon, because if you lock your keys in your car, you can call OnStar® and they'll remotely unlock it. Or you can call them and get them to flash the lights and horn so you can locate your car in a crowded car park. From their own adverts, in the last year, they've called the emergency services for over 500 airbag deployments, but they've unlocked over 34,000 vehicles. It seems to me that this is a self-fulfilling prophecy. Because people now know that it doesn't matter if they forget where they parked, or leave their keys in their car, they do it more often. OnStar® caters so much to the lowest common denominator of morons and idiots that it's affectionately known as BlondStar now. GM are helping to condition a nation of people too stupid to put one foot in front of the other let alone own or drive a car. So as well as being able to help out idiots, they can book dinner for you because its a hands-free cellphone with operator service. Great - so they provide the distraction for you whilst you're driving too. That normally leads to them alerting the police to your location via GPS when they detect an airbag has gone off because you crashed whilst your attention was diverted talking to a fucking OnStar® advisor! In fact, given the complexity of their system and how deeply
http://www.carbibles.com/nannycars.html (3 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Nanny Cars

it's embedded with the vehicle's onboard computers and engine management systems, they can perform OBD engine diagnostics remotely, which implies they most likely have the power to remote start and remote stop your car from GM HQ. Now if that scares you, then you probably shouldn't think too much about a design "feature" that isn't advertised. OnStar® can remotely activate the in-car microphone and listen to everything you're saying. At your end, you don't even get a red LED to tell you it's on. Worse, they can (and do) actively spy on OnStar®-equipped vehicles and set a precedent in 2005 by having a drunk driver arrested after spying on him using the system. Do you want that sort of invasion of privacy in your vehicle? (full story) Of course all this "convenience" comes at a price. Currently it's $17 a month, and according to some studies, most OnStar® subscribers cancel their subscription after only a year....... Social engineering and OnStar® OnStar® are not the most secure system on the planet either. I decided to perform an experiment in 2003. OnStar® generously list all the vehicles they equip on their website, and the TV commercials at the time were including free subscription to OnStar® in certain promotions. So I travelled the parking lots one day looking for a new GMC Yukon with delivery plates on it. I found a nice black one and took down the info from the delivery plate, which included the dealership where it was bought. Like most Americans, the owner of this vehicle had no regard for crime-prevention, and there on his back seat was a plush briefcase with some documents on top, one of which had his name and address on it. I took a note of them, and the vehicle VIN which is prominently displayed through the windscreen on all American cars. I went down to the dealership and walked around to their service department, and like so many places, they had their identification codes for the various financing partners on a crib sheet on the wall next to the servicing desk, along with the 1-800 numbers for each institution. I'm not going to outline the exact conversations that went on because I don't want to give anyone a "how to" on stealing OnStar®-equipped vehicles, but suffice to say that within two phonecalls, they quite happily unlocked this vehicle for me even though I wasn't the actual owner. Now, I'm not a criminal mastermind, but for 30 minutes work, I basically just got GM to give me a brand new black GM Yukon for nothing! I could have got in, hotwired the car and driven off complete with Mr X's briefcase. Because I'm not a criminal, I opened the vehicle and re-locked all the doors, and left it there, "secure" again. The point of this was to show that OnStar® is fallible. Very fallible. Given the patience and the right set of circumstances, it is possible to use this service for bad rather than good. Imagine if OnStar got hacked, if someone were able to remotely kill your engine when you were travelling at speed....... That isn't something I want in my vehicle.

More electrical "luxury" gizmos = more to go wrong.
On the face of it, companies that built 2-ton steel boxes capable of 125mph in all weathers ought to offer more than 10,000 miles of guarantee. But they tend not to, because they know stuff goes wrong. If they've been building cars for decades and stuff is still going wrong, how then are we supposed to blindly accept the multitude of electronic gizmos which creep into cars to supposedly make our lives easier? That many computers and components just have to be buggy. Of course they are. A website called AutoSpies has had hundreds of readers write in to complain about technological backfires, including buggy software in the BMW 7 series that causes the sports cars to stall at freeway speeds, and electronic suspension failures in Range Rovers that convert the $70,000 SUV into gangsta-style low riders. So bad is the Range Rover problem that some companies have sprung up (pun intended) making an honest living out of ripping the unreliable air-bag system out and replacing it with proper suspension. Worse, the current crop of Toyotas have throttle- and brake-by-wire. And an alarming number of them have driven themselves off without any input from the drivers. A widely posted Associated Press story reported that the Thai minister of finance was trapped inside his BMW when a computer malfunction locked the car's doors and windows; a bystander had to break one of the car's windows with a sledgehammer to let him escape. I don't want drive by wire. I don't want electronic opening doors. I don't want hi tech trip computers, in-car GPS, driving computers, sensors, data input devices and all the other electronic crap that they're putting into cars now. What I want when I buy a car, is, strangely enough, a car. Not a 2-ton entertainment complex on wheels that "interprets" my input. I could care less if the car doesn't like that I've stomped on the accelerator. That probably means I want to go somewhere pretty quick. It does not mean I want the car to analyze why I've stomped on the gas, and then go at it's own pace that it has decided is better for me.

"Integrated" peripherals, hackers and virii.
http://www.carbibles.com/nannycars.html (4 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Nanny Cars

If there's one thing which should put you off getting a car with OnStar, or any other "integrated" system that can communicate via cellphone, it's this: hackers are actively writing and distributing virusses that target in-car computers and get downloaded by integrated cellphones. So that all-singing all-dancing BMW you're driving with the oh-so-useful handsfree built-in cellphone? Don't be surprised if the engine dies unexepectedly. Worse still, if you own a Mercedes, Lexus or any other high-end car with wire-controls (brake-by-wire for example), don't be surprised if one day you put your foot on the brake and nothing happens. Because it won't take very long for a hacker to figure out how to override the car's control computer......In February 2005, Lexus already admitted that it's a problem and "several" owners of its vehicles have had their cars totally disabled by virusses.

Safety cocoons and cosetted drivers
There's a reason people drive around in Volvos, SUVs, and other supposedly safety-conscious cars. It's because it gives them the impression of being safe, of being a safe driver. When you're driving one of these things, it really doesn't matter how you drive because deep down, you know that you'll be safe. Run into a lamp post? The crumple zones and airbags will save you. Shoot a light and get t-boned in the middle of an intersection? Don't worry, the side airbag curtains and indoor crash beams will save you. Drove over a motorcyclist because the thick beams and pillars (full of airbags) obscured 70% of your forward view? Don't worry, the suspension will soak up that dead motorcyclist and his wreck. The problem is that cars are so "safe" to drive now that people's driving habits are deteriorating rapidly. With the THXcertified 8-speaker surround system, the double-pane noise-insulating glass, the air conditioning, the in-seat video units, the cup holders, the buttons, the knobs, the controls, the displays, the GPS navigation system, the OnStar nanny, the power seats, power windows, power roof, power steering adjustment and all the other distrations, cars are actually getting more dangerous to drive, not less. They're not cars, they're mobile living rooms. Volvo's collision prediction system. Volvo have a new "safety" system in their cars now - a collision warning system. A radar sensor is designed to monitor the area in front of the car. If the driver does not react when the car approaches another vehicle from behind, a red light is reflected on the windscreen and a buzzer sounds to alert them of the impending crash. Their TV commercial is brilliant in its utter retardedness; it shows a woman driving along whilst looking down on her passenger seat, riffling through a pile of papers. The buzzer sounds and she looks up to see she's about to crash and applies the brake. It's not bad enough that these super-cossetting steel cocoons are turning marginal drivers into bad drivers, now Volvo are actually implying in their commercials that it's perfectly OK to be driving whilst paying no attention to the road in front of you. This is another in a long-line of so-called "safety" aids which do nothing more than remove responsibility from the driver for their actions. The more safety crap they put into the cars, the worse people drive because they're being led to believe that it doesn't matter how shite they are behind the wheel, they'll be just fine when they have their inevitable crash.

The Spike
The solution of course is simple. Many people have suggested it, but it's politically incorrect to manufacture such a device. Strip the car of everything but the drivers instruments and possibly the radio, and fit a huge, micro-tipped chrome spike to the steering wheel. I guarantee road accidents would plummet and road safety would skyrocket.

http://www.carbibles.com/nannycars.html (5 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Nanny Cars

And so to really badly designed cars
It seems to me that the big auto manufacturers have taken leave of their senses in the last few years, and have mastered the ability to build some truly terrible cars. My most recent experience was with the 2004 Oldsmobile Alero. It seems like an unassuming car from the outside, but when you drive it....well. Where to start? The 'A' pillar is enormous. It's like an elephant's trunk. The result is that it obscures massive amounts of the driver's view of the road. That can't be safe! Yet it's a design feature of a new car. The doors. Very odd. They don't open quite far enough, and have a vicious snap-back mechanism. Several times, I opened the car door and as I let go of the handle, the door bounced off it's bumpstops and closed itself again. Come on guys. Is this really necessary? Then there's the traction control system. This is a modern marvel. When its on, it takes a good one or two seconds to realise you've lost traction. And when its off - well - actually you can't turn it off. There's a button that claims to turn if off, but if, as I did, you spin the wheels for more than three seconds, the car "decides" to turn traction control back on. Ummm? Why? Seemingly simple things like the trip meter reset button - every other car has it in the instrument cluster somewhere. Not the Alero. It's on the dash, tucked behind the steering wheel out of sight of the driver. Should you try to find it and use it when you're actually driving, I hesitate to think of the carnage that would ensue. Still, there's a glimmer of light at the end of the tunnel. GM finally killed off Oldsmobile in 2004 - cars designed by octagenarians for octagenarians. At least we won't have to deal with those dangerous eyesores for much longer. What about the instrument clusters? There's a worrying trend in vehicles now to put the instrument cluster in the centre of the dashboard instead of in front of the driver. Renault have been doing this for years, and the new Mini and some of the new Toyota's have it too. It's not a design thing - it's so that the manufacturers only have to have one set of parts for left-hand and right-hand drive cars. It's dangerous and idiotic design though. In these vehicles, to see your instruments, you have to turn your head and look down, rather than just flick your eyeline down as you would in a normal vehicle. This means your attention as well as your line of sight is off the road completely as you look to the middle of the car to see your speed (or whatever). It's not just American cars either. The current Vauxhall Astra - apart from the awful look of it, the stalks for the indicators and windscreen controls are so short that you can't operate them with your hands on the wheel. You have to reach around the back of the steering wheel to use them. Even if you could just reach them with your fingertips, the ends of the stalks are gloss, black plastic, so there's nothing to grip. Its not just the details that amaze me. In some cases, it's the brazen inyour-face design that just slaps you so hard that you have to say "what the heck?" Take the Chevy Avalanche. That thing must have been designed by a cubist. Look at it. It's hideous. The square arches over round wheels, the acres of black tupperware girdling the bottom of the truck. The 'face' of the truck - did the designer have no sense of proportion or pride? People remember the front of a vehicle. In this case, swathed in plastic and with those horrible square-ish headlights. It's awful. Further design tomfoolery can be seen in vehicles such as the 2004 Nissan Quest (are Coca Cola going to sue them for misuse of the Coke 'Wave' shape), and the abhorrent Infiniti FX. Good Lord would you look at that thing? The wheels are too big, for a start, and the football-field of metal under the side windows is just vile.

But the current grand daddy of truly hideous vehicle "design" has to be the Pontiac Aztek:
http://www.carbibles.com/nannycars.html (6 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Nanny Cars

The exterior of this vehicle is just wrong on so many levels, I don't know where to begin. Again the massive wad of metal under the side windows. The double-stacked nose that so many vehicles are coming out with nowadays (who thought that looked good?). The shunted-up rear end that looks like the designer got 75% of the way through the design and then left the company. What happened to beautiful cars? Some people still make them - the Aston Martin Vanquish is proof of that. And old-school manufacturers used to make them look at the 1960s Ford Mustang. Have the manufacturers now decided that utilitarianism is more important than style? Do they think people want to be safe but could care less what the vehicle that they're driving looks like? I wonder if its the massive asset-guzzling of certain companies which is making this problem worse rather than better? Go to the GM website and you'll see that they now own Chevy, Pontiac, Oldsmobile, Cadillac, Buick, GMC, Saturn, Hummer, Saab and Opel. Go to the Ford website and you'll see that they own Ford, Lincoln, Mercury, Mazda, Volvo, Jaguar, Land Rover and Aston Martin. So much for choice and variety. Bascially, 95% of us are driving around in either a Ford or a GM by any other name. Is nothing sacred? Ford owning Aston Martin for chrissake? That's like - like - like - damn it's so bad I can't even think of a simile to describe it! (Or is that a metaphor?)

Huge engines, terrible performance, appalling gas mileage.
The door swings both ways though, and it seems to hit the designers and the enginemakers on the arse either way. Look at the current Ford Mustang. Fantastic car to look at. Guzzles fuel like it is water and can't drive in anything other than a straight line. So close, yet so far. It never ceases to amaze me how the US car manufacturers are able to build such massive engines with such little power and performance, and such high fuel consumption figures. I think they must have some of the smartest minds in the country working for them, because you really have to be trying hard to make that combination. I mean large engines typically have large power. Not in the US. Large engines tend to be fuel efficient. Not in the US. A colleague of mine recently bought his wife an Audi TT. This has a 1.8 litre engine in it which is turbocharged. He could not believe the power and handling of it compared to his US-built FordChevyGMC. Then the gas-mileage. How could it have so much power and consume so little fuel? When I tackle people about this particular question, the inevitable answer is "American cars, engines and transmissions are designed for comfort, not performance." How can you have a sense of comfort when you drive a car that has a 6-litre V8 engine it, that has such a remote feel to the accelerator that you have to concentrate to tell if the engine is actually on and doing anything? If I stomp on the accelerator of my Subaru Impreza 2.5RS, it takes off like its arse is on fire. If I do the same thing in my friend's 2004 Chevy Impala, a vehicle with twice as many cylinders and three times the capacity, it growls and has a lovely throaty sound, but accelerates like the Queen Mary (whilst no doubt guzzling 6 times as much fuel). The suspension on these vehicles is boaty and remote. The steering is so overpowered that you actually have to steer many American cars in a straight line. Let go of the wheel and the car will start to meander all over the road, eventually ending up on its roof no doubt as the power steering efficiently tries to make a 90 degree turn at 70mph. Things looked up with the Cadillac Catera a few years back. The marketing blitz was "The Caddy That Zigs". I drove one. It had the handling of a 1970's European car, yet it was cutting-edge by American standards. How is it possible with so many imported German, Swedish and Japanese cars, that the US manufacturers can still get away with these sorts of boaty, lousy, wallowy fuel-thirsty vehicles? It's not like the public are uneducated. The aforementioned imports have seen to that.
http://www.carbibles.com/nannycars.html (7 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Nanny Cars

7/70 warranties and tip angles
According to the US motor vehicle testing system, it's actually okay for an SUV to have two wheels leave the ground in an emergency maneuver. I suspect then, that the much-touted 7/70 warranties on Jeeps and the like is a guarantee that they will roll 7 times when you swerve to avoid something at 70mph. I know the reason for the sheer volume of rollover crashes in America. It's the power steering. In line with the nannycar mentality, clearly we're all weak and feeble, and it's the car designer's responsibility to remove the hassle of heavy steering. Ok, this is fine at low speeds - power steering is a great feature when you're parking, or turning at low speeds. But it needs to be moderated. We don't need turbo steering pumps operating at full capacity when we're on the motorways. Last time I drove a Ford Taurus, the power steering was so light that I had to steer the car in a straight line at 70mph. It was the most exhausting drive of my life. Every time I loosened my grip on the wheel, the tyres found a tiny rut in the road, the over-eager power steering kicked in and we were off, weaving left or right. Imagine that same system when someone doses off, is distracted by the in-seat video, is putting on their makeup, reading their annual reports etc, and they realise that they're actually in a car and that to avoid ramming the truck in front of them, they need to change lanes. Jerk-reflex, yank the steering wheel to change lanes. Power steering is at maximum, even though they're doing 70mph. A simple touch of the wheel spins the front wheels of the car to full lock. The car starts a violent turn which flicks the back end out. Once the car has started to slide and is at about 30° to the direction of travel, those front wheels are now at 90° to the direction of travel. They dig-in, the momentum high-sides the car and it goes into a roll. This could all be alleviated by a simple design change - speed-sensitive power steering. Full power at standstill, to zero power steering once you're above 40mph. Here endeth my musings on the subject of the various foibles of car design and manufacture. All comments are truly welcomed.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/nannycars.html (8 of 8) [2/6/2008 7:21:00 AM]

Car Bibles : Fact vs. Fiction about speeding

The Car Bibles - Separating the fact from the fiction about speeding and speedtraps.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Why this page?
So why talk about speeding in a site dedicated to information about car maintenance. Well predominantly to illustrate a point about anti-lock brakes in the Brake Bible but also to show how car maintenance overall plays into accidents in surprising ways.

Speeding - the emotive issue.
A long time ago, I ran a site called the Speedtrap Bible; its purpose was to educate the public about the technology invoked by the police to catch and prosecute people for speeding. Some thought the site was the saviour of drivers, whilst others pretty much directly accused me of single-handedly promoting child murder. Speeding - it's an emotive issue and one which the police and government always use as leverage whenever they get a chance. Constable Tim NiceButDim, when interviewed next to a smouldering pile of twisted metal on the side of the M25 will say "This accident was caused by people speeding, plain and simple." Similarly, Highway Patrol Officer Chad SteroidAbuse, when interviewed next to a smouldering pile of twisted metal on the side of Interstate 15, will say "This accident was caused by excessive speed and nuthin' more." It's the same the world over, but separating actual fact from emotive fiction is always difficult. As part of my research when authoring the Speedtrap Bible, I spent a day at the Transport Research Laboratory in Crowthorne, in England. It's the government's vehicular research centre, with high speed test tracks, crash rooms, drag strips, banked curves and all manner of other test areas set in the lush forests around Bracknell in England. They test everything there from the effectiveness of seatbelts inside a car to the effectiveness of road surfaces and crash barriers outside the car. I was particularly interested in their studies on speed in relation to the cause of accidents. The library at the TRL has copies of all their reports, and the two I spoke to their technicians about (and ended up buying) were TRL323 entitled "A new system for recording contributary factors in road accidents" and TRL325 - "The factors that influence
http://www.carbibles.com/speeding_facts.html (1 of 6) [2/6/2008 7:21:24 AM]

Car Bibles : Fact vs. Fiction about speeding

a driver's choice of speed."

Is speed a contributing factor in most road accidents? TRL323
The short and politically incorrect answer is no, and here's why. TRL Report 323 entitled "A new system for recording contributary factors in road accidents" was a joint project between the TRL and the DETR (Department of Environment, Transport and Regions). It was designed to give true figures for the real causes of accidents taken across 8 representative police forces over 6 months in the summer of 1996. They devised a system based on two main categories: what went wrong, and why? Each of those is divided into subcategories such as failures of the driver or rider, failures of pedestrians etc. The report is a fascinating read for someone like me who has a website to maintain, but could be incredibly dull to most people. So to cut to the chase, there's two sections of information we need to look at. 1. Overall incidence of contributary factors This is a categorised list of all the factors in the report which could contribute to but not necessarily cause an accident. I've reproduced the top 5 items from the report here: All factors involved in accident Description Failure to judge other person's path or speed Behaviour - carelessness / thoughtlessness / recklessness Inattention Looked but did not see Excessive speed Number 623 513 465 436 424 % 10.7% 8.8% 8% 7.5% 7.3% Definite factors involved in accident Number 218 210 130 149 126 % 10.3% 10% 6.2% 7.1% 6%

What this means is that in 7.3% of the accidents, speed was one of many factors, and in only 6% of the accidents was it a definite causal factor. Look at the top 4 factors and you'll see that they can generally be categorised as the old police adage of "driving without due care and attention." More to the point, if you take into account "loss of control" accidents (which covers a multitude of sins including wheels coming off the vehicle, black ice, etc) then according to the report, only 4% of all accidents are caused by loss of control of the vehicle with excessive speed as the primary contributing factor. 2. Incidence of commonest precipitating factors, by type of accident. This is perhaps a more telling chunk of information which aims to show the most common factors involved in different types of accident, such as vehicle-pedestrian, single-vehicle etc. Excessive speed doesn't feature directly in this information because it is considered to be a subcategory of "loss of control" (see above). The government and road safety campaigners will always tell us that pedestrians are killed because of speeding motorists. This simply is not the case. Would you believe a staggering 84% of pedestrians involved in accidents are killed or seriously injured due to their own incompetance? In the TRL report, the prime factors involved in pedestrian fatalities are listed as:
● ● ●

Pedestrian entered carriageway without due care (84%) Vehicle unable to avoid pedestrian in carriageway (12%) "Other" (4%)

So in the real world, it's not motorists tearing up and down town centre roads at speed that is to blame for pedestrian fatalities, but the pedestrians themselves for stepping in front of moving vehicles without bothering to look where they're going. This simple fact alone explains the push in current car design to make more pedestrian-friendly front ends for vehicle. If you can't stop the idiots from blindly wandering into the road, then you need to try to damage them as little as possible when you inevitably run them down. An amusing little sub-note for you here - another report further subcategorises "entering the carriageway without due care", and shows that after dark, 77% of all adult pedestrian fatalities are caused when the pedestrian is above the legal drink-drive limit - ie. is technically classified as drunk - and staggered into the path of an oncoming vehicle. For other types of accidents, the "loss of control" figures were as follows:
http://www.carbibles.com/speeding_facts.html (2 of 6) [2/6/2008 7:21:24 AM]

Car Bibles : Fact vs. Fiction about speeding
● ● ● ●

single vehicle, built-up area - 77% single vehicle, non built-up area - 85% multi-vehicle, built-up area - 15% multi-vehicle, non built-up area - 22%

Remember that "loss of control" covers a wide variety of factors. Excessive speed contributes to only 4.04% of all "loss of control" accidents. On a side note, there's one other grouping of figures which makes for a good read too. It's not technically to do with speeding, but I'm going to include it here so you can see the other sorts of statistics that TRL323 assembles. This one particular section is headed "Attribution of precipitating factors in accidents which involved one car and either a pedestrian or one other vehicle." In other words, where a car was involved, what percentage of those accidents were actually attributable to, or caused by the car?
● ● ●

Car collides with pedestrian - 12% Car collides with bicycle - 79% Car collides with motorcycle - 90%

If you've read my bikes page then you'll know I also own a motorbike and enjoy riding it. I just thought it was an interesting figure that 90% of all motorbike-to-car accidents were caused by the car. And I bet the most common excuse was "didn't see you mate".....

Will reduced speed limits reduce accidents? TRL325
TRL325 - "The factors that influence a driver's choice of speed." This is another TRL report which I bought and had a good old look through. It's a survey of 5080 drivers in an effort to find out what factors contributed to them speeding in the first place. More importantly it also looked at the correlation between speed and accidents and asked the question: if you drop the speed limit, does the accident rate go down? During this study, TRL determined that there were many causes of "speed variation". These included:
● ● ● ● ● ● ●

demographics (age, sex, driving experience, exposure to driving) visual ability driving skill (hazard perception, car handling, judgemental skills) psychological factors (risk tolerance, social deviance, thrill-seeking) temporary states (mood, fatigue, impairment due to drink or drugs, illness) trip characteristics (length, purpose, urgency) car characteristics (performance, comfort, noise levels)

http://www.carbibles.com/speeding_facts.html (3 of 6) [2/6/2008 7:21:24 AM]

Car Bibles : Fact vs. Fiction about speeding
● ●

road environment (road type, design, speed limit, enforcement levels, maintenance) environmental factors (passengers, pedestrians, time of day, signs, local knowledge, weather)

By grouping these factors and arranging them in order of importance, these become: i. Site effects. This includes things such as people's estimation of their speed based on the geometry of their surroundings. ie. you might be used to associating a certain frequency of seeing lamp posts with a certain speed. In a new area, the lamp posts might be further apart, but you're trying to maintain the frequency of site geometry that you're accustomed to, thus driving faster without realising it. ii. Driver effects: age, sex and exposure. This includes things such as how often you drive, and how far you drive. iii. Psychological variables. This includes things such as modern cars being quieter and more comfortable than older cars, thus making it more difficult to determine the speed you are going without glueing your eyes to the speedometer. It also includes factors such as "do you own the car?" - people are more inclined to speed in company cars because the psychological factors tell them the vehicle isn't their responsibility. So what does all this mean? Well, it means that there's not one single feature that causes people to speed. You cannot arbitrarily drop the speed limit, bung up a camera and expect people to slow down. It simply does not work. More to the point, the last paragraph of the report sums up the entire study of why people speed, and how speed is related to accidents: By using predicted speeds as an explanatory variable in the model of accident involvement it is possible to obtain an apparent relationship between speed and accidents. This relationship suggested that a 1% change in an individual driver's choice of speed is associated with a 7.75% change in that individual's accident liability. This 'elasticity' is much greater than that observed between changes in mean speed and accident change on a specific section of road. Of course, the fact that there is an apparent strong "cross-sectional" association between between speed and accidents does not necessarily imply a causal link between the two, and it cannot be assumed that reductions in speed by a particular driver will result in any accident reductions of a size predicted by this association. The association arises from the fact that both speed and accidents are related in similar ways to the same variables - particularly age, experience and exposure.

Speed Cameras Save Lives - the other great lie. TRL595
As a side note, it's worth talking here about another TRL report that was commisioned by the UK government and then quietly hushed up when it too failed to support the 'speed kills' mantra. TRL595 makes for some jolly interesting reading. It is a motorway safety performance study carried out on behalf of the Highways Agency between November 2001 and July 2003. The phrase most often touted about this study is this: "The study showed that there was no significant difference in the rate of Personal Injury Accidents when road works were present." That is in fact entirely true, but one of the things this report also looked at was the presence of speed cameras and their effect on accidents. And this is where it gets interesing. In England, for as long as I can remember, the government have insisted that speed cameras reduce accidents. They insist that cameras are only put in at accident blackspots. Driving groups and individuals like me have always argued that speed cameras are only ever installed to make money, and this belief has always put us at odds with the government's hard line. I was once served with a cease and desist order against my old website (The Speedtrap Bible) by the department of transport, West Sussex police and Thames Valley police. They claimed that by giving out technical information on the operation of different speed monitoring devices, as well as their locations and how to fight speeding tickets, I was essentially putting drivers in danger because (and here's the mantra again) "speed kills and you are condoning speeding." So TRL595 and speed cameras - what's the big deal? I'll give you the executive summary first: At 29 major motorway and road works sites, recording Personal Injury Accident details for an exposure of 4,176 million vehicle kilometres: 1. 2. 3. 4. GATSO-style wet-film speed cameras increase the accident rate at road works by 55% GATSO-style wet-film speed cameras increase the accident rate on open motorways by 32% SPECS-style digital speed cameras increase the accident rate at road works by 4.5% SPECS-style digital speed cameras increase the accident rate on open motorways by 6.7%

There is little statistical error in those numbers - 18 months and 4,176,000,000 vehicle km is, in statistical terms, a bloody huge sample set. The conclusion of this particular section of the report was "The non-works with speed camera PIA rate is significantly greater than the without speed camera rate."
http://www.carbibles.com/speeding_facts.html (4 of 6) [2/6/2008 7:21:24 AM]

Car Bibles : Fact vs. Fiction about speeding

For the anal-retentives amongst you, here is table 3.18 from TRL595 reproduced in all its glory. PIA's Without speed camera Works 6.42 Non-works 6.17 Aggregate Digital Analogue Other With speed cameras Works 20.35 39.60 13.60 6.00 Million vehicle km Without speed camera Non-works Works 19.12 39.97 11.12 7.00 71.80 With speed cameras Non-works 189.70 420.31 94.73 88.03 PIAs Without speed camera Works 0.089 With speed cameras Ratio Without Non-works speed cameras 0.101 0.095 0.117 0.080 1.0 With speed cameras 1.036 0.973 1.172 0.815

Non-works Works 69.03 194.96 428.05 98.89 92.59

Non-works Works 0.089 0.104 0.093 0.138 0.065

How do you get the increase in accident rate out of that table? It's pretty easy. Take a look at the PIA figures for analogue type cameras on open motorway (highlighted in bold). According to the report the accident rate difference in 'non works' areas between those without cameras and those with is 0.089 to 0.117. Some elementary maths to calculate a percentage difference between those two figures gives you 0.117 / 0.089 which is 1.3146, or a 31.46% increase.

Speed cameras vs. drivers - the escalating arms war.
Reports like TRL323, TRL325 and TRL595 do put a bit of a fly in the ointment when it comes to the official line that "speeding causes accidents" Despite the facts, the police and local governments continue to try to strengthen this myth, and use it as their excuse for installing speed cameras. The simple truth of the matter is that speed cameras don't reduce accident numbers. They're simply a method of earning more revenue from unwary drivers. So as new technologies come out to trap motorists, so too do new technologies come out to help them evade the traps. First the police had radar guns, so the motorists got radar detectors. Then the police got laser guns, so the motorists got combined laser and radar detectors. Then the police got speed cameras which were hard to detect with radar detectors, so the motorists got GPS devices with built-in locations for all the cameras. This ridiculous and escalating arms race is all because those in power refuse to admit that they're wrong, and for as long as this situation exists, we, the drivers, will be forced to deal with more and more so-called safety aids in our cars. The ultimate outcome of this is that drivers are dumbing down because they're now expecting their vehicles to be responsible for avoiding accidents, because we're all being fed a constant lie about traffic accident causes. It's a sad cause-and-effect but to quote Al Gore, it's an inconvenient truth.

Blaming the motorist for everything
In case you hadn't figured it out by now, I'm very pro-car and pro-motorbike and totally against the motorist being blamed for everything. Where I live in Utah, there's now a campaign to make drivers solely responsible for mowing down pedestrians who wander out into traffic without looking. That's totally the wrong message, in my book. It places all the burden on the driver to avoid a pedestrian, rather than making the pedestrian responsible for their actions. Things would be different if they all used pedestrian crossings, but they don't - the wander out into traffic like lemmings and get themselves injured and killed on a daily basis. They don't seem to understand that the road is for cars and the pavements (or sidewalk) is for pedestrians. This current campaign makes as much sense as allowing car drivers to drive on the pavements and making the pedestrians responsible for damaging cars in the ensuing carnage (pun intended). Actually, maybe we should drive on the pavements - there seems to be less chance of hitting a pedestrian there. Once again though, ridiculous campaigns like this play into the hands of car manufacturers who will tell you that ABS would help in a situation like this, and once again we're burdened with more 'safety' devices we don't need. This inattentive pedestrian thing is so epidemic that in Europe now, cars are being manufactured to be pedestrian-friendly - to damage them less when you hit them. Another classic case of treating the symptoms of the problem rather than the cause. The picture on the right shows one of the campaign posters on the back of a bus, taken by a passenger in my car with my crappy cellphone camera.

http://www.carbibles.com/speeding_facts.html (5 of 6) [2/6/2008 7:21:24 AM]

Car Bibles : Fact vs. Fiction about speeding

Conclusion : Speeding isn't the problem.
So speed doesn't kill. Well - it does - but in nowhere near the numbers we're told. The police and governments should be spending more time on educating people to drive properly and pay attention - less loss-of-control or inattention accidents would be the result of that. They should spend more time making pedestrians responsible for their own actions instead of blaming drivers. That would reduce the pedestrian culling. They should spend more time and resources banning cellphones and arresting drivers for drunk and drugged driving - all major causes of accidents as supported by dozens of reports. But speeding remains the lowest fruit in the tree and consequently the easiest one to pick, even though it's the single least responsible line item for the cause of accidents. All interesting reports then. I'm not saying they're gospel, but I am far more prepared to believe this type of study than I am prepared to believe politicians. According to these reports, speed is neither a contributing nor definite factor in the majority of road traffic accidents. Nor will reducing vehicle speeds necessarily lead to any reduction in accident rates. Thanks to the TRL for an interesting day out, and the TRL's library and publication services for helping me to find and purchase TRL323 and TRL325 reports.

Links
All the links for relevant sites have now been moved to a dedicated links page which you can find here.

These pages were last updated on 1st February 2008. Copyright © Chris Longhurst 1994 - 2008 unless otherwise noted. The author will respond expeditiously to any intellectual property infringement. Reproduction in whole or in part in any form or medium without express written permission of Chris Longhurst is prohibited. Important Copyright info.

http://www.carbibles.com/speeding_facts.html (6 of 6) [2/6/2008 7:21:24 AM]

Car Bibles : The Fuel and Engine Bible Page 2 of 3

The Fuel and Engine Bible, covering everything you need to know about fuel, petrol, gasoline, octane rating, power, bhp, gas types and grades, 4-stroke and 2-stroke engines, how combustion engines work, carburettors, fuel injection, tuning, tweaking, nitrous, turbos, superchargers, chipping, hybrids, how to keep your engine running at peak fitness and much more.

The Car Bibles

●

Win free stuff

●

What's New?

e-Book / Images

●

Donate!

Copyright, contact, feedback

●

The Bike Bit
●

Rants & Raves Search

I am in no way affiliated with any branch of the motor industry. I am just a pro-car, pro-motorbike petrolhead who is into basic car maintenance. The information on these pages is the result of information-gathering, research and hands-on experience. This site was originally established in 1994 to answer frequent questions in the old transport-related usenet groups. By reading these pages, you agree to indemnify, defend and hold harmless me (Christopher J Longhurst), any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your car or motorbike as a result of what you read here. In short : the advice here is worth as much as you are paying for it.

Page 1 ------ Page 2 ------ Page 3

And so to fuel (or gasoline or petrol)
Petrol (or gasoline if you're American) is a distilled and refined oil product made up of hydrogen and carbons - a hydrocarbon. A long-chain hydrocarbon to be exact (so don't get it on your skin - its carcinogenic). It's designed to be relatively safe to handle, if you're careful. ie. it doesn't spontaneously combust without extreme provocation. When you have a petrol fire, it's not the petrol itself that is burning, it's the vapour, and this is the key to fueling an engine. The carburettor or fuel injectors spray petrol into an air stream. The tiny particles of petrol evaporate into a vapour extremely quickly, and combined in a cloud with the air, it becomes extremely combustible. The smaller the particles from the carburettor jet or fuel injector, the more efficiently the mixture burns.

Detonation, pre-ignition, pinking, pinging and knocking.
Remember I said petrol doesn't spontaneously combust? Well it can if the conditions are right, and the conditions are extreme heat and pressure - exactly the conditions you find in the combustion chamber. When this happens, it's called detonation or pre-ignition. Diesel engines rely on this process because they don't have a spark plug in the traditional sense of the word. However in petrol engines, when this happens (also known as dieseling), it's a Very Bad Thing. Engines are designed to have the fuel-air mix burn at a fixed point in the cycle, not explode randomly. Whilst it might look like an explosion, if you could film it on a super high-speed camera, you'd see the mixture actually burns up very quickly rather than exploding. The video on the right is just that - in-cylinder video of the 4stroke combustion cycle. The intake valve is on the right, the exhaust valve on the left. Detonation, dieseling or preignition are all terms for what happens when the fuel-air mix spontaneously explodes rather than burning. Normally this happens when the mixture is all fouled up, and the engine is running hot. The temperature and pressure build up too quickly in the combustion chamber and before the piston can reach the top of its travel, the mixture
http://www.carbibles.com/fuel_engine_bible_pg2.html (1 of 26) [2/6/2008 7:22:34 AM]

Car Bibles : The Fuel and Engine Bible Page 2 of 3

explodes. This explosion tries to counteract the advancing piston and puts an enormous amount of stress on the piston, the cylinder walls and the connecting rod. From the outside of the engine, you'll hear it as a knocking or pinging sound. The precise sound is very hard to describe because every engine sounds slightly different when it happens. But the best way I can describe it is a constant 'toc toc toc' type knocking sound.
Video credit: Original source unknown. Video also available on YouTube and Google Video.

Compression ratio.
The compression ratio of an engine is the measurement of the ratio between the combined volume of a cylinder and a combustion chamber when the piston is at the bottom of its stroke, and the same volume when the it's at the top of its stroke. The higher the compression ratio, the more mechanical energy an engine can squeeze from its air-fuel mixture. Similarly, the higher the compression ratio, the greater the liklihood of detonation.

Octane ratings - how to stop detonation
So you know that a fuel-air mix, given the right conditions, can spontaneously combust. In order to control this property, all petrols have chemicals mixed in with them to control how quickly the fuel burns. This is known as the octane rating of the fuel. The higher the rating, the slower and more controlled the fuel burns. Put on the geek-shades for a moment and I'll explain octane in more depth. If you don't like being blinded by science, skip down a few paragraphs. For the rest of you, octane is measured relative to a mixture of isooctane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane. An 87-octane gasoline has the same knock resistance as a mixture of 87% isooctane and 13% n-heptane. The octane value of a fuel used to be controlled by the amount of tetraethyl lead in it, but in the 70s and 80s when it became apparent that lead was pretty harmful, lead-free petrol appeared and other substances were introduced to control octane instead.

Measuring octane - RON, MON and the difference between America and the rest of the world.
Just so you know, the octane number is actually an imprecise measure of the maximum compression ratio at which a particular fuel can be burned in an engine without detonation. There are actually two numbers - RON (Research octane number) and MON (Motor Octane Number). The RON simulates fuel performance under low severity engine operation. The MON simulates more severe operation that might be incurred at high speed or high load and can be as much as 10 points lower than the RON. In Europe, what you'll see on the petrol pumps is the RON. However, in America, what you'll see on the petrol pump is usually the "mean" octane number - notified as (R+M)/2 - the average of both the RON and MON. This is why there is an apparent discrepancy between the octane values of petrol in America versus the rest of the world. Euro95 unleaded in Europe is 95 octane but it's the equivalent of American (R+M)/2 89 octane. In America, low altitude petrol stations typically sell three grades of petrol with octane ratings of 87, 89 and 91. High altitude stations typically also sell three grades, but with lower values - 85, 87 and 89.

What factors affect detonation?
There's a bunch of things that can affect how likely an engine is to have detonation problems. The common ones are ambient air temperature, humidity, altitude, your engine's ability to stay cool (ie. the cooling system) and spark timing. Fortunately, nowadays the engine management system of modern cars can compensate for almost all of these by advancing and retarding the ignition timing. This is where the computer slightly adjusts the point in the ignition cycle at which the spark is generated at the spark plug. With older engines that used mechanical points to send current to the spark plugs, adjusting the timing was a manual affair that involved adjusting the distributor cap orientation. Knock sensors. Most modern cars have knock sensors screwed into the engine at multiple places. These actually detect the vibration or shock caused by detonation (rather than trying to detect the sound) and can signal the engine management system to change the ignition timing to reduce or eliminate the problem.

Octane and altitude
http://www.carbibles.com/fuel_engine_bible_pg2.html (2 of 26) [2/6/2008 7:22:34 AM]

Car Bibles : The Fuel and Engine Bible Page 2 of 3

The higher the altitude above sea level, the lower the octane requirement. As a general rule of thumb, for every 300m or 1000ft above sea level, the RON value can go down by about 0.5. For example an 85 octane fuel in Denver will have about the same characteristics as an 87 octane fuel on the coast in Los Angeles. As a practical example of this, I currently live in Salt Lake City which is at around 4,200ft. We travel to Las Vegas from time to time which is at around 2,000ft. Our Subaru has a minimum octane requirement of 89 at sea level - so about 87 where we live. Last time we drove to Vegas, the petrol station we stopped at had run out of 'premium' products so we had to fill up with 85 octane. This, combined with the drop in altitude caused the 'check engine' light to come on because we'd effectively taken the engine from 87 octane at altitude to the equivalent of 83 octane at altitude - way below the minimum required by our car. The following graph gives a rough idea of how the three main grades of petrol in America perform with respect to octane at altitude.

Octane and power
It's a common misconception amongst car enthusiasts that higher octane = more power. This is simply not true. The myth arose because of sportier vehicles requiring higher octane fuels. Without understanding why, a certain section of the car subculture decided that this was because higher octane petrol meant higher power. The reality of the situation is a little different. Power is limited by the maximum amount of fuel-air mixture that can be jammed into the combustion chamber. Because high performance engines operate with high compression ratios they are more likely to suffer from detonation and so to compensate, they need a higher octane fuel to control the burn. So yes, sports cars do need high octane fuel, but it's not because the octane rating is somehow giving more power. It's because it's required because the engine develops more power because of its design. There is a direct correlation between the compression ratio of an engine and its fuel octane requirements. The following table is a rough guide to octane values per engine compression ratio for a carburettor engine without engine management. For modern fuel-injected cars with advanced engine management systems, these values are lowered by about 5 to 7 points.
http://www.carbibles.com/fuel_engine_bible_pg2.html (3 of 26) [2/6/2008 7:22:34 AM]

Car Bibles : The Fuel and Engine Bible Page 2 of 3 Compression ratio 5:1 6:1 7:1 8:1 9:1 10:1 11:1 12:1 Octane 72 81 87 92 96 100 104 108

Octane and gas mileage
Here's a good question : can octane affect gas mileage. The short answer is absolutely, yes it can, but not for the reasons you might think. The octane value of a fuel itself has nothing to do with how much potential energy the fuel has, or how cleanly or efficiently it burns. All it does is control the burn. However, if you're running with a petrol that isn't the octane rating recommended for your car, you could lose gas mileage. Why? Lets say your manufacturers handbook recommends that you run 87 octane fuel in your car but you fill it with 85 instead, trying to save some money on filling up. Your car will still work just fine because the engine management system will be detecting knock and retarding the ignition timing to compensate. And that's the key. By changing the ignition timing, you could be losing efficiency in the engine, which could translate into worse gas mileage. Again as a practical example, my little tale above about our trip to Vegas on low octane gas. (Whether you want to believe some bloke on the internet or not is up to you). On the low octane gas on the trip down, we could barely get 23.5mpg out of the Subaru. Once I was able to fill it up again with premium at the recommended octane rating, we got 27.9mpg on the way back. A difference of 4.4mpg over 450 miles of driving. Doing the maths, you can figure out that by skimping on the price during fill-up, you may save a little money right there and then, but it costs in the long term because you're going to be filling up more often to do the same mileage. My advice? Do what the handbook tells you. After all it's in the manufacturers better interests that you get the most performance out of your car as you can - they don't want you badmouthing them, and in this day and age of instant internet gratification, you can bad-mouth a large company very quickly and get a lot of publicity.

Octane boosters
In some extreme cases, the highest octane fuel available might not solve a knocking or detonation problem. That's normally a symptom of a deeper problem in the engine involving carbon deposits on the cylinder heads, bad spark timing, faulty engine management systems or similar. In these cases, some people choose to add octane booster to their petrol. Basically you fill the tank as normal, then put in a measured amount of octane booster and it further raises the octane level in an attempt to stop the detonation. One of the downsides of this is that it can make the engine harder to start from cold, because the octane booster has made the fuel so much less volatile that it's hard to get it to ignite on the first couple of strokes. Products like Klotz and Redex octane boosters are readily available over the counter in most auto parts stores. Octane boosters are typically used by mis-educated motorcyclists who believe the myth (explained above) that high octane = more power. Octane boosters tested by Fifth Gear. To try to lay the myth about octane boosters giving more power to bed for once and for all, in 2007 the UK TV show Fifth Gear picked four likely candidates and subjected them to rigorous testing. They picked Nitro Hot Shot, NOS Race Only Octane Booster, Wynn's Power Booster and STP Power Booster. All four products make the usual wild claims about increased gas mileage, more bhp and so on and so forth. They took the products to Oxford Brooks University's engine testing lab. The engine was static-mounted so measurements were made at the flywheel. The throttle was computer controlled so they could reproduce the same scenario over and over again. They first did a baseline test to find out peak bhp with regular unleaded petrol. This involved various constant-throttle settings as well as acceleration and deceleration testing, and
http://www.carbibles.com/fuel_engine_bible_pg2.html (4 of 26) [2/6/2008 7:22:34 AM]

Car Bibles : The Fuel and Engine Bible Page 2 of 3

a 1-hour constant-speed run to emulate driving on a motorway in clear traffic. Each product was tested using the identical setup, with a 15 minute 'pure' petrol flush being used in between each test to ensure there was no cross-contamination. The results were interesting. Nitrox Hot Shot, NOS Race Only Octane Booster and Wynn's Octane Booster all reduced the overall power by 2bhp. STP Power Booster reduced it by 6%. Now remember this was measured at the flywheel so by the time you induce all the drag of the gearbox and driveline into that equation, you'd likely be looking at a 5% to 10% drop at the wheels. Impressive results for products that claim to increase your engine's power. In England, octane boosters are typically also sold as "lead replacements" or "4 star additive". A lot of European cars relied on the lead in 4-star petrol for the increased octane. Lower octane unleaded fuels caused a lot of problems when they first appeared, especially with cars that didn't have engine management systems. Knocking and detonation became evident in a lot of cars and for some reason French and German engines were more susceptible than most. Dumping a shot of octane booster in the tank when filling up solved the problem by raising the RON a few points to make it the equivalent of what old leaded petrol had been. Eventually, by the late 90s, most English and European petrol stations introduced LRP lead replacement petrol, and the problem went away. Well. Sort of......
Picture credits: Halfords and Channel 5

Lead Replacement Petrol (LRP) and valve seats
Whilst LRP solved the problem of lower octane unleaded petrol, it introduced a new problem. The lead in leaded petrol also had a secondary function and that was to lubricate the valve seats - the top of the engine block where the valves "park" when not being opened by the cams. With the advent of LRP, detonation went away but the chemicals used to increase octane didn't have any lubricating function. Some older engines started to suffer from increased wear to the valve seats, to the point where the valves could no longer properly close and seal the intake and exhaust ports. There were a couple of high profile cases before I left for America in 2001 but I've never been able to find out the end result. If you have any information on what happened in these cases, drop me a line and I'll include the info here.

The supermarket petrol debate
During the 90s, in England, supermarkets started a price war with the mainstream fuel vendors by opening their own petrol stations and undercutting the Esso's and Shell's of the world by as much as 5%. People flocked to these cheap outlets without doing any proper research and after a couple of years, a lot of vehicles began to suffer as a result. There's an old saying that begins "if it's too good to be true....." In the case of supermarket petrol, there was an obvious reason why it was cheaper - it was the lower grade fuel that the mainstream outlets wouldn't take. Stuff which had been rejected in quality control, or had less additives and detergents than what you might get from Texaco or Philips66. As a result, engines started clogging up and failing emissions test. Gas mileage went down. Engines became lumpy and rough running and eventually the supermarkets were forced to fall in line with the Big Boys, so much so that nowadays they're normally less than 1% cheaper. Skip forwards to 2005 and the summer of high fuel prices in America. Lo and behold, supermarkets started to sprout petrol stations and at the time of writing, a lot of people are in the same "cheap fuel" euphoria that the English were in 10 years ago. Sooner or later there'll be a high profile lawsuit that will put paid to that though. As a substitute for genuinely cheaper fuel, a lot of European supermarket chains now offer cheaper fuel at a price. The catch is that you have to shop with them. Once you buy a certain amount of stuff from their store, they'll knock off a percentage of the price of petrol if you buy it from them. The fuel isn't the cheap and nasty sub-standard stuff of yesteryear that they used to use - it's good, mainstream product. But they can hide the price drop in the cost of the groceries and other items you buy in store. From your perspective, you save £2 a tank when filling up. From the store's perspective, you just spent £100 in shopping so giving you £2 back on your tank of gas is pocket change. In America, some of the big-box chains, like CostCo and Sam's Club are now doing the same thing. Rather than go the "dodgy crappy petrol" route, they're offering discounted petrol for shopping in their stores, discounting the petrol by a couple of cents per gallon as long as you've bought more than $50 of products from them.

http://www.carbibles.com/fuel_engine_bible_pg2.html (5 of 26) [2/6/2008 7:22:34 AM]

Car Bibles : The Fuel and Engine Bible Page 2 of 3

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Fuel filters - without them, all this means nothing
As all this information about petrol and gasoline is starting to run out of your ears, it's worth bringing up the topic of fuel filters. Without fuel filters, none of this information on petrol is worth anything. Why? In an ideal world, every time you fill your tank, the petrol would come from brand new underground tanks, through brand new hoses and nozzles, down a pristeen filler tube into a brand new gas tank. However, back in the real world, that simply isn't the case. Tiny bits of metal flake off components. Things rust. Grit and grime gets into the fuel through many different sources. For the most part, this sediment settles at the bottom of the underground tanks in a petrol station, and at the bottom of the petrol tank in your car. If you're unlucky enough to fill up just after the petrol station has received a load of fuel from a tanker though, all that sediment will be nicely mixed into the petrol, and you'll get a petrol-sediment mix in your petrol tank. Similarly, if you insist on running your petrol tank down to the 'E' mark on the fuel gauge, you'll be sucking up petrol-sediment mix from the bottom of your own tank. It's a good job then that the men in lab coats decided to put in-line fuel filters in your car. These are relatively simple little devices that come in two basic flavours. Carburettor engine fuel filters. These are the plastic in-line fuel filters. They look like a little plastic container with a wavy yellow pad in them. They're typically designed to have the fuel sucked through them via a mechanical crank-driven fuel pump up near the carburettor. In some tuner vehicles you'll find this has been replaced with a tasty little aluminium item, usually anodised in a nice colour, designed to make it nearly impossible to find. Fuel injection filters. These are the metal cannister-type fuel filters that are normally buried under the car somewhere. They're designed to have the fuel pushed through them by an electric highpressure fuel pump, and so the pressure in the fuel line is much higher. This is why they're made of metal. Internally, the filter material is normally finer too.

Why filter the fuel? Won't the debris just burn?
Generally speaking, unless it's metal filings, then yes, most debris that you'd find in a fuel system would burn during combustion but that's not the problem. The problem is getting the fuel into the engine in the first place. Further back up this page you (hopefully) learned about carburettors and fuel injectors. The one thing common to both is the tiny hole at the end of the line where the fuel is finally atomised into the air. A good sized grain of sand would be all it took to block that tiny hole and once that happens, it doesn't matter how clever your engine is, it won't be getting any petrol. That is why you have to filter fuel - to keep particulates from clogging areas of the fuel system vital to its operation. Most manufacturers will tell you that fuel filters are sealed-for-life, or life-time-of-the-car items. Excuse my French but that's total bollocks. In normal operating conditions, in 'first-world' countries, you should change your fuel filter every 75,000 miles (120,000km) or so. If you're into extreme motoring, like round-the-world touring, or working in 'third-world' countries, your fuel filter might need changing as much as every 5,000 miles. That's not a slur on those countries, it's just a fact that the cleanliness of petrol station holding and delivery systems isn't really a hot priority in those countries. Plus, if you're involved in that sort of driving, chances are most of your petrol will come from a rusty metal jerry can.

Why change the filter?
The job of an in-line fuel filter is to filter out sediment and particulates in the petrol that might otherwise cause problems further down the line in the engine. If you think about it, the average car probably has 40 to 50 litres of petrol go through the fuel filter every week. It stands to reason then that eventually the filter is going to become clogged with debris. Once your filter gets clogged, you start to get all sorts of followon problems. In carburettor
http://www.carbibles.com/fuel_engine_bible_pg2.html (6 of 26) [2/6/2008 7:22:34 AM]

Car Bibles : The Fuel and Engine Bible Page 2 of 3

cars, you'll get sporadic and weak fuel supply which will lead to a stuttering engine, or an engine that seems to have no power under acceleration. In a fuel injection system where the fuel line pressures are much greater, a clogged filter can lead to a burned out petrol pump or a b