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Truck tyre basics Seminar report ’05
1. INTRODUCTION
The good old pneumatic tyre is now well over a hundred years old, and has
not really changed much from its original concept. John Boyd Dunlop registered
this pneumatic tyre with the British Patent Office in 1888 and is therefore
generally considered to be its inventor. The pneumatic tyre is now an
indispensable feature of our motorized society. Complex tyre behavior is a direct
result of the tyre construction. The two main functions of the tyre, is force
generation in the road plane and suspension of the vehicle mass. The force
generation is made possible by the rubber tread, causing a high friction coefficient
with the road surface. Naturally, there are more areas to take into account when
the combination of components for the tyre is to be selected and calculated.
Areas such as comfort, traction and cornering are covered. Market surveys
carried out in Europe reveal that nowadays more than three quarters of all freight
is transported by truck. In comparison, the next most popular mode of transport,
the railway, carries only an eighth of the total.
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From the cross ply to the radial tyre
After the invention of the pneumatic tyre, it was a further thirty years before the
first crossply tyres were developed for commercial vehicles. Progress in
commercial vehicle technology imposed substantial requirements on crossply
tyres which - despite all the advances made - they were eventually unable to
meet. There are very distinct differences in the construction of radial and cross ply
tyres. Whereas the carrying “air container” on crossply tyres is made from criss
crossing layers of rubberized fabric, on radial tyres it is formed by radially running
plies (casing plies) of rubberized cord (on commercial vehicle tyres steel cord is
normally used). A so-called belt, made up of 3-5 rubberized steel cord belt plies,
prevents or reduces tread deformation caused by tyre deflection or swelling when
the tyre is inflated. On firm road surfaces the radial tyre is superior to the crossply
tyre in many ways. One of the strong points of the crossply tyre, however, is its
good self cleaning tread pattern; its stiffer sidewalls also enhance resistance to
tipping on vehicles with a high centre of gravity, such as cranes. The radial tyre,
however, definitely dominates today's truck sector.
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It was only with the introduction of the radial tyre concept, where substantially
improved design and Materials meant the tyre could meet the necessary
requirements, that development was able to progress and reach the standards we
have today.
The materials that make up a truck tyre
A tyre comprises different components, all of which contain elements in varying
compositions. These elements vary with the size and type of tyre. Listed in the
example below are the elements used
2. TYRE COMPONENTS AND THEIR FUNCTIONS
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1 Tread strip
Material; Rubber compound
Function The tread strip has to provide high wear resistance and good grip under
all road conditions. In some instances the tread strip combines two different
materials (cap and base); the base is there to minimize the tread temperature and
the rolling resistance.
2 Multi-ply steel belts
Material Steel cords embedded in rubber compound
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Function Enhances driving stability reduces rolling resistance and gives the tyre
its long service life. Restricts casing growth and increases the tyre's structural
strength.
3 Steel casing
Material Steel cord
Function Gives the tyre its structural strength and its deflection characteristics;
substantially determines driving comfort.
4. Inner lining
Material Rubber compound
Function Major factor in preventing diffusion of air and moisture in tubeless tyres.
5. Sidewall
Material Rubber compound
Function Protects from lateral scuffing and the effects of the weather.
6 .Bead reinforcement
Material Nylon, aramide, steel cord
Function Securing the end of the steel cord ply on the bead core. Reinforcing the
bead against high shear forces.
7 .Bead core
Material Steel wire embedded in rubber compound
Function Ensures the tyre sits firmly on the rim.
3. TYRE MANUFACTURING
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Supplier industries and manufacturing compounds
The tyre industry draws its raw materials from various sectors of industry. After
appropriate pre-treatment, these materials are then further processed to form
individual semi-finished products.
The steel industry
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Provides high tensile steel, the basic material used in the manufacture of the belt
and the casing (steel cord), as well as in the bead cores (steel wire).
The chemical industry
Supplies a variety of raw materials and accessory agents needed in tyre
manufacture. These are primarily various synthetic rubbers and additives, which
affect, for example, the tires wear resistance, grip and ageing stability.
Natural rubber
Is extracted from specific trees by cutting into the bark. The milky-like liquid
(latex) clots when acids are added and, once it has been washed with water, it is
pressed to form solid bales.
The textile industry
Provides the basic materials for cord manufacture: rayon, nylon, polyester and
aramide fibers. These are used, for example, to manufacture bead
reinforcements. Natural and synthetic rubber bales are divided up, appropriate
quantities measured out, weighed and mixed with other additives in several
stages, in accordance with strictly specified recipes. More than ten different
natural rubber compounds are processed to form the individual components of
modern tyres. These individual tyre components and their functions are described
in detail on pages 10 and 11.
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4. MANUFACTURE OF SEMI-FINISHED PRODUCTS
Steel cord
Steel cord, pre-treated and delivered on bobbins, is fed into a calender via special
coiling devices. It is then embedded in one or more layers of natural rubber.
Depending on the tyre size, this “continuous belt” is cut at a specific angle and to
specified dimensions using guillotine shears; it is then rolled up for further
transport.
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Tread strips
The ductile material manufactured in the mixing plant is extruded to form a
continuous strip. After extrusion, the weight is checked and the tread strip
immersed in a cooling tank. Once it has been cut to the required lengths the
weight is re-checked.
Textile cord
A number of individual textile fibers are fed into the calender via special coiling
devices and then embedded in a thin layer of natural rubber. This “continuous
belt” is cut to the required widths on the shearing machine and rolled up for further
transport.
Steel bead core
The core of a tyre bead is made up of several steel wires, shaped to form a ring
and individually coated with rubber. This ring is then additionally covered with a
core profile made from rubber compound.
Sidewall/inner lining
The extruder is used to produce sidewall patterns featuring different geometry,
depending on the tyre size. The inner lining is impermeable to gases and is
extruded on the calender to a wide, thin layer.
Assembly and vulcanization
The semi-finished products manufactured in the various individual stages referred
to above are gathered on the assembly machine and combined in two stages
(casing and tread layer) to form a moulded blank. Before being vulcanized, the
“moulded blank" is sprayed with a special liquid. In the vulcanization press heat,
pressure and time give it its final shape.
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Final quality controls and dispatch
After vulcanization, the tyres are checked optically and undergo various other
checks. Once the tyres have passed all the tests, they are taken to the delivery
warehouse to be prepared for dispatch.
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5. LEGAL AND STANDARDIZED MARKINGS USED ON
THE TYRE SIDEWALL
1 Manufacturer
(Brand name or logo)
1a Tread pattern reference
2 Size designations
315 = tyre width in mm
80 = aspect ratio (section Height to section width) =80%
R = radial construction
22.5 = rim diameter (code)
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3 Service descriptions
Consisting of 154 = load index for single fitment
150 = load index for dual fitment
L = code letter for speed rating
4 Country of manufacture
5 US load designation
Of single/dual fitment and indication of max. Inflation pressure in psi (1 bar = 14.5
psi)
5a Load range
In accordance with US standard
6 Data as per US safety standard
On inner construction or number of plies, in this case
Tread: under the tread there are five steel cord plies (including carcass)
Sidewall: viewed from the side there is one steel cord ply (in this case the
carcass ply)
7 TWI
Tread Wear Indicator
8 Recommended applications
Only Continental Truck Tyres
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9 Regroovable
The manufacturer has designed the tyre for regrooving
10 Tubeless
Tube Type
11 E = tyres complies with value set forth in ECE-R 54
4 = country code for the country in which the approval number was issued
(Here: 4 = Netherlands)
12 DOT = U.S. Department of Transportation
(Responsible for tyre safety standards)
13 Manufacturer code:
• Tyre factory
• Tyre size
• Tyre model
• Date of manufacture
(Production week/year)
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The most important markings
315/80 R 22.5 154/150 M 156/150 L tubeless
315 - Tyre width in mm
80 - Cross-sectional ratio H: W in %
R - Radial design
22.5 - nominal rim diameter of 15° tapered rim (code)
154 3750 kg tyre load capacity S (single tyre fitment)
150 3350 kg tyre load capacity Tw (twin tyre fitment)
M Speed 130 km/h (81 mph) (156/150)L
Alternative permitted operating code tubeless
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6. TYRE TIPS
Tread depth
The following requirements are law in the majority of European countries:
• Pneumatic tyres on trucks and trailers have to feature tread grooves or sipes
round their entire circumference and over the whole width of the tread area.
• The main grooves on truck tyres have to have a tread depth of at least 1 mm,
1.6 mm or 2 mm, depending on the law in each country. The limit in the UK is
1mm.
The depth of the tread pattern is to be measured in the grooves or sipes; bridge-
like protrusions or reinforcements in the tread base should be ignored in this
context.
• On tyres with wear indicators (TWI = Tread Wear Indicators), the tread depth
should be measured in the grooves where the wear indicators are located.
Wear indicators on commercial vehicle tyres are bridge-like protrusions 1.6 mm
high, which show whether the tyre has reached the wear limit.
The tread depth should therefore never be measured on the wear indicators, but
next to them.
Tyre inflation
One of the most important causes of excessive tyre wear and damage is incorrect
tyre pressure. Service manuals produced by the vehicle manufacturers and
technical documentation from the tyre manufacturers provide information about
correct tyre pressure. These values apply without
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exception to the cold tyre, as the inner pressure of the tyre increases in operation.
Tyre pressure should be checked every 2 weeks, at the latest every 4, on the cold
tyre. Spare tyres must also be checked.
Under inflation leads to
• increased flexing, which makes the tyre overheat and may cause tyre failure;
• increased wear = shorter service life;
• Higher rolling resistance and subsequently increased fuel consumption;
• Irregular wear.
7. REGROOVING
Tyres which can be regrooved are designated
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REGROOVABLE
On the sidewall area. These tyres feature an additional “rubber layer” between the
belt sector and the tread grooves, which is currently between 2 and 4 mm
depending on the tyre size and tread pattern. This rubber layer can be used to
achieve a longer tyre service life by having the tyre regrooved once the
appropriate wear limit is reached on the original tread pattern. A basic continuous
layer of 2 mm must still cover the belt.
8. CONCLUSION
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A 50 per cent reduction in the depth of tread on a new tyre produces a 20 per
cent improvement on rolling resistance. This means that less power is required to
drive a car for a given speed that leads to less fuel consumption. The reduced
power requirement also means a reduction in harmful exhaust emissions
escaping into the environment. While motorists may prefer to have a deeper tread
depth for a longer tyre life, they may not be prepared for the extra fuel
consumption that the 20 per cent worsening of rolling resistance represents.
9. BIBLIOGRAPHY
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www.automobiletyres.com
www.continentaltyres.com
http://www.driveradviser.com/tyre/sidewall.shtml
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ABSTRACT
Complex tyre behavior is a direct result of the tyre construction.
While looking much like a simple rubber doughnut attached to the rim, the tyre
construction is vastly more complex, the two main functions of the tyre, is force
generation in the road plane and suspension of the vehicle mass. The force
generation is made possible by the rubber tread, causing a high friction coefficient
with the road surface. The suspension of the vehicle mass is managed by the
belt, radial cords and beads. The radial cords work like the spokes of a bicycle
rim; a pretension must be exerted by pressurized air inside the tyre to carry the
loads. Naturally, there are more areas to take into account when the combination
of components for the tyre is to be selected and calculated. Areas such as
comfort, traction and cornering are covered.
First and foremost a tyre must have an adequate load capacity and be able
to transmit
• drive
• Brake and
• Lateral forces under all conditions.
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CONTENTS
1. INTRODUCTION ....................................................................... 1
2. TYRE COMPONENTS AND THEIR FUNCTIONS .......4
3. TYRE MANUFACTURING ....................................................6
4. MANUFACTURE OF SEMI-FINISHED PRODUCTS .8
5. LEGAL AND STANDARDIZED MARKINGS ................ 11
6. TYRE TIPS ................................................................................. 15
7. REGROOVING ......................................................................... 17
8. CONCLUSION .......................................................................... 18
9. BIBLIOGRAPHY ..................................................................... 19
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ACKNOWLEDGEMENT
I extend my sincere thanks to Dr.T.C.Peter, Head of the Department
for providing me with the guidance and facilities for the seminar.
I express my sincere gratitude to seminar coordinator
Mr.AlexBernard, Staff in charge, for his cooperation and guidance for
preparing and presenting the seminar.
I also extend my sincere thanks to all other faculty members of
Mechanical Engineering Department and my friends for their support and
encouragement.
SHAMSHEER.E.K
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