VIEWS: 3 PAGES: 2 POSTED ON: 2/27/2010
Gear Chart for a 53/39 Chain Ring and 11 – 23 Cassette Cogs ( back 39 (Small Chain 53 (Big Chain Ring cassette) Ring – Front - Front Outside) Inside ) Smallest (Outside) > 11 93.7 127.3 12 85.9 116.7 13 79.3 107.7 14 73.6 100.0 Middle of Cassette> 15 68.7 93.3 Middle of Cassette> 16 64.4 87.5 17 60.6 82.4 19 54.2 73.7 21 49.1 66.7 Biggest (Inside) > 23 44.8 60.9 Explanation Cross Chaining Cross-chaining is using gears that put your chain at an extreme angle causing it to "tick" your derailleur as you ride. The gear combinations that cause this are inside front with far outside rear or outside front with far inside rear. Cross-chaining causes extra wear on the chain and on the sprockets you use that way. The same gear is available with another combination of sprockets which allows a straighter chain line. And… Cross chaining will do damage to your chain and rear derailleur. It causes the chain to bend out of its appropriate chain line and puts undue stress on the pivots of the chain. It can also cause the rear derailleur to twist a bit to the left which will put undue stress on the main pivot of the derailleur. Although Shimano has created a 9 speed cassette, it isn't best to make the bike use all 9 speeds per front chainring. A good general rule is to stay away from using the 2 rear cogs that are opposite the front chainring in use. If you do continue to use your 12T cog so frequently, you may also find yourself replacing your cassette sooner than later. This is because your chain is not distributing its force evenly over more cog teeth, which in turn will elongate the few teeth that you are using. In time your chain will begin to skip over the teeth. Having the chain rub the side of the big chainring while using the 12T cog, is not uncommon on any bike. If we were to shim out the bottom bracket to the right to compensate for the chain line, it would cause a worse situation in the opposite orientation (53T,25T). It may also adversely affect the chain line we desire in the lower gears (39T,25T). A more beneficial solution will be use a different gear combination (53T,16T). So from my Gear Chart, if you are using the Big Chainring –( outside front) and the Biggest Cog ( rear inside left cog) (53 and 23) your gear would be 60.9 but you would be cross-chaining. The better gear position would be using the 39 (small gear ring – front) and the 17 (more middle cog at the back) for a gear of 60.6. This would put the chain in more of a straight line. From the colour-coding in the chart, you can see how the gears relate and see the overlap between the big and small chainrings.
"Cogs _ back cassette_"