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Cogs _ back cassette_


									               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


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.


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.

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