Originally Posted by
cny-bikeman
The chain is too long, even if you are in the small-small on a triple (though that gear should indeed be avoided). Go to Sheldon's or Park tool site and follow carefully the instructions on how to size a chain.
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+1,
The chain is too long for use with the small/small combinations.
Pull the chaiin's lower loop forward and see how much you'd need to shorten t to solve the problem.
However b
efore you cut it, shift (off the bike) to the big/big combination and see how much chain you have to spare. Test by pulling the lower loop forward until it's almost straight with the RD's lower pulley above it. Leave some margin for additional movement, and count how many links you could safely pull forward, and this is the maximum number of links you can cut off.
If the number of links you want to cut off is more than the big/big combination would allow, the RD has insufficient take capacity for your gear combination. You have two choices, replace the RD with one of greater capacity (longer cage), or cut the chain based on the big/big combination, and live with some limitations with the small chainring.
It's absolutely critical, that the chain can safely loop the big/big pair with an inch to spare, because if you were to (accidentally) shift into a combination for which it's too short, the chain will cause serious to the RD, hub, and/or crank set.