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Chain length for short cage mech

dandldandl Posts: 24
in Workshop
I want to (possibly temporarily) use a short cage rear mech on a set up that should ideally have a medium cage. Front chainrings are 50/34 and rear sprockets are 11-34. I wont be bothering the biggest 3 or 4 sprockets in the big ring so happy to use the short cage mech that is on the bike at the moment if I can. My question is, what is the best way to calculate chain length for this? Should I take for instance the 26 tooth sprocket as my largest and measure chain length using that or would I just be better using my largest 34 sprocket for the measurement as normal.

Posts

  • MattFalleMattFalle Posts: 11,644
    https://www.parktool.com/blog/repair-help/chain-length-sizing
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • dandldandl Posts: 24
    So basically, use the tried and tested methods as for the correct length rear mech? I'll do that and see how it goes.
  • MattFalleMattFalle Posts: 11,644
    yes.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • lesfirthlesfirth Posts: 1,381
    edited March 2022
    Make sure that your chain is long enough to go on big ring and sprocket. I know you do not intend using that combo but the chain is not long enough and you forget and select big/big , you will get a very expensive bang. If your chain is too long in small ring and small sprocket you will have a droopy chain ,that is no problem but you will not be using that combo anyway.
  • masjermasjer Posts: 2,357
    edited March 2022
    I'd adjust the rear mech (L-screw) so you can't accidentally select 1st or 2nd. As lesfirth has said, you could rip the mech off. Some short cage mechs can handle a larger cassette, but the older ones aren't so forgiving.
  • dandldandl Posts: 24
    Makes perfect sense. I will ensure enough chain for big ring/big sprocket just in case. Thanks.
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