Chain length question

mr.b-campag
mr.b-campag Posts: 413
in Workshop
Hi,

Just a quick question - I'm about to replace my chain and also swap to a cassette with a larger bottom gear (28 vs. 25 previously). I'm assuming I would keep the same number of links and the rear mech will provide the additional length required? Just wanted to double check before I take the links out of the new chain.

Thanks in advance for any help.

B

Comments

  • fenix
    fenix Posts: 5,437
    Why not just measure big big and cut it from there ? That's the easiest option if you've changed things.

    https://www.ilovebicycling.com/determine-bike-chain-length/
  • wongataa
    wongataa Posts: 1,001
    Read the installation instructions for your drivetrain manufacturer. In that it will tell you how to size the chain. Going from a 25 to 28 max cog will most likely mean you need a longer chain.
  • mr.b-campag
    mr.b-campag Posts: 413
    Thanks that's a useful link. The problem is I'm waiting on the new cassette to be delivered and the old chain needs to go so as not to cause (any more) damage to the existing cassette and chainrings.
  • mr.b-campag
    mr.b-campag Posts: 413
    OK I'll see what Shimano have to say on the matter as well, good shout.
  • fenix
    fenix Posts: 5,437
    How long have you had the chain ? Can't see a couple more rides making much difference tbh.
  • mr.b-campag
    mr.b-campag Posts: 413
    Not that long, but been doing a lot of long steady rides with loads of gear changes now I'm cycling more in Kent than Surrey! :-)
  • david37
    david37 Posts: 1,313
    its a bike not a mars lander, relax. when yur new chain / cassette arrive use the big big plus 2 and all will be well.

    Take the knee

    your white privilege is causing these ridiculous questions
  • DeVlaeminck
    DeVlaeminck Posts: 9,104
    Cut the new chain slightly longer - can always shorten it later.
    [Castle Donington Ladies FC - going up in '22]
  • reaperactual
    reaperactual Posts: 1,185
    edited June 2020
    fenix said:

    Why not just measure big big and cut it from there ? That's the easiest option if you've changed things.

    https://www.ilovebicycling.com/determine-bike-chain-length/

    This is the way I've always done it on 3x drivetrains. Once fitted put big to big and as long as the rear mech has some forward cage swing left it's long enough. Then put in small, small and providing there isn't any chain sag or slack and mech cage is still under tension then it's all good.
  • ugo.santalucia
    ugo.santalucia Posts: 28,312
    It shouldn't make any difference, as you shouldn't use the big/big combination. I use a range of cassettes and never change the chain length, but I never use the first two sprockets on the big ring
    left the forum March 2023
  • reaperactual
    reaperactual Posts: 1,185
    ugo.santalucia said:

    It shouldn't make any difference, as you shouldn't use the big/big combination. I use a range of cassettes and never change the chain length, but I never use the first two sprockets on the big ring

    Hi Ugo. You're absolutely right about not cross chaining.

    I didn't quite make my intentions for this method clear. It was just a work stand test that I performed to check appropriate chain length after fitting.
  • DeVlaeminck
    DeVlaeminck Posts: 9,104
    If as his name suggests he's on campag he should be fine using big-big occasionally without chain rub - the odd time isn't going to hurt.
    [Castle Donington Ladies FC - going up in '22]
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