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Cassette change, new chain length?

pete54pete54 Posts: 488
edited August 2010 in Workshop
My chain is worn and I want to change my cassette from a 12-23 to a 12-25 at the same time. I'm not too confident in sizing chains, so would I be correct in assuming that making the new chain one (or two) links longer than the old one would be ok?




  • alfabluealfablue Posts: 8,497
    Just set the chain to the correct length (it is unwise to assume it was correct in the first place). Do this by threading through front and rear mechs (i.e. installed as normal) and set the length so that whilst on big chain ring and small rear sprocket, the jockey wheels on the rear mech are vertically aligned. (This is the method recommended by Shimano, there are other approaches but this works fine on road bikes).
  • domhopsondomhopson Posts: 259
    Have a look at this "how to"

    That should have all the info you need
  • pete54pete54 Posts: 488
    Thanks, I guess it's best to do the job properly. I'll have a look at the Park website. It's not a road bike (Specialized Sirrus), but has a Sora rear mech and a Sugino triple chainset, so I guess that the same principles apply.

  • sungodsungod Posts: 16,058
    as alfablue says, for sora the shimano instructions are that with the chain on largest chain ring and smallest sprocket, the chain length should be adjusted so that the axles of the jockey wheels are verticaly in line

    see for full details
    my bike - faster than god's and twice as shiny
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