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Changing cassettes and chain length(3 posts)

Changing cassettes and chain lengthLong_and_slow
Jun 12, 2001 9:43 AM
I changed my normal cassette of 12-21 (8 speed) to a 12-25 for a ride in the hills last weekend. At the time I installed a new chain since the old one had some stretch. Now I would like to go back to my 12-21. Will I need to shorten this new chain? Should I buy a new chain for the 12-21 and not mix chains between the two cogs?

Thanks for the help,
re: Changing cassettes and chain lengthGrand Strand Cyclists
Jun 12, 2001 10:33 AM
measure the length of the old chain or compare same to the new chain. the 12-21 and 12-25 should be compatible.
Definitely maybeKerry Irons
Jun 12, 2001 6:32 PM
Since we don't know whether you had the right length for the 12-25, it's hard to tell if you need to shorten by two links (1 inch) with the 12-21. Rule of thumb: unless the chain is hanging slack in your 39/12, you don't need a shorter chain. And if you never use the 39/12 (or XX/12) due to chain angle, then consider whether it hangs slack in your XX/13 before removing any links. Things may well work fine with one chain on both cassettes.