Do I need to replace the chain if I replace the cassette?
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  1. #1
    EDG is offline
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    Aug 2009

    Question Do I need to replace the chain if I replace the cassette?

    I have a Felt F75 with shimano 105 setup. Shimano 105 SS short cage, shimano chain and a 11-25T cassette. I would like to change the cassette by 12-27 or 11-28 because I have a lot of hills in my area. Now the bike has only 120 miles, is new. I'm not decided yet between SRAM or ULTEGRA. Any advice?
    Thank you!

  2. #2
    Reputation: andulong's Avatar
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    Nov 2006
    More than likely you will need to replace the chain too..unless it is a bit long already. Good info here:

  3. #3
    pmt is offline
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    Aug 2009
    You're probably ok; certainly you're never going to cross chain, so it shouldn't be a problem. Since it's easy enough to swap cassettes, put the new one on and see.

  4. #4
    Banned forever.....or not
    Reputation: MR_GRUMPY's Avatar
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    Aug 2002
    Most people recomend that you replace the bike when you replace the cassette............
    In real life, a two tooth increase in the large cog, seldom requires a chain replacement.
    If your opinion differs from mine, ..........Too bad.
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  5. #5
    Rub it............
    Reputation: frdfandc's Avatar
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    Nov 2007
    Most would recommend replacement of the chain when replacing the cassette. But with only 120 miles on it, I would use the current chain.
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  6. #6
    RoadBikeReview Member
    Reputation: Uprwstsdr's Avatar
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    Jul 2002
    I switched 9-speed Dura-Ace drive chain from a 12-23 to a 12-27 cassette and kept everything else the same with no problems. YMMV.

  7. #7
    RoadBikeReview Member
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    Jan 2009
    With only 120 miles I wouldn't replace the chain.

    But as a general rule understand that while chains wear at a fairly constant rate regardless of the age of the sprockets, the opposite isn't true. Chains will rapidly age sprockets to match their own relative age, so running an older chain will cost you significantly in cassette life.

    If the chain had about 500 miles and had a reusable link, I'd remove it and save it, using a new chain now, and then rotating with the first one every 500 miles or so. Rotating chains prolongs cassette life.

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  8. #8
    Reputation: Mel Erickson's Avatar
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    Feb 2004
    With only 120 miles on the chain there's no reason to replace it unless it will be too short when you go to the larger cog. Make sure your short cage derailleur can handle the new cassette. Shimano states the max capacity for a short cage derailleur is 27 (large ring-small ring + large cog - small cog) but you can typically get a bit more. If you're running a typical crank setup of 53/39 and an 11/28 cassette then you need a derailleur capable of handling 31 (53-39) + (28-11) = 31. That's probably too big for a short cage derailleur. It gets worse if you've got a typical 50/34 compact crank (but then you probably wouldn't need to run a 28/11 cassette).
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