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  1. #1
    Senior Member CaptDon's Avatar
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    Changing 12-25 Cassette to 12-27

    I've got a Trek 2.1 Pilot with Ultegra 10 speed system. I would like a litle lower gear and would like to install a 12-27 cassette. Any problems with going to a slightly larger 27 tooth cassette? Would it be a simple cassette swap?

    Thanks,

    Don

  2. #2
    Senior Member Mash Master's Avatar
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    I went from a 11-23 to a 12-27 without any issues. I just swapped the casettes myself and it worked easy. The only thing needed is the special bolt to unlock the casette from the hub.
    - Dave

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  3. #3
    Senior Member CaptDon's Avatar
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    Thanks......already have the tools for the job, just wanted to make sure. Did you notice much of a difference in low gear?

    Thanks,

    Don

  4. #4
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    I think the Ultegra derailleurs are designed to handle 27t and can be tweaked to handle 28t.

  5. #5
    Senior Member z415's Avatar
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    Yes, however, you might need to lengthen your chain depending on how much slack there is already.

    If the chain does indeed turn out to be too short, you would just need to add a link.

    http://bikeforums.net/showthread.php?t=266045

    That is a link to a question I posted concerning something about the chain that should give you and idea of how long the chain needs to be - you can pretty much tell if your chain is off when everything is adjusted correctly and the chain still "auto-shifts".
    Falling is learning...[SIGPIC][/SIGPIC]...learn to not fall in a box.
    Any good American will watch THIS -and- WHERE WAS MY BIKE MADE?

  6. #6
    Senior Member
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    Very unlikely that you would need to adjust the chain length. Just check the big to big combination to make sure the rear derailleur doesn't "bottom out".

    Al

  7. #7
    Senior Member Mash Master's Avatar
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    Quote Originally Posted by CaptDon
    Thanks......already have the tools for the job, just wanted to make sure. Did you notice much of a difference in low gear?

    Thanks,

    Don
    For me it made a huge difference since I went from a 23T to a 27T. I live on top of a 10% hill so it was a god send. I don't notice the gain of one tooth from 11T to 12T, although I suppose I could just mix and match from the casettes to make a franken casette. I'm not that concerned though.
    - Dave

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  8. #8
    Senior Curmudgeon Halfast's Avatar
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    What I liked about the change from 25 to 27 was that I almost never get off the 39 ring on my 53-39-30 triple, and I live in the hill country of central Tejas!! When I do go to the 30, it is some hill!!
    "The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."

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