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  1. #1
    Senior Member Plow13's Avatar
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    replacing a chainring

    i have a 46/36 crank up front (cross bike) and 12-25 in the back...Is it possible to remove the 36 ring and replace it with a 34? Or would i be better off going with a 12-27 in the back...
    Cervelo S1 2010 (road) Lemond Alpe d'Huez 2004 (road)
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  2. #2
    cab horn
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    Quote Originally Posted by Plow13 View Post
    i have a 46/36 crank up front (cross bike) and 12-25 in the back...Is it possible to remove the 36 ring and replace it with a 34? Or would i be better off going with a 12-27 in the back...
    You need to answer this question yourself. We're not going to be riding the bike you are using.

    http://www.sheldonbrown.com/gears/
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  3. #3
    Senior Member Torchy McFlux's Avatar
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    Yes, it is possible to replace your 36t ring with a 34. They are available, will fit your crank, and will work fine with your existing front derailleur.
    A Shimano short-cage rear derailleur can handle a maximum cog size of 27t, so you could install that too if you want.

  4. #4
    Senior Member Plow13's Avatar
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    i just wasnt sure if the 12 tooth jump would be too much....i may go with a 34 and 12-27
    Cervelo S1 2010 (road) Lemond Alpe d'Huez 2004 (road)
    Trek 4500 2006 (mtb) Gary Fischer Utopia 2008 (commuter)
    Redline Conquest 2009 (cross) Redline 925 2009 (single speed)

  5. #5
    Senior Member z415's Avatar
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    Operator is on the right path. Knowing the gear inches would help you know how much the differences in gears would affect you. What would be better would be a chart of them all. Google for one - they are pretty common and I have one as a background on my other computer.
    Falling is learning...[SIGPIC][/SIGPIC]...learn to not fall in a box.
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  6. #6
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    If you really need a lower gear, do both. A 36x25 produces a 39 gear-inch low gear and a 34x27 gives you a 34 gear-inch low gear so the difference is significant 13%.

    Shimano's 12x25 and 12x27 cassettes differ only in the largest two cogs so you give up nothing in the smaller, more used, cog spacing.

  7. #7
    Ridin' Hard. planyourfate's Avatar
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    You may also want to replace the chain so you get equal wear.

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