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  1. #1
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    going from 50/34 to 53/39 crank

    Other than moving the front derailleur, do I need to lengthen the chain or anything else?

  2. #2
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    Very possibly the chain... Check the big/big combination and note whether the rear derailleur pulley has enough clearance.

  3. #3
    Senior Member c.miller64's Avatar
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    I just did this in reverse swapping an Ultegra 53/39 for a 50/34. Adjusted the FD and took a couple of links out of the chain.

    More than likely you'll have to add a couple.

  4. #4
    Low car diet JiveTurkey's Avatar
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    Possibly need to lengthen the chain. If the chain was previously sized to be as short as possible with the 50T ring, then it will be too short for 53T. See here: http://sheldonbrown.com/derailer-adjustment.html#chain

    Before adding links, think about this:
    1) Does the chain require a special connecting pin (Shimano) or quick-link? The design of newer chains allows the chains to be stronger, but removing and re-connecting the same pin can damage the outer plate, creating a significant weak spot.

    2) How old is the chain? If it's stretched enough, it may be best to just replace the whole chain.
    Quote Originally Posted by slopvehicle View Post
    Not wearing a helmet makes me more aware of my surroundings. I find myself anticipating the hardness of concrete 50 or 100 feet in front of me, it's almost a zen-like connection between my face and the pavement.

  5. #5
    Low car diet JiveTurkey's Avatar
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    Also, going to a new crank may require a new bottom bracket if the crank/bottom bracket interface is different (square-taper vs. ISIS vs. External, etc.) or a different spindle length is required.
    Quote Originally Posted by slopvehicle View Post
    Not wearing a helmet makes me more aware of my surroundings. I find myself anticipating the hardness of concrete 50 or 100 feet in front of me, it's almost a zen-like connection between my face and the pavement.

  6. #6
    Determined Survivor ejbarnes's Avatar
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    Don't bother changing the botom bracket or even the crank arms.
    Chances are your 50/34 is a 110 not a 130mm.
    I made the same move as you.
    I just ordered a 52/38 set of chain rings.
    The theory is that the change only cost about $150 and if I am planning on a big hard hilly Century the chain rings can go back to 50/34 in a couple of minutes.

    My problem with the 50/34 was that I didn't like the big gear spread. If you are just looking for speed it is not rally going to gain you very much. Why not install a 23-11 or a 25-11 cog? or If you really believe that you have power to burn try a 21-11 cog.

    Much easier to change sprockets than chain rings.
    Life is short. Enjoy the ride.
    James

  7. #7
    cab horn
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    Quote Originally Posted by jtuba View Post
    Other than moving the front derailleur, do I need to lengthen the chain or anything else?
    You have to check the chain length in the big/big combo.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  8. #8
    Senior Member
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    If the problem is the big ratio jump between the 50 and 34 another option would be replacing the 34 with a 36.

    Al

  9. #9
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    Thanks for all of the input. I'm in the process of acquiring parts so I can build up a second bike. I would put the 53/39 on my main bike and put the compact on a second bike. Some good CL deals on cranks now. I'll get some advice from the LBS as far as chains go too.

  10. #10
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    Measure the chain with a good steel ruler.

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