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  1. #1
    mtbr member
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    Mar 2006
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    10

    73mm x ??? bottom bracket

    I have a new frame that accepts a 73mm bottom bracket. While I'm building this bike up I want to transfer some of the older components from my first bike to this one to save on costs for the time being.

    I'm transferring a Shimano Acera crankset purchased about 10 years ago. The old bike had a 68mm bottom bracket so unfortunately the BB won't transfer over. I want to buy a bottom bracket that will fit into this new frame and still allow me to use my old crankset.

    My question is: how do I determine what the second digit in the bottom bracket specs should be? It looks like I might have a choice of 73/110 or 73/113. BTW it's a mountain frame and the crankset has 3 chainrings up front.

    Thanks for the help!

  2. #2
    mtbr member
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    Jan 2004
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    2,659
    Someone will correct me if I'm wrong, but the second(longer) number is the spindle length. That is what your crank arms attach to. As for the length well it depends on the chchainline and that depends on the mfr's specs. A "mountain frame" is generic and you need to be specific. Who is the manufacturer?

    Oh if you buy the wrong length it not only will shift improperly it's likely to wear out your drivetrain prematurely.

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