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  1. #1
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    New Ultegra crank on a 73mm BB shell, can it be done?



    I'm wondering if there's anything that can be done, short of grinding my BB shell down to 68mm, that will make one of these cranks work. Thanks.

  2. #2
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    And another question, is there any way to adjust the chainline of cranks like these, or even swap out the axel for a longer one?

  3. #3
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    I don't think you can make the Ultegra cranks fit on a 73 mm bb shell. Either you have to use a MTB crank (IIRC, XTR and XT use similar external bearing bbs) ) or you have to face the shell down to 68 mm. That's a lot of metal to remove but it can be done.

  4. #4
    Elitist Troglodyte DMF's Avatar
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    Talk about providing the bare minimum of info! You want help, help us help you. I'll assume you're using a Hollowtech II crank as pictured.

    You cannot change the axle or axle length on the crank, or the implied chainline. The "bottom bracket" is simply two screw-in bearings separated by a spacer tube. They screw into the frame so the size, thread, and handedness must match.

    Is your problem that you can't find a 73mm BB? (I don't recall seeing one.)

    How could "grind down" a shell that's already too small?
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  5. #5
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    Quote Originally Posted by DMF
    How could "grind down" a shell that's already too small?
    His shell is already too big. It's 73 mm and the crank requires a 68 mm bb shell.

  6. #6
    Elitist Troglodyte DMF's Avatar
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    Well, he doesn't say what he intends to grind on...

    Btw, there *are* 73mm BBs in the mountain bike line. But I'll say no more until tanner deigns to honor us with more typeage.
    Stupidity got us into this mess - why can't it get us out?

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  7. #7
    no brakes,no problem! -Blanco-'s Avatar
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    Have you tried using the spacers provided with the XTR/XT hollowtech cranks? I don't know if that'd work/be safe etc but its worth a try if you can find them
    "Everyone makes mistakes, the trick is to make the mistakes when nobodys looking"

  8. #8
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    Quote Originally Posted by -Blanco-
    Have you tried using the spacers provided with the XTR/XT hollowtech cranks? I don't know if that'd work/be safe etc but its worth a try if you can find them
    Read the original problem. The spacers are provided to allow XTR/XT cranks to be used on a 68 mm bottom bracket. The make the bb shell WIDER. The problem here is the OP ALREADY HAS a 73 mm bb shell and wants to use a crank that requires a 68 mm shell. He needs to make the shell NARROWER.

  9. #9
    biked well well biked's Avatar
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    Since the frame in question is presumably a mountain bike frame (73mm bb shell), I'm curious, why are you wanting to put such a high end road crankset on it?

    edit: I just noticed this thread is a few months old-
    Last edited by well biked; 12-23-06 at 07:21 PM.

  10. #10
    Senior Member shider's Avatar
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    Just as a side note, road tandems occasionally come with a 73mm bb. (Cannondale for one.)

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