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Thread: Difference between bb30 x1 cranks and gxp x1 cranks

  1. #1
    Senior Member the drizzle's Avatar
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    Default Difference between bb30 x1 cranks and gxp x1 cranks

    My mate just got some new x1 cranks to fit on his sb6c

    He bent the others so needed to replace them.

    Grabbed some gxp from velo gear and the spindle is 145mm whereas the x1 cranks he pulled off the spindle is 110mm.

    Just wondering if anyone knows if the bb30 cranks will have a shorter spindle?

    What is the difference between the two other than being designed around different bottom brackets?

    I'm a shimano man and want to help him out but have nfi about sram stuff.

    Cheers

  2. #2
    Senior Member The Duckmeister's Avatar
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    BB30 uses a shorter, fatter spindle and narrower BB shell in the frame. There are adaptors to enable fitting a GXP crank to a BB30 frame, but it is not possible to go the other way.
    Just ride the bloody thing and enjoy yourself!

    I build wheels... :wink:

  3. #3
    Senior Member JTmofo's Avatar
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    There are 2 types of sram bb30 spindles, wide and narrow.
    I can't remember off the top of my head what the dimensions are, but there are definitely 2 different widths.
    145mm sound like fat bike cranks..... where 110mm sound closer to the mark. Sb6 is pf42 bb shell.

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    Senior Member JTmofo's Avatar
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    Here's a photo of the bb30 spindles

  5. #5
    Senior Member Zaf's Avatar
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    I've got this covered thanks to my Stumpy teaching me, the hard way, about BB30/PF30.
    Essentially BB30 is narrower spacing across both the Shell and spindle width, but uses much larger diameter bearings to make up the stiffness. The cranks usually cinch down using wave washers or some such mechanism to remove any lateral play, and these make up the difference in shell and spindle width.

    The easiest thing for him to do at this point, if he owns the GXP crank already, is to get a Praxis Kit or a wheels manufacturing external BB that essentially thread into each other inside the BB30 shell, and space the bearings outboard in the same width as a 73mm BSA would. It also solves most, if not all, of the issues with BB30 creaking.

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    Last edited by Zaf; 12-04-2017 at 08:03 PM.

  6. #6
    Senior Member JTmofo's Avatar
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    Sb6 bb is not bb30 compatible. Its press fit 68/73mm, or pf41/bb92.
    Old mate has got the wrong gxp crank, I'd suggest it's a fat bike gxp crank.
    A bb30 crank will not fit.... no matter what adaptor he tries to buy.
    His options are
    1. Send them back and get a 68/73 GXP crank.
    2. Buy a different crank and bb to suit (anything except bb30)

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  7. #7
    Senior Member The Duckmeister's Avatar
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    Quote Originally Posted by JTmofo View Post
    Sb6 bb is not bb30 compatible. Its press fit 68/73mm, or pf41/bb92.
    Make your mind up. It's one of 68mm or 73mm BSA threaded, or 89.5x41 or 92x41 or 92x42mm threadless press-fit, aka BB92.
    Just ride the bloody thing and enjoy yourself!

    I build wheels... :wink:

  8. #8
    Senior Member the drizzle's Avatar
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    ah sweet, thanks gents

    i thought maybe the spindle was longer as gxp has an external shell whereas bb30 was internal but sounds like it isn't even bb30. 2015 sb6c stock build. He said the width of the axle on his gxp cranks was perfect just the spindle was waaaay to long.

    does sound like he may have got fat bike cranks

  9. #9
    Senior Member The Duckmeister's Avatar
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    Seems like it. The assembled width of an external cup threaded or BB92 press-fit GXP-type BB is 96mm. Then allow around 15-20mm extra spindle for the left crank to fit on, a standard GXP should have a spindle around 120mm, give or take a couple.
    Just ride the bloody thing and enjoy yourself!

    I build wheels... :wink:

  10. #10
    Senior Member Zaf's Avatar
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    Just Praxxis Kit it and use the GXP crank.



    Edit: ignore me!! It's a PF92 system, I'm getting it mixed up with the SB5C which runs the PF30. Praxis won't work here.
    Last edited by Zaf; 12-04-2017 at 08:35 PM.

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