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  1. #1
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    SRAM bottom bracket + shimano crank compatibility?

    I have a SRAM gx (24mm spindle) bottom bracket and just got a new shimano xtr crank- also 24 mm.

    Are there any compatibility issues?

    Thanks
    Mike

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  2. #2
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    I believe your Sram crank is GXP, which has the NDS end of the crank spindle stepped down to 22mm. Shimano cranks are straight 24mm so won't fit through the NDS bearing in a GXP BB.

    I have seen a GXP bb where the 22mm bore in the NDS bearing was created with a reducing insert with a shoulder that created the correct inner race length and offset for GXP. It was possible to remove the insert to fit a Shimano crank. Out of a lot of BBs, I've only seen this one time.
    Do the math.

  3. #3
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    Quote Originally Posted by Lone Rager View Post
    I believe your Sram crank is GXP, which has the NDS end of the crank spindle stepped down to 22mm. Shimano cranks are straight 24mm so won't fit through the NDS bearing in a GXP BB.

    I have seen a GXP bb where the 22mm bore in the NDS bearing was created with a reducing insert with a shoulder that created the correct inner race length and offset for GXP. It was possible to remove the insert to fit a Shimano crank. Out of a lot of BBs, I've only seen this one time.
    Thanks
    It's a SRAM bb92 - would that be different than the GXP?

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  4. #4
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    Quote Originally Posted by crankpuller View Post
    Thanks
    It's a SRAM bb92 - would that be different than the GXP?

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    Put simply, you will need a Shimano BB92 if you want to use that Shimano crank.

  5. #5
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    Right. BB92 basically refers to the BB fitting the frame shell. The BB you get also needs to fit the crank spindle. A GXP spindle is stepped 24/22 mm whereas a Shimano crank is straight 24mm. And, of course, some spindles won't fit a given frame no matter the BB if the spindle is too short or too big in diameter.
    Do the math.

  6. #6
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    Quote Originally Posted by Lone Rager View Post
    Right. BB92 basically refers to the BB fitting the frame shell. The BB you get also needs to fit the crank spindle. A GXP spindle is stepped 24/22 mm whereas a Shimano crank is straight 24mm. And, of course, some spindles won't fit a given frame no matter the BB if the spindle is too short or too big in diameter.
    Awesome- thanks!!!

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  7. #7
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    Quote Originally Posted by Lone Rager View Post
    Right. BB92 basically refers to the BB fitting the frame shell. The BB you get also needs to fit the crank spindle. A GXP spindle is stepped 24/22 mm whereas a Shimano crank is straight 24mm. And, of course, some spindles won't fit a given frame no matter the BB if the spindle is too short or too big in diameter.
    If you want to be technical, a BB92 bottom bracket specifies both a 41mm ID bb shell (92mm wide) AND a 24mm STRAIGHT spindle.

    The wording SRAM uses for their BB that fits the same frame (and GXP stepped 24/22mm spindles) is PF GXP. Same bb shell, different crank.

    It's best not to go too far beyond that, because bottom bracket naming conventions suck balls. Someone who makes a bunch of different bb's needs to step in (like how Cane Creek did for headset sizes) and clear up the muckymuck bb naming.

  8. #8
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    I agree

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