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  1. #1
    bikerpilot
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    SRAM BB30 crank in MTB OSBB help

    I'm working on a 2010 Stumpjumper Expert Carbon 29er. The bottom bracket bearings are fried. According to this chart from Specialized, the BB shell in this bike is not compatible with SRAM BB30 cranks. http://service.specialized.com/colla...om-Bracket.pdf The crank is a SRAM X9, so I was expecting it to be a GXP crank. However, when I pulled the cranks it was a BB30 crank. This leaves me puzzled as to what type of bearings to get. Any suggestions?
    BMC FS01 29 X0
    Redline Monocog 29
    Jamis Supernova
    Rocky Mtn Flow DJ

  2. #2
    old fart
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    Quote Originally Posted by Andrew-FSR View Post
    I'm working on a 2010 Stumpjumper Expert Carbon 29er. The bottom bracket bearings are fried. According to this chart from Specialized, the BB shell in this bike is not compatible with SRAM BB30 cranks. http://service.specialized.com/colla...om-Bracket.pdf The crank is a SRAM X9, so I was expecting it to be a GXP crank. However, when I pulled the cranks it was a BB30 crank. This leaves me puzzled as to what type of bearings to get. Any suggestions?
    If it has BB30 bearings, replace with the same. I assume it is PF30 with press-in BB30 bearings?

  3. #3
    bikerpilot
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    I guess they're BB30 bearings since they accepted a BB30 crank. The shell inner diameter is 42mm, is that standard for a BB30 bearing? Also confused as to how the SRAM BB30 crank fits when the Specialized chart says it's not compatible.
    BMC FS01 29 X0
    Redline Monocog 29
    Jamis Supernova
    Rocky Mtn Flow DJ

  4. #4
    old fart
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    Quote Originally Posted by Andrew-FSR View Post
    I guess they're BB30 bearings since they accepted a BB30 crank. The shell inner diameter is 42mm, is that standard for a BB30 bearing? Also confused as to how the SRAM BB30 crank fits when the Specialized chart says it's not compatible.
    PF30 & BB30 use the same bearings. Can you confirm the use of press-in (PF30) cups?

    As to why the difference between your bike and the docs - duno. Are you sure it is not a 2012 bike?

  5. #5
    bikerpilot
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    It's not PF30, there's no press in cups, just bearings. The bike is definitely a 2010. I think I figured it out though. A BB30 standard bottom bracket shell would be 42mm ID x 68mm wide. The BB shell in the bike is 42mm ID x 84.5mm wide. Therefore a crank built for a standard BB30 BB shell would have a spindle that was too short, so the Specialized chart lists them as incompatible. This crankset is BB30 diameter, but obviously has a longer spindle for whatever reason that is sufficient for the width of this shell. I need to look into this more, but it's what makes sense. The bearings seem to just be BB30 bearings, I got a pair and will press them in tomorrow and expect that will solve the issues. Thanks for the tidbits that helped me figure it out.
    BMC FS01 29 X0
    Redline Monocog 29
    Jamis Supernova
    Rocky Mtn Flow DJ

  6. #6
    bikerpilot
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    Update: when I went to put it back together I figured out that the crank spindle is too long and the shop had rigged some crazy spacer in there to make it work. Guess the Specialized chart was right after all.
    BMC FS01 29 X0
    Redline Monocog 29
    Jamis Supernova
    Rocky Mtn Flow DJ

  7. #7
    old fart
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    Quote Originally Posted by Andrew-FSR View Post
    Update: when I went to put it back together I figured out that the crank spindle is too long and the shop had rigged some crazy spacer in there to make it work. Guess the Specialized chart was right after all.
    How much is the Q of the crank? How big are the spacers?

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