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  1. #1
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    Using a SI BB30 Road Crank on a MTB

    I've got an SI road crank that needs a home and wondering if I can use it on a mtn bike. Wondering about spacing and clearance.

    Would be using a PF30 Bottom bracket which from I see in the archives would work fine. More concerned about spacers. Guess I also need a different spider to run 2x10 SRAM rings.

  2. #2
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    Which road crank?

    If the spindle is bonded to either crank arm its a definite no because of the short spindle length associated with road cranks. If its the current Hollowgram SL all you have to do is swap the spindle and the chianrings/spider and you can run it easily on a mountain bike.

  3. #3
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    Quote Originally Posted by amillmtb View Post
    Which road crank?

    If the spindle is bonded to either crank arm its a definite no because of the short spindle length associated with road cranks. If its the current Hollowgram SL all you have to do is swap the spindle and the chianrings/spider and you can run it easily on a mountain bike.
    Yeah I can separate the 104mm spindle from both crank arms.

    Do I need a 131mm spindle?
    Does it matter if it is SL or SI?

  4. #4
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    Post a pic.

    The Si's came before the SL's and arnt as light, thats about the only difference.

    I have the 132 on my Flash, its what Cannondale recommends for mountain use. I cant speak on how the 131 would work. I would assume it does though, only 1mm difference.

    For the spider removal/installation of the mountain one you will need Cannondale tool KT012/

  5. #5
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    No pic as I don't have the bike yet, just trying to figure out if it would work with a PF30 BB on a mtn bike. Otherwise I guess it goes to ebay. Thinking even the SI crank would be lighter and maybe stronger than the SRAM XX crank.

    Was reading the SL Owners Manual and it does call a 132 spindle and also calls out a 12mm spacer and 0.5mm shims, neither which I have. Hopefully I can get those from my local C'Dale dealer ala carte.

    That 12mm spacer sort of confuses me. Seems that the cranks won't be centered about the BB if that is used.

  6. #6
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    The Hollowgrams and a picture breakdown of each part of the Hollowgram XX and their weights are in my sig titled "MTB parts on the scale." Subtract maybe 2-3g's off the BB weight because I didnt use some of the spacers to optimize my chainline. They are definitely lighter than XX cranks.

    The Hollowgrams would work in a PF30 frame, the PF30 is just Sram's version of BB30. The difference between the two is that instead of pressing the bearings directly into the frame, the bearings are pre-pressed into a plastic sleeve, which is pressed into the frame. The PF30 and the BB30 are at heart the same thing and therefore there shouldnt be any compatibility issues.

    Quote Originally Posted by Quarq.com
    Press Fit 30 (PF30) is a SRAM-developed version of the BB30 system where the bearings are housed in press-in plastic cups, which are in turn pressed into the frame. This system facilitates looser manufacturing tolerances and promotes improved bearing life. BB30 and PF30 use the same cranks. Link

  7. #7
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    Quote Originally Posted by riding29 View Post
    No pic as I don't have the bike yet, just trying to figure out if it would work with a PF30 BB on a mtn bike. Otherwise I guess it goes to ebay. Thinking even the SI crank would be lighter and maybe stronger than the SRAM XX crank.

    Was reading the SL Owners Manual and it does call a 132 spindle and also calls out a 12mm spacer and 0.5mm shims, neither which I have. Hopefully I can get those from my local C'Dale dealer ala carte.

    That 12mm spacer sort of confuses me. Seems that the cranks won't be centered about the BB if that is used.
    The larger spacer is present for all mtb applications of the Hollowgram crank. It is merely a spacer to cover the "extra" width of the spindle on the drive side to allow for the wave washer and shims to provide preload to the system.

    The cranks will indeed be centered. The Q factor on mtb cranks is obviously going to be wider on both sides, so you will see a lot more spindle showing between the crank and bottom bracket on the mtb vs the road bike. The 12mm spacer merely takes up this space on the drive side.

    The picture in the owners manual is confusing though. It shows the crank splines immediately next to the bearing lip, which is not the case. See photo.
    Attached Thumbnails Attached Thumbnails Using a SI BB30 Road Crank on a MTB-qc070_001.jpg  


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