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Discussion Starter · #1 ·
I purchased a new RaceFace Evolve Crankset with a 68 108mm ISIS SRX combo on ebay a month ago nothing thinking about sizes due to my ignorance and newbieness. During installation everything went smooth. The problem I have is that my front deraileur wacks the crap out of the top crank during low shifting.

I realize that the BB is short and after doing some research on my IronHorse Warrior, a guy in WA stated by his books its at 68/116 BB that I need to add. I have looked for a ISIS BB in that size but they all seem to be 68 113 or 68 118? I would like to find a decent quality ISIS for XC riding.

Hopefully this is my fix to my problem. :( Any posts or comments would be appreciated.

Thanks.
 

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slza805 said:
I purchased a new RaceFace Evolve Crankset with a 68 108mm ISIS SRX combo on ebay a month ago nothing thinking about sizes due to my ignorance and newbieness. During installation everything went smooth. The problem I have is that my front deraileur wacks the crap out of the top crank during low shifting.

I realize that the BB is short and after doing some research on my IronHorse Warrior, a guy in WA stated by his books its at 68/116 BB that I need to add. I have looked for a ISIS BB in that size but they all seem to be 68 113 or 68 118? I would like to find a decent quality ISIS for XC riding.

Hopefully this is my fix to my problem. :( Any posts or comments would be appreciated.

Thanks.
I would measure the current chainline and base the new BB size on this calculation. Shoot for a 48 - 50 mm chainline .
 

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Discussion Starter · #3 ·
New to MTB drivetrains. Can you point me in the right direction, online guide on how to properly do this. Thanks.

keen said:
I would measure the current chainline and base the new BB size on this calculation. Shoot for a 48 - 50 mm chainline .
 

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Well I can't help you with the size BB unfortunately, but I will tell you to stay away from that cheap a$$ POS BB from RF. The SRX is an absolute POS and won't last you very long - the 1 that came w/ my new Trance didn't even last 300miles before it developed play.
 

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slza805 said:
New to MTB drivetrains. Can you point me in the right direction, online guide on how to properly do this. Thanks.
Park tools or Sheldon Browns websites should have this mentioned. Flip the bike over and mark the frames BB shell in the exact center, then measure to a middle chainring tooth - this is the current chainline. Say its 45mm w/ the 108 BB you need roughly 3-5 mm more BB spindle length - a 118mm BB would yeild a 50mm chainline as the extra 10mm is divided equally across the centerline of the frames BB shell.
 

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