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Hello all,

Here comes another one of those "BB ./. Crank compatibility" threads - I did my best to research things on my own, but I'd appreciate it if someone could confirm its accuracy:


I just bought a new bike (BMC Agonist 2018, similar to this one) - the only thing I cannot get used to are the Rapid Fire Shifters and the antiquated 2x10 drivetrain - it seems like a no-brainer to convert this to a SRAM GX Eagle 1x12 setup with twist shifters.


Originally, the bike came with a Shimano setup - more specifically a really ugly Shimano Deore M617 crankset with a Shimano Hollowtech 2 bottom bracket.
According to the spec sheet of the bike, the bottom bracket specification is "PF92". I believe this means that my cranks have a spindle diameter of 24mm.


I am now trying to figure out my options for a new crankset (which will be compatible with SRAM Eagle), while possibly keeping the current Hollowtech 2 bottom bracket.
I have identified the Race Face Aeffect/Ride cranks are available in a 24mm variant (for example these)


Am I right in assuming I should be able to remove my old crankset and use these Race Face cranks as a drop-in replacement? Race Face has a document that is supposed to help with compatibility questions but its more confusing than it helps. Then there is also this "PF92" vs "BB92" discussion which adds further confusion.
Another thing which is a bit foggy to me is "spindle length", which the Race Face document mentions - but I can't find any cranks for sale with different spindle length, just different crank lengths ....


Any help is greatly appreciated - thanks!
 

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since 4/10/2009
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BB naming conventions are stupid. Nobody is consistent on how they name stuff. PF92 doesn't exist, but some people use the term and it only adds to the confusion of BB standard naming. It's BB92 (a standard developed by Shimano, actually), which can also be called PF41 (92mm is the bb shell width, 41mm is the bb shell diameter on the frame). There are fatbike variants of the name, too (which is mostly where PF41 comes from, but you may also see BB121 used, since 121mm happens to be the bb shell width of the frame, or rarely BB131), but those don't matter for your case.

Yes, a Race Face Aeffect or Ride crank is a drop in option for a straight spindle 24mm bottom bracket.

It definitely is available in different spindle lengths. Many retailers split them up into separate listings and just call the others the "fat bike" version. But the RF fit charts specify exactly which spindle lengths are available. It just might take some work to find some of those specific lengths if that's what you're after.
 
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