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Cynical Bystander
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6,770 Posts
Discussion Starter · #1 ·
IM probably going to be getting some Shimano FC-751 cranks for my Titan but the bb the guy has is a 73mm and I need a 68mm. My question is when looking at the Shimano splined bbs will they work with these cranks? It seems most of them say to be used with the 752 model but Im not sure if there is any sort of difference as far as how it is or anything like that. Also this is probably a stupid 'newbie' question but a 73mm probably wont work for my bike since i need a 68 huh? lol.

Any help would be great.
 

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Derailleurless
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9,122 Posts
The ES71, 70, 51, 50, and 30 are all v2 Octalink spline patterns and all will work with your FC-M751 XT cranks. A 113mm spindle length will get you a 47.5mm chainline, and a 118mm spindle length will get you a 50mm chainline. I don't know enough about your frame to know whether it has a preference for the 50mm chainline, but this is often a safe bet.

You can use the 73mm assembly on your 68mm shell by installing 3mm worth of spacers underneath the drive side flange. If you install the 73mm cartridge without the spacers, if it is the 113mm spindle length, you'll end up shifting your chainline in far enough that you may have difficulty shifting to the granny ring. If it's the 118mm spindle, your chainline will be where it would have been if you had a 68x113 BB installed. In either case, you'll offset your whole crank assembly to the left by 5 millimeters (probably imperceptible to the rider).
 
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