Bicycle Mechanics - BB/Crank question

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DougG
08-03-07, 07:49 AM
I'm planning on replacing my Sora/Tiagra-based 3x8 speed drivetrain with 105 3x10 components this winter. Yeah, I know it would be more cost-effective to buy a new bike, but I'm doing it mostly for the fun and learning experience.

Anyway, the one component that I have never worked on so far is the BB/crankset. My current bike (Specialized Sequoia) has a Sugino BB/crank that is listed as having a "68mm axle". Is this a standard size and can I expect that the BB for the 105 crank will install with no problems in my frame?

Also, my current crank has 172.5mm arms. Is there any reason not to get the same length with the 105 crank? I'm strictly a recreational rider and have no particular issues with the current crank setup.

DMF
08-03-07, 10:53 AM
Read up on bottom brackets on Sheldon's site. The Sugino BB is not a good example for the others. The old and new (105) crank/BBs are significantly different — the 105, for instance, doesn't really have a BB.
DougG
08-03-07, 11:20 AM
Read up on bottom brackets on Sheldon's site. The Sugino BB is not a good example for the others. The old and new (105) crank/BBs are significantly different — the 105, for instance, doesn't really have a BB.

Thanks for responding, but I probably wasn't entirely clear with my question. The bike currently has the Sugino BB & crank. I will be replacing it with a FC-5603 crankset and SM-FC5600 BB from Shimano, and was just trying to ensure that it was compatible with my frame, which I have since determined it is.