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BB Sizing?(2 posts)

BB Sizing?sugarman
Jun 1, 2001 9:22 PM
is there a way to figure out what size+type my bottom bracket is? or do I have to take it into the shop and have them tell me?

I need to replace mine and better deals are to be had on the net than in the shop...

Thanks, Chris
re: BB Sizing?zelig
Jun 2, 2001 4:01 AM
First determine the width of your BB. Generally most Italian bikes used to be 70mm with English, Japanese and American bikes at 68mm. Again, this is a generality so measure.

Then you need to know if its standard or British thread. British means that on your non drive side, that the thread is left handed. Instead of your normal righty/tighty and lefty /loosey, its the other way around. We'll not go into why but the theory is well founded. Generally the 68mm bb's are British and the 70's are standard thread.

Then the type of crank arms including if they fit a normal square axle, type of taper or if they're the more recent Shimano spline or ISIS pattern.

Lastly, you'll need to know the axle length. At the very least, you'll need to take off your crank arms to measure this with a pair of calipers.

Much of this can be avoided if you know the make, model and year of the cranks and tell this to your LBS or mailorder house.