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Bottom bracket width?(5 posts)

Bottom bracket width?Flothru
Apr 12, 2002 5:26 AM
I am moving parts over from my old frame to my new frame but my current BB got stuck and I need to buy a new one. I am not sure how to figure out what width BB spindle i need. How do you figure out what width spindle to use for a given set up? Any sites that have calculators or is there something I need to measure on my new frame that will give it away? Should I just use the same size that came with my old bike/

Thanks in advance,
re: Bottom bracket width?Spoke Wrench
Apr 12, 2002 6:49 AM
Assuming an English threaded bottom bracket shell, there are two key dimensions you need to know.

The first is bottom bracket shell width. For most road bikes it will be 68mm. For most mountain bikes it will be 73mm.

The second is spindle length. The crankset is the biggest factor in determining this length. Although you will naturally need a 5mm longer spindle if you are going from a 68mm to a 73mm bottom bracket, in almost all other cases the old spindle length will be fine.
re: Bottom bracket width?curlybike
Apr 12, 2002 9:52 AM
Buy the BB that your brand of cranks require. Match that to the frame threading. English is 68 wide shell, It. is 70. As long as the frame threading is the same, buy one just like what you had. Why did it get stuck? Were you turning the drive side the wrong way? It is left hand on English threading.
re: Bottom bracket width?Flothru
Apr 12, 2002 11:43 AM
Thanks for the info. I think it is corroded in place I bought the old bike used and i know I never had the BB out, I suspect that the fellow before me never did either. Anyhow off to the LBS I go for a new BB.

Thanks again.
Here's the techniqueKerry
Apr 12, 2002 5:20 PM
Having just removed a severely corroded BB from a frame, I can tell you how to get this one out. If we assume that it is Shimano, and that you have the splined BB tool, clamp the tool vertically in a bench vice, turn the frame on its side and engage the tool, and then use the frame as the lever to free it up. Since it sounds like you don't care about this frame or the BB, you have nothing to lose from this simple effort. Remember, left side of BB is right hand thread, right side is left hand (assuming English threaded BB).