Centurion BB Axle

The width of your bottom bracket shell is almost surely 68mm. If it was my bike, I'd measure it to be sure. Then I'd measure end to end of the square tapers on your bottom bracket spindle. Then I'd get a Shimano cartridge replacement bottom bracket with those dimensions. You'll probably need to buy a new splined tool to install it.

Robert Gardner said:

I am repairing a Centurion Le Mans RS that I recently acquired. The cups of the bottom bracket are not nice and shiny but show no pitting. However the bearing surfaces of the axels are rough and badly pitted. The components are Shimano SLX. Where could I obtain a new axel? How do you specify the size of an axel? Or is it possible for me to build the bottom bracket with sealed bearings or even a cartridge? In those days when most of us were riding Centurions, I remember some of the fellows were installing sealed bottom brackets of some form. I owned two and maybe three Centurions and have all of the tools for working on them. The headset of this one requires some serious work because someone has put a notch in the races by over tightening the headset. That I can take care of when I come to it.

Easiest and most economical thing to do would be to get a Shimano taper-spindle cartridge BB (such as Shimano BB-UN53-about $20 or so) in the length of your old BB and that matches the BB shell width on your frame. You would need to get a Shimano BB installation tool as well, which is about $15 (or borrow one) and can be used with a large open end wrench or square ratchet drive.

If you want something higher quality, SKF and Phil Wood make high quality square spindle BBs. The Phil Wood requires special lockring tools but the SKF can be installed with conventional BB tools.