Going to replace bearings...which size do I need?
 

Well, since I will be taking the cranks apart this week to check the straightness of my chain rings, I have decided to change out the bottom bracket bearings. The only problem is that I do not know which size I need. It is a Centurion Le Mans from 1988. Thanks!

1/4" is the standard bearing diameter for bottom brackets. There are some exceptions, though they shouldn't apply to Centurion of that vintage.

Alright! Thanks for the help. What size are the bearings in the original Shimano Exage Sport hubs? I have noticed that they are "sealed" by thick "O" rings that sometimes need to be pushed back in. And what should I pack the bearings with? My dad has some LubriMatic Marine Corrosion Control Bearing Grease. Will that work?

Exage Sport hubs should be 1/4" balls for the rear, and 3/16" balls for the front.
The Lubrimatic grease is more than adequate. And the marine spec will be good for corrosion and water resistance.

An inexpensive measuring caliper has been very helpful to me. Every home mechanic should have one!

Splurge and buy a metal vernier caliper. Mine from Harbor Freight has held up well. Another nice tool* is a 'gauge'. It has cutouts to determine nut and bolt size as well as a variety of holes for other things.

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