Originally Posted by dwood

What you've drawn makes it look like a standard ball bearing is like a planetary gear system. It is not. The balls are not held stationary . . . the cage containing the balls rotates in the direction of the outer race [in the pedal example]. And because the ball/cage assembly is allowed to rotate . . . their is no scuffing of the balls on the races.

As an example of this take a planetary gear system. The gears in it do not 'scuff' [they can't], yet the outer and inner rings turn freely. The ball bearing is no different . . . imagine it as a planetary gear system with infinitely small gear teeth.

As for precession that SB talks about . . . I believe it has nothing to do with the bearings in the pedal. It is the precession effect of the rigid spindle and the way it is threaded into the crank. The spindle is cyclicly loaded as you pedal. Any looseness in the thread allows the pedal to attempt to 'walk out' of its thread.

The solution: tighten the pedal properly.

DON