Originally Posted by
JohnDThompson
Yeah, that's why I think rollers are more appropriate for a headset than a bottom bracket. Unlike bottom brackets, or other bicycle bearings, for that matter, headsets are not in continuous rotation when in use, so the additional friction is far less pertinent.
under extreme pressures/shocking, small, "Low Count" roller bearings can shatter.
automotive U-joints use longer needle bearings, and as many as they can fit in the cups... they are also low rotation, low twisting load, and high friction.
i've watched people try to re-use a cup after screwing one up on a new u-joint... the cups are matched to the assembly, and shouldn't be reused on a different assembly.
the precision bearings honda uses in their transmissions and engines, in general, come in varying tolerances, depending on WHERE they're used... a tight press fit into a casting compresses the outer race... retainer installs were tighter than press fits...etc.
we would carefully measure the crank bearing bores in the cases, after normalizing the case temp, before ordering the correct toyo crank bearings for race engines.