Originally Posted by
3alarmer
...ball bearings and how they work have been thoroughly researched. Cone and race surfaces are case hardened, at the very least, in a quality bearing assembly. I honestly do not see how what you have described can occur.
Certainly excessive bearing load (to the point where the wheel no longer spins freely under the weight of the valve stem) ought to be avoided. But like @
davidad, Mr Brandt, and a lot of other people I have preloaded both headset and wheel bearings on bicycles for many years now, with no noticeable ill effects.
But I'm a test subject group of one, which is why I asked for a source.
Bingo! Because this well adjusted hub is not the usual for the vast majority of bikes sold, at the time of sale. Just about every bike I have pulled out of a box, and had cup and cone hub bearings, had bearings too tight to achieve this standard. The time to adjust the hubs as well as their grade can be isn't time that makes the shop any money, so most shop assemblies I see have really tight bearings. There's so much leverage at the tire over the bearing, that when the bearings are new the preload is hard to notice. Unless the wheel is removed from the bike this preload isn't likely to be discovered until the bearings start to wear badly.
The preload thing is a shade of gray. A tiny amount is good, much more gets bad fast. (and I draw a difference between radial and angular contact WRT radial's sometimes need for end play). Andy