Old 06-20-10, 09:38 PM
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Originally Posted by dscheidt View Post
Damage is from fretting. It's lubrication failure. There's fore-and-aft motion in the steerer (typically road vibration), and no rotation (except when you steer). this depletes the film of oil on the balls, which produces lots of friction, which produces heat, which welds the parts together microscopically, and then they're ripped apart. Getting the pre-load right certainly helps prevent the damage from fretting, but it's hard to get right if there's already damage.
Interesting to note that in the early days of rail transport, automotive wheel bearings suffered the same fate when transported over long distances. They couldnt figure out why bearings were trashed from the factory. When the root cause was found, The industry quickly resolved the issue by suspending the cars by axles and letting the wheels float. Didnt eliminate but greatly reduced it... Cartridge bearings are the best way around index shifting, just replace when steering goes bad... Im assuming that the factory preloaded auto wheel bearings properly and they still had the issue... Im not sure there is a way to avoid it.
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