I realize this, and suppose that in the absence of a film of lubricant some wear could occur on the sliding ball. The thing I wanted to understand was how *unloaded* balls could be worn.

I've been servicing the ball bearings on my own bikes for around 60 years. The only balls I have ever seen wear on were those in a hub that had water incursion with resulting rust. Even on hubs with race wear the balls looked good. In recent years I have used magnification (4.5x loupes). My experience is limited, however.

My best "worn ball" story is from a trip to Daytona for Speed Week in 1979. I was returning on my BMW R69S when the rear drive seized, luckily as I stopped for gas. I opened the oil drain plug, and all the balls fell out. Each one looked custom-peened. End of trip!


4.5x loupes with LED headlight. Used for work, but boy do they come in handy in the shop sometimes!