Originally Posted by
closetbiker
The races are the smooth part inside the headset that the bearing rotate on and brinnelling occurs when the races are set too tight together, not allowing for the bearing to roll and causing indentations of the races.
"Brinnelling" is caused by loss of lubricant in the headset and not by misadjusted headset. Even if you hammer on the headset it will not create indentations. If you look at a bearing race that does have the indentations you'll notice each one is surrounded by rust. See
Jobst Brandt.
Overhauling your headset once a year will prevent it or you can put fenders on the bike and overhaul it every five or ten years. Adjusting threaded headsets correctly is pretty easy for even the most casual of home bike mechanics.
So this eliminates one of the threadless headsets purported advantages.