Quote Originally Posted by Ross77 View Post
Did you notice if the balls in the smaller external dia. are smaller? Reduced mass seems to be one of the critical points for High speed so would be a bonus for the deep groove ones, as I could use 4 or 5 to regain the strengh
Have you considered bearings with ceramic balls? There's quite a few around on eBay. Apparently they're good for 30% faster than steel.

I wonder if buying normal bearings and replacing the balls with ceramic yourself is an option - probably not.