I rebuilt a rotor bearing today.

So... apparently you aren't supposed to be able to do that or even change the bearing in things like the 7SXX. I did both, on a 7015 rotor. Basically, the inner diameter of the bearing (where it's threaded) is about .05 or some mm larger on the 7015. Needless to say I ruined a top plate before I broke out the micrometer. The difference is so small there is no way to tell without measuring the post or ruining parts (got both those covered).

Anyways, I digress. I was trying another rotor because the teeth on the bearing for the one in the 7015 were rusted away total. So, given the (7015) threaded inner was the right size I cut the race with the bad teeth off it, saved the bearings and then disassembled a 7S26 bearing, saving the outer race, bearings and keeper. It was just a matter of laying the bearings onto the inner race while it was in the outer, centering carefully, then pressing the collar back on. Just that easy.... Hope this can help someone else.