Brushless motor rotor Shims?
 

Is there a specific king of shims I should be using to shim the rotor? Can I use the same shims as I'd use for other stuff like diffs or bearings?

Motive has a nice kit:

http://motivrc.com/store/#!/MOTOR-SH...egory=13438641

The others are probably a different size, I do not know any other use of such a small bearing RC Wise (other than perhaps a micro RC) that would use such a shim. Maybe also for TC Hinge Pins. But best off to use a kit as designed for motors.