Painting them should work for a while. Another option is going with 2-piece rotors with aluminum hats. That's an expensive option, but if you need to replace the rotors anyway, these are lighter than stock. See:
http://www.ecstuning.com/News/BMW_Bi...013/ES2550968/
__________________
2009 135i, Alpine White, 6MT, M-Sport, iDrive, iPod/USB, Heated Seats, Premium Sound, BMW Assist