Well , when i got my tpro for a long while i didn't want to grind my rim because i was worried it would weaken the rim. But ,my mates were grinding there rims and noticed there braking power being immense.. I decided to go for it! At first i just turned the grinded on and then off and stroked it accros the rim, this made it a lightish grind, i then tryed a smigde of tar on it and its even better! i would reccomend it!