on my old rst tubo it started to do it when i had the tracking done and got decent new tyres on it before it just used to light the tyres up and not really do it.i put it down to a bit more grip or tryes fitting for grip more as handle as still ok so not like a bush and suspension was all new and still took a beating everyday so didnt seem to be clutch or diff or gearbox as id have thougt they would have destroyed themselves if it was?
maybe you just got more grip now too