Originally Posted by syndr0me
Huh, interesting. Wouldn't sanding the rings with something more coarse than 600 grit achieve essentially the same effect of running the diff in with polishing compound? Maybe like 400 grit or something?
Well, if you sand the diff, you still have a flat surface. When running it un with this rubbing compound you create a grove where the balls run in -> instead of eg. 0.05mm of surface between the balls and the plates you will get 0.30mm of surface between the balls and the plates.
I know that in polishing compounds you have a variety of how "gritty??" it is, the one from Motip I have is extremely aggressive, after that I normally again do this but with something more mild (the stuff they call paint renovator), to even out the groove somewhat.
But this works really well, couldnt believe it when I first tried it. Btw, I redo my diffs on the BD about once a month when driving outside. No new plates, just cleaning and relubing and the still run extremely smooth. (-> I run a 4.5r...)