Jack9216 said:Personally I wouldn't bother about it as I don't care what my rims look like, as long as theyre not buckled, and the black marks shouldn't affect the grip of the brakes on the rim as it will mostly be rubber, which, if anything, will make the brakes more grippy.
gavintc said:The black goo is a grinding paste and it is slowly eating away at you rims every time you brake. I was always informed that if you clean only 1 thing on a bike, clean the rims.