1stly, i was expecting the next word to be "SHOWER" 2ndly, i can see petrol being pretty good actually, i would rip the crap out of the rim (rubber, mud, old tar etc) and when petrol dries is leaves a small amount of residue, which i can see acting like tar, but obviously not as long lasting! 3rdly, tried diesel yet? 4th..ly, ignore 3rdly 5th..eth, if you wanna get your rim spanking clean, use brake and clutch component cleaner, its pretty pricey, but really does strip all the gunk out and leaves no residue whatsoever!