How clean does the transmission need to be kept on my road bike? On my first MTB, I managed to destroy the transmission in 5 months because I was religiously lubing the chain, but not cleaning it. The resulting grinding paste made very short work of it. I've just spent half hour thoroughly cleaning the transmission on my SCR which has done 176 miles from new as it seemed to have a fair bit of Black gunk on it. Does it need to be kept very clean or can I just oil the chain after every other ride ?