Monitor your brake pad thickness and don't let the pads wear
down to metal. This will cause damage to your brake rotors ("discs")
at least and possibly your calipers as well. Rotors and calipers are much more
expensive to replace than pads. There is no such thing as
"cleaning" a brake pad while it is still on a car - the friction
between the pad and rotor will eradicate any outside substance almost
immediately.
