Whether composed of ceramic, semi-
metallic, or organic materials, brake pads
erode each time you depress the brake pedal. If the pads wear down too much without being replaced, then the metal housing for the pads will make contact with the metal rotors (or drums). Not only a safety issue but a situation where the rotors and drums need to be replaced as a result of the prolonged contact of metal parts without the pad buffer. Calipers can become stuck from not bleeding the system.
Today's braking systems are composed of a number of integral parts all work together to ensure your vehicle stops properly. Generally speaking, by depressing the brake pedal, you are telling the master cylinder to compress brake fluid, which in turn sends hydraulic pressure through brake lines that activate your vehicle's brake pads. (or shoes). These pads (or shoes) then make contact with spinning rotors (or drums), slowing down or stopping the vehicle. More complex systems use sensors to activate the brake system, but the net desired effect is the same