Braking naturally creates a substantial amount of heat and friction, so rear disc brakes will wear from natural use. Routine rear disc brake inspections can prevent excessive wear from damaging other brake components like calipers and rotors. Completely worn brake pads can cause calipers to squeeze metal on metal, which will damage the rotors. Some disc brake pads have a wear indicator strip that makes a whistling sound to notify you when brake pads need replacements.
Sometimes the calipers can stick and keep from retracting all the way, which can cause quicker wear on brake pads. Squealing and grinding noises are the first sign of disc brake issues, but be sure to seek a rear brake repair service for your disc brakes at the first sign of any trouble. Properly working disc brakes are important for your safety and the safety of other drivers on the road.