Rotors are the disc component of disc brakes and are bolted directly to the wheel. When the brake pedal is depressed the brake pads squeeze on the rotor to slow the vehicle down. As this happens day in and day out, both the rotor and the brake pads slowly wear down. Eventually the rotor will become so worn that the brake pads cannot safely contact the rotor surface and your braking performance will be reduced. Another condition that can lead to reduced braking performance is a warped rotor. Warped rotors are usually caused by excessive heating due to repeated aggressive braking.