My huge blog on fuel injector service
You may have rotor surface issues if either your brake pedal or your rotor itself starts vibrating. If your brakes start squealing when you press on the brake pedal, get your car into your favorite repair shop to determine whether brake repair is necessary. If your brakes squeal after you have released the pedal, have your brake wear indicators checked as they may be scraping against the rotors. Grinding or growling noises result from metal to metal contact; you most likely need new brake pads. Experts recommend that you seek brake repair as soon as any of these signs appear, before the problem gets any worse.