Close up of rotor and caliper face. Improper servicing can cause vibration and dreaded brake squeal. (Photo by C Kugler)Brake squeal is really a high frequency vibration. In disc brakes, it can be caused by vibrations between the pads and rotors, the pads and calipers, or the calipers and their mounts. We can't stand it, even if it is "normal" for many vehicles today. Most people want nice, quiet brakes that stop smoothly with a reassuring "shhhhh' sound. No scraping noises. No high pitched squeals. No concerned looks or stares from passengers, other motorists or nearby pedestrians who wonder if the vehicle is going to stop or not.