Squealing Brakes:

    Nothing is more annoying than grabbing your brake and hearing a noise that could wake the dead. On the surface, this squealing seems like it should be easily remedied. However, the harmonics involved can actually be quite complicated to resolve.
    On rim brakes, the rim surface of the wheel, the brake pads, and the brake’s pivot points all wear over time. Play in the pivot points on the brake itself can cause a vibration that turns into a squeal. Likewise worn, contaminated, or hard brake pads can cause a squeal, as can a contaminated or worn rim. Frustratingly, replacing old worn pads with new pads on a brake that was not squealing can cause that brake to start squealing. Sometimes the solution is a different style or brand of brake pad. Sometimes the solution is a new brake.
    With disc brakes, the rotor, the brake itself, and the pads, can all contribute to brake squeal. The most common source of disc brake squeal is contaminated pads and rotors. If oil or grease get onto the rotor, and then into the brake pads, the brake will still stop well, but it will most assuredly squeal. Sometimes, cleaning the rotor and sanding the pads will do the trick. Usually, however, new pads are in order, along with new rotors. If the old rotors are used, there is always the possibility of contaminating the new pads. Rotors develop a coating on the surface that usually can only be removed with heat. That’s how an old rotor can contaminate a new pad: the pad and rotor heat up under braking and the coating on the disc melts into the pads. Pads that have been contaminated with grease or oil, can sometimes work quietly again by burning the contaminants out of the pads with a propane torch. This is a smelly and time consuming process. If you are a DIYer, and have a torch, have at it. If, however, you are paying a mechanic to do the work, it is cheaper to get new pads. Most shops, including mine, will not guarantee their work unless both the pads and rotors are replaced.