Q: I just had new brake pads installed, but now I hear a squealing noise when I come to a stop. What could be causing the squeal?
A: Brake squeal comes from brake components vibrating. Sometimes new brake pads are made out of a harder semi-metallic material than the original equipment pads. I would always recommend installing OEM (original equipment manufacturer) brake pads or the highest quality that are available. High-quality pads will commonly have the front and back edges of the pad material cut at 45 degrees, which reduces the likelihood of vibration against the rotor. When a technician puts in new pads, the backs of the pads that come in contact with the caliper piston should be coated with an anti-squeal compound or have anti-squeal shims to prevent the metal from the brake caliper piston and the back of the pad from vibrating during braking. Vibration will cause a high-frequency noise. If applicable, anti-rattle clips should be reinstalled and in some cases replaced. In addition, the rotors should be replaced or resurfaced with a non-directional finish to help the new pads wear in properly. The rotors should also be thoroughly cleaned with a brake cleaner before reinstalling. Another component that may have been overlooked is the caliper glide, which moves in and out. When installing new brake pads the caliper glides/pins should be cleaned and new caliper grease applied to enable the caliper to move freely.