Question

Why do brakes make squealing noises while applying them from time-to-time (they stop making noise once pressure is released)?

Answer 1

Squealing noises from brakes when they are applied can have several possible causes:

1. Brake Pad Material: Most modern brake pads contain small metal wear indicators called "squealers." When the brake pads wear down to a certain point, these indicators come into contact with the brake rotor, producing a high-pitched squealing sound. This serves as a warning sign that the brake pads need to be replaced soon.

2. Glazing: Brake pad glazing occurs when the brake pads become overheated, causing a hard, smooth surface to develop on the pads. This glaze can reduce friction between the pads and the rotor, leading to squealing noises when the brakes are applied. In some cases, roughening the surface of the brake pads or replacing them may be necessary to eliminate the noise.

3. Contaminated Brake Pads or Rotors: Contaminants like dust, dirt, or moisture can accumulate on the brake pads or rotors over time. These contaminants can interfere with proper brake pad-to-rotor contact, resulting in noise when the brakes are applied. Cleaning or replacing the affected components can often resolve the issue.

4. Uneven Pad Wear or Rotor Surface: If the brake pads wear unevenly or the rotor surface becomes uneven due to wear or damage, it can lead to noise during braking. Resurfacing or replacing the rotors, along with proper brake pad installation, can help eliminate the noise.

5. Lack of Lubrication or Anti-Squeal Shims: Insufficient lubrication between the brake pad backing plates and caliper brackets, or the absence of anti-squeal shims, can cause vibrations and noise during braking. Applying a suitable lubricant or installing anti-squeal shims can help dampen the vibrations and reduce noise.

It's worth noting that occasional squealing noises when applying brakes may not always indicate a serious problem. However, if the noise is persistent, excessively loud, or accompanied by other issues like reduced braking performance or vibrations, it is advisable to have the braking system inspected by a qualified mechanic to ensure everything is in proper working order.