Brake squeel:
It is no secret that a rushed brake job can leave some things undone that may
contribute to noise and comebacks. So let’s start with the brake discs being the
number one cause of squealing brakes.
Brake discs
Discs must be smooth, clean and flat to provide optimum braking. If the brake disc is
rough, warped, scored or glazed the pads are going to vibrate or chatter every time you
apply the brakes. If the brake discs are to thin the brake system will operate at a higher
temperature resulting in glazed pads. For every 1mm taken of a disc it adds between 80-100
degrees to the operating temperature of the brake system.
Brake pad vibration
Another form of brake squeal is caused by the Brake Pad vibrating when brake pressure
is applied. Heavy braking usually stops the squeal because the extra pressure dampens the
vibration. If heavy braking does not stop the squealing it is a sign of a significant
problem. Squealing that appears under light braking is not a safety concern; it is just
very annoying.
When this type of squealing occurs it is usually the leading edge of the Brake Pad that is
in contact with the rotor causing a twisting force on the pad making the trailing edge
want to lift away from the disc.
Vibration dampers
One option to help reduce the Brake Pad squeal is to fit Brake Pad vibration damper
pads. The vibration dampers are a self-stick fibre material shim that sticks to the back
of the brake pad. Some Brake Pads have a spring at the back of the backing plate located
in the middle of the pad. The spring fits tightly into the piston with the fibre shim
sticking to the back of the brake pad. The theory is that the fibre shim will help
cushioning the vibration of the brake pad.
Anti-squeal compounds
A second option is to coat the back of the Brake Pad with a quality anti-squeal
compound. This is applied to the back of the brake pad. It is said that a combination of
vibration dampers and a coating of anti-squeal compound usually reduces low speed squeal.
Article by Stephan Visser
issued by Safeline: June 2002
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