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Silencing Disc Brake Squeal

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Like fingernails scraping across a blackboard, disc brake squeal is enough to make anybody's hair stand on end. For some neurological reason that is not fully understood, human beings react negatively to high-pitched squeals like crying babies, sirens and screeching breaks. So if your brakes are squealing, you want the noise to go away.

Brake squealing is produced by high-frequency vibration in the brakes. With disc brakes, vibrations can occur between the pads and rotors; the pads and calipers; the calipers and mounts; and/or within the rotors themselves. With drum brakes, the vibrations can originate between the shoes and the backing plates, and/or within the drums.

The noise is not dangerous as long as there is no metal-to-metal contact, the brakes are working properly and there is adequate lining thickness. But, it sure can be annoying. So, to get rid of it, you first have to figure out what is causing the brake noise.

DISC BRAKE SQUEAL
Complaints about brake squeal became a problem when front-wheel drive and semi-metallic brakes arrived on the scene in the 1980s. Semi-metallic pads are harder than their asbestos counterparts, and thus are more apt to chatter and squeal if there are any irregularities or roughness on the rotor surface, or if you notice looseness between the pads and calipers.

Some types of caliper designs are more apt to be noisy than others. The pads in these calipers may not be held as tightly and/or the caliper itself may move around a lot when the brakes are applied. And, as we said earlier, the greater the play in the system, the greater the tendency to make noise. That's why some new car dealers try to dismiss the problem by telling their customers some noise is "normal", leaving the customer no alternative but to live with the problem or to get it fixed by somebody else.

Trying to fix a squeal problem the wrong way can often make the problem worse. If somebody does a quick brake job and replaces the brake pads but doe snot resurface the rotors, the result can be an even louder squeal. The same can happen if the rotors are resurfaced incorrectly, too quickly or with dull tools. Excessive rotor runout can also cause problems.

DRUM BRAKE NOISE
One of the leading causes of brake squeal in drum brakes is poor contact between the shoes and drum. Heel and toe contact between the shoe and drum is often the culprit, and the cure is to either replace the shoes with new ones or to resurface the drum slightly to increase its inside diameter. New shoes are ground with a slight eccentric to compensate for drum wear.

This moves the point of contact away from the ends of the shoes toward the middle. In the old days, mechanics used to arc shoes to match their shape to the drum. But, with the concerns about asbestos, shoe grinding is pretty much a thing of the past (although some say it will make a comeback as more and more new cars switch to non-asbestos linings on their drum brakes).

INSPECTING THE BRAKES
Motorists usually take their car in for brake work because they are having a problem, so the first thing that needs to be done is a complete inspection of the brake system:




More Brake Articles:

Eliminating Brake Noise
Say No to Brake Noise
Eliminating Brake Dust
Asbestos still a hazard
Brake Pads: Choosing the Best Brake Lining Materials
Ceramic Brake Pads
More on Ceramic Brake Pads
Brake Rotors
More on Brake Rotor Service
Fixes For Common Brake Problems
Doing A Complete Brake Job

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