What Causes Brake Chatter With Old Pads & Rotors?

Whatever situation calls for continued use of a brake system that needs attention, it is best short-lived, if tolerated at all. Serious shortfalls may have already occurred by the time audible symptoms develop. Brakes that chatter, squeak or grind are signaling a problem that is sure to affect performance. Whether postponed maintenance, or severe driving conditions are responsible for newly displayed noises, the predicament deserves quick action. A brake inspection may reveal a trivial concern, or prevent some dangerous mishap. Many auto repair shops offer this service at no cost, and that may be the best free offer a motorist can receive.

Pads and Plates

The friction material, or lining, of a brake pad is attached to the metal backing plate in one of two ways. One method employs powerful epoxies to fix the friction material to the plate, while the other uses rivets to secure the linings. A rivet can lose its grip over time, for various reasons, but creates little concern on its own. However, when several rivets fail, the lining may move about on the backing plate during brake applications. A clicking or chattering can result, and eventually pieces of the lining may break away from the backing plate altogether. The loss of friction material of linings bonded by epoxy is only experienced in extreme cases of brake system neglect.

A Tight Hold

Some brake systems require that the pad backing plates are secured to the caliper by tabs that extend from the metal plates. The small tabs, or tangs, are bent around a portion of the caliper after installation. A chisel or punch may also be used to stake the tangs firmly to the caliper surface. Extended maintenance intervals, or extreme driving conditions, can result in the metal tangs losing their grip. The loosened fit may allow slight repetitive motions to make a chatter when braking or coasting at low speeds. Spring-steel clips on the backing plates of other pads can fail for the same reasons, often with the same result.

Grips and Gripes

Amateur repair attempts may show some appreciation for firmly attaching the pads to the caliper, but seldom achieve effective results due to other considerations. Chatter may still occur if the calipers themselves do not receive proper maintenance. Bushings meant to cushion the movements of the caliper can wear, and permit the caliper to travel fore and aft when the brakes are applied. Other caliper parts that act as slides or springs to steady and quiet functions, can also suffer from deterioration over time. Excessive caliper or pad movements cause abrupt metallic contacts, and the noises produced can range from light chatters to bone-jarring clunks.

Time and Temperature

In the normal course of duty, disc brakes generate impressive heat loads. The high temperatures take their toll on pads and calipers, and affect the friction surfaces of the rotors as well. Hard spots can be burned into the rotors, and these, or other more pronounced irregularities, can force the pads out of position repeatedly. Brake rotors can become distorted from excessive heat loads, and the warped surface can cause a pulsating sensation when braking. Radial cracks found on rotors subjected to abusive driving habits or excessive weight loads can gouge at the brake pad lining in all driving conditions. Severe rotor defects could cause brake chatter, but system performance degrades alarmingly, and to the point where any noises may seem secondary.