Causes of brake discs grinding

Written by dennis hartman
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Causes of brake discs grinding
Keeping brakes in good condition is essential for safe driving. (wheel image by sasha from

A car's brakes are among its most important components, both in terms of safety and performance. Brakes help the driver keep control and avoid accidents. The two major types of automotive brakes are disc brakes and drum brakes. Today most passenger cars have front disc brakes, and high-performance or luxury models often have disc brakes on the rear wheels as well.

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Worn Pads

Disc brakes use a spinning metal disc, known as a rotor, and a pair of brake pads. When the driver depresses the brake pedal, the caliper closes around the spinning rotor, forcing the pads to pinch the rotor from both sides. Over time, brake pads wear down. The "brake dust" drivers see on their wheels is actually the brake pad material that has come loose from friction.

Once a brake pad has little or no material left, the metal brackets that attach the pad to the rotor become exposed and can cause a grinding noise, along with vibration, as they come into contact with the rotor. Some brake pads include wear indicators that will cause a softer noise and vibration to alert the driver that the pad is nearly worn out and requires changing.

Semi-Metallic Pads

Automakers and third-party parts manufacturers offer several types of brake pads. One of the most common and least-expensive options is semi-metallic construction. These pads use a mix of scrap metals along with a binding agent to hold the metal flakes together. Because the shards of metal in a semi-metallic brake pad are of different hardness levels, some will cause the brake to grind temporarily until the spinning rotor wears down the metal and makes the pad smooth again. This type of disc brake grinding is normal and stops after several applications of the brakes.


If dirt or other road debris gets into a disc brake mechanism, it can cause grinding and vibration. The space between brake pads and rotors is partly shielded by the wheel, but alloy wheels with large openings can allow dirt to enter the space easily. Most road dirt is too soft to damage the brakes and will eventually be ejected by the force of the brake.

Improper Installation

Replacing brake pads and rotors is a fairly simple process that many auto enthusiasts do at home. But even at auto shops, technicians sometimes make mistakes. Improper installation can cause a disc brake to grind if the pad isn't parallel to the rotor. Loose mounting brackets or other hardware can cause the pad to fall out of its proper position and grind against a different part of the rotor. This also hurts the brake's ability to stop the car and should be fixed as soon as possible.

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