Brake Pads Squeal and Grind Noises Explained

If you’re reading this, there’s a good chance at one point in your driving career you heard strange noises coming from under, over, or inside the car. Some of the most scary such noises are those coming from the brakes of the car because, well, once you hear such a noise, you can’t refrain from wondering if your car will stop safely this time.
Brake squeal is not usually a reason for immediate concern 1 photo
Photo: Youtube screenshot/Porsche
The simplest fix to those fears is understanding that noises coming from the brake pads are normal and usually just warn you that, sometime in the near future, brake pads will have to be changed. They’re also normal because, after all, brakes are made of pieces of metal or other materials rubbing against each other as you press the pedal inside the car.


When a car travels down or up a road, it generates kinetic motion. When it needs to stop, it needs to dissipate that kinetic energy somehow. And that’s where the brakes come in: by using friction, they do just that, and slow the car down.

There are in fact two levels of friction involved when it comes to the process of braking. The first level implies the brake disk and the brake pads. By pressing on the pedal inside the car, the driver orders the pads, with the help of hydraulic pressure, to squeeze harder onto the disk, thus slowing its motion.

The disk then sends the same reaction to the wheel itself, to which it is connected. The wheel’s friction with the asphalt is level two, and as the speed decreases, more friction force is generated between the wheel and the tarmac.


Noises generally occur when the disk pads are pressed against the brake disk. As they are continuously used, the brake pads, usually made of metal alloys and ceramics, begin to wear off. Temperature and humidity can also make the brake pads squeal.

There are several types of noises possible, difficult to render in writing, but generally they are described as squealing or grinding.

When you hear a high-pitched squealing while applying the brake, that means there is usually reason for mild concern. Although you are not in immediate danger, such a sound usually means that the brake pads are beginning to wear off.

Each break pad is fitted with a so called metal wear indicator, a piece of metal embedded into the brake pad material that only surfaces when the pads have been worn enough.

When it reaches a certain level, the material on the pads allows the wear indicator to rub against the brake disc and emit a sound. This is, if you like, a safety feature built into the pads to alert you when it is time to change them.

Hearing this high-pitched squealing should prompt you to make a visit to a car service and have the brake pads checked out. Especially when the sound caused by the wear indicator is heard when the brake pedal is not pressed at all.

A grinding sound can mean different things, so you should keep an ear out to better understand what they mean. Grinding sounds in the morning, or after a period of time during which the car hasn’t been moved, are normal. During the night, brake pads become cool and at times covered in condensed vapors. Until they warm up and the moisture evaporates, they will make some grinding noise. It should go away after several stops.

When they don’t, then there’s reason for concern. In extreme cases, such noises may be the first signs of the pads beginning to chew their way into the brake disc itself. They do this because the wear of the pads is so severe, that now their underlying metal rubs directly against that of the disk.

To help us better understand brake noises, German manufacturer Porsche released in the beginning of 2018 a short video explaining why usually brake noises are not something to be scared of. You can watch it below.

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About the author: Daniel Patrascu
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Daniel loves writing (or so he claims), and he uses this skill to offer readers a "behind the scenes" look at the automotive industry. He also enjoys talking about space exploration and robots, because in his view the only way forward for humanity is away from this planet, in metal bodies.
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