Why does the brake pads make a strange noise?

Abnormal braking noise - the last problem we want to encounter before buying a car. This time, we are not talking about the sound of interior components after bumpy roads during driving, but rather from the foot! So, why does the brake make a strange noise?

1. Problems caused by wear and tear

Zhi Zhi "and" Gu Leng "

In daily life, if you carefully observe, it is not difficult to find that many cars will make squeaking noises as the speed gradually decreases during the braking process. In addition, when the brake pedal is fully pressed and the ABS is not activated, another kind of gurgling sound may also appear.

So how does the braking system work?

For example, most of us can ride bicycles, and the working principle of this structure can be clearly understood with the naked eye. The purpose of deceleration is achieved through the friction between the brake pads and brake discs. Although the brake system on a car has a slightly complex structure, the principle is the same.

Due to the need for greater braking force during car braking, the entire system uses hydraulic pressure to increase assistance. When braking, the piston is pushed outward through the hydraulic system, and its return speed is relatively slow because the braking system has an automatic compensation function. When the brake pedal is pressed, the piston will reduce its retraction under the influence of oil pressure, allowing the brake pads to come into contact with the brake disc faster during the next brake application, reducing braking time. Therefore, the release and return speeds are not as smooth as the commonly seen bicycle "brake shoes".

In the braking system, the brake pads play the role of ultimately "pinching" the brake discs, so there are strict requirements for their materials in its design and manufacturing processes. Wear resistance, friction coefficient, heat resistance, strength, and environmental friendliness, which have become increasingly important in recent years, are all issues that cannot be avoided during the design phase.

Due to the fact that the contact between the friction block and the brake disc will directly affect the braking distance, the friction coefficient is also a design focus during the development process. Whether it is early asbestos based friction pads or later developed semi metal mixtures or asbestos free organic brake pads, their friction coefficients are mostly in the range of 0.25 to 0.45.

Despite the continuous development of materials science, the current wear rate of brake pads and brake discs is still different. In terms of replacement cycle, there is a widespread saying among the people that two sets of brake pads, one set of brake discs, or three sets of brake pads, one set of brake discs. In many cases, after replacing the brake pads, abnormal noises come with them. What is the problem?

2. A single slap cannot make a sound

As the mileage of the vehicle increases, the number of braking times increases, and the wear of the brake pads also increases day by day. After replacement before reaching the wear limit, the brand new brake pads and the unreplaced brake discs are in the same brand new state. Although the installation position has not changed, it is this old and new state that has become the cause of the abnormal noise.

In addition to creaking noises caused by wear and tear on old and new brake discs and pads, the carbon fiber ceramic brake system selected in some performance vehicles in recent years may also produce abnormal noises due to its physical characteristics. However, this part of the abnormal noise is mostly caused by the material itself, and there are not many simple and easy solutions.

In addition, during the driving process of the vehicle, the tires will roll up small foreign objects such as dust and stones on the road surface, and some of these foreign objects have a certain chance of being carried onto the brake pads and discs. These foreign objects may come into contact with relevant parts and friction may also cause abnormal noises. Therefore, some vehicle braking parts are equipped with a baffle mechanism.

Another cause of abnormal noise is that sometimes when the driver steps on the brake pedal fiercely, he can hear the sound of rumbling. In fact, this is also one of the abnormal noise of the brake system, which is caused by the surface states of the brake disc.