As we all know, the braking system of a car is related to driving safety. Once the braking system fails, the consequences will be disastrous. Therefore, when using the car (especially after driving to a certain number of kilometers), you should always check whether the brake system is damaged or needs to be replaced.

Brake pads and brake discs are two very important components in a car’s braking system. It can be said that whether they work properly or not is related to the life safety of the passengers in the car. Today I will teach you how to judge whether the brake pads and brake discs need to be replaced.

How to judge whether the brake pads need to be replaced?
At present, the brake systems of most family cars on the market are mainly divided into two types: disc brakes and drum brakes. Disc brakes, also called “disc brakes”, are mainly composed of brake discs and brake calipers. When the wheel is working, the brake disc rotates with the wheel. When the brake is working, the brake caliper pushes the brake pad to rub against the brake disc to produce braking. Drum brakes are composed of two bowl-shaped objects combined into a brake drum. The brake drum has built-in brake pads and return springs. When braking, the friction generated by the expansion of the brake pads inside the brake drum and the brake drum reaches deceleration braking effect.

1. Determine whether the brake pad needs to be replaced by looking at its thickness.

For most disc brakes, we can observe the thickness of the brake pads with the naked eye. In the long-term use of the brake pads, the thickness will become thinner and thinner with the continuous friction during braking. Generally, the service life of brake pads is about 40,000 to 60,000 kilometers, and the harsh driving environment and aggressive driving style will shorten its service life in advance. Of course, some models cannot see the brake pads with the naked eye due to the design of the wheel hub or brake caliper (drum brakes cannot see the brake pads due to structural reasons), so we can ask the maintenance master to remove the wheel every time we maintain Check the brake pads.
The thickness of a brand new brake pad is generally about 37.5px. If we find that the thickness of the brake pad is only about 1/3 (about 12.5px) of the original through visual observation, we need to observe the thickness change frequently. When about 7.5px is left, it needs to be replaced (you can ask a technician to use a caliper to measure it during maintenance).
There is a raised mark on both ends of the brake pad, which is about 2-3 mm thick. This is the thinnest replacement limit of the brake pad. If you find that the thickness of the brake pad is almost parallel to this mark, you need to replace the brake pad immediately. If not replaced in time, when the thickness of the brake pad is lower than this mark, the brake disc will be severely worn. (This method requires the tire to be disassembled for observation, otherwise it will be difficult to observe with the naked eye. We can ask the operator to remove the tire and then inspect it during maintenance.)

2. Listen to the sound to judge whether the brake pads need to be replaced

For drum brakes and individual disc brakes where the brake pads cannot be seen with the naked eye, we can also use the sound to judge whether the brake pads have been worn thin. When you lightly brake, if you hear a sharp and piercing “cici” sound, it means that the thickness of the brake pads has been worn below the limit marks on both sides, causing the marks on both sides to directly rub against the brake disc. At this time, the brake pads must be replaced immediately, and the brake discs must also be carefully inspected, because the brake discs are often damaged at this time. (It should be noted that if there is a “squeak” sound as soon as the brake pedal is stepped on, it can be basically judged that the brake pads are thin and need to be replaced immediately; It may be caused by the workmanship or installation of the brake pads or brake discs, which needs to be checked separately.)

How to tell if the brake disc needs to be replaced
When braking, the constant friction between the brake pads and the brake disc will also cause the thickness of the brake disc to become thinner and thinner. Depending on the driving mode of the vehicle, the service life of the front and rear brake discs is also different. Taking a front-wheel drive car as an example, the service life of the front disk is about 60,000 to 80,000 kilometers, and that of the rear disk is about 100,000 kilometers. Of course, this is also closely related to our driving habits and driving style.

1. Observe the groove to determine whether the brake disc needs to be replaced.

Generally, there are three small grooves distributed on most brake discs, which are called wear indicators. When the brake disc is worn until the small grooves are no longer visible, it means that it has reached its wear limit and the brake disc needs to be replaced immediately.

2. Use your finger to touch to determine whether the brake disc needs to be replaced.
   Due to frequent friction, it is normal for many small scratches to appear on the brake disc. But if the scratch is obviously deep and forms a shape similar to a small groove, we can use our fingers to touch the edge of the groove. If the edges are sharp, it means the grooves are deep, then we should go to the 4S store to inquire whether the brake disc needs to be replaced.
3. Use the indicator light on the instrument panel to determine whether the brake disc needs to be replaced.
   If the brake light on the dashboard comes on, the car’s braking system is malfunctioning. At this time, we should focus on checking whether the brake pads and brake discs are excessively worn. If the brake pads and brake discs are not obviously excessively worn, it may be that there is insufficient brake fluid or there is a problem with the circuit, causing the brake indicator light to stay on. At this time, you should go to the 4S shop for inspection and repair as soon as possible.