1.     Brake pads composition and structure

Brake pads are generally composed of steel plates, adhesive heat insulation layers and friction blocks. The steel plates must be painted to prevent rust. The SMT-4 furnace temperature tracker is used to detect the temperature distribution during the coating process to ensure quality. The heat insulation layer is composed of materials that do not transfer heat, and the purpose is to heat insulation. The friction block is composed of friction material and adhesive, and is squeezed on the brake disc or brake drum to generate friction during braking, so as to achieve the purpose of decelerating and braking the vehicle. Due to friction, the friction block will gradually be worn out.

2.     Classification

Automobile brake pads are divided into types:-brake pads for disc brakes-brake shoes for drum brakes-brake pads for large trucks


The brake pads are mainly divided into the following categories: asbestos brake pads (basically eliminated), semi-metal brake pads, less metal brake pads, ceramic brake pads.

3.     working principle

The working principle of the brake is mainly from friction. The friction between the brake pads and the brake discs (drums) and the tires and the ground is used to convert the kinetic energy of the vehicle into frictional heat energy to stop the car. A good and efficient brake system must provide stable, sufficient and controllable braking force, and have good hydraulic transmission and heat dissipation capabilities to ensure that the force exerted by the driver from the brake pedal can be fully and effectively transmitted to the master cylinder And each sub-cylinder, and to avoid hydraulic failure and brake degradation caused by high heat.

4.     The principle of replacing brake pads

The replacement cycle of brake pads often depends on specific conditions such as the operating conditions of the vehicle, the type of the vehicle, the weight of the vehicle, and the type of brake pads. For example, it is often the case in real life that a kind of brake pad can be used for 50,000 or 60,000 km on a certain car, and may have to be replaced when it is only used for 25,000 km on another car. The frequency of vehicles stopping and driving on the road is an important factor. Generally speaking, the replacement cycle of brake pads of a car that has been driving on urban roads for a long time is significantly shorter than that of a vehicle that has been driving on a highway for a long time. Driving on flat roads is shorter, and trucks have a shorter replacement cycle than light vehicles. Therefore, in fact, no “authority” can tell how long the brake pads can be used, only one thing can be determined-the wear of the brake pads should be checked frequently.

5.     Four methods to determine whether the brake pads need to be replaced

1. Look at the thickness: the thickness of a new brake pad is generally about 1.5cm, and the thickness will gradually become thinner as it is continuously rubbed during use. When the thickness of the brake pads is only about 1/3 of the original thickness (about 0.5cm) when observed by naked eyes. The car owner will increase the frequency of self-checks and be ready to replace them at any time. Due to the design of the wheel hub, some models do not have the conditions for visual inspection, and need to remove the tires to complete.


2. Feel the strength: When driving on the road and stepping on the brake, if you feel very strenuous, there will always be a soft feeling. It is often necessary to step on the brake deeper to achieve the previous braking effect. When the emergency brake is taken, the pedal position will be clearly felt If it is low, it is possible that the brake pads have basically lost friction and must be replaced at this time, otherwise it will cause a serious accident. In addition, the reduced braking effect will lead to increased brake fluid consumption. Therefore, when replacing the brake pads, check the condition of the brake fluid.

3. Listen to the sound: If the brakes are lightly tapped and accompanied by the “iron rubbing iron” squeaking or screaming (it may also be caused by the running-in of the brake pads at the beginning of the installation), the brake pads must be immediately replace. Because the limit marks on both sides of the brake pad have directly rubbed the brake disc, it proves that the brake pad has exceeded the limit. There is a raised mark on both sides of each brake pad. The thickness of this mark is about two or three millimeters. This is also the limit for the thinnest replacement of the brake disc. If the thickness of the brake pad is already parallel to this mark, it must be replaced. Therefore, when the thickness of the brake pad is close to this mark, the owner must observe and prepare at any time, but it is difficult to accurately observe with the naked eye without disassembling the tire. It is recommended to go to a 4S shop or a regular repair shop for inspection to determine whether it needs to be replaced.

4. Use the brake warning light on the dashboard as the basis for judging whether to replace the brake pads. Some high-end cars have brake warning lights and generally speaking, only the front brake pads have the brake warning line. When the warning light is on, it is quite dangerous if it is not changed until then. This is because some of this warning system directly senses the thickness of the brake pads, and some of them cause the warning light to light up after the brake pads have been completely worn out and the brake fluid has dropped extremely. If it is the latter, when the warning light is on, the metal base of the brake pad and the brake disc are already in the state of iron grinding. At this time, you will see bright iron cuts on the edge of the tire near the rim. Therefore, we recommend that you regularly check the wear of the brake pads to see if they can be used, instead of just trusting the warning lights.

John Doe
28th Aug 2020