After buying a new car, the brakes will feel very sensitive, and the braking force will be stronger when you step on the brake pedal a little. But after driving for tens of thousands of kilometers, many drivers will feel that the brake system begins to soften, and the duration of stepping on it becomes longer, as if stepping on a cotton cover. What's going on here?

    The first reason is that the wear of the brake pads and the brake disc leads to the thinning of the thickness. For example, in disc brakes, the caliper (also called the brake pad) clamps the brake disc for a long time. Over time, the friction will make the surface of the caliper and the brake disc thinner and thinner, which will make the stroke of the brake pedal longer.

    The second reason is tire wear. The life of the tire is generally about 60,000 kilometers. The tire tread of the near-life tire will be worn very thin, reaching the wear mark in the tire groove. The long-term friction between the tire and the ground will also deteriorate, resulting in a long braking distance. When you step on the brake, you will feel that you are stepping hard, but the braking effect of the car is relatively slow. . But these two reasons are not the most important. In fact, the softness of the brakes is mainly related to the brake fluid.

    Now, the braking system of most cars is hydraulic braking, that is, it needs to be pressurized with brake fluid to transmit the braking force to the brake pads. After the brake fluid is compressed, the volume is not easy to reduce. To put it bluntly, it is not easy to be compressed. This is one of the reasons why the brake must use professional brake fluid. However, we know that friction generates heat. When the brake pads are vigorously applied to the brake disc, high temperatures will be produced, and the high temperature will be transmitted to the brake fluid through the brake pads and the brake cylinder. At this time, if the brake fluid contains water, it will be more troublesome. At this high temperature, the water will evaporate and vaporize and become a gas that can be compressed. Even if this water vapor is small, it exists in the brake pump. People feel that the brake pedal becomes soft, and the soft part is actually to compress the vaporized water.

    But many friends may have a question, isn't it brake fluid, why is there still water? The moisture in brake fluid mainly comes from the following aspects:

    First of all, the pipeline of the brake system is not sealed. There is usually a small hole on the oil storage pot for ventilation. Because the oil level will rise and fall when braking and lifting the brake pedal, this vent is used to ensure that the oil can rise and fall normally.

    In addition, the pipeline interface of the braking system may not be tightly sealed. In rainy days or when driving in water, water may enter the brake fluid. Coupled with the fact that brake fluids are also hydrophilic to a certain extent, it leads to the absorption of moisture into the brake fluids. After combining these factors, after the car has been driven for a few years, the brake pedal will become very soft, feel like cotton, and not so sensitive.

    Here, I will also tell you about the maintenance cycle of the brake system components.

    Brake fluid is generally replaced every two years or 40,000 kilometers, and each time is about 2 liters to 4 liters. The replacement of brake pads and brake discs depends more on braking habits. Some people drive on the brakes more frequently and may replace them earlier. However, the criterion for judging whether to replace the brake pads is that if the wear thickness of the brake pads is less than 3 mm, it must be replaced. If we must estimate an approximate date, it is about 30,000 kilometers, and we must pay attention to maintenance and inspection to see if this standard is met. The brake disc has a relatively longer life. Generally, after 80,000 kilometers, it should be checked every time it is maintained.

    There is also a tire replacement cycle of 2 years or 60,000 kilometers, but generally it will take longer than this. There is a protrusion of wear mark in the tire tread. When the thickness of the tire tread reaches the wear mark, it must be replaced as soon as possible.