The brake system of a car is the most important safety component of a vehicle, and it may move thousands of times a day. So the daily inspection and maintenance are also what everyone is concerned about. Today, Brother Xu will introduce to you whether the brake disc can be used normally after it is worn out?
（1） The role of the brake disc
The brake disc is used for braking as the name suggests, and it rotates synchronously with the drive shaft. The braking force comes from the brake caliper. When we step on the brake pedal, the brake master cylinder drives the brake cylinder piston through the hydraulic system, and then the brake caliper tightens and clamps the brake disc, so that the brake pads generate friction braking force.
figure 1
（2） Reasons for brake disc wear
Is there an accurate replacement cycle for the brake disc? The answer is no, because brake disc wear has a great relationship with the number of brakes and the quality of the brake pads.
①If it is a low-quality brake pad with more metal materials, it will wear the brake disc. In order to improve the wear resistance of the brake pads, some manufacturers increase their hardness, which will severely wear the brake discs （see Figure 2）， but the brake pads are intact. Therefore, you must choose branded products when replacing brake pads.
②When the brake pads are about to run out, failure to replace them in time will also cause the brake discs to wear. Now high-end models have brake system warning lights, if they are lit, don't drive anymore, because the bottom layer of the brake pads is metal, so the brake discs will be scrapped in a few seconds.
figure 2
（3） Can I continue to use it after repair?
As shown in Figure 2, there will be a lot of "grooves" on the disk surface after wear. Many old drivers take the repair method in order to save the maintenance cost, which is to take the brake discs to the lathe to repair. However, attention must be paid to the remaining thickness and whether the high temperature causes annealing. Generally, the thickness of the front disc of a new brake disc is 32mm, and it cannot be less than 29mm after repair; the standard thickness of the rear brake disc is 28mm, and it cannot be less than 25mm after repair. Otherwise, high-speed driving will cause the danger of disc surface fracture. In addition, if the temperature is too high during repair, the brake disc will lose its original strength and cause danger.
（four） daily maintenance
①The car cannot be washed immediately after the vehicle is running at a high speed. Because the temperature of the brake disc is too high, it will deform when it encounters cold water, and it will cause brake jitter in the long run.
②If the instrument brake warning light is on, you must check the thickness of the brake pad. If it is too thin, the brake disc will be scratched. Many car owners think that the warning light is on because of lack of brake fluid, but it is not. When we checked the brake fluid, it was indeed insufficient, but this was due to the thinning of the brake pads.
③If we make a metallic sound when we lightly step on the brake, it means that the brake pads are basically exhausted. At this time, check it immediately, otherwise the brake disc will wear out into a deep groove.
Summary: If the total wear depth on both sides of the brake disc reaches 2mm, it must be replaced, and there is no need to repair it. Brake discs that are too thin will bend or even break when braking at high speeds, with disastrous consequences.