Now most passenger cars use disc brakes, which are not only small and light in size compared with drum brakes, but more importantly, good heat dissipation, so the brake stability of disc brakes will be better. The brake disc (also called brake disc) is an important part of the disc brake, its structure is disc-shaped, with the wheel rotation, it is through the friction between the brake pad and the brake disc to achieve wheel braking. We usually press the brakes, and the result is to push the piston movement of the brake sub-pump, so as to press the brake pads to the brake discs.
Brake discs are not replaced as often as brake pads, but they must be replaced if:
1. When driving at medium and high speeds, the steering wheel shakes as soon as you step on the brakes:
This is because the lateral runout of the two front wheel brake discs exceeds the specified limit, which varies from model to model, generally 0.04~0.07 mm. If the amount of runout is too high, it will cause the brake disc to swing left and right when rotating, and a violent vibration will occur when braking, and this vibration will be transmitted to the steering wheel through the steering wheel, making the steering wheel shake. The greater the lateral runout of the brake disc, the more the steering wheel shakes.
It should be noted that in the past, brake discs were very expensive, and they were often solved by using lathe light brake discs. Now the brake discs are replaced directly for the cost performance.
2. When driving at medium and high speeds, when you step on the brakes, you will feel that the brake pedal will vibrate:
When driving at medium and high speeds, you feel that the brake pedal vibrates very badly when you lightly press the brakes, which is mainly caused by the unevenness of the surface of the brake disc and need to be replaced.
If you feel that the brake pedal is vibrating when braking hard, this is generally ABS in action, which is normal.
3. The groove on the brake disc is worn, and the depth is more than 1.5 mm:
The brake disc is grooved and is easy to produce brake noise when replacing the brake pads. The brake discs of various models have a specified standard thickness and limit thickness, and the thickness value varies depending on the model. Generally, the brake disc must be replaced when it is worn to the limit thickness, and in the actual daily maintenance, because there is no standard thickness value, it is often judged according to the depth of the worn groove.
If the brake disc is deeply worn and the groove is not replaced, when the thickness of the brake disc is less than the specified limit thickness, it may cause brake weakness or even no brake, which is quite dangerous. Because at this time, even if the piston of the brake sub-pump reaches the maximum stroke, the brake pad cannot be pressed against the brake disc.