Case: An Audi A6L 2.0T, when the low-speed slow brake, the left front wheel part emits metal friction sound, when the brakes are heavy, there is no such sound. Is this what is going on?
Answer: Reflect the abnormal noise when the light is stepped, mainly the friction between the brake pad and the brake disc. When you step on the brake pedal, the brake pad will always be in slight contact with the brake disc, resulting in an increase in the friction temperature between the disc and the sheet, so that the material surface of the brake pad is carbonized. A hard substance that causes an abnormal sound when it is slightly rubbed.