The different hardness of brake discs during manufacturing will lead to different wear degrees, which will not have much impact. If noise is heard in the cab (at the brake pedal), it may be that the nylon bushing on the brake pedal fixing bracket is worn and the brake pedal fixing pin rubs him.
If it is a hard spot, the easiest way is to run backwards at a speed of about 5 kilometers and step on a few feet, which can generally remove the hard spot. Suggestions or omissions are not too loud and have no effect on driving. If the iron touches the iron, the disc should be replaced immediately. In addition, at this time, the brake of the instrument did not give an alarm, so it is necessary to check whether there is a problem with the sensor connected to the brake failure light.