What Causes the Metal Friction Sound from Brake Pads?

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Metal friction sounds from car brake pads can be caused by excessively hard brake pads, excessive wear of the brake pads, excessive wear of the brake disc or brake drum, rust on the brake caliper, slow return of the brake master cylinder, among other reasons. Below are the replacement standards for brake pads: Mileage: Under normal driving conditions, the front brake pads should be replaced approximately every 30,000 to 50,000 kilometers, and the rear brake pads every 60,000 to 100,000 kilometers. Once severe wear is detected, they should be replaced promptly. Wear Level: Generally, new brake pads are about 1.5 centimeters thick. If they wear down to one-third of their original thickness, meaning less than 5 millimeters, it is recommended to replace them immediately; If a metal friction sound is heard during braking, this may indicate that the brake pads have worn down to their minimum thickness, causing the limit indicators on both sides of the pads to contact and rub against the brake disc, producing abnormal noises—prompt replacement is necessary; If the brake pedal feels lighter than usual, or if braking feels laborious and ineffective, it indicates severe wear and insufficient thickness of the brake pads, requiring immediate replacement.