What Causes the Brake Noise in BMW 3 Series?
2 Answers
BMW 3 Series brake noise may be due to uneven wear of the brake discs. When measured with tools, excessive radial runout beyond standard values may be detected, and uneven surfaces may also occur during use, resulting in noise when the brake pedal is pressed. The solutions are as follows: 1. Brake pad wear: If the brake pads are worn to their limit, new brake pads should be replaced and chamfered to prevent catching on the raised outer edges of the brake discs. Apply noise-reducing paste to the surface of the brake pads, and after installation, press the brake pedal several times to restore braking force. Drive cautiously during the initial period to allow the brake pads to wear in more evenly. 2. Rusty brake discs: If the brake discs are found to be rusty due to prolonged disuse, press the brake pedal several times while driving to remove surface rust. For brake discs worn to their limit with thickness below the standard, replacement is recommended.
A few days ago, I repaired a BMW 3 Series with brake squeaking. The owner said there was a squeaking sound when braking, which was really annoying. The most common issue is worn brake pads—when the thickness falls below the safety line, the metal backing plate contacts the rotor, causing noise. It's best to measure the thickness and replace them promptly. Alternatively, an uneven rotor surface with rust or scratches can generate noise when rubbing against the pads, requiring resurfacing or replacement. Occasionally, small stones or sand get stuck between the pads, which may dislodge after a few brake applications, but don’t ignore the risk. New brake pads may also squeak before proper bedding-in; the noise usually fades after a few days of driving. Wet or humid conditions can cause temporary but noticeable squeaking. I recommend visiting a professional auto shop to check for loose calipers and inspect the entire braking system—safety is no small matter. Remember, don’t wait until braking performance degrades to fix it; this is a critical component for high-speed safety.
