What Causes Abnormal Noise When Braking in Reverse?
2 Answers
The main reasons for abnormal noise when a car is reversing are as follows: 1. Break-in period causes directional wear on brake pads. Since the brake disc itself develops scratches, the contact area with new brake pads is initially small, resulting in weak braking force at first. However, prolonged contact and friction cause the surface imprints to align, ensuring sufficient braking force during braking. Yet, this break-in process also creates directional characteristics in the friction layer of the brake pads. 2. Vibration and squealing due to disrupted torque balance. Due to the principles of physical torque, the friction pressure at the front and rear ends of the brake pads differs. The front-end pressure is generally significantly lower than the rear-end pressure. Therefore, in some "multi-piston" caliper products, the pistons closer to the front end of friction are often smaller, leading to abrupt braking engagement during reverse braking and accompanying squealing noises caused by torque imbalance. 3. Accumulation and re-entrainment of wear debris into the friction surface. During operation, brake pads inevitably produce some wear debris, which consists of particles shedding from the surface of the brake pads. These debris accumulate on one side of the brake pad as the brake disc rotates. Reversing suddenly changes the friction direction, causing the debris to be re-entrained between the brake disc and brake pads.
I've been driving for over 20 years and have encountered many situations where there were abnormal noises when braking in reverse. The most common cause is rust on the brake discs, especially after parking in rainy or humid weather, when a layer of rust forms on the surface. When reversing, the direction of the wheels changes, and the different friction angles produce that harsh squealing sound. Another reason is when the brake pads are worn to their limit, the sound of the thin pads rubbing becomes more pronounced. Sometimes, foreign objects like sand or dust stuck in the brake pads can also cause abnormal noises. This situation is not only annoying but can also affect braking performance. If the brakes fail to work in an emergency, it could be dangerous. I recommend going to a professional shop for an inspection promptly. Regular cleaning of the brake discs or replacing parts can prevent major issues. Safe driving is no small matter.
