Why is there a strange noise when braking in reverse gear?
4 Answers
It is normal to hear unusual noises when braking in reverse gear. Since the vehicle moves forward for 99% of its total mileage, the brake pads and discs wear predominantly in one direction. The brake pads contain metal components, which can develop metal burrs over time. When braking in reverse, these burrs come into contact with the brake disc, causing the strange noise. The steps for reversing an automatic transmission vehicle are: 1. Press the brake and shift to R gear; 2. Release the handbrake and check the rearview mirror or turn around to observe the intended reversing path; 3. Gently release the foot brake; 4. After reversing to the desired position, fully depress the foot brake and engage the handbrake; 5. Shift from R gear to N gear while pressing the foot brake; 6. Release the foot brake to complete the reversing process.
I've been driving for over a decade and have encountered the issue of strange noises when braking in reverse several times. Based on my experience, this sound usually stems from the interaction between the brake discs and brake pads. Especially right after washing the car or during humid weather, the surface of the brake discs tends to rust, which causes that 'squeaky' friction noise when braking in reverse. Some cars use harder brake pad materials, making this noise even more pronounced. The most troublesome scenario is when the caliper guide pins lack sufficient lubrication, increasing resistance during reverse braking and producing odd sounds. Personally, I make it a habit to rinse the brake components with neutral car wash detergent to remove debris and reduce noise. If the noise persists for several days, I always go for a brake pad thickness check—safety comes first after all.
When I first bought the car, I noticed a metallic scraping sound whenever I braked while reversing. I specifically consulted a friend who works at a repair shop. He said this issue is very common, and it's likely caused by hard spots on the edge of the brake pads rubbing against the brake disc. When reversing, the force direction on the brake pads is opposite to that when moving forward, so the problem that usually goes unnoticed becomes apparent during reverse braking. He advised me to press the brakes several times after rain or washing the car to let the brake pads wear off any surface rust. If the issue persists, it might be due to poor retraction of the brake caliper, requiring lubrication of the guide pins. Warped brake discs are also a possible cause, leading to abnormal vibrations and noise when braking in reverse. Now, during every maintenance session, I make sure to have the guide pins checked and lubricated, as neglecting these minor issues can eventually damage the brake discs.
After studying numerous cases of brake noise, I've found the key to squealing during reverse braking lies in pressure distribution. When reversing, the force direction on brake caliper pistons and pads is completely opposite to forward motion. This causes unpolished spots on the rotors to suddenly contact the pads, especially noticeable when the disc surface has grooves or rust. The first reverse brake after cold start also tends to squeak due to moisture condensation on rotors rubbing against pads. The solution is actually simple: firmly pump the brakes several times to warm up the pads and grind off contaminants. However, frequent occurrences warrant checking the rotor flatness.
