What Causes Loud Brake Noise When Reversing?
4 Answers
The reason for loud brake noise when reversing is: Brakes primarily operate during forward vehicle motion, causing prolonged unidirectional wear on the brake pads. This creates burrs on the reverse side, which produce abnormal sounds when rubbing against the brake disc during reverse braking. This issue can be resolved by removing and smoothing the brake pads or replacing them with higher-quality ones. More details are as follows: 1. The automotive brake system, also known as the automotive braking system, functions to: forcibly decelerate or stop moving vehicles as required by the driver; maintain stationary vehicles on various road conditions (including slopes); and stabilize speed during downhill driving. 2. Currently, most domestic automakers use front-disc-rear-drum brake systems for small and medium-sized production vehicles, with some models featuring four-wheel disc brakes. Compared to drum brakes, disc brakes are more technologically advanced, lighter in weight, and offer superior heat dissipation, braking performance, and adaptability to complex weather and road conditions.
As a car owner, I deeply understand the loud noise when braking in reverse. This situation is usually caused by abnormal friction between the brake discs and brake pads. When parked, the surface of the brake discs is prone to rust, especially on rainy days or in humid environments, forming a thin layer of rust on the metal surface. When reversing, the brake pads scrape against this rust, producing a harsh metal friction sound. Additionally, when the brake pads are worn to their limit, they can also produce abnormal noises because the metal warning plate on the back starts to directly scrape the brake disc. Last time my car had this issue, the noise disappeared after replacing the brake pads. Foreign objects in the braking system can also be a problem—sometimes small stones get stuck in the gaps of the brake pads, causing a rattling sound when reversing. In my opinion, occasional noises like this aren’t a major concern, but if the noise persists every time you reverse, it’s best to have the braking system checked at a repair shop.
I've encountered the issue of reverse braking noise many times during car repairs. It's primarily a problem with the friction materials. When your car sits idle for extended periods, the brake disc surface oxidizes and rusts. When reversing, the brake pads rub against the rusted surface in the opposite direction, causing that screeching sound. Additionally, many modern brake pads use semi-metallic materials which have high friction coefficients but also produce more noise. These materials don't make much noise during forward driving, but tend to create high-frequency squeals when reversing. The last car I worked on had abnormal resonance due to improperly installed brake pads. In some cases, it's caused by parking brake springs not retracting properly, resulting in a whining sound when reversing with the brakes dragging. My recommendation is that when owners hear unusual noises while reversing, they should apply the brakes several times to wear off the rust. If that doesn't work, wheel removal and inspection is necessary. Never randomly spray lubricants yourself - that will only compromise braking effectiveness.
A loud abnormal noise when braking in reverse is quite common, especially on winter mornings. This phenomenon is mainly related to the properties of metal. Brake discs are mostly made of cast iron, which is prone to rust when exposed to water vapor, and the rust layer increases the friction coefficient. More critically, when reversing, the relative movement direction between the brake pads and the brake disc changes, turning the original friction surface into a scraping action. The small burrs on the edges of the brake pads and the rust on the surface of the brake disc create intense friction, making the noise particularly harsh. Additionally, some brake pad formulations contain copper fibers, which can also produce unique sounds during high-intensity friction. I recommend that car owners try pressing the brake pedal firmly several times to wear off the rust. If the noise persists for two consecutive days when reversing, it's time for an inspection. To prevent this, avoid parking in standing water and, for long-term parking, it's best to release the handbrake to prevent sticking.
