Why is there a scraping sound from the undercarriage when lightly pressing the brakes?
3 Answers
Here are the main reasons for the scraping sound from the undercarriage when lightly pressing the brakes: 1. Brake pad wear: The friction between the brake pads increases when braking, causing abnormal noises. 2. Loose undercarriage components: When the undercarriage is loose, it can cause friction between various parts, leading to abnormal noises. 3. Aging of undercarriage rubber, resulting in reduced performance. 4. Faulty lower control arm. Below is an analysis of the reasons for abnormal noises from the undercarriage: 1. When turning, abnormal noises from the undercarriage may indicate faults in the steering system or suspension system, as the vehicle's tilt during turning causes deformation in the suspension system. 2. When driving on good road conditions, abnormal noises from the undercarriage may be due to faults in the braking system components, such as loose or worn parts, out-of-round brake drums, or uneven brake discs. 3. Abnormal noises from the undercarriage may also indicate issues with the bearings connecting moving and stationary parts. If there is a problem with the bearings, the driver can identify it by lightly pressing the brakes. If the noise remains unchanged during uniform motion, it indicates a bearing issue. 4. When driving on poor road conditions, abnormal noises from the undercarriage are mostly due to suspension system abnormalities or loose braking system components, with the suspension system often producing friction sounds.
I often hear a scraping sound from the undercarriage when lightly pressing the brakes while driving, which is a sharp metallic friction noise. The most likely cause is excessively worn brake pads. When brake pads wear down to their limit, the metal backing plate directly scrapes against the brake disc, producing this noise—especially noticeable when the discs are rusty after rain. Another common reason is small stones or sand trapped between the brake pads and disc, causing unusual noises during friction. If not addressed promptly, the brake disc may wear out or warp quickly, leading to repair costs ranging from hundreds to over a thousand yuan. It's recommended to visit a professional repair shop as soon as possible to check the brake pad thickness and remove any debris. Generally, pads thinner than 3mm should be replaced. Regular maintenance, such as inspecting the braking system every six months, can prevent such issues and ensure driving safety.
As a car enthusiast, I understand the principle of scraping sounds when lightly applying the brakes, which are usually caused by abnormal friction in the braking system. For example, uneven brake pad surfaces with grooves can generate noise when rubbing against the disc; or rust on the brake disc that produces sound when initially scraping off the rust layer; or foreign objects like road dust stuck between the disc and pads. These issues are not only annoying but also affect braking performance, posing significant risks if the brakes fail. It's advisable to first conduct a simple check around the tires for any loose components, but it's best to visit a professional shop for a tool-assisted diagnosis. Neglecting these issues could lead to the need for replacing both the brake discs and pads, doubling the cost, so it's better to address them early to save money. Additionally, avoiding sudden braking during normal driving can help extend the lifespan of the braking system.
