Why does it feel like scraping the undercarriage when braking?
2 Answers
The main reason for the sensation of scraping the undercarriage when braking is excessive wear in the braking system. Here is a detailed explanation of the causes: 1. The most worn parts in the braking system are the brake pads and brake discs. When these are excessively worn, braking can cause a scraping sensation. 2. The friction material on the brake pads may be completely worn away, exposing the underlying metal. During braking, the metal rubbing against the brake disc produces a metallic scraping sound similar to that of scraping the undercarriage. 3. If there are pits or unevenness on the brake disc, severe braking noise can also occur when the vehicle is braking. In such cases, the brake disc may need to be replaced or resurfaced.
I've been repairing cars for over twenty years, and every time a car owner says that stepping on the brakes feels like scraping the undercarriage, I first inspect the brake discs and pads. It could be due to uneven surfaces on the brake discs, such as grooves or rust, causing the brake pads to squeak when pressed, giving the sensation of the undercarriage being scraped. Another possibility is that the brake pads are completely worn out, with the metal backing plate directly contacting the disc surface, producing a harsh scraping sound. Don't underestimate this noise—it indicates abnormal wear in the braking system. Ignoring it can lead to faster disc deformation and doubled repair costs. I once handled a case where the owner delayed for months, resulting in the disc being completely ruined, costing nearly two thousand to replace both the disc and pads. My advice is to measure the brake pad thickness immediately upon hearing such abnormal sounds; if it's below 3 millimeters, they need replacement. Additionally, check if the undercarriage guard plate is loose—sometimes rocks stuck in it can also create a false impression. In short, safety comes first. Brakes are a matter of life and death, so take your car to a professional shop for inspection as soon as possible.
