What Causes Grooves on Brake Discs?
3 Answers
Scratches on brake discs are a normal phenomenon, and generally, as long as the scratch depth does not exceed 0.6 millimeters, there is no cause for concern. There are two scenarios that lead to deep scratches: Here are the relevant explanations: 1. Only the front or rear brake discs have grooves. This situation is usually caused by driving habits or uneven distribution of braking force between the front and rear. 2. Only one brake disc has grooves while the others are normal. This is typically due to material issues or external forces. Possible factors include: a. Foreign objects getting stuck between this brake disc and the brake pad, coinciding with heavy braking. b. Uneven force distribution from the brake caliper. c. Manufacturing defects in the brake pad, resulting in uneven composite materials that make the pad too hard or contain large metal particles. Recommended solution: Remove the brake pads with grooves, place low-grit sandpaper on a flat surface, and sand the brake pads both horizontally and vertically until they are smooth.
As a mechanic with years of experience, I've found that the most common cause of grooves in brake discs is small debris like sand or pebbles getting mixed into the brake pads. When you apply the brakes, these particles get wedged between the disc and pad, acting like sandpaper that gradually grinds grooves into the surface. Sometimes, low-quality brake pads with uneven material distribution can have metal particles that turn into 'mini files'. Another frequent issue is when car owners delay replacing worn-out brake pads - once the friction material is completely gone, the backing plate starts directly scraping against the disc, creating deep grooves. If these grooves exceed 1mm in depth, you'll feel strong steering wheel vibration during braking, almost like a smartphone's vibration mode. At that point, the disc needs to be resurfaced or replaced entirely to fix the problem.
My old car had the issue of scratched brake discs before, producing a harsh metal grinding noise every time I braked. Upon disassembly, radial grooves were found all over the disc surface. The mechanic said it was mainly because I often drove on construction sites, causing the brake pads to pick up too much grit, which repeatedly ground grooves into the discs. Additionally, the humid climate in the south accelerates oxidation and flaking of the brake pad surfaces, turning the debris into tiny blades that scrape the discs. Now during maintenance, I always make sure the mechanic checks the brake pad thickness, as replacing them early can prevent such problems.
