Should Brake Discs with Grooves Be Replaced?
2 Answers
Brake discs developing grooves is a normal phenomenon, and replacement is not necessary if it does not affect braking performance. Relevant details are as follows: 1. Most brake discs will develop scratches or grooves during use, mainly due to the material composition of the brake pads. Brake pads are made of a combination of various materials, including hard metal powders. If there are relatively large metal particles in the powder, friction between these particles and the brake disc will cause scratches or even grooves. This occurs because metal particles are quite hard and share the same material as the brake disc, leading to damage when they rub against each other, hence the grooves on the brake disc. 2. Brake discs should be replaced when the wear depth exceeds 2 millimeters. Generally, brake discs should be replaced after changing brake pads 2-3 times. If vibration occurs during braking, this may also indicate an issue with the brake disc, possibly due to uneven wear or deformation. In such cases, the brake disc should be removed and resurfaced using a lathe. If the problem persists, a new brake disc should be installed.
Having worked in car repairs for over a decade, I've seen countless brake disc groove issues. To check groove depth, stand a 1-yuan coin on its edge for comparison—if the groove is significantly deeper than the coin's thickness, replacement is needed. But context matters: if the steering wheel vibrates like a phone alert during braking or there's screeching metal noise, it's likely caused by excessive groove depth. Never assume resurfacing will suffice—overly thin discs dissipate heat poorly, risking brake pad damage from overheating. I recommend direct thickness measurement—most OEM discs are ~28mm thick; replacement is mandatory if worn below 25mm. Pro tip: always replace pads when changing discs, otherwise new discs will quickly regroove.
