Do brake discs need to be replaced when worn by 2mm?
2 Answers
The replacement standard for brake disc wear is around 2 millimeters. If the brake disc wear exceeds this standard, it is prone to the phenomenon of the brake disc being clamped and fractured. The most reliable method for measuring wear is to use a micrometer to measure the remaining thickness of the brake disc. If deep grooves or uneven surface wear are found on the brake disc, it should also be replaced promptly. Otherwise, the brake disc may experience severe vibration during braking, and braking performance may decline. The classification of brake discs is as follows: 1. Brake discs are divided into solid brake discs and ventilated discs by structure: (1) Solid brake discs are simply metal discs used for braking, without any special construction. (2) Ventilated discs are divided into two types: slotted discs and drilled discs. Both treatments aim to improve the cooling performance of the brake disc, reduce its thermal fade, and provide better braking capability. 2. Brake discs are divided into carbon fiber ceramic brake discs and metal brake discs by material: Due to the excessively high manufacturing cost and poor braking force at low temperatures of carbon fiber ceramic brake discs, despite their excellent resistance to thermal fade, they are still not chosen by most vehicles. To enhance resistance to thermal fade, some manufacturers treat metal brake discs with carbon fiber, improving this capability while avoiding the poor low-temperature performance of carbon fiber ceramic materials.
I've been repairing cars for over 20 years and handled countless brake disc issues. While 2mm of wear may sound insignificant, the key factors are the disc's current thickness and its original thickness when new. Typically, new brake discs measure between 28 to 30 millimeters in thickness, with manufacturers specifying a wear limit usually between 19 to 22 millimeters. If the remaining thickness is still well above the limit - say 26mm - it's perfectly fine to keep using them for a while. But if it's approaching the limit, like 20mm remaining, you should replace them immediately. Don't just focus on the wear amount; actually measure the thinnest part with calipers since brake discs often wear unevenly. Neglecting this could lead to longer braking distances or even failure, especially with increased overheating risks during downhill driving. Have your mechanic check them during regular maintenance - it's both reassuring and safer, and saves money in the long run.
