What Causes Noise in Newly Replaced Brake Pads?
2 Answers
It is normal to hear noise when braking after replacing new brake pads. There is a break-in period required between the brake pads and brake discs, which usually takes about 500 kilometers to complete. The brake discs may have been worn unevenly by the old brake pads, while the surface of the new brake pads is smooth. Initially, the contact area between the new brake pads and the brake discs is small, which can cause noise during the break-in process. If there is abnormal noise after replacing new brake pads, the following reasons may be the cause: 1. The brake pads may contain metal wires or other hard material particles of larger size. When the brake pads wear down to these materials, they may produce noise against the brake discs. After further wear, the noise will disappear and will not affect safety. 2. After replacing new brake pads, incorrect installation may cause noise. Common installation errors include installing the brake pads upside down, with the metal side facing the brake disc, which can lead to abnormal noise. 3. Sand or debris in the brake discs may cause noise: If foreign objects such as sand or small stones get between the brake pads and brake discs while driving, the brakes may produce a sharp hissing sound. Continuing to drive normally will usually dislodge the debris, eliminating the noise. If the noise persists for a long time, it may be necessary to remove the wheel and extract the debris.
Last week I also helped a car owner deal with a similar issue. New brake pads making noise is mostly due to improper installation details. Some repair shops take shortcuts by directly installing new pads without grinding the chamfered edges of the friction surface, causing squealing when the pads engage with the rotors. Other issues include insufficient lubrication of the caliper guide pins or not resurfacing the grooves on the old brake discs, making the new pads 'dance'. The most troublesome is improperly installed noise-reducing shims on the back of the brake pads, creating a metal-on-metal screech like nails on a chalkboard. The solution is simple: have the mechanic remove the brake pads, sand a 45-degree bevel on the edges, reapply special grease to the guide pins, and the noise should stop. Remember to brake gently for the first couple of days after installing new pads, just like breaking in new shoes.
