Diagnosing abnormal brake squeaks can be a frustrating process, and the process of figuring out which squeak (squeak, rattle, or knock) is causing you can be frustrating, no matter how experienced you are. noise engineer. Because this kind of rattling often occurs while the vehicle is running, you can neither touch nor lock the mechanism it produces.
Another puzzling situation is how to correctly distinguish brake noise from brake squeal and what subjective evaluation methods should be used to identify problems in the early stages of project development (pre-prototype), prototypes, programs and pilot vehicles The early stage is extremely important (this is not the point of this short article, I will sort out the subjective evaluation method of the current mainstream OEMs on the abnormal brake sound in the following article).
Encountering such a thorny problem, the first thing we need to do is to judge the characteristics and working conditions of various noises as much as possible through the operation on the road.
This noise is more pronounced when the vehicle is driven in rough road conditions. To determine if the noise is coming from the brake calipers, it is usually necessary to lightly depress the brake pedal at the moment the noise occurs. If the noise disappears and reappears when the brake pedal is released, the lower boot needs to be replaced. At the same time, it is necessary to compare the similarities and differences of the abnormal noise in the forward and backward operation.
The specific operation steps and requirements are as follows:
1) Raise and properly support the vehicle (the first step is safety is the most important).
2) Remove the wheel and tire (as long as you can change the tire in this step).
3) Reinstall and tighten 2 lugs to secure the rotor to the hub (not all brake calipers have this structure, flexible).
4) With a large C clamp, compress the piston into the caliper bore, and remove the C clamp (if you are really unfamiliar with the braking mechanism, you should first analyze an old part to improve your understanding of the structure).
5) Remove the lower caliper guide pin bolt (don't lose it).
6) With the brake hose still attached, pivot the caliper upward and secure the caliper with mechanic’s wire (see Fig. 1).
7) Remove the lower caliper guide pin, being careful not to damage the pin boot (be careful!).
8) Remove the rubber bushing from the caliper guide pin (see Fig. 1).
9) Clean the caliper guide pin and install replacement bushing. Lubricate the guide pin and bushing with high temp brake silicone lubricant (try to do this step honestly).
10) Remove the support wire and rotate the caliper into position over the disc pads (be careful of your little "pig feet" when turning).
11) Install the lower caliper guide pin and torque to the required value (remember to apply full torque).
12) Repeat the procedure on the opposite side (contrast is important).
13) Swap them.