Although the piston seals and dust seals of brake calipers give the impression of being structurally shielded from the outside air, the grooves in the dust seals that are closer to the outside air are definitely being eroded by the accumulation of dirt. Moisture is absorbed by the brake fluid as it is deposited during driving in the rain, and this appears as chalky sludge. The removal of this sludge is of great significance. Let’s maintain brake performance with aggressive cleanup here.
Note the caliper piston seal groove!
Sludge accumulates in the piston seal groove, which is responsible for maintaining an airtight seal between the caliper body and the brake piston, due to the moisture absorption properties of brake fluid. The piston seals to prevent fluid leakage when the piston operates, but even a very small amount of fluid seepage can cause moisture to collect and form sludge. As sludge accumulates, the cross-sectional shape of the inside of the seal groove changes, and the ring-shaped piston seal is deformed so that it is partially pressed down. This is a major cause of the significant deterioration of the brake piston’s operability. It is difficult to maintain the condition of the brake pistons in perfect condition, no matter how thorough you think you have been. That is why we should “periodically overhaul brake calipers” to clean up the inside of the seal grooves. In such a case, the work progresses efficiently by using a car wiper bone tool, but there are also special tools available for cleaning up the caliper seal groove. The product in the image is an original product made by Straight, a well-known automotive specialty tool store. It is a caliper seal groove cleaning tool.