BMW Brake Caliper Repair Kit - Frenkit 244955

Brake calipers are paramount to your BMW's braking performance. However, when you dissect a brake caliper you will be surprised to see how basic they are. A single-piston brake caliper consists of an aluminum or steel brake piston that is sealed inside the caliper bore via a rubber square-cut seal. The piston is forced outward to squeeze the brake pads by the force of the brake fluid behind it. The square-cut seal in this process rolls slightly and when the brake fluid pressure is reduced the square-cut seal pulls the brake piston back slightly.

In the case of the popular P4.20 and P2.44 Brembo calipers, the biggest shortcoming of these calipers is the phenolic pistons installed from the factory. While they do not suffer the typical corrosion problems steel pistons may have from water-logged brake fluid they are known to crack when they get very hot (track days, HPDE, etc) and this is a long-term liability. Furthermore, used calipers which are often purchased as an upgrade, are a crapshoot unless you know the history of the brake calipers.

This repair option from Frenkit includes aluminum brake pistons, new square-cut seals, dust boots, and internal crossover seals. We have added a separate package of crossover seals for this kit since we have found the included crossover seals from Frenkit are slightly too thick and can get pinched between the two caliper halves. We recommend using the ATE crossover seals included separately as opposed to the prepackage seals in this kit.