GIRODISC TS-0991-4 Termoplastyny Perednikh Kolodok 6-Porshnevoho Suporta (Tytan) For PORSCHE 911 GT2/GT3/Turbo (996/997)

The problem of brake fluid boiling is caused by heat transferring from the rotors and pads directly into the fluid through the caliper pistons. When brake fluid boils, it releases air, which is normally part of the fluid's molecular structure. This air, of course, compresses, and the brake pedal goes to the floor instead of actuating the caliper pistons. Production cars typically suffer from this on track days because they lack the extensive cooling passages and exotic brake materials found in true race cars. True racing brake calipers are usually fitted with titanium pistons for one reason. Titanium, as a material, has low thermal conductivity. This means it transfers heat very poorly. Which is very good if you are trying to keep your fluid cool.

Girodisc's solution to prevent fluid boil is to use a thin titanium shim placed between the back of the pad and the pistons so that heat from braking is not transferred to the pistons and fluid. Here is a comparison of materials and their relative thermal conductivity ratings:

Titanium 6AL-4V 6.7 W/mK Steel 52 W/mK Aluminum 130 W/mK

It can be seen that titanium transfers significantly less heat than steel and especially aluminum. For cars that are going to spend several days at the track, these shims are an inexpensive insurance policy against losing your pedal due to boiling at an inopportune moment, which would make for a very expensive day.