The problem of brake fluid boiling is simply traced to heat transferring from the rotors and pads directly into the fluid through the caliper pistons. When brake fluid boils, it releases air that is normally part of the molecular structure of the fluid. This air is compressible, of course, and the brake pedal goes to the floor instead of moving the caliper pistons. Production cars tend to suffer from this on track days because they don't have the extensive cooling ducts and exotic brake materials found on racing cars.
Race-only brake calipers generally come with titanium caliper pistons for one reason: titanium has low thermal conductivity. This means it's very bad at transferring heat, which is good if you're trying to keep your brake fluid from boiling. Here's a comparison of materials and their relative thermal conductivity ratings (lower is better):
- Titanium 6AL-4V = 6.7 W/mk
- Steel = 52 W/mk
- Aluminum = 130 W/mk
Most fixed calipers use aluminum pistons which are, unfortunately, excellent at transferring braking heat to your brake fluid. Our solution is to place Girodisc's thin titanium shims between the brake pad and the caliper pistons. This helps prevent braking heat from transferring into the pistons and, thus, into the fluid.
For cars that are going to see hard or multiple track days, these shims are affordable protection from losing your brake pedal at the wrong time and making your track day very expensive.
Water jet cut to exact size; no cutting, grinding, or swearing involved.
Price is per axle (four shims)