If you fail to make ducting and airflow improvements a few laps

If you fail to make ducting and airflow improvements a few laps into any race caliper drag will develop and you will witness brake fade.



Remember the higher the fluid spec the faster it will deteriorate, China automotive brake Manufacturers flushing through by changing fluids 2-3 times a year in any performance driving environment is advised.



Race drivers have also complained that as races go on, fade develops.



The effect of caliper drag is for the pad operating temperature to shoot up several hundred degrees higher than target which causes a spongy brake and brake fade.



Vapour lock happens when the water content, which all brake fluid has, starts to boil. Water boils at 1 bar atmospheric pressure at around 100 degrees C or 212 degrees F. Also brake fluid of the highest wet boiling point should be used to avoid vapour lock.



The conclusion is that this is not so much a pad material fault as a system fault caused by caliper drag. There are brake fluids around that withstand boiling to well over 160 degrees C or 300 degrees F such as EBC BF307 which is an ideal fluid for performance use. We hear race drivers reporting heat paint temperatures of 800 degrees C, that is way above what discs and calipers should ever run and clearly shows a lack of ducting getting to the brake itself. For this reason calipers used in racing must be in superb condition and seals changed at intervals to prevent hardening or the caliper changed for a unit designed for performance use..



Another important consideration is how hot your calipers are getting.



In Dyno work in the EBC lab in the UK where a target brake torque of 1200 Nm was required during race test cycles, almost 300 Nm was already measured before the brake was applied due to caliper drag. This of course means the starting temperature of the brake test in later cycles was already several hundred degrees higher than in early brake cycles of the test. As the seals age or the caliper gets hot the ability of the seals to retract becomes less or zero, hence the pad drag. This was encountered when using a stock EVO or Impreza four piston caliper which is a very good performance caliper during laps 5 and higher of Brake drum Suppliers the standard EBC race brake simulation..


This happens for two reasons. Caliper seals are essentially square in cross section with a very small one or two degree angle on the outer diameter which pulls the piston back and allows the brake pad to become free from the disc. This is the issue caused by caliper drag, as the caliper gets hotter drag sets in and later stages of the race, brake fade is experienced. This happens as the caliper gets hotter but also it is worth remembering that pad retraction in any caliper is totally reliant on seal 'pull-back'. Of course the pad IS ACTUALLY fading but not through any fault of its material design. Seals in standard road going calipers are simply not made for race use and may harden and cause drag or the calliper body itself may shrink and tighten on the seals and pistons increasing caliper drag...



This is often confused with pad fade and the brake pad is criticised. This of course is nothing a different pad compound could ever improve upon, consider improving airflow to calipers in any way you can on your street based race car.first when a street based car brake system is used for track driving and second when brake fluid of a poor quality, or old fluid is used which causes vapour lock