Brake fluid is hygroscopic, which means it is chemically designed to readily absorb water from its surroundings and hold this water in suspension. This design is intended to protect the internal components of the brake system from the effects of corrosion.

The down side of this is that the water molecules held in suspension reduce the ability of the brake fluid to withstand high temperatures, and heat created by repeated hard braking will cause the water molecules held in suspension to boil at relatively lower temperatures.  "Boiling the brakes," as the condition is referred to, results in enough steam in the brake lines to cause a sudden and complete failure of the brake system. Although cooling the brakes will generally condense the steam and return the brakes to normal operation, reaching the end of the front straight at speed and being entirely unable to apply the brakes is not acceptable.  Luckily, boiling the brakes is entirely avoidable with proper maintenance.

To maintain a safe environment for all participants, brake fluid must be no more than 6 months old and you must be able to substantiate that the brake fluid has been flushed by presenting the work order with your completed mechanical inspection form.

Due to lower expected speeds and brake temperatures, winter school participants are exempted from the requirement for a brake fluid flush.