Brake fluid is one of those overlooked items of motorsport technology that has a profound impact on racecar performance. Its purpose is to ensure the brakes maintain their optimal functionality from start to chequered flag. That isn’t straightforward when you consider the high temperatures exerted on a racecar’s mechanical components and systems.
Brake fluid transfers the force of a driver pressing the brake pedal through to the callipers, which reduce the speed of each wheel. When the driver hits the pedal, pistons in the master cylinder compress, releasing brake fluid under pressure towards the braking system. There are several characteristics whose properties a motorsport brake fluid must sustain over a wide temperature range to ensure the brakes give consistent, predictable feedback to the driver. The main ones are boiling point, compressibility, lubricity and viscosity. Halo by Orthene, a UK-based racecar brake fluid manufacturer that supplied this year’s LMP2 winner at the 24 Hours of Le Mans, has helped to explain how these characteristics can be managed.
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High boiling point
Brake fluid needs to have a high boiling point, otherwise it will result in vapour lock, which causes the callipers to no longer respond to the driver?s action due to the presence of a gas in the brake system. This could potentially result in a high-speed accident due to lack of deceleration.
Most racing brake fluids have a dry boiling point of at least 300degC, but there is sc...