Brake fluid is the lifeblood of a braking system. Nothing moves without it.
Auto brake systems are driven by hydraulics. In more formal terms: liquid controls and transmits mechanical power as necessary. In other words, when a driver pushes the pedal down, the fluid works to slow then stop the car.
What Is Brake Fluid?
Brake fluid is a necessary hydraulic element that drives caliper pistons on- demand. These pistons drive brake pads against a brake rotor and create the friction that stops a brake rotor from turning.
What Types Of Vehicles Use Brake Fluid?
Every vehicle relies on a specific type of hydraulic brake system. Each system uses one of three primary Department of Transportation (DOT) viscosities – DOT 3, 4, or 5. There is a sub-set of DOT 5.1, but those are largely exotic blends and are not relevant to performance or race purposes.
Can You Mix Different Types Of Brake Fluid?
Just because you can do a thing, doesn’t mean you should. Along with viscosities, DOT fluids also harbor different levels of corrosion that can cause damage to brake lines and fittings if mixed. So…don’t do it!
What Is “Bleeding The Brakes”?
Hydraulic brake systems operate best when air is purged from the system. You bleed a brake system by pumping the pedal until only fluid remains in all lines.
Do I Need A Brake Fluid Flush?
End-to-end brake flushes are not necessary as long as the brake system is maintained properly and topped up with fluid regularly. However, if components are replaced or retrofitted, a flush is called for since there may be some clag left in the sealed system.
What Types Of Brake Fluid Apply To Performance Cars?
US Department of Transportation (DOT) compliant brake fluids are sold on the basis of two measured operating values. The first relates to the moisture absorption and the second involves how well brake fluid resists overheating at particular temperature ranges. Altogether these metrics are referred to as viscosity.
DOT viscosity requirements range for consumer-only braking systems to modified street performance cars to track-only racing packages. In all cases, excessive moisture and/or uncontrolled heat can trigger caliper boil-over, which can create operating problems if the wrong DOT value is employed.
Understanding and applying the proper fluid is critical.
Necessary DOT Ranges
Dot 3 – Consumer grade. Suitable for daily-driver road cars and less applicable to performance cars.
Dot 4 – This value is race-designed with viscosity necessary for hard braking for extended periods.
Dot 5 – For a synthetic manufacturing process. Most seen in heavy-duty military equipment and some vintage performance cars since its corrosive characteristics do not damage paintwork (that could result from the splash-over or leakage).