VP 622 Brake Fluid

What Does Brake Fluid Do?

What is brake fluid and what does it do? Brake fluid is one of the most overlooked performance parts within a braking system. Whether you’re driving to work or enjoying a day on the track, the most important mechanical system in your car or powersport vehicle may be your brakes.

The chief purpose of brake fluid is to convert brake pedal pressure into stopping power while remaining stable in a variety of conditions. To illustrate, when the brake calipers (and the fluid reaching them) get hot, the fluid will often boil. The boiling process produces gas, which is more compressible than the fluid. Consequently, it leaves you with both a soft, spongy brake pedal feel and a longer travel time when applying the brakes. It can be a very unsettling feeling, not to mention unsafe.

Additionally, brake fluid is hygroscopic. In other words, it absorbs moisture from the atmosphere. This takes place over a period of time. When the fluid contains water, it starts to boil with less heat. Because brake rotors and brake calipers generate an exorbitant amount of heat, brake fluid must have a high heat tolerance. Otherwise, the fluid would simply vaporize inside your brake lines and create a dangerous situation because your brake system will not function properly.

Brake pad and rotor

Dot 3 vs. Dot 4 Fluid (and don’t forget Dot 5)

The US Department of Transportation (DOT) established specifications defining several properties to which brake fluid must adhere. Those specifications relate to the boiling point of the fluid (both dry and wet), how viscous (flowable) the fluid is, and the stability of the fluid at high temperatures, among other properties. Dry boiling point refers to when the fluid is new (0% water), while wet boiling point refers to when the water content in the fluid reaches 3.7%.

The most common fluid for brakes is DOT 3, and it is primarily glycol ether. DOT 4 is also glycol ether-based, but it has borate esters added to increase the boiling points. They manufacture DOT 5 fluid using silicone, which does not absorb water.

Fluid Classifications

Dry Boiling Point Wet Boiling Point
DOT 3 205o C / 401o F 140o C / 284o F
DOT 4 230o C / 446o F 155o C / 311o F
DOT 5 260o C / 500o F 180o C / 356o F
DOT 5.1 270o C / 518o F 190o C / 374o F

 

Source: Federal Motor Vehicle Safety Standard No. 116, Motor Vehicle Brake Fluids (49 CFR 571.116)

Dodge Challenger high performance car

How Often Should You Change the Fluid?

Maintaining your fluid via regularly scheduled service replacement intervals is important. Performance will decline as the fluid ages. Brake bleeding intervals heavily depend on vehicle use and the type of fluid being used.

For a street car, where a balance of performance and affordability may be important, consider bleeding your brakes and replacing the fluid once per year.

For a combination street and track car, the brake priorities change. Therefore, a fluid with low compressibility becomes important to maintain a consistent pedal feel. A high dry boiling point is also important for performance under sustained track sessions. For track use, it is recommended that you bleed the brake calipers after each weekend and replace the fluid.

Race cars
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What Kind of Brake Fluid Do I Need?

For a race car, you want a a fluid with high lubricity, dry boiling point (above 600o F), and low compressibility for maximum stopping power and resistance to brake fade.

The experts at VP Racing Fuels design a high-performance, fully synthetic Dot 4 brake fluid. We formulate it for the demands of automobile and powersports racing. In addition, you can use it on the street in extreme performance vehicles. It’s fully synthetic and maintains stability under high temperatures, resists vapor lock and fade, and delivers one of the highest wet boiling points of any DOT 4 fluid (399 o F) on the market.