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The Importance of Changing Your Vehicle's Brake Fluid

Published by Mark Link
Wednesday, October 03, 2018

The Purpose of Brake Fluid 

 Brake fluid is the "hydraulic fluid" used in the braking system to facilitate the transfer of force from the brake pedal to pressure on the caliper piston in order to effectively slow your car down. However, in order for the brake fluid to effectively enable this process, the fluid must be able to resist compression and remain in a liquid state despite the heat produced by the friction created in the braking process.


Why Replace Your Brake Fluid?

 Because of the described heat created in the brake lines from the braking process, brake fluid needs to be heat tolerant with a high boiling point. If your brake fluid boils, gasses are released into the brake lines which can reduce the efficiency and effectiveness of the braking system. This is what can cause a mushy pedal, and sometimes complete failure of the brakes.

Unfortunately brake fluid compounds that tend to be heat tolerant, also tend to be hygroscopic-that is they attract and absorb moisture. Moisture can enter the brake system through the rubber seals and brake hoses. Because the boiling point of water is lower than the boiling point of the brake fluid, the absorption of this moisture can cause the boiling point of your brake fluid to decrease to what is known as the "wet boiling point." Over time, as your brake fluid absorbs more moisture and becomes less heat tolerant, it may need replacement to prevent subsequent brake failure. Additionally, this moisture can cause corrosion (rusting) on the inside of the braking system which can also deteriorate the brake lines. While most brake fluid contains anti-corrosives, these degrade over time and become less efficient at preventing internal rusting.


How Often Should You Change Your Brake Fluid?

How often you should change your brake fluid depends on your vehicle's manufacturer and the type of driving that you do. For the average daily commuter, we recommend changing your brake fluid every 2-3 years (or every 30k miles) for optimal brake maintenance. However, be sure to check your owner's manual for the manufacturer recommendation. If you are driving under heavy braking conditions (tow vehicles, emergency response vehicles etc.) we recommend changing your brake fluid more often as it is key to prevent boiling of the brake fluid. For those who participate in autocross events, we recommend you change your brake fluid annually. Dedicated race cars should have their brake fluid changed after every track weekend or more frequently if needed.


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