What is Brake Fade?
Brake fade can be a terrifying and dangerous experience in certain situations, and if you’re lucky, you’ve never had to experience it. When brake fade occurs, it feels like the brakes are working fine one minute and completely gone the next. Every driver on the road should know what brake fade is and how to prevent it from happening.
What Causes Brake Fade?
Brake fade is ultimately caused by excessive heat and the braking component’s inability to deal with it. The brakes are responsible for converting the vehicle’s motion into heat in order to come to a stop. Since the brakes deal with such a high amount of heat, they must be effective at dissipating that heat. There are a few different ways that excessive heat can affect the brake system. Let’s take a closer look at what happens.
Brake Fade Due to Friction Material
Friction fade is one of the main causes of brake fade. Friction fade can happen in a situation such as driving downhill with the brakes constantly applied. The heat generated by the brakes keeps building up as long as the pedal is depressed. When this occurs, some of the friction material compounds and bonding agents in the brake pads reach a temperature at which they release gasses. The gasses are released where the pads contact the rotor. The gasses create a sort of boundary film that pushes the pads away from the rotor, resulting in a loss of friction.
A few measures can be taken to prevent brake friction fade. When traveling on a downgrade, shift the transmission to a lower gear to provide an engine braking effect. When applying the brakes, press firmly on the brake pedal and release to give the brakes a chance to cool down.
Brand new brake pads are the most susceptible to brake fade. This type of brake fade is often called Green Fade, in which the normal effects of friction fade are multiplied. This phenomenon is due to the large amount of gasses released by the bonding agents and resins in the brake pads. The gasses must be released after the new brakes are installed during a procedure known as bedding-in. Be sure to follow the manufacturer’s recommended bedding-in procedure after replacing the brake linings.
Brake Fade Due to Brake Fluid
Another type of brake fade is due to the effect that heat has on the brake fluid. A lower boiling point of the brake fluid means less resistance to brake fade, as brake temperatures can reach well over 500 °F during continuous braking periods. While the brake rotors dissipate most of this heat into the air, the brake fluid still absorbs some of the heat. Brake fluid is hygroscopic in nature, which means it has an ability to absorb moisture from the air. DOT 3 brake fluid has a boiling point of 401 °F when it has no moisture content. As the brake fluid absorbs moisture, the boiling point is lowered. At a moisture content of just 3.7%, the brake fluid boiling point is lowered to 284 °F. Hydraulic brake fade occurs when the brake fluid begins to boil and vaporize inside the brake lines. This causes the brake fluid to compress, whereas there would be no compression if the fluid remained a liquid. When this happens, the pedal will begin feel spongy and braking ability will be significantly reduced and may even be totally lost.
To avoid hydraulic brake fade, it is important to follow your vehicle manufacturer’s recommended service intervals for brake fluid replacement. This is one maintenance item that many drivers tend to neglect. Always use brake fluid from a sealed container, and make sure that your master cylinder reservoir is properly sealed.
Combating Brake Fade
If you are driving down a steep hill, and your brakes become soft or your brake pedal becomes hard or unresponsive, downshift into a lower gear. The engine will help to slow the vehicle when the transmission is in a lower gear. Once the vehicle has come to a stop allow the brakes to cool down for at least an hour. Don’t touch the brakes or wheels to check how hot they are, because they can be hot enough to cause severe burns to the skin. Once the brakes have cooled, proceed safely in a low gear to a repair shop.
Hydraulic brake fade can be avoided by regularly flushing the brake system and replacing the fluid with a high quality fluid that meets your vehicle’s specifications.
Brake pad friction material plays a big part in resistance to brake friction fade. Generally, semi metallic pads have the most resistance to brake fade compared to ceramic and organic friction materials. Brake rotor composition and design also play a role at how well the brakes can dissipate heat.
When replacing the brake pads or shoes, be sure to follow the manufacturers recommended bedding-in procedure. Most brake pads require an initial break in period. Try to avoid hard or extended periods of braking for the first 300 miles to allow the brakes to break in properly.
When in doubt, have the vehicle checked by a knowledgeable and trustworthy mechanic, and be sure to check us out at NewParts.com for all of your brake parts needs. We carry thousands of quality brake parts from the top brands in the industry to help you fade away into the sunset, not off into a ditch.