Understanding Brake Fade and How to Prevent It

brake fade can lead to car crashes, but it can be prevented
Brake Fade Can be Dangerous and Scary, but It's Entirely Preventable. http://www.gettyimages.com/license/691036819

Brake fade just doesn’t come up all that often in discussion, but it deserves your consideration if you are a driver or mechanic, no matter whether you drive or repair commuter cars, sports cars, light trucks and SUVs, or heavy trucks and SUVs. Brake fade is a sudden reduction of braking ability related to excessive heat in the brake system, usually because of excessive braking under high loads or at high speeds.

While driving and braking excessively, until the brakes start to fade, braking feel and stopping power will seem normal. Braking power generally increases as the brakes heat up, but only to a certain point, when suddenly the brakes won’t feel effective or brake pedal will go soft. In either case, brake fade can be scary and dangerous, but car crashes related to brake fade might be entirely preventable.

What Causes Brake Fade

in this rally car, you can see the heat built up in the brake system
These Brakes Show the Heat They're Generating to Slow the Rally Car Down. http://www.gettyimages.com/license/129233745

The brake system is designed to convert the kinetic energy of your vehicle into heat energy – hybrids and electrics convert it to electrical energy – it is constructed to absorb and release a certain amount of heat. Under normal driving circumstances, braking will heat up brake and suspension components. Even under repeated braking, most brake components are good up to a few hundred degrees. Brake pads are usually good up to 700 °F, and brake fluid up to 450 °F – some brake pads are rated up to 1,200 °F and some brake fluids up to 600 °F.

Brakes are usually only applied momentarily, during which heat is absorbed by the brake system. When the brakes are released, the brake system dissipates that heat to the air and other components. Aggressive driving, riding the brake, braking down a long hill, or driving an overloaded vehicle can all cause excessive heat to build up in the brake system, and brake fade can occur just a few degrees beyond that.

Three Brake Fade Types

just a few of the brake parts designed to turn kinetic energy into heat energy
Brake Pads and Brake Rotors Generate Heat from Your Vehicle's Kinetic Energy. http://www.gettyimages.com/license/183260268

Really, there is only one cause of brake fade, excessive heat, but heat affects different components of the brake system in different ways. Depending on the nature of the brake system, the parts involved, and the manner of overheating, there are three types of brake fade:

  • Pad Fade: The friction surface of a brake pad is constructed from high-friction materials and an adhesive binder. The brake pad is set under high temperature and pressure, much higher than it should ever experience in use, but overheating could push beyond those limits. Overheated pads can melt, having a lubricant effect on the brake rotor. The brake pedal will still feel normal, but braking power will be significantly reduced. Usually, a unique burning smell – some say like burning carpet – will warn the driver of impending brake fade.
  • Fluid Fade: A small mention of brake fluid temperature rating was made earlier, which refers to boiling point. “Dry” brake fluid will boil between 450 °F and 600 °F, depending on the type, but it does one good to note that brake fluid is hygroscopic. Brake fluid absorbs water, which lowers its boiling point. “Wet” brake fluid can boil between 300 °F and 500 °F, or even lower. Overheated brake fluid can boil, flashing into pockets of vapor. The brake pedal will feel “spongy” and the brakes won’t feel very responsive. The driver might be able to pump the brakes to get moderate braking, but nothing like they should be. There may be no warning at all to the driver, just a sudden spongy or sinking brake pedal the next time they need to brake.
  • Green Fade: Green fade refers to pad outgassing under high temperatures. When the pad heats up, some of the binders may flash into a vapor, which gets trapped between the pad and the rotor. The result is something like hydroplaning, when a tire can’t push water out of the way, so it rides on top of the water – braking and steering are impossible. In this case, the brake pad is held away from the rotor by a pocket of hot vapors. The brake pedal will still feel good, but almost no braking power will be felt. As with pad fade, a burning smell might be all the warning the driver will get of impending brake failure.

How to Prevent Brake Fade

following the speed limit is just one way to prevent brake fade
Following the Speed Limit is One Way to Prevent Brake Fade. http://www.gettyimages.com/license/2674320

The causes of brake fade are easily understood, having to do with driving habits, equipment limitations, or brake fluid failure. In each of these cases, brake fade is easily prevented.

  • Drive Responsibly: Overusing the brakes can easily overheat them. Driving responsibly gives the brake system time to dissipate the heat.
  • Downshift on Hills: On long hills, especially if hauling or towing, shift into a lower gear and do not ride the brakes. Shifting into a lower gear gives you engine braking, which won’t wear anything out. Use the brakes sporadically for speed control, but let the engine do most of the work. This works with both manual and automatic transmissions.
  • Pull Over on Long Hills: On some long hills or steep hills, even downshifting may not be enough. Pull over and let the vehicle rest and cool off. Some roads, such as the Mount Washington Auto Road, even have turnouts for drivers to let their brakes cool down.
  • Use the Right Brakes: Street brake pads will fade in racing conditions, but strip and race brake pads don’t provide much braking until they’re heated up on the track. Use brake pads fit for the task. Upgrade your brake calipers if you plan on racing or heavy hauling.
  • Use the Right Brake Fluid: Similarly, street brake fluid can’t handle track temperatures. Use brake fluid fit for the task.
  • Replace Brake Fluid Annually: Because the brake system isn’t perfectly sealed, it will absorb water throughout the year, lowering its boiling point. It’s a good idea to replace brake fluid annually.
  • Break In New Pads: Brake pad manufacturers have adjusted processing to address green fade, but brake technicians and DIYers should always follow a break-in procedure to “bed” new brake pads. Brake pad manufacturers usually include these steps, to prevent green fade from occurring after installation.

If you ever experience brake fade, downshifting and pumping the brakes might be the only way to get out of it. The brake system simply needs time to cool off and return to normal. Of course, the best way to get out of brake fade is to prevent it from occurring in the first place.

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Jerew, Benjamin. "Understanding Brake Fade and How to Prevent It." ThoughtCo, Oct. 2, 2017, thoughtco.com/how-to-prevent-brake-fade-4152020. Jerew, Benjamin. (2017, October 2). Understanding Brake Fade and How to Prevent It. Retrieved from https://www.thoughtco.com/how-to-prevent-brake-fade-4152020 Jerew, Benjamin. "Understanding Brake Fade and How to Prevent It." ThoughtCo. https://www.thoughtco.com/how-to-prevent-brake-fade-4152020 (accessed December 12, 2017).