Brake fade is a term used to describe the reduction or complete loss of braking power when you apply your vehicle’s brakes. It occurs when your vehicle’s brake pads and brake rotors no longer generate sufficient friction to slow down the vehicle. The end result is poor braking and increased stopping distances.
Brake fade is caused by overheating of the brake pad, therefore any vehicle which uses a brake pad rubbing on a brake rotor to convert the vehicle’s motion into heat has the potential to develop brake fade. Because brake fade occurs when the brake pads are overheated, the phenomenon is only temporary and normal braking returns once the brake system has cooled down.
You should know the difference between brake fade and spongy brakes. Spongy brakes is a term used in the automotive trade for “when using a vehicles brakes seem to take up most of the braking pedal travel.” It sort of feels like one is stepping on a stiff sponge, which is where the term comes from. Take it from Pearson Toyota (Newport News, VA), spongy brakes are not a temporary, heat-related, issue and they need a mechanic to look the system over.
The brake pad in any brake system is designed to work within certain operating temperatures and if they get too hot, your brakes might not work. The reason? The friction compound of modern organic brake pads is a precise mix of many different materials and these individual materials perform differently under temperature.
There are two general types of brake fade. “Green Fade” is quite common and almost normal when new brake pads are installed on a car. It is merely the “burning in” of the new brake components and may be gone after a few brake presses.
It is also worth considering that brake pads are to a degree porous, hence they will absorb a small percentage of water vapor when they are new from the surrounding air. Water, of course, boils when heated and instances of green fade which are observed as a result of water content in the pad. This water vapor will quickly burn off as soon as you get some temperature into the pads.
“Dynamic fade,” this is when your brakes get overheated while driving and they don’t work as well. Dynamic brake fade is particularly undesirable during fast driving, since once the driver has committed to stopping their vehicle within a certain distance, there is very little they can do to make the brakes work better.
Organic brake pads inherit their name from the organic phenolic resins used to bind together the different compounds used in the pads construction. There are many types of thermoset phenolic resin, but most have a maximum temperature threshold. What happens is that the phenolic resins create a film of gas at the pad-rotor interface which effectively holds the two apart. If there is no way for the gasses to escape, the opposing force as a result of the outgassing causes brake fade.
Note: any brake manufacturers offer drilled brake rotors today. These high performance brake components help sweep out the gas build up every time a hole passes over the pad surface. Cost, coupled to the fact that the vent holes can become clogged with brake dust, makes this concept inadvisable for standard factory brakes.
And then there are weekend racing warriors for whom brake fade is a serious issue. When they take their street-based car to a race track and drives at speeds not seen on the highway and brakes, this immediately superheats the pad and causes gasses to generate. kills the friction compound Typically, brake temperatures shoot past 1000 degrees F and few standard brake pads will tolerate that. If you experience brake fade on the road or on the track, consider installing an oversize brake kit with larger diameter rotors and curved internal vanes to help with heat dissipation and eliminate unwanted fade.