Brake fade is described as the temporary or complete drop in a vehicle’s braking power. It happens when the rotor and pad fail to create enough friction to slow wheel motion. The result of this usually involves unexpected or inconsistent brake failure, which often means simply that your car’s stopping distance goes up that one time. However, there is no guarantee that such instances will remain confined to safer driving scenarios – you could just as well be negotiating a hairpin when this happens – and that makes brake fade an immensely dangerous prospect.
The basic cause of this is the brake pad overheating. The vehicle uses the rubbing action between this overheated pad and the rotor to dispel absorbed kinetic energy as converted heat, but the existing heat adds to that and blocks the intended action. For it to turn out this way, you need the pads to be already heated to a sufficient point, which is why brake fade is a temporary phenomenon. Braking performance returns after that heat has been let out, but a single time is enough for irreparable disaster. Brake fade can be classified into the following two types.
Early-Life/Green Brake Fade
This type of brake fade is so common that it is considered even normal when they occur in new brake pads. It is nothing more than the components settling down after they have been installed, and the effect disappears after the brakes have been applied a few times. Still, it is best to drive carefully when your brakes are still new, as well as leave some additional braking distance for the duration of the bedding period (500 miles or less under urban use). The green fade period can also be shortened if you use the brakes positively while driving along a safe, quiet stretch of road, raising pad temperature, and consequently burning off whatever volatiles might have caused the fade in the first place.
Just make sure beforehand that the pads are seated properly, and that they are fully contacting the rotor. Go easy with the newly installed pads when doing this. A handful of stops between 10 and 50 mph should be enough to bring the pads out of the green fade phase. Even any water absorbed after manufacture and before fitting would turn to vapor and escape the pores of the pad.
There are brake pads coming out these days that are “surface-scorched”, meaning they have undergone a process, which burns off volatiles and surface organics present in the pad. This almost fully takes care of the green fade issue, especially for race drivers and fast road drivers. A surface-scorched pad can be dropped into a caliper, and would start performing straight off at maximum efficiency.
In-Stop/Dynamic Brake Fade
This type of fade is a more serious issue, and if you have it happen while you drive, you can conclude hands-down that your brake pads are not meant for the kind of use you are putting them to. Either you got ripped-off, or you chose the wrong pad type for your driving or vehicle style. Sometimes even caliper drag can be caused in-stop brake fade, which traces back to improper maintenance of the caliper, which prevented its full release after the brake was applied. Dynamic brake fade is essentially the variety of fade that occurs when you have passed the bed-in period for the pads. It can be much more dangerous than green brake fade, especially in track driving and fast-road conditions. After the driver has decided on and committed to a certain stopping distance, they have few options left when it comes to corrections inside the mid-braking zone.
Dynamic brake fade was mostly seen in drum brake systems, because they cooled relatively slowly, and had to manage really heavy vehicles, which means that the friction material often evaporated inside the drum, causing the vehicle to lose braking power completely for a time. Disc brakes systems can claim better cooling as well as better chosen materials for most driving scenarios, meaning with these, you only risk dynamic brake fade about a half of the time.
That said, it is vital to exercise care when picking out pick out brake pads, because there is no saying that brake fade will not occur even if you happen to be driving at a reasonable speed. The right brake pad capable of handling surplus braking demand is crucial if you have a heavier vehicle, or if you frequently approach high speeds on the road. Even drivers that make a lot of high energy back-to-back should pay attention to this aspect of picking out parts for their braking system. Racecar drivers are better off picking performance pads as well as grooved rotors. An even better alternative is to fully upgrade the existing braking system, and putting an oversize brake kit in its place.