What is brake fade?
Brake fade is a term used to describe the partial or total loss of braking power used in a vehicle brake system. Brake fade occurs when the brake pad and the brake rotor no longer generate sufficient mutual friction to stop the vehicle at its preferred rate of deceleration and can happen on motorcycles cars and trucks.
The brake pad in any brake system is designed to work at certain operating temperatures. Being made of many different formulations brake pads perform in very different ways under temperature. This certainly indicates the fitness of a brake pad for application and its general quality.
There are however two very different kinds of brake fade.
1.Green fade or early life brake fade
This is quite common and almost normal when new components are fitted. It is merely a settling down of the components after install and can be gone in a few brake applications. To minimise or avoid this effect it is wise to drive cautiously when new brakes are fitted and give yourself a little extra braking distance for the bedding in period. This can be anywhere up to 500 miles urban use.Let the brake pads seat to the rotors and then use the brakes positively on a quiet and safe road area to show them some heat energy and this will be gone a lot quicker.
Some manufacturers now “Surface scorch” brake pads to avoid green fade. This process is called heat searing or scorching of brake pads. The process removes surface organics or volatiles totally.
2.Dynamic fade or in stop brake fade
This is more serious and means that you have either chosen or been sold the wrong grade of pad for your vehicles or the pad quality is suspect. Dynamic brake fade, which is best described as loss of brake during the stop outside the bed in period, is dangerous and needs to be remedied.
In early days of drum braked vehicles brake fade was more prevalent. Towing a caravan down a long descent often resulted in brake fade where the brake liners were actually vaporising inside the brake drum and traffic authorities even built vehicle run off sand traps as an emergency route for vehicles descending out of control.
The advent of disc brakes which are better vented and employ modern technology brake materials improved this a lot but there are of course many different brake pad qualities and types on the world markets. These are of course Performance Brake Pads and are a serious consideration for track day and race use. Brake fade can also be caused by caliper drag.
When brake fade occurs the brake pad is actually skidding on a film of gas created by the over heating of the constituents of the brake pad. This does not always mean a poor quality brake pad has been used and in performance use pads can fade due to overloading the brake pad compared to its design targets. Trackday driving is a typical example. A weekend warrior takes a street based car to a race track and drives at speeds not seen on the highway and brakes till his eyes pop out of his head at a corner instead of smoothly decelerating the vehicle into the corner as a professional race driver would do. This of course just kills the pad compound which it was not designed for. Brake temperatures shoot past 1000 degrees F and few standard brake pads will tolerate that.
Brake pads that have more heat capability are required in such cases and also better ducting of air to cool the brake system is needed.
Brake fade should not be confused with Fluid vapour lock.
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