Brake fade

When fading (English: to fade = vanish ) or brake fade is referred to an undesirable decrease in braking performance of a mechanical brake system by heating the brake. Here, the braking distance can extend critical to safety after repeated or prolonged braking. The problem occurs especially with long, steep downhill in everyday life.

Occurrence

Fading occurs mainly in drum brakes. At a temperature around 400 ° C, the braking force can already be reduced by 50 % due to the lower coefficient of friction between the brake drum and brake shoes. In disc brakes, the risk of fading is low, because the resultant braking heat is dissipated more efficiently.

Partial fading occurs after installation of new brake pads. Since these have not yet adapted to the grooves of the brake drum or brake disc ( lapped ), it can come during emergency braking to a local overheating. At these points, fading occurs.

The formation of water vapor bubbles in a hydraulic brake system filled with brake fluid, which has a longer brake lever or brake pedal a result, is often mistakenly referred to as fading. This technical defect can only occur if the braking is interrupted, because only then can the pressure relief evaporate water in the brake fluid and push back the thereby occurring increase in volume of a part of the brake fluid in the brake fluid reservoir.

Countermeasures

Vehicle Technology

• Because of their susceptibility to fading drum brakes for motorcycles, passenger cars and vans today hardly installed, if required, to the rear axle.
• The brake is cooled by air.
• With disc brakes, internally ventilated brake discs can be used for motor vehicles. For bicycles perforated brake discs are common.
• With disc brakes, the risk of fading can be reduced through the use of high-temperature brake pads especially for bicycles.
• With heavy motor vehicles for longer braking a retarder, for example, an eddy current brake or retarder used.
• Ceramic brakes are less prone to fading.

Driving

• Retarder should be avoided if possible. Interval brakes are the brakes time to cool in between.
• For long downhill with motor vehicles is reduced by using the engine brake or a lower gear speed to relieve the brakes.
• For long downhill with bikes high speeds can be avoided by each timely braking to relieve the brakes.

See also: brake, brake (rail ), brake ( motor vehicle ), bicycle brake

• Braking technique