24h Le Mans
During the legendary race, spectators witness a spectacular phenomenon. In the darkness of the Le Mans night, brake discs burn bright red during heavy braking. But why?
Brake reddening is due to extreme heat caused by friction between the pads and discs during braking. At temperatures as high as 600°C, a disc – made of carbon in the Hypercar category – begins to emit a visible red glow. This colour indicates the energy emitted in the form of heat.
When temps exceed 1000°C, common in certain areas of the circuit, the brakes shine even brighter, especially at night. This is a normal, expected and fully controlled phenomenon provided the intended operating limits are maintained.
The 13.625 km circuit alternates between long straights and tough braking zones. The two chicanes in the Mulsanne Straight are the most taxing after cars reach in excess of 320 kph before needing to brake sharply to navigate the upcoming tight turns. The deceleration is violent, the braking intense and the discs then reach extreme temps, causing them to glow. Other areas, such as Mulsanne, Indianapolis and Arnage, also put brakes under severe strain, but with less intensity than the two chicanes.
Red-hot brakes are not a bad sign in and of themselves. On the contrary, they indicate the system is operating at high revs, which is typical of a 24-hour endurance race. The materials used, namely carbon discs and high-performance calipers, are designed to operate within extreme temperature ranges.
But, it's all a question of balance. If the temperature becomes too high and heat dissipation is insufficient, this can lead to premature wear of the pads and discs, a loss of braking efficiency and risk to driver safety.
To prevent brake overheating and loss of efficiency while racing, it is essential to keep the air ducts that cool the brakes clean. They must be free of debris or obstructions that could reduce airflow and compromise disc cooling.
Additionally, precise management of disc temperature is crucial. This requires adjusting air duct openings and increasing or decreasing airflow to the brakes. During the race, teams can regulate in real time to maintain an optimal thermal range to avoid overheating and ensure consistent performance without compromising longevity.
The driver can feel the brakes overheating at the pedals. When that happens, brake fluid can boil causing air bubbles to form in the system. However, air is compressible, unlike fluid. As a result, the pedal becomes "softer" or "longer" with a less direct response. This is a sign of a loss of efficiency, and drivers must adapt their driving to compensate.
Glowing red does not necessarily indicate dangerous overheating. At the 24 Hours of Le Mans, engineers, technicians and drivers know how to monitor, anticipate and master this occurrence. Thanks to customised design and rigorous thermal management, the brakes can burn red…without ever weakening.
