- A braking event converts the car’s kinetic energy into heat in a few seconds.
- Brakes have a working window: too cold gives low friction, too hot causes fade and wear.
- Duct sizing is a trade-off between brake temperature and aerodynamic drag.
Where the heat comes from
Kinetic energy grows with the square of speed. When a race car brakes from high speed for a slow corner, most of that energy ends up as heat in the discs and pads within a couple of seconds. On circuits with many heavy stops, the brakes have little time to cool before the next event, so temperatures build up over a lap.
The working window
Every friction pair has a temperature range in which it performs well. Below it, friction is low and inconsistent; above it, pads fade, wear accelerates and discs can crack or oxidise. Carbon–carbon systems used in top categories need high temperatures to work, while cast-iron discs used in many GT and touring series operate in a lower range. The engineer’s job is to keep the system inside its window for the whole stint.
Cooling hardware
- Inlet ducts capture air from high-pressure areas and feed it to the disc and caliper.
- Disc ventilation — internal vanes or many small drilled holes in carbon discs — pumps air through the disc as it rotates.
- Caliper cooling protects the brake fluid from boiling and the seals from overheating.
- Blanking on cold days or slow circuits keeps the brakes up to temperature.
The aerodynamic trade-off
Every opening in the bodywork adds drag and disturbs the flow around the wheel. Bigger ducts mean cooler brakes but a slower car on the straights. Teams use CFD and track data to find the smallest duct that keeps temperatures safe, and often bring several duct sizes to each event.
Data and validation
Infrared sensors and thermocouples log disc and caliper temperatures, while wear is measured between sessions. Engineers correlate these with brake pressure, speed and ambient conditions to build thermal models, then predict cooling needs for the next track.
Thermal management in racing shares physics with road vehicles — compare it with EV battery cooling. To study vehicle dynamics, aerodynamics and motorsport engineering in depth, see our automotive and motorsport programmes.
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