Since the rotor receives the most thermal energy, or heat, it's very important to control this heat effectively. The use of vented rotors has become more common because the rotor itself features internal cooling passages that work like an impeller. When it spins, air is pulled through the "eye," or center, and is evacuated through the outside of the rotor. A downside to this is the resulting radiant heat-in other words, the rotor will actually heat everything surrounding it.
A vented rotor should be the only choice for a performance brake system, since a solid rotor must rely solely on ambient air to control temperature, while the vented rotor is continually moving air through it to better control heat. More air moving across the surface or through the rotor results in increased cooling ability.
Race cars and some street cars benefit from extensive use of brake-cooling ducts to draw cool air onto the rotor surface or rotor eye. This can lower temperatures as much as a few hundred degrees, allowing the brakes to perform better.
"When we set up a brake system for a customer on a race team, brake cooling ducts are fundamental," says Emmanuelle. "We ask them to focus on the cooling, because cooler rotors allow everything to perform better."