The temperature of tires affects grip, traction, and wear, which can significantly impact lap times and race outcomes. Wheel covers are an essential tool dirt racing teams use to control tire temperature. These covers are designed to cover the wheels and brake rotors, which helps trap heat inside the tire. As the tire heats up, the temperature causes the rubber to become more pliable, increasing the tire's grip on the track surface.
There are three types of covers used in dirt racing.
Solid covers can be metal, plastic, or composite. They hold in heat and protect the wheel from mud buildup that can cause the wheel and tire to become out of balance, resulting in a part failure.
Vented covers can be metal, plastic, or composite. They have holes or louvers to vent hot air and lower overall tire operating temperature while protecting from mud buildup.
Foam covers or inserts offer little to no mud buildup protection but maintain tire temperature by acting as a thermal insulator. As the tire and brake system builds heat, the foam stores that heat energy. They are keeping the operating temperature longer under cooldown periods such as cautions and reducing the likelihood of the tire sealing over under caution due to cooling down too rapidly.