They build cars for the short tracks, like Bristol Motor Speedway in Tennessee, where top speeds are lower and turns are tighter. They also build cars for the super-speedways, like Talladega in Alabama, where top speeds are higher but engine power is limited. The goal in designing a short-track car is to create as much downforce as possible. Downforce is an aerodynamic force that tends to press the cars tightly against the ground, which allows the tires to grip the track with more force. This makes the cars go around the tighter turns as quickly as possible.
Extensive testing is done in a wind tunnel to optimize the body design for maximum downforce.
This helps the car create extra downforce. The front fenders on short-track cars are much more pronounced and curved, which also helps to produce downforce. On the super-speedways, the track is much longer and straighter and the banking is high, allowing cars to maintain a high speed all the way around the track. The goal in building a car for super-speedway tracks is to reduce drag as much as possible. These tracks require the use of restrictor plates that reduce engine power from about 750 horsepower to 450 horsepower.