Cars of NASCAR

While the manufacturers and models of automobiles for Nextel Cup and Busch Series racing are named for production cars (Dodge Charger, Chevrolet Monte Carlo, and Ford Taurus, with the Fusion replacing the Taurus for 2006), the similarities between Nextel Cup cars and actual production cars are limited to some shaping of the nose and grill areas. A fourth model, the Pontiac Grand Prix, was used until it was retired in 2004, when Pontiac ended its sponsorship with NASCAR. In the Craftsman Truck Series, the Chevrolet Silverado, the Dodge Ram and the Ford F150, as well as the only non-American brand, the Toyota Tundra namesakes are used. NASCAR rules state the cars or trucks must be manufactured in the US if they are to be used in races. Tundra qualifies since it is now manufactured in the US. Toyota has been rumored to be producing a car for future Nextel Cup competition.

The cars are high-powered, low-tech hot rods with a roll cage chassis and thin sheet metal covering, and are powered by carbureted engines with 4 speed manual transmissions. The engines are limited to 355 cubic inches (5.8 L), with cast iron blocks, one camshaft and a pushrod valvetrain. However, significant engine development has allowed these engines to reach exceedingly high levels of power with essentially 1950s technology.

The automobiles' suspension, brakes, and aerodynamic components are also selected to tailor the cars to different racetracks. The adjustment of front and rear aerodynamic downforce, spring rates, rear track bar geometry, and brake proportioning are critical to the cornering characteristics of the cars. A car that is difficult to turn in a corner is said to be "tight", causing the car to want to keep going up the track with the wheel turned all the way left. While one that has a tendency to slide the rear end out is said to be "loose", causing the back end of the car to slide around which can result in the car spinning out if the driver is not careful. These characteristics are also affected by tire stagger (tires of different circumference at different positions on the car, the right rear being largest to help effect left turns) and tire pressure (softer being "grippier").