Template:ImageStackRight Open-wheel car (Often single-seater car, in UK English) describes cars with the wheels outside the car's main body. In the majority of cases they have only one seat. Open-wheel cars contrast with street cars, stock cars, or touring cars, which have their wheels below the body or fenders. Open-wheel cars are usually purpose-built for racing, frequently with a degree of sophistication unknown in other forms of motorsport.
In the United States, it is common to refer to open wheel cars as Indy Cars because of their recognizable appearance at the annual Indy 500. However, these vehicles have also historically been called champ cars (short for 'championship car') due to their racing heritage at the highest levels of competition even prior to the Indy 500.
A typical open-wheeler has a minimal cockpit sufficient only to enclose the driver's body, with the head exposed to the air. In modern cars, the engine is often located directly behind the driver, and drives the rear wheels. Depending on the rules of the class, many types of open-wheelers have wings at the front and rear of the vehicle, as well as a very low and virtually flat undertray that helps achieve additional aerodynamic downforce pushing the car on to the road.
Some major races, such as the Monaco Grand Prix (sanctioned by Formula One) and the Long Beach Grand Prix (sanctioned by the IRL), are held on temporary street circuits. However, most open-wheel races are on dedicated road race circuits, such as Road America in the US, Nürburgring in Germany, and the Bahrain International Circuit in the Middle East. In the United States, some top-level open wheel events are held on ovals, both short tracks and superspeedways. The most famous and most well-attended oval race in the world is the Indianapolis 500 in Speedway, Indiana, sanctioned by the IRL.
Open-wheeled racing is among the fastest in the world. Speeds on ovals can range in constant excess of 210-220 mph (335-350 km/h), and at Indianapolis in excess of 230 mph (370 km/h). In 1996, Paul Tracy recorded a trap speed of 256.948 mph (413.52 km/h) at Michigan International Speedway. In 2000, Gil de Ferran set the one-lap qualifying record of 241.426 mph (388.54 km/h) at California Speedway. Even on tight non-oval street circuits such as the Grand Prix of Toronto, open-wheel Champ Cars attain speeds of 190 mph (305.77 km/h).
Driving an open wheel car is substantially different from driving a car with fenders. Virtually all Formula One drivers spent some time in various open-wheel categories before joining the F1 ranks. Open-wheel vehicles, due to their light weight, aerodynamic capabilities, and powerful engines, are often considered the fastest racing vehicles available, and therefore, among the most challenging to master. Wheel-to-wheel contact is dangerous, particularly when the forward edge of one tire contacts the rear of another tire, resulting in the vehicle being suddenly and powerfully flung upwards.
The lower weight of an open wheel racecar allows for better performance. While the exposure of the wheels to the airstream causes a very high aerodynamic drag at high speeds, it allows improved cooling of the brakes, which is important on road courses with their frequent changes of pace.