Open-wheel car

An open-wheel car is a car with the wheels outside the car's main body, and usually having only one seat. Open-wheel cars contrast with street cars, sports cars, stock cars, and touring cars, which have their wheels below the body or inside fenders. Open-wheel cars are built both for road racing and oval track racing. Open-wheel cars licensed for use on public roads (street legal), such as the Ariel Atom, are uncommon, as they are often impractical for everyday use.

American racecar driver and constructor Ray Harroun was an early pioneer of the concept of a lightweight single-seater, open-wheel "monoposto" racecar. After working as a mechanic in the automotive industry, Harroun began competitive professional racing in 1906, winning the AAA National Championship in 1910. He was then hired by the Marmon Motor Car Company as chief engineer, charged with building a racecar intended to race at the first Indianapolis 500, which he went on to win. He developed a revolutionary concept which would become the originator and forefather of the single-seater (i.e. monoposto) racecar design. Harroun has also been credited by some as pioneering the rear-view mirror which appeared on his 1911 Indianapolis 500 winning car, though he himself claimed he got the idea from seeing a mirror used for a similar purpose on a horse-drawn vehicle in 1904.

Prior to World War II, street automobiles generally had wheels that protruded beyond the vehicle's main body, though they were typically covered with mudguards to protect the car body and following traffic from water and mud spray. With the advent of unibody vehicle construction, the desire to maximise interior space, to improve aerodynamics, and aircraft-inspired styling trends of the era, by the end of the 1950s the majority of new road-registerable vehicles had wheels that were under the main body of the car, and thus the open-wheel design became almost exclusively associated with racing vehicles.

Formula One cars have almost exclusively used the open-wheel design throughout the history of the championship. The only notable exception was the "Monza body" variation of the Mercedes-Benz W196 racer of 1954–55, which covered the wheels with bodywork for aerodynamic reasons. Modern Formula One regulations mandate the open-wheel configuration.

A typical open-wheeler has a minimal cockpit, sufficient only to enclose the driver's body, with the head exposed to the air. In the Whelen Modified Tour and other short track modified series, the driver's head is contained in the car. 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 onto the road. While many other categories of racing cars produce downforce, the top categories of open-wheel racing cars (particularly Formula One and IndyCar) produce far more downforce relative to their mass than any other racing category, allowing much higher corner speeds on comparable tracks. However, this is not always the case; some open-wheel categories raced primarily as development or amateur categories, such as Formula Ford or Formula Vee, do not permit the use of wings or ground effect aerodynamics.

Virtually all modern open-wheelers have a mid-engined configuration with the engine between the driver and the rear axle line. While most early Formula One cars had a front-engined layout, the mid-engined Cooper T12 appeared in Formula One in the second-ever race in 1950. In 1958, a later mid-engined Cooper car won its first race and in 1959, Jack Brabham won the first championship in a mid-engined car. Every championship since has been won by a mid-engined car, and the vast majority of racing open-wheeler designs have followed this pattern. Notable modern exceptions include asphalt modified cars, such as the Whelen Modified Tour, and the Caterham Seven and its many imitators.

Some major races, such as the Singapore Grand Prix, Monaco Grand Prix (sanctioned by Formula One) and the Long Beach Grand Prix (sanctioned by IndyCar), are held on temporary street circuits. However, most open-wheel races are on dedicated road courses, such as Watkins Glen in the US, Nürburgring in Germany, Spa-Francorchamps in Belgium and Silverstone in Great Britain. In the United States, some top-level open-wheel events are held on ovals, of both short track and superspeedway variety, with emphasis more on speed and endurance than the maneuverability required for road and street course events. The Whelen Modified Tour is the only opened wheeled race car series endorsed by NASCAR. This series races on most of NASCAR's most famous tracks in the United States. Other asphalt modified series race on short tracks in the United States and Canada, such as Wyoming County International Speedway in New York. The best-attended oval race in the world is the annual Indianapolis 500 (Indy 500) in Speedway, Indiana, sanctioned by IndyCar; in the United States it is quite common to refer to open-wheel cars as IndyCars, because of their recognizable appearance and widespread popularity across America at the Indy 500. Compared to covered-wheel race cars, open-wheeled cars allow more precise placement of the front wheels on the race course, as the tires are clearly visible to the driver. This allows the maximum potential of the cars to be achieved during cornering and passing. Furthermore, open-wheeled cars are less tolerant of vehicle-to-vehicle contact, which usually results in vehicle damage and retiring, whereas some level of contact is expected in covered-wheel racing, as for example in NASCAR. Open-wheeled drivers must be extremely precise to avoid contact.

Regulations tend to permit much lower open-wheel car weights than in categories that more closely resemble street-legal vehicles, such as sports, touring, and stock cars. For instance, a Formula One car must weigh at least 798 kilograms (1,759 lb); the minimum weight for NASCAR is 1,500 kilograms (3,200 lb).