This article is about the sport of stock car racing. A stock car is also a type of railroad freight car

Stock car racing is a form of automobile racing found mainly in the United States held largely on banked concrete oval tracks of between approximately 1/2 mile and 2.66 miles (about 0.8 to 4.2 kilometres) in length, but also raced occasionally on conventional racing circuits. Ovals shorter than one mile (1.6 km) are called short tracks; unpaved short tracks are called dirt tracks; longer ovals are typically known as superspeedways. Races are generally 200 to 600 miles (320-965 km) in length. Average speeds are around 160 mi/h (275.5 km/h), compared to 220 mi/h (354 km/h) in open wheel racing. (Some tracks are built to allow cars to travel at speeds close to those in open-wheel racing.)

Stock cars

A stock car in the original sense of the word is an automobile which has not been modified from its original factory configuration. This term was used to differentiate such a car from a race car, a special, custom-built car designed only for racing purposes with no intent of its ever being used as regular transportation.

When NASCAR was first formed to regulate stock car racing, there was a requirement that any car entered be made entirely of parts available to the general public through automobile dealers, and that all cars must be from a model run of which at least 500 cars of that model were sold to the general public. In NASCAR's early years, the cars were so "stock" that it was commonplace for the drivers to drive themselves to the competitions in the car that they were going to run in the race.

This was eventually modified, however, primarily in the interest of safety, as race drivers are subjected to forces unheard of by drivers of cars in ordinary use, and require a far higher level of protection that is normally afforded by truly "stock" automobile bodies. Modern racing "stock" cars are stock in name only, using a body template modeled after currently-available automobiles, but the chassis, running gear, and equipment have almost nothing to do with those of ordinary automobiles.

Modern stock cars superficially resemble standard American family sedans, but are in fact purpose-built racing machines built to a strict set of regulations governing the car design ensuring that the chassis, suspension and such are architecturally identical on all vehicles. Ironically, these regulations ensure that stock car racers are in many ways technologically less sophisticated than standard cars on the road. For example, NASCAR (the premier stock car organization in the US) requires carbureted engines in all of its racing series, while fuel injection is now universal in standard passenger cars.

Engines, whilst containing varying components from the various manufacturers who compete in the series, are of fixed size, and are generally designed to ensure all entrants have near-equal vehicles. There are several categories of stock car racing, each with slightly different rules, but the key intention of cars that look like production cars, but with near-identical specifications underneath, remains true.

The closest European equivalent to stock car racing is probably touring car racing, though these are raced exclusively on road circuits rather than ovals.

Stock car series

The most prominent championship in stock car racing is the NASCAR championship, currently called the Nextel Cup after its sponsor (formerly known as Winston Cup after a previous sponsor). It is the most popular racing series in the United States, drawing over 6 million spectators in 1997, an average live audience of over 190,000 people for each race. The most famous event in the series is undoubtedly the Daytona 500, an annual 500-mile race at Daytona Beach, Florida. The circuit's second-biggest event is probably the Brickyard 400, an annual 400-mile race held at the Indianapolis Motor Speedway, the legendary home of the Indianapolis 500. NASCAR also runs the Busch Series, a stock car junior league, and the Craftsman Truck Series, a junior league where pickup trucks are raced. Together the two car-based series (Winston Cup and Busch Series) drew 8 million spectators in 1997, compared to 4 million for both American open-wheel series (CART and IRL). In 2002, 17 of the 20 US top sporting events in terms of attendance were NASCAR races. Only football drew more television viewers that year.

Besides NASCAR, there is IROC (International Race of Champions) and the IPower Dash series, formerly known as the Goodys Dash series. There is also stock car racing in Canada organized by CASCAR, and Australia once had the AUSCAR but it didn't enjoy success comparable to the V8 Supercars

Stock car racing is also a popular local event. Many tracks exist in the United States (and a few in Canada) catering to a wide variety of car types and fans. There are a few organizations that cater to these local short tracks, such as ARCA, ASA and IMCA. NASCAR also supports local short track racing with their Elite Division and Weekly Series racing.

Criticism

Fans of other racing series, such as Formula One, often have low opinions of the series and its fans. They regard the drivers, cars, and fans as interesting relics of less sophisticated times, with the restrictive regulations removing any possibility for technical innovation. Whilst it is undoubtedly true that stock car racing is less technically sophisticated than many other forms of motorsport, the relative equality of the machinery makes the racing closer and results much more of a test of driver and pit crew ability than more technically-oriented motor racing series that are often decided in wind tunnels and on CAD terminals well before any actual racing takes place.

Whilst the challenges of driving and setting up the cars around near-identical banked ovals are probably fewer than learning varied road circuits, the aerodynamic factors giving advantages to a tactically-savvy driver lead to interesting contests which bear some resemblance to some forms of track cycling. In particular the aerodynamics ensure that cars which are following each other both have less drag than either car alone. Therefore it is in the drivers' interests to cooperate in forming chains of cars with low drag. Yet a driver must at some point end cooperation in order to win the race. The combination of cooperation and non-cooperations leads to some very sophisticated strategic decision making. Also it should be noted that the tracks, at least those used by NASCAR, are not identical, with some being oval, some being tri-ovals, one being essentially triangular, and two of them in fact being road courses that are also used by road racing series.