While rules vary from country to country, most series require that the competitors start with a standard body shell, but virtually every other component is allowed to be heavily modified for racing, including engines, suspension, brakes, wheels and tires. Wings are usually added to the front and rear of the cars. Regulations are usually designed to limit costs by banning some of the more exotic technologies available (for instance, many series insist on a "control tyre" that all competitors must use) and keep the racing close (sometimes by a "lead trophy" where winning a race requires the winner's car to be heavier for subsequent races). In this, it shares some similarity with the American stock car racing (governed by NASCAR); however, touring cars are actually derived from production cars while NASCAR vehicles are custom built (although in the early days of NASCAR, stock cars were in fact built from production cars, much like current day touring cars). Touring cars race exclusively on road courses and street circuits, while its American counterpart primarily utilizes oval tracks.
Whilst not nearly as fast as Formula One, the similarity of the cars both to each other and to fans' own vehicles makes for entertaining, well-supported racing. The lesser impact of aerodynamics also means that following cars have a much easier time of passing than F1, and the more substantial bodies of the cars makes the occasional nudging for overtaking much more acceptable as part of racing.
As well as short "sprint" races, many touring car series include one or more "endurance" races, which last anything from 3 to 24 hours and are a test of reliability and pit crews as much as car and driver speed.
For the casual observer, there can be a great deal of confusion when it comes to classifying closed-wheel racing cars as 'touring cars' or 'sports cars' (also known as GT cars). In truth, there is often very little technical difference between the two classifications, and nomenclature is often a matter of tradition.
In general, however, touring cars are based upon 4-door 'family' saloons or, more rarely, 2-door coupés, while GT racing cars are based upon more exotic vehicles, such as Ferraris or Lamborghinis. Underneath the bodywork, a touring car is often more closely related to its road-going origins, using many original components and mountings, while a top-flight GT car is often a purpose-built tube-frame racing chassis underneath a cosmetic body shell. Many touring car series, such as the BTCC and the now-defunct JTCC distinguish themselves from sports-car racing by featuring front-wheel drive, four-wheel drive and rear-wheel drive cars with smaller engines.
However, while touring cars have a lower technical level than sports cars in general, there are notable exceptions to the rule. The Deutsche Tourenwagen Masters (DTM) is considered to be one of the most technologically advanced racing series in the world, with cars that, underneath their four-door shells, are more purebred racing machines than most FIA-GT vehicles.
The DTM series, the initials standing for Deutsche Tourenwagen Meisterschaft until 1996, then following a hiatus, revived as Deutsche Tourenwagen Masters in 2000, features advanced purpose built V8-powered space frame machines, covered with carbon fibre bodyshapes resemblant of the manufacturers' road machine. In order to lower costs, the engine power is limited to , and transmissions, brakes and tyres (Dunlop) are standard parts for all. Also, dimension and aerodynamics are equalized. The approx. light DTM cars corner incredibly quickly and wear spectacular bodykits incorporating huge wheel arches and diffusors.
More than 20 works-backed entries of Opel Astra, Audi TT and Mercedes-Benz CLK contested the revived 2000 DTM series but a serious issue developed for the series when Opel pulled out ahead of the 2006 season. The series has survived this hurdle and remained popular with 18 Audi A4 and Mercedes-Benz C-Class contesting the present series.
Since 1997, and nowadays still on the over long famous old Nürburgring, in average over 150 touring cars compete in the VLN series of ten typically 4 hour long races. Cars range from old road legal compacts to Porsche 996 and even modified DTM cars (). Most entrants of the 24 Hours Nürburgring collect experience here.
Formerly the Australian Touring Car Championship. The current formula was devised in 1993 (based on Group A regulations) and branded as 'V8 Supercars' in 1997. The series features grids of 31 650+ hp (480 kW) Ford Falcons and Holden Commodores. The weight limit for a V8 Supercar is . At one time the cars were billed as the "biggest, heaviest, fastest and most powerful" of all touring cars. In terms of outright power, size and weight this is still likely to be true however DTM vehicles are probably faster around a track. However, V8 Supercars provide the closest racing of any touring car category, with the top 20 usually qualifying within 1 second of one another.
As the series has grown, major international motorsport organisations have become involved. Several teams now benefit from the involvement of Tom Walkinshaw Racing, Triple Eight Race Engineering and Prodrive. In addition to regular appearances in New Zealand the series ventured to China in 2005 and since 2006 has raced at the Bahrain International Circuit. The growth of the series has seen motorsport equal Rugby League as Australia's third most watched sport.
The British Touring Car Championship (BTCC) currently competes at nine circuits in the UK with cars built either to BTC-Touring or Super 2000 specification, with ballast being used to equalise the two types. Cars are 2.0 Litre saloons with around and can be front wheel drive, 4 wheel drive, or rear wheel drive. There are currently only two manufacturer teams (Vauxhall and SEAT, who enter "Super 2000"-spec Vectras and Leons respectively) although because BTCC budgets have been kept relatively low there is a strong independent and privateer presence in the championship. Manufacturers represented by privateers include Volvo, Vauxhall, Chevrolet, Honda, Lexus, BMW, Peugeot, Alfa Romeo and MG.
Prior to 2001 the BTCC was contested by cars built to 2.0 litre supertouring regulations and had in its heyday up to 9 different manufacturers. Joachim Winkelhock stated on several occasions that it was the best touring car championship in the world, and many champions of that era now race in the World Touring Car Championship (WTCC). Between 2002 and 2006 the BTCC ran its own Touring class with Super Production/Super 2000 cars making up the numbers; the Touring class is now being phased out (only privateers are eligible to run old Touring cars) with the intention of a pure Super 2000 series.
Modern World Touring Car Championship (WTCC) started in 2005, evolving from the reborn European Touring Car Championship. It is generally considered to be the most prestigious touring car championship in the world.
Running at major international racing facilities, this series is heavily supported by BMW, SEAT and Chevrolet, with Alfa Romeo also showing limited support. It features 2-litre cars built to Super 2000 regulations based on FIA Group N.
Following the trend of recent FIA rules, cost control is a major theme in the technical regulation. Engines are limited to 2000 cc. Many technologies that have featured in production cars are not allowed, for example: variable valve timing, variable intake geometry, ABS brakes and traction control.