Officially called ADAC 24h Rennen Nürburgring in German ('ADAC 24 hour Race Nürburgring'), it was introduced in 1970 by the ADAC as a real race, unlike the earlier endurance contests that covered 12, 24 (in 1961 and 1967), 36, 84 and even 96 hours, like the
Marathon de la Route. This substitute for the Liége-Rome-Liége and Liége-Sofia-Liège rallies was held on the Nürburgring from 1965 to 1971.
It is similar to the Spa 24 Hours, which had been introduced in 1924, following the 24 Hours of Le Mans. The ADAC had held its first 1000 km Nürburgring sports car racing event in 1953. As the 1000 km Spa had been introduced in 1966, the 24h at the Ring gave both circuits a pair of endurance racing events at very long tracks, at least until Spa was shortened in the late 1970s.
Just like the VLN series with its 4-hour races, the 24h race is mainly aimed at amateurs, in order to fill a starting field of around 200 cars. Unlike the VLN races, the 24h is officially an international event, with bilingual (German and English) organization and documentation. Entry fees are due, in 2010 these were €7508 per car, of which €3000 was an advance payment for fuel. Typical entries range from second hand standard road cars to European Touring Car Championship vehicles and GT3 sports cars like the Porsche 911 GT3. The participation of manufactures and professional teams and drivers has varied over the decades. As spectator numbers had dropped in the 1990s when only rather standard FIA Group N cars competed, more spectacular vehicles were admitted since 1999, like the Zakspeed Chrysler Viper GTS-R which originally was built by Oreca to FIA GT2-spec, turbo-charged Porsche, modified Deutsche Tourenwagen Masters cars from Opel and Abt Sportsline-Audi, and the Schnitzer Motorsport-entered BMW M3 GTR V8 that had been run in the 2001 American Le Mans Series.
Due to various changes and versions of the Grand Prix Strecke, the overall length of the track varied from the original 22.835 km (14.189 mi) to nearly 26 km (16.2 mi) of the maximum length configuration which was in use in 2002 and 2003, after the GP track had been extended by the Mercedes Arena. As this section and its large paved run-off areas was useful as extra paddock zone for the competitors of the support races, it is bypassed with a sharp Z-shape chicane since 2005 for a 25.3 km (15.7 mi) track length.
For practice, 230 cars are allowed, 210 qualify for the race, driven by 800 or more drivers, as 2, 3 or 4 can share a car. One driver is allowed to drive 150 minutes non-stop, and can enter on two cars, yet a rest time of at least 2 hours has to be observed between two turns of the same driver.