In 1966, the FIA introduced new racing categories, including one for highly modified touring cars, officially known as Group 5 Special Touring Cars. The regulations permitted modifications beyond those allowed in the concurrent Group 1 and Group 2 Touring Car categories. Group 5 regulations were adopted for the British Saloon Car Championship from 1966 and for the European Touring Car Championship from 1968. The Special Touring Cars category was discontinued after the 1969 season.
The Group 5 classification for Sports Cars emerged from a desire to manage the increasing speeds of unlimited-capacity Group 6 Prototype cars, such as the 7-litre Ford GT40, at circuits like Le Mans. To encourage manufacturers of 3-litre Formula One engines to participate in endurance racing, the Commission Sportive Internationale (CSI) announced the International Championship for Makes would be run for Group 6 Sports-Prototypes limited to 3 litres from 1968 through 1971. To ensure participation, the CSI also allowed 5-litre Group 4 Sports Cars, built in quantities of at least 50 units, to compete. This targeted existing cars like the Lola T70 coupe. In April 1968, recognizing a lack of entries in the 3-litre Prototype category, the CSI reduced the minimum production figure for Group 4 Sports Cars to 25 units, starting in 1969, to facilitate homologation of cars like the Ferrari 250 LM and Lola T70.
Porsche responded to this rule change by embarking on an ambitious project to win the 24 Hours of Le Mans. Beginning in July 1968, Porsche designed and built 25 examples of the 917, based on the 908, incorporating a new 12-cylinder engine and lightweight materials. When CSI inspectors requested 25 assembled cars, Ferdinand Piëch famously displayed 25 917s parked in front of the Porsche factory on April 20. Simultaneously, Enzo Ferrari, with financial support from FIAT, manufactured 25 Ferrari 512S cars to compete against Porsche. While Porsche provided comprehensive factory support to teams like JWA Gulf and Martini Racing, Ferrari’s privateer teams received less direct assistance.
The FIA limited the use of adjustable wings in May 1969, impacting the 917. Porsche addressed the car’s instability with the 917K (Kurzheck) variant, alongside the long-tail 917L. Ferrari responded with the 512M (Modificata) which featured revised bodywork similar to the 917K. Group 5 Sports Cars contested the FIA's International Championship for Makes in 1970 and 1971. The FIA decided to replace the existing Group 5 Sports Car category at the end of the 1971 season, leading Ferrari to focus on a 3-litre Ferrari 312PB for the 1972 regulations, though many 512s continued to race with private teams. Sports car racing popularity declined following this rule change, not recovering until the advent of Group C.
For 1972, the FIA applied the Group 5 classification to what had previously been known as the Group 6 Prototype Sports Cars category. These cars, now officially Group 5 Sports Cars, were limited to a 3-litre engine capacity and were the main competitors in events counting towards the FIA's World Championship for Makes from 1972 to 1975. Unlike the earlier Group 5, there was no minimum production requirement.
For the 1976 season, the FIA introduced a new Group 5 "Special Production Car" category, allowing extensive modifications to production-based vehicles homologated in FIA Groups 1 through 4. These cars competed in the World Championship for Makes series from 1976 to 1980, and then the World Endurance Championship in 1981 and 1982. The Deutsche Rennsport Meisterschaft also used these regulations from 1977 until 1981. The only non-circuit events that used Group 5 cars were in the Giro d'Italia automobilistico rally.
The rules restricted car width, leading to cars being built with standard body widths and wide mudguard extensions. The regulations required only the bonnet, roof, doors, and rail panel to remain unmodified. A loophole regarding headlight heights allowed Porsche to race the 935 with its characteristic flat nose. The category is also associated with wide, boxy wheel arches and extravagant body styles. The category was abolished after 1982 in favour of Group B regulations but continued to compete in JSPC, IMSA GTX, and other national sports car racing championships for several more years.
European Touring Car Championship (1968 to 1969)
British Touring Car Championship (1966 to 1969)
International Championship for Makes (1970 to 1971)
World Championship for Makes (1972 to 1975)
World Championship for Makes (1976 to 1980)
World Endurance Championship (1981 to 1982)
Deutsche Rennsport Meisterschaft
Giro d'Italia automobilistico (1977–80)
Australian GT Championship (1982–85)