Group 5 (motorsport)

Group 5 was an FIA motor racing classification which was applied to four distinct categories during the years 1966 to 1982. Initially Group 5 regulations defined a Special Touring Car category and from 1970 to 1971 the classification was applied to limited production Sports Cars restricted to 5 litre engine capacity. The Group 5 Sports Car category was redefined in 1972 to exclude the minimum production requirement and limit engine capacity to 3 litres. From 1976 to 1982 Group 5 was for Special Production Cars, a liberal silhouette formula based on homologated production vehicles.

In 1966 the FIA introduced a number of new racing categories including one for highly modified touring cars, officially known as Group 5 Special Touring Cars. The regulations permitted vehicle 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.

For the 1970 season, the FIA applied the Group 5 classification to the Sports Car class which had previously been known as Group 4 Sports Cars. The minimum production requirement remained at 25 and the engine capacity maximum at 5 litres as had applied in the superseded Group 4. Group 5 Sports Cars contested the FIA's International Championship for Makes in 1970 & 1971, alongside the 3 litre Group 6 Prototype Sports Cars.

During 1970 the FIA decided to replace the existing Group 5 Sports Car category when the rules expired at the end of the 1971 season, so the big 917s and 512s would have to be retired at the end of that year. Surprisingly, Ferrari, which in late 1970 had updated the 512S to 512M spec similar to the 917K, decided to give up any official effort with the 512 in the 1971 International Championship for Makes in order to prepare a 3-litre Ferrari 312PB for the new 1972 season regulations. But many 512s were still raced by private teams, most of them converted to M specification. As a result of the rule change, sports car racing popularity suffered and did not recover until the following decade, with the advent of Group C which incidentally were forced out of competition in favour of the 3.5 atmo engine formula, reminiscent of events nineteen years previous.

In an effort to reduce the speeds generated at 1967 Le Mans and other fast circuits of the day by the unlimited capacity Group 6 Prototypes such as the 7 litre Fords, and to entice manufacturers of 3 litre Formula One engines into endurance racing, the Commission Sportive Internationale (then the independent competition arm of the FIA) announced that the new International Championship for Makes would be run for Group 6 Sports-Prototypes limited to 3 litre capacity for the four years from 1968 through 1971.

Well-aware that few manufacturers were ready to immediately take up the challenge, the CSI also allowed the participation of 5 litre Group 4 Sports Cars manufactured in quantities of at least 50 units. This targeted existing cars like the aging 1965 Ford GT40 Mk.I (which received permission for modifications) and the slightly newer Lola T70 coupe.

In April 1968, the CSI announced that, as there were still too few entries in the 3 litres Group 6 Prototype category, the minimal production figure to compete in the Group 4 Sport category of the International Championship of Makes would be reduced from 50 to 25 starting in 1969 through to the planned end of the rules in 1971. This was mainly to allow the homologation in Group 4 of cars such as the Ferrari 250 LM and the Lola T70 which had not been manufactured in sufficient quantities to qualify (unless, in the case of the Lola T70, the open Can-Am cars were counted as well).

Starting in July 1968, still in secret, Porsche made a surprising and very expensive effort to take advantage of this rule. As they were rebuilding race cars with new chassis every race or two anyway, they decided to conceive, design and build 25 versions of a whole new car for the Sport category with one underlying goal: to win its first overall victory in the 24 Hours of Le Mans. In only ten months the Porsche 917 was developed, based upon the Porsche 908, with remarkable technology: Porsche's first 12-cylinder engine, and many components made of titanium, magnesium and exotic alloys that had been developed for lightweight hillclimb racers. Other ways of weight reduction were rather simple, like a gear lever knob made of Balsa wood.