Tyrrell P34

Mid-1970s Formula One regulations stipulated a maximum front wing width of 1.5 metres. With standard front tyre sizes, the tyres projected above and to the sides of the wing, creating drag and disrupting airflow to the rear wing. Gardner's objective was a tyre small enough to fit entirely behind the front wing — reducing drag on straights and providing cleaner airflow to the rear wing.

The required tyre was 10 inches (250 mm) in diameter, too small a contact patch for acceptable cornering. Using four front wheels instead of two solved this while also increasing total brake area. The steering system complexity this introduced was addressed by connecting the steering wheel to the front pair of wheels, which were then linked to the rear set via a bell crank. Observer Joel Rosinsky later described the result as "so gentle and absolutely free of reaction that you might have thought it was power-assisted."

The design was unveiled at the Heathrow Hotel in late September 1975, initially concealed under a tarpaulin with hoops over the wheels to suggest a conventional car — leading to astonishment when the cover was removed. Some observers believed it was a publicity stunt. The car first ran at Silverstone on 8 October 1975. After further testing, Tyrrell built two more examples with a slightly longer wheelbase for the 1976 season.

The stretched versions debuted at the 1976 Spanish Grand Prix and proved highly competitive. Jody Scheckter and Patrick Depailler both drove the P34. The car's defining moment came at the 1976 Swedish Grand Prix at Anderstorp, where Scheckter and Depailler finished first and second — making Scheckter the only driver ever to win a Formula One race in a six-wheeled car. The car was particularly effective on circuits featuring long corners and straights, including Anderstorp, Watkins Glen, Mosport Park, Fuji, and the Österreichring. It struggled on bumpy circuits such as Brands Hatch, Jarama, and the Nürburgring, where uneven surfaces caused one of the small front tyres to lose contact while the other on the same side remained grounded, producing variable grip. Depailler praised the car continuously while Scheckter was unimpressed, leaving the team at the end of the season and calling the six-wheeler "a piece of junk."

For 1977, Scheckter was replaced by Ronnie Peterson. The car was redesigned as the P34B with cleaner aerodynamics, and some modifications were made to Peterson's car to accommodate his height. The P34B was wider and heavier than its predecessor, weighing 190 pounds (86 kg) over the 1,268 pounds (575 kg) Formula One minimum. Both Peterson and Depailler produced some promising results, but the car was clearly inferior to its 1976 form. Tyrrell attributed the decline to increased weight, which strained the brakes and hurt cornering. Others blamed Goodyear's failure to develop the small front tyres adequately. Late in 1977, attempts to fix the handling by increasing the front suspension track moved the tyres out from behind the wing, eliminating the concept's original aerodynamic benefit.

In November 1977, Tyrrell unveiled a conventionally configured car for 1978 and announced the end of the six-wheel project. Tyrrell retained the chassis on which Scheckter had won and sold the remaining examples.

The P34 later appeared competitively in historic racing after the Avon tyre company agreed to manufacture bespoke 10-inch tyres for Simon Bull, owner of chassis No. 6. In 1999 and 2000, the resurrected P34 competed in the FIA Thoroughbred Grand Prix series at British and European circuits, driven by Martin Stretton, who won the series outright in 2000. Chassis No. 5 repeated that success in 2008 in the hands of Mauro Pane; that example is now owned by Pierluigi Martini alongside chassis number 2. Stretton also achieved numerous pole positions and class wins at the Grand Prix Historique de Monaco. The P34 has also appeared at the Goodwood Festival of Speed.

The P34 was not the only six-wheeled Formula One car. March Engineering, Williams, and Scuderia Ferrari also built experimental six-wheeled chassis, though all of these had four wheels at the rear rather than the front. The Williams FW07D and FW08B and the March 2-4-0 used tandem rear wheels, reducing drag by employing smaller front wheels in place of the typical larger rear ones. The Ferrari 312T6 featured four rear wheels on a single axle. None of the March, Williams, or Ferrari designs was ever raced. In 1983, the FIA prohibited cars with four driven wheels from competing; later regulations set four as the maximum number of wheels permitted in Formula One.

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