 With this in mind, Herd drew up plans for a six-wheeled car with four driven wheels at the rear and all of the wheels the same 16" diameter.His theory was that with all six tyres the same size as the regular F1 front tyre, the car would not only be slimmer than normal F1 cars but would possess improved aerodynamic performance at the rear with much cleaner air passing over the wing.Four driven wheels would also mean better traction and, unlike the Tyrrell, there would be no problem with tyre development since the car would use exactly the same rubber as a conventional F1 car.