With the change in profile of the rear bodywork, the rear wheel arch can either be moved upwards or increased in diameter.
This is the standard rear wheels and arch arrangement (16in wheel) before the rear bodywork re-profile. From an aesthetic viewpoint the 16 inch diameter wheel is about as large as you can go due to profile and width restrictions. The tyre outline exactly matches the arch with minimal gap, but there is an off-road style 8 inches of ground clearance and barely any room for suspension movement. In the 1960’s, when this car was designed, a 13inch wheel was the norm.
The goal is to gain a level 6 inch (152mm) ground clearance along the length of the car.
Unfortunately, it is not as simple as replacing the 16 inch wheel with a lower profile 19 inch version because of the limited tyre sizes available. The drawing below depicts 215x35x19 tyres (green line). The effect on suspension geometry and height of the rear differential will be dealt with later.
The above picture shows 30mm clearance between tyre and arch and a total of 75mm upwards suspension movement.
It was at this stage that the idea of a complete redesigned was born.
A popular misconception is that low-profile tyres instantly give better grip. Unfortunately, as tyre profiles decrease, the importance of certain suspension parameters become an issue. With certain suspension designs it is a balancing act between unwanted tyre distortion and loss of contact area.