Porsche and Opel are two brands not often spoken in the same sentence. However, as Porsche continued development of its 928 model (which was supposed to replace the 911 at one point), engineers had a problem.
So the story goes, according to Road and Track, the 928 had an incredible tendency to oversteer and the steering often presented itself as incredibly unstable. Per the report, “lateral forces in curves cause the outer rear wheel to switch to a positive track as if a person’s foot were turned out. What’s almost even worse is that releasing the accelerator during a curve causes a frontward shift in the car’s center of gravity, which lowers the load on the rear.”
Porsche had identified the problem in the 1950s, though no solution had arisen since then. But, Wolfhelm Gorissen, Manfred Bantle and Helmut Flegl finally found an answer.
The team took a standard Opel sedan and created a simulation tool to create the undesired effects the 928 grand tourer exhibited. With two steering wheels (one in the front, and one in the rear), Bantle drove the car normally while Walter Näher created the unstable steering feel from the rear steering wheel.
During the trials, the team was able to find that even small angles could fix the unstable feelings and they developed the Weissach axle. The axle features rubber bushings between the axle components and suspension to produce more neutral handling. And it worked, thanks to an Opel development car.