How to exploit positive Ackerman steering for aerodynamic benefit.
(cars)
Anti-Ackerman steering means the outside wheel while a car is cornering toes in, or turns in, more than the inside wheel does. This means that you are inducing more slip angle on the more heavily loaded wheel, which naturally should have more grip. Toe in however is detrimental to the underfloor aerodynamics of a car. When you steer a car, the inside wheel toes out, and the inside wheel toes in. Toe out while being more beneficial for aero, is worse in a dynamic sense, in terms of steering feel, and stability.
If you run positive Ackerman, the outside wheel does't toe in as much as the inside wheel toes out. However if the outside wheel has less toe in, and by extension less slip angle, you will get less steering force from the outside tire, meaning more steering lock will be required. This is of course assuming the rear doesn't move during its travel. If it does move, and it most certainly does, then the rear has it's own toe curve during suspension displacement. This can be adjusted with suspension geometry, allowing more toe out during suspension compression and or extension for instance.
This would force more car rotation, and would allow one to run positive Ackerman in the front while maintaining favorable conditions for the underfloor aerodynamics under yaw. Running a negatively biased toe curve in either direction(compression/extension) in the rear would improve aerodynamics, and would counter any understeer induced by running positive Ackerman in the front.
The problem with this kind of suspension setup is of course that it's difficult to control because although the rear will rotate, it can rotate too much, and become snappy. So the mechanical instability has to be tempered with aerodynamic stability, this means a slightly rearward center of pressure, that is the bulk of the aerodynamic loads happening behind the center of gravity. If this is not possible, if at least COP can be maintained near the neutral COG, not all hope is lost, because under braking the COG would naturally move forward, while the COP would not drift as much, this would improve aerodynamic stability under braking. It would however work in the opposite direction under acceleration, as the COG would drift behind the center of pressure, and create an oversteer condition.
Tuning then becomes a game of inducing the right amount of toe out in the rear, to work with the aero, and the understeer tendency of having positive Ackerman steering in the front.
The benefit of running positive Ackerman in the front is that the outer wheel would toe out more, and would benefit aero performance at the front, especially under yaw.
