We can learn by looking at a variety of motor sport. Drag race funny cars are an example.
1. Over the past several years, front and rear wheel openings have become smaller and biased toward the rear. The front of the opening is close to the tire and the back is spaced to the rear.
2. The back of wheel openings are getting more radiused so air can exit the under car and to not "catch" air flowing past the wheel opening.
3. Front, and sometimes rear, wheel openings have a "Gurney" lip from the lower front edge to the top of the opening. Similar to the Corvette Z-06, I think.
We may be able to learn the most about drag racing -- airflow is implied in the name, at least.
Honestly though, too much lift makes the vehicle unstable at the limit -- it still has to go straight. Too much downforce is a waste of horsepower.
Clearly, the goal for GS vehicles is to make highway speeds more efficient -- so drag racing, or top-speed (Bonneville Salt Flats) kinda stuff seems appropriate.
Is it possible to take a showroom stock vehicle and make it "Interstate Unstable" with a few aero changes? Probably not. So F1 seems to be out for the most part.
The only road-based aero disaster of recent years has been the first-gen Audi TT. At Autobahn speeds, the rear tended to break loose and a few bad accidents happened. Those were recalled and a lip spoiler added -- same with all models moving forward. Solved the problem at 120+ MPH. That's at un-FE-like speeds, tho...
The only road-based aero disaster of recent years has been the first-gen Audi TT. At Autobahn speeds, the rear tended to break loose and a few bad accidents happened. Those were recalled and a lip spoiler added
Rode past one of these bespoilered beasties parked on the street today and thought of just that story. If I had one, I'd take it off