[JulianEdgar]

Originally Posted by AeroMcAeroFace

Presumably you are talking about the mk1 audi TT, I don't believe you when you say that lift is the sole cause of the issue here, that is a simplification. The issue in that case was lift but also suspension issues.

No I am not talking about the Audi

The real issue is unequal lift and/or centre of pressures ahead of the centre of mass. Planes do not suddenly crash when they get to 50% of their weight on their tyres.

The proposition seems to keep changing a bit each post. From originally 'why don't cars fly' to now something quite different.

When you added those side fins on your insight, you got extra rear lift but because the centre of pressure moved rearwards the stability improved?

No I had true downforce both before and after fitting the fins, so I was able to assess the difference that downforce alone made.

If unequal loading was the sole cause of the problem we wouldn't have cars with weight distributions up to 70/30.

You are constantly equating aerodynamic lift forces with static weight distribution but the published research on car stability and aero lift doesn't agree with this.

But it isn't, because my cars aren't designed with aerodynamic stability in mind, they are aerodynamically unstable and rely on the tyres to stop the car from going sideways. This is a thought experiment about a car that is aerodynamically stable.

I don't know why you say this - it varies from car to car. Some cars are quite aerodynamically stable in yaw.

I have driven cars with front end lift, and I know it isn't pleasant, but then I have flown planes and gliders with much more lift and they have no directional stability issues. As I mentioned earlier the real issue is directional stability, rather than specifically lift.

Again, look at the published research. Front end lift on cars is of far less importance than rear lift.

Drop a plane and it will point in the correct direction, drop a car and it will tumble. Why? Aerodynamic directional stability.


On typical road cars maybe, but a plane becomes more stable as more lift occurs, due to more corrective aerodynamic pressure. Handling, again on a typical car, but this imaginary car can cut the lift, and has control surfaces so that evidence doesn't apply. Braking, air brakes would be employed, lift cutting and added downforce would be employed.

I am not saying that it would be in any way easy to do, or legal to do, but I still see no reason why a car specifically designed for it, such as in a university challenge like a solar challenge, wouldn't work.

Again, go read the research. In fact, it as a solar car that I was referring to above that had handling control problems with 14 per cent rear lift. Do you honestly believe that the solar teams have overlooked something like you suggest? Given that many of these cars have aerodynamic lift, it would have been obvious in their testing if total resistance fell with speed - especially if there were no downsides.

Another thing you're ignoring: total aero drag normally goes up with increased ride height.

Tyre grip is not linear no, but I was approximating it to linear because the linear region is where most car tyres are. However, the graph you provided suggests that halving the force on the tyres leads to only a 25% reduction in grip.

I don't think you are considering where cars are on the tyre grip versus load curve.

I think what you are suggesting is a very bad idea, and it doesn't get much better as you keep altering the proposition. To be honest I am pretty surprised that you've put this idea forward as there's plenty in the published literature (that you normally read) to show how such an approach would be nightmarish in the real world.