Well my curiosity is satisfied and I had a short nap.
What I take away from 'Stability and Performance' is "The air entrained (by the tire tread) shoots out with a lot of force that go to hit the bottom of the vehicle"; the vehicle should be as low as possible but for minimum drag the wheelwell should only shroud the top half of the tire; and overtaking a truck should only be investigated by trained professionals.
Small diagrams and lots of overpainting and erasing of green lines. Watch them at 1.25 or 1.5 speed.
mikeyjd --
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