Is there more tire grip if air suspension is on LOW setting vs standard?

Depends what you mean by "grip." Negative camber turns the wheels in towards the top of the vehicle. As you can imagine, this distorts the contact patch, resulting in it narrowing slightly at rest. So, generally, in a straight line you'll see decreased grip by running more camber. That's the trade-off. The benefit is that you'll get increased grip on the corners. As the car compresses onto the outside tires into a turn, that tire levels out. What used to hit the ground at an angle is now square, providing better grip.

The above is a simplification, but that's the general idea.

Lower center of gravity means better handling, though. With 21-inch wheels and Michelin PS2's, I can definitely feel the added stability at highway speeds while in low mode.

ToddRLockwood said:

Lower center of gravity means better handling, though. With 21-inch wheels and Michelin PS2's, I can definitely feel the added stability at highway speeds while in low mode.

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The question was about tire grip, not the car's handling, exactly. It's not necessarily the same thing you're talking about. Indeed the increased camber at the lower ride height has some effect on your perception of handling as well as the lower center of gravity.

In any case, the tire's grip is only affected by ride height insofar as it affects the camber.

Gizmotoy said:

In any case, the tire's grip is only affected by ride height insofar as it affects the camber.

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Almost. If the centre of gravity is lower, there will be less weight transfer from front to back or side to side (depending upon whether you're accelerating, braking, or turning) so the tires will actually grip slightly better. Because the centre of gravity in the Model S is very low to start with, you might need some sensitive equipment to measure the difference. No doubt that when cornering the camber change would have the most effect.

The other point to bear in mind is that as the car lowers and the camber increases, the ride will feel different as bumps in the road will be less well absorbed. Anyone noticed that? Mind you, a firmer ride suits some of us.