Nifty.
I had a bit of a paragraph going and started looking for an article I read 30 years ago in Road & Track, but found something else instead:
http://www.performancesimulations.com/w ... -pressure/tl/dr: Avon published some tests on racing tires showing contact patch relative to tire pressure and load, using F3000 front and rear tires. Tire pressure has less to do with contact patch than expected, wider tires have more contact patch at a given load and pressure than a narrow tire (surprised me), and if you believe ALL the data, some strange things happen with tire pressure on the front tires. Skeptical me says they reversed some data on the front tires between 24 and 28 psi, but take that for what it's worth.
Racing tires tend to like pressures way below 30 psi, and I've seen many Nascar races where race teams will run fastest when the tire pressures are lower than the minimum recommended by Goodyear, until the tire fails and the car plows into the wall. All, and I mean ALL, of my experience on street tires tells me that more pressure gives more grip (on dry roads) and more responsiveness, but I've never driven a race car.
Common racing lore is that lower the pressure to get more grip, and more grip comes from greater contact patch. Lowering the tire pressure in the front generally increases front grip, and vice-versa with the rear, suggesting that lower pressure = more contact patch = more grip. Avon's published data suggests that contact patch doesn't come easily, and you have to cut half the pressure (or double the load) to get a 50% increase in contact patch (should double, theoretically). But there you have it.
My personal feeling is that on a race car, the chassis is so stiff that lowering the tire pressure reduces front roll compliance just as much as reducing the sway bar, plus it increases grip over smaller bumps (basically the whole car becomes "sprung weight", with only the bottom of the tire carcass moving up and down). A street car is so much less torsionally and laterally rigid than a race car, playing with tire pressures doesn't alter lateral load distribution one bit. It still helps balance the chassis, but mostly in crispness and turn-in.
On street tires, raising the tire pressure stiffens the sidewalls and the carcass and doesn't let the tire tread squirm as much and the tire generally performs better. What happens with the contact patch? Well with the generally stiffer tire I predict that contact patch changes even more disproportionate to tire pressure, and with the higher tire pressures on a street tire you've got to make an even greater change in pressure to get any change in contact patch. Tread blocks on a stable carcass squirm less and generate less heat and more grip, so increasing tire pressure brings more benefit here.
That's what I believe, anyway.