I downloaded a form from I believe The Tire Rack, about the effect of tire pressure on grip...and it said, raising tire pressure increases grip...I see a lot of people talk about raising tire pressure to get the car to rotate(less grip i assume)...so, if this is the case, there must be a point where grip becomes slip......Am i getting this right?????

Thanks for any help

 

Ya, in general, if you plot "grip" of a typical passenger car tire as a function of pressure, it looks like some kind of upside down parabola or a mountain or something. At low pressures, grip increases with air pressure until you have some "optimum" pressure where grip is maximum. Then grip starts to decrease with increasing tire pressure.

The problem is that curves like this have many variables, so the "optimum" pressure, even with identical tires, can vary by car and even which end of a particular car the tire is on. Suspension geometry and wheel width and things also make a huge difference.

I think that the two "main" competing effects are the effects of the sidewall stiffness at low pressure (I think the stiff sidewalls reduce force on the center of the tread at low air pressures, making the force on the contact patch uneven), and high pressures simply reducing contact patch. That's probably an oversimplification, but I have a pretty simple mind