hydroplaning

[Ameer Antar]

since the original issue was hydroplaning, can anyone give any formulas or 
relationships between tire width, weight, and hydroplaning? How much is too 
much for a given weight?

Anyways, I think the formula is correct. Orin has confirmed this. And Phil 
doesn't seem to have a problem w/ it... The first way to tell if an 
equation is wrong, is when the units are wrong. But they work here.... 
contact patch [sq in.] = load [lbs.] / pressure [lbs./sq in.]. Everything 
adds up and in testing it out it works out if you keep a few physical 
impossibilities in mind. If there is 0 load, there is 0 contact patch, even 
if there is pressure. So when you fill up a tire off the car, there is 0 
load, but there is pressure in the tire. Pressure in the tire has nothing 
to do w/ the weight of the car. pressure = (amount of gas molecules) * 
(constant R) * (temp) / (volume). It has nothing to do w/ the force applied 
on it. A force on a non-rigid object deforms it, that why you can increase 
the pressure in a balloon by squeezing it...it decreases it's volume. The 
only way to increase the pressure is by putting in more gas, raising temp, 
or decrease volume.

At 0 psi, the formula gives an answer of infinity. Plug in a psi value of 
.5 psi and you get 1600 sq. in. of contact patch. Of course that makes no 
sense for that # or 5 or even 10 psi. At those low pressure, the tire will 
be so deflated, that the inside of the tread of tire will be touching the 
rims. This is a limit, not accounted for in the equation, b/c the amount of 
deflation that can occur depends on how tall the sidewalls are. The 
equation is right, as long as the tires have enough pressure in there to 
keep the back of the tread from touching the wheels. I think that should 
make sense...

-ameer