I hate to guess at stuff too.

Tell you how this discussion started, a friend was watching me pump up a tire. He said something like this: I never could understand, why, if you inflate a tire to 60 psi, and then add the weight of a vehicle, it doesn't change.

Thanks Frank for your experiment.

The volume of the tire is the same. It's sealed up, locked inside.

Correct me if I'm wrong! But the air pressure inside of a tire will increase, as the temperature rises.

Just say that the truck does have a HUGE load of firewood, and we're driving down the road 40 miles per hour. The sidewalls of the tires are really flexing, too hot to touch after 3 miles. The tires are getting soft, and the air inside expanding. That's likely to cause a blow-out. Correct?

But let me ask you this: Just say that I have an air tank, exactly 1-cubic foot in size. At sea level, zero pressure inside the tank, it contains exactly 1-cubic foot of air.

Now, just say I'd pump that tank up to 100 psi, how many cubic feet of air would that translate to, at zero pressure?

Or look at a scuba diving tank, exactly 1-cubic foot in size, pumped up to 3,000 psi. How many cubic feet would we have at sea level?

I know that there's a formula, without searching all day, what's the answer? I'm just curious!