Originally posted by speedyHAM
If you have moisture in your tires some of it will be in liquid form as small droplets on the inside of the tire for normal driving. Hard driving will heat these droplets into vapor, which makes a huge difference in the pressure in the tires. If you fill your tires at a typical gas station air line you can usually see water droplets coming out of the line when you start the air flowing. That water in your tires causes the pressure build up.
This is the part that's not so clear. Water droplets represent a reduction in volume, water is essentially noncompressible at these pressures. When in turns to vapor you trade off that volume reduction for an increase in the n term of the ideal gas law. So does this produce a net increase in pressure???? And if so is it greater than the increase due to just the temperature change???