Quote:
Originally Posted by Utahtrapper
From fulltilt
If you would allow me to point out a few important points, the pressure listed on the tire is calibrated for 70 degrees F, this is the temperature that many industries use as a basis, not just the tire industry, you extrapolate from there. So for every 10 degrees + or -, outdoor temperature, you have to alter your pressure by 2%. There is also an altitude adjustment but I haven’t felt the need to use that.
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There are two approved sets of government regulations for setting and maintaining recommended cold tire inflation pressures. First is the Federal Motor Vehicle Safety Standards (FMVSS). Those standards guide the fitment and inflation pressures for all automotive vehicles, including RV trailers. Second is the Federal Motor Carrier Safety Administration (FMCSA). Their rules differ considerably from the FMVSS standards. Therefor, one is not applicable to the other.
The explanation of "cold inflation pressures" is determined by tire down time, meaning they have not been used or in highway service for at least three hours before inflation pressures are adjusted. In the lower 48 cold is cold. The recommended cold inflation pressure provided at 10,000 feet above sea level will still be correct at the vehicle manufacturers placard recommendations. Same for those tires at sea level. Increased inflation pressures acquired while in motion have been factored in during the manufacturing process for each tire. If you must have a specific answer, look-up tire thermodynamics and combine with tire equilibrium.