Air pressure variances

[Loren]

Tire pressure changes due to temperature are relative to the beginning tire pressure.

For instance, if you start at 28 psi, and the temp goes up 20 degrees, you might see 30 psi. If you start at 44 psi and the temp goes up 20 degrees, you might see 47-48 psi or more. "1 psi per degree of temperature" is only going to be accurate (relatively) for a particular range of pressures, probably somewhere around 25-30 psi. It might be better to look at it as a percentage change. Say... 10% for every 30 degrees or something like that. Then, 30 psi would become 33 with 30 degrees of temp increase, and 44 would become 48.4 with the same temp increase. A little more realistic.

Best bet, especially when running really high pressures, is to check your pressures with the tires HOT because there's going to be a HUGE variance in pressure between cold and hot. Typical tire tread temps are up around 110-130 degrees after you've been driving for a while. If you started at 80 degrees, that can be up to 50 degrees of temperature change... enough to make 45 psi cold equal well over 50.