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xYoSoYx OP t1_ixrxxlg wrote

Reply to comment by TheJeeronian in ELI5: why does tire pressure decrease in the cold? by xYoSoYx

Had another thought after rereading your last statement about water…

Would this mean that going from an extremely humid climate to an extremely dry climate would also impact the tire pressure? Just less significantly than a change in temperature?

Just curious if there is some mathematical equations that would represent the multiple factors you’ve laid out to explain the impact on the tires psi.

You’ve pretty much answered my initial question, just the math nerd in me wondering if this is a thing, so had to ask lol.

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TheJeeronian t1_ixs7fvp wrote

It shouldn't. As I mentioned, outside air pressure is pretty much fixed. There's a bit of variation but almost none. None big enough to be significant compared to tire pressure.

Humidity within the tire matters when it's inflated. A tire inflated with hot and humid air will lose a lot of pressure as it cools, but a tire inflated with cold and dry air will not gain nearly as much pressure as it heats up. This is because the amount of air and water in the tire is fixed, but the water may expand or contract quite a bit with temperature. The outside humidity once the tire is sealed makes no difference.

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xYoSoYx OP t1_ixs8lhk wrote

That makes total sense, again - thank you!

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