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      10-31-2012, 05:52 PM   #6
Marathon Man
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Drives: 2013 X3
Join Date: Jul 2012
Location: Houston

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Dandanio is correct - air or nitrogen would have no noticable difference in response to changing temperature.

96_Impreza's approximation of 10 degree F temperature change = 1 psi pressure change is pretty good. So a 25 degree drop in temperature could drop your tire pressure 2.5 psi. This is likely the cause of the sudden alarm on 4 tires. The tires were probably already toward the low end of acceptable and the temperature change moved them low enough to alarm.

I would need to know more about how the TPMS works to comment on the affect of a hurricane (low atmospheric pressure) would be on the TPMS reading. But a normal pressure gauge actually measures the difference between the inside tire pressure versus atmospheric pressure. A drop in atmospheric pressure from a hurricane moving through would show a INCREASE in tire pressure. The pressure inside stays the same but the gauge reading would go up since the reference atmospheric pressure went down. Plus the most impact on pressure you would likely see is about 1 psi difference one way or the other unless you are checking your tires as a Cat 3 storm passes over you. I've been in a Cat 3 storm and I was NOT worrying about my tire pressure! Sandy, while a large storm with a huge impact on people, was only a Cat 1 storm.

All of this assumes the tires don't change in volume too much with changing temperature and atmospheric pressure. I have no data on that!
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