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QUESTION: If a car tire's pressure drops, for example 2 pounds when the outside temperature drops 20 degrees, will the pressure go back up when the outside temperature goes up? Or is that drop an actual loss of air and needs to be replenished? Thanks!

ANSWER: James,

Sorry for the delay in responding.  We had a large lightening strike near the house and it took out several electronic things, including my cable modem.

The air inside a tire behaves according to the laws of Physics - so, yes, the pressure goes up and down according to the temperature - unless there is a leak.

---------- FOLLOW-UP ----------

QUESTION: No problem, sorry about the lightening strike. So does that mean if I put 36 psi in my tires and they go lower due to outside temperature, but then go back up, theoretically, I would never have to add air to the tires unless there's a leak? Thanks


No, not exactly.

When the pressure is low - even if it is due to a drop in temperature - the pressure is low.  That causes the tire to run hotter - and it's the internal running temperature that is important.

So when the weather turns cold, a bit of overinflation might be a good idea.  We're only talking 3 to 5 psi.


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Barry Smith


I have over 30 years experience in the design, manufacturing, and testing of tires. I have served as the technical advisor to the "800" number. I have authored or co-authored many publications - usually without credit. I can answer almost any technical question, but please don`t ask me to compare brands. I probably have prejudices because of my work experience.


Member SAE (Society of Automotive Engineers) Member Tire Society (Tire Technical Organization) SCCA Regional Competiton License holder Authored many training manuals on tires, their care and use.

SAE (Society of Automotive Engineers) SCCA (Sports Car Club of America) Tire Society

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I am a graduate of the University of Dayton, Dayton, OH - BME, 1971 I attended graduate school at the University of Akron - but did not complete my PhD - something I regret.

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