Tires: pressure

Question
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

Answer
James,

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.