I had much thought about what happens to the pressure in the tire while the temperature changes – it is what I do…
Now, we all (should) know that if you check your pressure before a drive and after one you will see an increase of up to about 3 PSI (no matter how fast you drive or how cold is it outside mind you!) and that is because the friction made the tire warmer and it in turn warmed the air inside (1 PSI for every 10 deg F ~5 C increase). That is a thing a lot of people know, and hopefully take into consideration when they check the tire pressure. I should add that this is a rule of thumb and it could change by a bit for some reasons).
About that – I think one should either check and fill the pressure after a very short drive (the air didn’t had time to get the hit energy) of about 1 mile (~1.5 Km) or if the service station is too far (as in most cases) should do it after a long drive (30 minutes or more) so the temperature rise made it to it’s finale values – and then just put in the recommended pressure+3 PSI. That said, it is better to check your pressure at any point other then what I suggested then not checking it at all…
After settling that issue we can discuss another aspect of temperature change in tire pressure. What about changes between winter and summer? or morning and noon? well, the physics are the same and the pressure will change as the temperature will. Now, the changing of the seasons will be addressed as you check your pressure every few weeks. And if you have a long drive through different climate areas (from a hot ocean front to a cold mountain ridge – can change pressure about 6 PSI) you should check the pressure along the drive. In addition if you stay at an extreme climate region but park your car in a temperature controlled garage you should check the pressure outside (with the tire being in the temperature long enough so the air inside got there too) as the temperature difference can be crucial.
A main issue is what to do if the area you live in has big temperature changes between morning and high noon? well, you should think if your drives are mostly when it is hot or cold or perhaps adjust the pressure for a temperature in-between.
Check out this clip for a really nice demonstration of this –
To conclude – the pressure given by the car manufacturer is the cold (tire = outside temperature) inflation pressure and so will change as the tire temperature changes. We need to make sure the pressure we see when we check is properly adjusted to the changes.