At what temperature should I set my tyre pressures?

Gay-Lussac's law of gases put simply is - in a given volume of gas (e.g in a tyre) the pressure is in direct proportion to the temperature. So as temperature increases so pressure increases and vice versa.
Therefore at what temperature should tyre pressures be set?

Asked on 17 June 2022 by willboy

Answered by David Ross
Good question. The usual advice is to check or set tyre pressures when tyres are 'cold' - in other words when the vehicle hasn’t been driven for at least two hours. The normal ambient temperature here would be 20°C.

For every decrease of 1°C, tyre pressure drops by approximately 0.19 PSI. So a good rule of thumb is that for every 10°C drop in temperature, tyre pressures will drop around 1 to 2 PSI.
Similar questions
As recommended by you, I have just fitted Michelin Cross Climates to my 2013 Mercedes C220 CDI. The garage set them at 32PSI, but the car spec states 36PSI. What do you recommend?
My Mazda MX-5 is covered for the winter and wired to my battery charger, so I cannot move it. The tyres are Bridgestone Portenza 205-45R17 84W CKC4509. What is the safest maximum I can inflate them to...
I recently fitted the full sized spare wheel to my Ford Mondeo as part of the tyre rotation process. I found that the wheel isn't fitted with a tyre pressure monitoring sensor. Obviously this has resulted...

Value my car