Tire pressure vs temperature. My chart

[LCHIEN]

With all this cold weather and global warming, how do we interpret cold tire pressure vs whatever temperture the car tires are really at?

I used the ideal gas laws to compute this chart of how pressures behave at different temperatures.


Using this chart you can find what the pressure change will be between two temperatures.
If you know the pressure at a starting temperature (i.e. the "cold pressure" at say 70 degrees) find that temperature on the horizontal axis. Travel vertically from there to find the pressure on the vertical axis. Find the colored line that crosses that point.
Follow that line... you can see what the pressure will be at any given temperature on the horiz axis, or knowing the temperature, you can see what the pressure will be at that temperature.

For example, My cold inflation temperature is 35 psi at 70 F, so when I got in the car at 25F yesterday I noticed it was 32 PSI on the tires. THe chart conforms this is correct.

[leehljp]

I am so glad you posted this. I almost posted a new thread a couple of months ago asking you to do this. You had discussed this some time ago. Thank you for posting this!

[LCHIEN]

A good approximation is 1 PSI change for every 12°F change

This is for 32 PSI 70F cold pressure but the others will be close. A little less for lower pressure and a little more for higher pressure.

[Jim Frye]

I normally run 32 psi in our car tires. The Hondas nag you at 27 psi. I still do my first of the month systems check (tire pressure, washer fluid, oil level, brake fluid level, and coolant level). After all these years the only thing I ever have to do pump up a couple of tires and fill the washer reservoirs.

[Dedpedal]

If it’s below 70°f I consider my tires frozen to the ground and can’t go anywhere. Good reference chart for people in the northern climes.

[Apither]

I quite like your example of using the chart to verify that your tires are properly inflated at 25 degrees F.

[LCHIEN]

I quite like your example of using the chart to verify that your tires are properly inflated at 25 degrees F.

Thank you.