Tire Pressure Vs. Ambient

Sorry, Dick. As Tireman9 (a retired tire engineer) stated in that link, cold is
not at a specific temperature, but before driving, exposure to sun, etc at whatever the ambient temperature is.

I, also, would like to know the source of that "interesting" inflation chart that contradicts all the major tire manufacturer's written inflation instructions.

Sure looks like another of those "if you read it on the Internet........" things.

So you want to go with an "anonymous" tire inflation chart with no idea who came up with this theory and something that is not endorsed by any tire manufacturer?
Me, I'm going to follow the tire manufacturer's charts.

Yeh, I have my suspicions also not knowing the providence of the chart.

On the other hand, it's right on the money based on my current ambient (90F) since the pressures have risen 5 psig and it was about 65F last time I adjusted the pressures.

I'm thinking I will use the chart since I can not see any harm. For example, I will be leaving when the temps are ~104 and within 3 days be in 60F temps. Worst case, be a little high but no chance of being low.

This is what Maxxis says about inflation of the tires I use;

"...In order to accurately assess your tires’ inflation pressure, please note that inflation pressure should be adjusted and/or checked when the tire is cold or before driving for the day."

I call BS on the 65* baloney and adjusting for temperature.

wolfe10 wrote:

Sure looks like another of those "if you read it on the Internet........" things.

And he's probably a French model too. Bonjour. ;)

I wonder why the chart DOES NOT follow it's own rule at the bottom that says:
Tire manufacturers never recommend inflating a tire to less than the specified cold inflation pressure. The bead of an RV/commercial tire can unseat
if its pressure gets too low resulting in a catastrophic tire failure. The general rule of thumb is to inflate a tire to a proportionately higher starting value when the ambient tire/temperature is hotter than 65 degrees and to the recommended Cold Inflation Pressure value at temperatures below 65
degrees F.

The chart then shows that at a recommended cold inflation pressure of 100psi, or any psi, if the temp drops to 32 degrees, it says you should inflate to less than the recommended cold inflation pressure. If it followed it's own advice, the chart would stop at 65 degrees. :R

Campfire Time wrote:

wolfe10 wrote:

Sure looks like another of those "if you read it on the Internet........" things.

And he's probably a French model too. Bonjour. ;)

Oui, Oui. Or in Texas we would just say, Wee Wee.

Never mind the fact that most of use pressure gauges with absolutely no idea of their accuracy or precision. While the physics may be sound, PV = nRT, it strikes me as needless hand-wringing and worrying.

"Gee, it's 72* outside, let me check the conversion chart... OK, now I'll pull out my $3 pressure gauge and check..."

bluwtr49 wrote:


On the other hand, it's right on the money based on my current ambient (90F) since the pressures have risen 5 psig and it was about 65F last time I adjusted the pressures.

Yes, the ideal gas law applies. For a given rise in Temperature, there WILL be a specific rise in Pressure. PV=nRT has been around for a LONG time.

Same basic physics that prove some of the ads for Nitrogen in tires are so much bunk. Nitrogen, like other gases DOES follow the ideal gas law, not "Bubba's marketing law 101".

Wow, two of us who remember our school physics/chemistry at the same time.