"Rod McInnis" wrote in message
It is generally accepted that all gases obey the ideal gas law if you stay
away from their condensation temperature.

Not true. Unless you introduce nitrogen to the tire under ideal
conditions, which would entail a vacuum process first. Do you really
think that people are going to do that, when all they need is a larger
tire?

Air is mostly nitrogen, then
oxygen, carbon dioxide, and traces of many other gases including water.

Bingo, you're starting to get it. Water.

Unless you have artificially introduced liquid water into the tire, or
inflated the tire with air super saturated with moisture, the typical
operating temperature of the tire will sufficienty above the dew point of
the air inside such that the air (complete with water vapor) will obey the
ideal gas law.

Again, unless introduced under ideal conditions, there WILL be water
vapor.

The nitrogen doesn't expand as much as air, for a given
temperature change.

Which gas are you saying doesn't obey the gas laws: air or nitrogen?

Niether.

What temperature and pressure are you making this claim for?

Operating range of the tire.