Correct Tire Pressure

Wheelholder wrote:
When they put the nitrogen in, they pulled a slight vacuum on the tire. Then used their machine to refill. At least that is what I was told. When I did return to have a bit more added, they do have a machine that is different from the normal air compressor.

They'd have to evacuate all the air from the tire... collapsing it like a vacuum-packaged piece of meat or one of those 'space bags' that you put sweaters and blankets in and suck out the air with a vacuum cleaner.
I thought maybe they could DISPLACE the air somehow - pump in a huge amount of N which would push the N + O2 (air) out, but they'd need a second valve stem, or they'd need to flood before the bead was set with a huge amount of high-pressure N, which would set the bead.
The only other thing would be to pressurize the tire with N, then release pressure - what comes out would be a mix of air and N, then re-pressurize with N, repeat a million times. It seems unlikely they'd ever get ALL of the other gases out.
They could burn it off somehow - but I don't know that a fire inside a new tire would be a good thing.
Wait, another one: you could mount the tire in a Nitrogen-filled room - wearing a respirator so you don't die.

Part of me wants to believe N is bunk, because air is already 80% N and we're talking about a compressed gas inside a tire.
Another part of me acknowledges that there are a few significant differences between air and pure N... one supports combustion and animal life, the other doesn't. Not sure how water vapor works in pure N.

In any case, pumping on over-pressure of N into a tire full of ambient shop air seems like wasted $ and wishful thinking. Maybe there's something I don't know.