Many years ago, on the track, I know guys started using N2 for tires, to try to avoid water getting in them - not sure why. We have dryers on our system at work - compressed air gets lots of moisture in it, which can cause a lot of issues - but not sure if that matters for tires/how much can get into a tire.

I know we talked about He, to try to reduce rotational mass, but there's something called He embrittlement, which apparently posed an issue.

The air you breath is 78% nitrogen, so that's not the reason it's used in tires.
When commercial nitrogen is bottled, it's moisture is almost completely removed.

Moist air is more sensitive to temperature and raises the pressure a bit more than dry air. Poorly maintained compressors that haven't had the water drain emptied often can introduce water into the tires.
Sometimes enough to create balance issues.

I didn’t even think nitrogen was an option for people who don’t own Nissan GTRs.

I don’t know how much difference it makes to gauge pressure, but it seems to me that tires are not rigid vessels. That’s why they look flat when they are low on air and can look distended when overfilled. So it follows that as you move to higher elevations with lower ambient pressure, the gauge pressure stays the same and the tire expands. But I’ll ask my son who is a chemical engineer by education.

FUN WITH SCIENCE: Air Force Academy Commissary, Colorado Springs. Saw bags of chips that were puffed up...bagged in New York City. Bought a bag. Put the chip bag in a (no longer free) Commissary plastic bag.

Drove up the road to Pikes Peak. Chip bag blow out at 13000 feet! I was so proud of myself

Get a good tire gauge and check them yourself. That is most likely the cause for the difference. One of the places used a faulty gauge (or read it incorrectly).

One of the “nanny” features I love on modern cars is the ability to read all four corners psi at a glance.

For the last year I had one tire that had a slow leak. Like add air every 2 weeks slow. It was nice to scroll to the psi page and know when it was getting to be time to pull the compressor out again.

quote:

Originally posted by konata88:
I don't understand how pressure increases with elevation. If you set the pressure at "home" and then drive to a higher elevation, ignoring temperature influences, the pressure in the tire seems like it should remain constant. No air has entered or left the tire. The ambient pressure may have reduced, thus encouraging tire expansion. This expansion, with larger volume, may lead to decrease in tire pressure. But I don't understand how / why the tire pressure would increase with elevation.

4MUL8R gave the long answer.
Tire gauges (and most pressure gauges) are relative to atmospheric pressure. P(absolute) = P(atm) + P(gauge) If P(atm) changes, P(gauge) will too, assuming tire volume and temperature DO NOT change. P(abs) is the same (it will vary some, but can be ignored)
Both Volume & Temperature have negligible affects/changes in 'normal' conditions.

Some ding-dong over inflated the tires, 50psi is too much on anything not hauling tons, probably drive like it was on a pogo stick. I can tell a ride difference in +/-5psi from my preference (35psi). At least 1 tire monkey* I frequent likes to put 42psi in everything. That's the max listed on the sidewall of passenger (P-sized) tires. At least he tightens the oil filter enough that it doesn't leak after 500mi.

*takes 1 to know 1....