In March 1991 I was attending an Army school in Virginia. One of my fellow students was from Ft Wainwright. His Wife wrote him and mentioned the weather was improving as the snow level was now below the house gutters!
That was my intended point. The less moisture in the tire, the less the air pressure will fluctuate because of temperature.
The difference is negligible.
My tires were filled with nitrogen because I bought them at Costco and you donāt get a choice there. I have observed no difference in temperature-related pressure changes between the nitrogen fill and my previous tires which were filled with regular air.
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Huh? Physics was never my best subject but what does moisture have to do with it? Air becomes more dense as temperature goes down which is why tires need to be pumped up, no? Just means as much moisture cannot be held in denser air is all than warmer air. Iāll defer to the engineers if Iām wrong but I paid over $500 for that class and would not be happy if I was taught wrong. Thatās why its easier to get a plane up in the air in the winter too than in the summer.
Nitrogen in a race car is helpful for fire safety.
If a tire bursts on a burning car there wonāt be a surge of oxygen feeding the fire.
For a road car no advantage, if one manages not to burn it down.
True, what happens is moisture can condense on or evaporate from the inside surface of the tire, depending on conditions.
That will cause pressure variations in addition to the ideal gas law.
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It matters in a race car because tire pressures are critical to performance. In a commuter car, not so much. Plus, the effects are really more relevant for hot tires. Weāre talking about filling the tire cold and resulting low pressure when the tire is even colder- well below the temps where water vapor/condensation comes into play.
Moisture has no effect on pressure, it does help get longer tire life because moisture is not good for rubber. Most of the time, moisture in a tire is in gas form, though not at -40 degrees. At that temp, it has condensed and frozen.
Some commercial air compressors use an air drier on them so that air doesnāt have much moisture in it either. Those Nitrogen fills are not 100% nitrogen either. I believe they run from 95 to 98% N2.
BTW, contrary to most of you, I would run under pressure at very cold temps, same as I always run a bit higher than recommended in hot weather or road trips.
Sure it does. When it gets heated up and changes to a gas, it has an effect on the tire pressure. Like I said before, this is not really relevant for anything but a race car. Again, as we have both stated, at the temperatures in question, it will not get hot enough to change to a gas so no effect from its presence.
When it entered the tire, it was already in vapor form.
My 2010 Kia TPMS illuminates when a tire reaches 29psi. It does not display pressures or even which tire is low. I have a good dial gauge in the glove box. Last year our lowest temperature was 2 days at +24F. TPMS illuminated. Pressure in all tires was the expected 29psi so I didnāt worry about it. Last month I had all 4 tires replaced. My local tire shop always inflates my tires to 35psi. This month we had several days with temperatures in the mid teens. No TPMS light. When I have the car serviced in April the dealership technician will adjust pressure to the placards 32psi. Why? Because they are forced to by lawyers. It will be warm weather so no problem. The next service will be in October. Hopefully my 5,000 mile rotation at the tire shop will be due shortly after that and pressures will be back to 35psi for the Winter. The 1psi drop per 10 degree temperature drop rule of thumb seems to be working for me.
At -40F, it wasnāt vapor long enough to get a gauge on it. BTW, my air lines without traps spit liquid water under the right conditionsā¦