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Hey guys,
the other day I had a set of wheels mounted and balanced at the dealership, normally they put nitrogen on my tires but I am noticing on my dash computer, that when I start driving the car if remeber correctly the psi Fron is 31 and rear 37 after driving for a couple of miles my psi changes to 34 and 39 could this be because I have air instead of nitrogen?
 

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Even with Nitrogen you will see an increase in pressure as they heat up. I have nitrogen and see an increase but hear that "air" (which already has a pretty high amount of nitrogen) will reach a little higher pressure during the same drive.

Look for green caps on your valve stems. Those are supposed to be used when filling with nitrogen.
 

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mine seem to also go up 3-4 psi per corner after a few miles of driving as they heat up. Just normal expansion.
 

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thanks guys, I was thinking Nitrogen does not expand :)
and no green caps on my valve stems.
All gases expand with increased temperature. In fact, all gases expand at the same rate per degree temp change at the same pressure (per Charles' Law), so it doesn't matter whether it's air or nitrogen we're talking about.

Air is already about 78% nitrogen as it is.
 

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The biggest difference between bottled nitrogen and air is the moisture content. Bottled nitrogen is dry, while air has some amount of humidity in it. As you know, when water condenses or evaporates, it undergoes a big change in volume. If you have small amount of water vapor in your tires, and it condenses, the pressure will drop considerably. Likewise, if these micro-droplets of water evaporate, the pressure will rise considerably. I'm not talking about puddles in the bottom of your tires, just some micro-droplets condensing or evaporating.

Dry air and dry nitrogen will expand and contract with temperature identically.

Unless you are in F1, the difference between bottled nitrogen and air should not be a concern.
 

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Mine goes up 10 PSI when I drive. 2-3 PSI? Phew, where are you driving to? Church? ;-)
 

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PS2s, stock pressures. Its not the distance though or length of the drive is the cornering. (I am jesting here a bit.) I should have been forthcoming and say - "at the track".

Tomasz
 

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PS2s, stock pressures. Its not the distance though or length of the drive is the cornering. (I am jesting here a bit.) I should have been forthcoming and say - "at the track".

Tomasz
That makes a lot more sense, especially if your track is Pacific Raceways.
 
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