Nitrogen In Vehicle Tires?

[KennyG]

Given that PV=nRT and R, the gas constant, isn't really constant for all gases, it can make a very small difference in pressure change with temperature depending on the gas in the tire. It does turn out that water vapor has a larger value of R than Nitrogen. However, Oxygen has a lower value than Nitrogen. In theory, it seems to me that dry air should maintain a more constant pressure with temperature changes than Nitrogen. (Anyone tried filling tires with pure oxygen?) The difference would be tiny, however. Remember that temperature in the equation is based on absolute temperature where freezing is 492 degrees Rankine.

 

[ruffdog]

I might add, when they fill your tires with N2 are they really just bringing them up to pressure with N2 or are they actually purging all of the "regular" air from the tires as they are filling them? It's a farse anyway.

Now....one time when the weather turned colder we had convinced someone at work that she needed to have the summer air removed from her tires and winter air added. The guy at the garage up the street laughed when she asked but then still did it for her and was happy to collect the $25 for doing it.

Purging the "air" before N is put in?

Maybe the tech just takes the black cap off and installed a green one....well worth the money. :wizard:

 

[plowhog]

If your nitrogen filled tire is a couple of psi low on pressure, and you inflate it using regular air, when must you switch the green caps back to black?

 

[Rock knocker]

Given that PV=nRT and R, the gas constant, isn't really constant for all gases, it can make a very small difference in pressure change with temperature depending on the gas in the tire. It does turn out that water vapor has a larger value of R than Nitrogen. However, Oxygen has a lower value than Nitrogen. In theory, it seems to me that dry air should maintain a more constant pressure with temperature changes than Nitrogen. (Anyone tried filling tires with pure oxygen?) The difference would be tiny, however. Remember that temperature in the equation is based on absolute temperature where freezing is 492 degrees Rankine.

I don't think that's right. R is a universal constant, basically to simplify the corrections for TPV based on the the unversal finding that one mole of any gas takes up 22.4 liters at STP

 

[Rock knocker]

Universal and Individual Gas Constants

 

[ruffdog]

Universal and Individual Gas Constants

I once had a dog that had constant gas......

 

[Rock knocker]

That's a universal thing with pet owners

 

[Industrial Toys]

The bigger/older tire dealer around here told me that it's a farce and they don't support it.

I wonder though, if using Nitrogen would slow down the leaking (corrosion) issue with alloy rims.

 

[Diggin It]

OK, so it isn't what makes your butt look fat after all.


Didn't think so.

 

[kc5dlo]

My wife's last car came from the dealer equipped with N in the tires. I was laughing at the reasons listed in the booklet in the glove box. The part that really got me was they said that since the molecules of O2 were smaller than N, they would seep out of the tires causing a need for constant re-inflation. Air is 78 % Nitrogen as previously stated. Sounds to me it would be easier to just put the air in and let the 02 seep out naturally leaving behind almost pure nitrogen.
Besides, any convenience that Pure nitrogen would provide would be more than wiped out by having to return to the dealer to add nitrogen or check pressures.