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This post really intrigued me. I did a little poking around the net and asked some guys here at work.
My thoughts and some links:
At moderate temperatures and pressures all gases exhibit close to ideal behaviour, that is pv=nRT; and at standard T & P 1 mole of any gas occupies the same volume. For the same initial tire volume, pressure and temperature, n will be the same for both gases, so for nitrogen and air pv = Tx(constant), thus both will exhibit the same pressure-temperature relationship.
Digging deeper, the specific heats -and so the value for gamma, is near identical for both gases.
Based on all this there is nothing to suggest the behaviour of a tire filled with air will be any different from one filled with nitrogen.
Dry air that is... There is that whole water vapor argument, but good dry air seems to be just as good as dry nitrogen for this purpose.
From my poking around on the net it seems that the two main reaons for inflating tires with nitrogen (seems to be done on indy cars and Planes) are to reduce the flamibility of the tire, reduce internal oxidation, and eliminate the water vapor.
The flamibility should not be an issue with pass cars. Personally I worry a lot more about my the asphalt wearing my tires out than the internal oxidation could... As far as the water vapor, use good quality dry air and you should be fine.
One article below seemed to suggest that nitrogen is less likely to leak out of a tire than Air. Oxygen's atomic weight is 16, while Nitrogen's is 14. Both are normally diamtomic in (N2 or O2). I am pretty sure the size of the molecules is about the same. If I had to guess I would say that Oxygen should be a larger molecule and therefor less likely to leak. That said even if N2 is less likely to leak, the tire would act as a filter of sorts that would retain the nitrogen and leak the oxygen out. Eventually the tire would be filled predominantly with N2.
Check out these sites if you are interested.
http://www.heavytruck.com/hdt/2000/01/016a0001.html
http://cartalk.cars.com/Columns/Archive/1995/March/07.html
http://www.bcbr.com/jul1400/nitronics2.htm
http://www.cs.wisc.edu/~lists/archive/vfr/9903/msg00936.html
http://www.physlink.com/ae192.cfm
All this said, I have no first hand experience with this. It just sounds a little odd to me. Anyone else play with this?
, Sun, 8 Oct 2000 16:23:45, Mon, 9 Oct 2000 12:27:53
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