Just a humble opinion, but typically nitrogen used for purging systems
and, I suspect in the filling of tires, is dry nitrogen, meaning that
water vapor has been removed along with the other gases during
fractional distallation.

While O2 and N2 should have indiscernable (for tire purposes)
volume/pressure fluctuation and follow to the gas laws, water volume at
normal atmospheric temperature ranges will fluctuate greatly, even to
the point of becoming solid.

I decided to check before sending and it seems all the opinions, per
this link, have some impact on the value of dry N2 in tires...

http://www.toyo.com.au/TechInfoPDFs/TTT-176%20Nitrogen%20Gas%20Inflation
.pdf

FWIW...
jack

-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On
Behalf Of Bruce Collins
Sent: Monday, February 23, 2009 2:38 PM
To: [log in to unmask]
Subject: Re: [HP3000-L] OT: Are dealerships to blame for slow car sales?

Craig Lalley wrote after Brice Yokem wrote:
> Leakage is a factor in such things.  There is no such thing as a 
> perfect seal.  I am not an automotive expert, but I bet the leakage is

> more significant than the reactivity.
> ****************************************
My understanding is that the oxygen reacts with the moisture and can
cause rust on a steel rim.Of course the amount of time it would take to
cause significant damage would be longer than the life of the car.-Craig

I first came across this in 2007:

> These cops in North Carolina are filling their tires using nitrogen
to save money:
>
> http://www.wral.com/news/local/story/1713452/
>
> According to the car dealer:
>
> "It's been used on the space shuttle, commercial aircraft for
decades," said car dealer David Hurd. "Nitrogen is not affected by
normal cold and hot conditions, so you don't have any fluctuation in the
air pressure."
> As a result, nitrogen is reported to extend the life of a tire and
provide better fuel economy.
>

It sounded like a scam to me, because air and Nitrogen follow the same
gas laws in terms of expansion/contraction due to changes in heat. But
then someone pointed out this:

There's a grain of truth, though the article got the details wrong:
http://en.wikipedia.org/wiki/Nitrogen#Molecular_nitrogen_.28gas_and_liqu
id.29

It occurred to me after I posted the article that one possible advantage
to using nitrogen over air is that by removing the oxygen component you
would reduce the oxidation of the rubber. The wikipedia article says
that it is not necessary for consumer automobile tires, but I could see
how it might make a difference with aircraft tires where I assume we are
dealing with greater pressures.

The difference in diameter of nitrogen versus oxygen and it's effect on
diffusion through the rubber didn't occur to me but I would think its
effect would be fairly small. If it was very large then the oxygen would
diffuse out faster than the nitrogen and you'd end up with nitrogen
filled tires anyway :-)

Bruce (still thinking it's a scam) Collins 

* To join/leave the list, search archives, change list settings, *
* etc., please visit http://raven.utc.edu/archives/hp3000-l.html *

* To join/leave the list, search archives, change list settings, *
* etc., please visit http://raven.utc.edu/archives/hp3000-l.html *