RE:

> > BS. Air is 78% nitrogen to begin with. All gasses follow Gay-Lussac's Law
> > extremely closely, unless at temperature extremes (think absolute zero
> and
> > plasma heat). There are 2 legitimate reasons to use N2 in tires - the
> > military uses it in some aircraft to eliminate a fire hazard from the
> oxygen
> > in air, and race teams use it because a bottle is cheap, and can be used
> to
> > fill tires without needing either a compressor or electricity (or they
> > believe the BS the N2 salesman told them). A third reason to use N2 is so
> > tire stores can make additional profit.
>

  Logical but misses one point that is the difference.  For tires (and
optics and other applications) the phrase/term that is normally used is 'dry
nitrogen'.  Bottled nitrogen contains no moisture.  Consequently the
expansion is less with heat than just using compressed air.  Also minimizes
(eliminates?) oxidation.  The optics repair shop in the business I worked in
for several years used dry nitrogen to purge air from the inside of the many
military optical instruments they worked on. Thus eliminating internal
condensation under cold situations.  Virtually all high end optics (like
binoculars) are sealed and have been filled with dry nitrogen at the
factory.  In fact in the shop it was used for blowing away dust and other
things in/on the the optics because it was clean coming out of the bottle.