"Viperdoc" wrote in message
...
The thread on brakes raised a question from the past- why nitrogen in the
tires of big jets and heavies? Air is around 78% nitrogen anyway, and the
coefficient of expansion of the remaining 20% that's oxygen can't make
that much difference in volume.

Why not just use dry air? I couldn't imagine that dry air or dry nitrogen
could make that much difference in corrosion, either.

I seem to recall someone giving me the rationale for this a long time ago,
but also seem to remember thinking it didn't make that much sense at the
time.

My local automotive tire dealer now has signs up touting the availability of
nitrogen. However, I agree with you that dry air should work about as well.
The big contributor to pressure change is water--since there isn't enough
CO2 in the air for its nonlinearity to be a major factor.

The only difference that would make nitrogen seen really beneficial to me
would be in the case of an aircraft which is kept hangared and seldom
operated. Then, if the tire threads last a number of years, and the tires
are sheltered from UV radiation, the inert nature of the nitrogen could be
usefull.

Peter