a wrote:
On Sep 15, 6:20 pm, a wrote:
On Sep 15, 6:09 pm, "Viperdoc" wrote:

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.
The legend is that the oxygen is reacting with the rubber. Even
though compressed air has the same fraction of oxygen as does the
atmosphere, the fact that it's compressed, it's been argued, increases
its reactivity. I can't validate the legend.

I got curious, did a quick check. The process also reduces water
vapor, and N2 does not migrate through the rubber as fast as does O2,
so pressure stays more predictable. So it's more consistent tire
pressure, less corrosion.

We bought a new Toyota and the salesman stated the tires were filled
with N2 since the molecule was larger and less corrosive than air which
contained O2. Now, how easy is it to find N2 around town. I can take it
to the airport where the mechanic has a tank. But, all the years of
owning a car, I never seem to really have a problem with tires going
down that quick. At the 3K oil changes they top them off anyway. I did
buy a small compressor for the hangar, but never really used it that
much. I have a couple of bikes that I have to air up before each ride.
Those tires really loose pressure. I brought the compressor home.

--

Regards, Ross
C-172F 180HP
KSWI