Why nitrogen?

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.

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.

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.

"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.

Consumer Reports noted:

"The National Highway Traffic Safety Administration (NHTSA) has seen
reduced aging of tires filled with nitrogen. Though the data does support
that passenger car tires could benefit by all the claims made for nitrogen,
tire manufacturers say that they already design tires to perform well with
air inflation. And while nitrogen will do no harm, manufacturers say that
they don't see the need to use nitrogen, which generally adds $5 or more
per tire charge."

From: http://blogs.consumerreports.org/car...nitrogen-.html

Also CR's Q&A answers imply that if you have a lot of tires (as on a truck)
then using N2 may be a net win, but probably not in other cases:

"The positive benefits of nitrogen in high(er) service pressure
applications, such as used in large truck tires, has been documented in the
industry. Our test centered on passenger tires, only. We are not
discrediting the use of nitrogen, but it is not a substitute for regular
inflation checks."

From: http://blogs.consumerreports.org/car...en-tires-.html

"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

"Viperdoc" wrote in
:

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.




Well, the greasemonkies say it preserves the rubber. Having said that we go
through them pretty quick and even considering retreads there wouldn't
be years of exposure or anything..
Wheel fires may be another good reason...


bertie

"Bertie the Bunyip" wrote in message
...
"Viperdoc" wrote in
:

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.




Well, the greasemonkies say it preserves the rubber. Having said that we
go
through them pretty quick and even considering retreads there wouldn't
be years of exposure or anything..
Wheel fires may be another good reason...


bertie


Right, they are called Napoleon tires. You heard of "Napoleon Blown Apart"
haven't you. :-)

--
Regards, Bob F.

It all sounds like BS to me- if it's the tire we're discussing, there's no
contact with the nitrogen, just the inner tube. The outer surface of the
tire is in air of course, along with exposure to UV light, salts, etc. The
tire is going to lose its rubber well before it starts to oxidize and crack.

A tube perhaps might be more subject to oxidation, but it's dark in there,
not a lot of UV to make stuff that cause oxidation like free radicals and
ozone, and the increase in the partial pressure of oxygen at 200psi is only
around 15fold, or from around 140mm Hg to around 2000mm. If it'sdry air, I
can't believe it would make that much difference.

Need to see the aging data on rubber kept in air versus nitrogen.

Just realized I was starting to sound like you know who, so will stop this
and have another cocktail.

"Bob F." wrote in
:

"Bertie the Bunyip" wrote in message
...
"Viperdoc" wrote in
:

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.




Well, the greasemonkies say it preserves the rubber. Having said that
we go
through them pretty quick and even considering retreads there
wouldn't be years of exposure or anything..
Wheel fires may be another good reason...


bertie


Right, they are called Napoleon tires. You heard of "Napoleon Blown
Apart" haven't you. :-)


groan!


A guy i used to work with witnessed the aftermath of someone trying to
fill a 707 nosewheel wiht an incorrect type reduction on the bottle. The
guy was pretty much vaporised. My friend spent months as a witness in
the subsequent lawsuit.

Bertie

"Viperdoc" wrote in
:

It all sounds like BS to me- if it's the tire we're discussing,
there's no contact with the nitrogen, just the inner tube. The outer
surface of the tire is in air of course, along with exposure to UV
light, salts, etc. The tire is going to lose its rubber well before it
starts to oxidize and crack.

Yeah, I kinda thought that myself which gave me the notion that the fire
thing wiht heavies might be more relevant we run anything up to 300PSI as
well, which might be a factor. I must ask around again.



Bertie