Nitrogen in tires?

[Tony LEE]

From the Goodyear Tyre Manual

Over the years, nitrogen inflation has
been proposed for various types of tires,
including large earthmover tires down
through small passenger tires. At the
present time, Goodyear endorses nitrogen
inflation for certain sizes of earthmover
tires used in particular applications, and
has issued detailed instructions for these
tires. Anyone concerned with applying
or maintaining earthmover tires should
be aware of the Goodyear Service
Department Bulletins and Off-the-Road
Tire Training Manuals that contain details
of nitrogen inflation recommendations
for these large off-the-road tires.
The issue of nitrogen inflation for
over-the-road truck tires is not quite so
clear. Various performance improvements
have been claimed, including better
treadwear, casing durability, and reduced
susceptibility to tire fires.
Although little actual controlled test
data exists, a summary of Goodyear's
experience with nitrogen inflation for
truck tires is the basis for the following
comments. Treadwear appears to be
affected negligibly by the tire inflation
medium. Specifically, there is little, if
any, tread life change to be expected by
using nitrogen inflation compared to
normal air. So far as casing durability
and retreadability are concerned, the
primary criteria is to avoid moisture in
whatever inflation medium is used. To
this end, we strongly encourage proper
selection of compressor equipment,
air-line routing, the use of air dryers,
and other good shop practices to avoid
the introduction of moisture into high
pressure air used for both initial tire
inflation and make-up air. Again, we
know of no significantly improved casing
durability or retread durability performance
to be expected from nitrogen inflation in
over-the-road truck tires.
Reduced rim or wheel corrosion has
also been cited as an advantage of nitrogen
inflation. However, corrosion is primarily
the result of excessive moisture introduced
by air that has not been properly dried,
rather than a direct result of air versus
nitrogen inflation.
An additional concern is that past
studies have shown that a very small
percentage of non-nitrogen make-up
inflation significantly contaminates the
contained nitrogen atmosphere within a
tire. In other words, if any benefits are
to accrue from nitrogen inflation, it is
essential that virtually all make-up inflation
throughout the life of the tire/wheel
assembly be diligently controlled to assure
a near 100 percent nitrogen environment.
A final issue is that of insuring against
tire fires and/or self-ignition of tires
resulting from excessive heat. For truck
tires, this concern has been greatly
reduced in recent years, primarily
because of the changes from bias to
radial tires and from tube-type to tubeless
tires. The tubeless radial tire is simply
much less susceptible to a tire fire than
a bias tube-type design. This is partly
because of the simplicity of the tubeless
design (i.e. no separate tube and flap to
create heat from rubbing or internal
friction when the assembly deflates or
runs severely underinflated or overloaded),
and partly because steel radial truck tires
require higher temperatures for a fire to
start than their fabric-reinforced bias-ply
counterparts.
In summary, nitrogen inflation
appears to have significant advantages
for certain sizes and applications of large
off-road tires, especially those operating
in extremely high load or speed
environments. However, nitrogen
inflation appears to have quite small,
perhaps insignificant, advantages for
over-the-road truck tires.

[Van]

From the C-130 etc use it in the Nitrogen/Hyd landing gear, also artillery use it in the recoil assy for the gun tubes, the M-1 Abrams recoil assembly can use up to 2,300 psi depending the set up called for(fine tuning), which can mean the difference in spilling your coffee (never fun )when you hit the trigger  

[gus]

Aircraft use nitrogen for the simple reason that  they go from one atmospheric pressure extreme to another in a matter of minutes and in struts dryness is also very important to prevent corrosion. Pressures in aircraft struts are extreme, thousands of psi, even in smaller aircraft.

We don't usually have these conditions in bus tires!!

[rgwilliams]

"Aircraft use nitrogen for the simple reason that  they go from one atmospheric pressure extreme to another in a matter of minutes and in struts dryness is also very important to prevent corrosion. Pressures in aircraft struts are extreme, thousands of psi, even in smaller aircraft."

Gus

You are correct about the extremes of pressure and lack of corrosion and our buses aren't subjected to these conditions.  However, nitrogen gas, while not a noble gas, but fairly inert, will not promote combustion.  The extreme pressures in a 747 strut on touchdown, causing severe compression of the gas, are more than ample to ignite the hydraulic fluid in the strut by dieseling- extreme pressure=a lot of heat- if there was oxygen(a constituent of compressed air) present in the strut.  The pressures in a diesel cylinder are only around 600psi, the strut at rest before a 1.5G impact is around 1500psi.  As for the nitrogen in aircraft tires, check the probable cause of this disaster in the 3rd last line of the Narrative.
http://aviation-safety.net/database/record.php?id=19860331-1&lang=en

Rob

[gus]

Rob,

I never really thought much about the fire aspect but this probably isn't a problem in bus tires.

I'm sure you're right, I hadn't thought in terms of 747s but I know my little ole Navion had strut pressures in the thousands of psi on full compression. I always aired it up at full extension which was still around 250 psi as I remember.

My son works on 747s and 777s at Everett, WA.

[Ed Hackenbruch]

I use Helium in my tires, make the bus lighter so i get better mileage. You can also use laughing gas if you want to keep your tires happy.

[gus]

Ed, I think you're on to something here!

However, be careful, you may have inhaled some of those gases!!!