[daptech]

Goodyear’s Research & Opinion on Nitrogen Inflation
"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 under inflated 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."
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more
there is a website that actually performed tests between air
& nitrogen & took various readings...........but I can't
post the link.
......http........powertank...........
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tests on air, nitrogen & co2
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Conclusion of Low Pressure Gas Test:
Through a 128ºF temperature swing from -11ºF to 117ºF all gas samples showed virtually an identical pressure increase of 17 PSI from 40 PSI to 57 PSI. For an automotive tire this temperature delta represents an extreme real-life case but it shows that the Ideal Gas Law formula does apply to these gases and when it comes to thermal pressure stability none has any apparent advantage over the other.

Conclusion of High Pressure Gas Test:
At the higher tire pressure commonly seen in RV tires we took the gases through a temperature range of 154ºF (-20ºF up to 134ºF). Our start pressure was 80 PSI @ -20ºF and over the 154ºF temperature increase we saw the gas pressures all increase virtually the same amount to within 2 PSI of each other. In the end, the N2 and "air" test samples topped at 108 PSI while the CO2 sample topped out at 110 PSI. Note that the pressure changes that we saw in our bottles are the same as what you'd experience in your big RV tires despite the difference in volume. What does this mean? No matter which of these gases is in your RV tires, your handling, performance and tire wear will be the same.