I figure there's a big message here for Landspeed cars, tow vehicles &
trailers so here is just about all you need to know on the subject.
Brian
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This Research section contains information on the use of nitrogen gas in
various applications.
TIRE RESEARCH
The following is an excerpt from a research paper prepared by Lawrence
Sperberg concerning the use of nitrogen gas for tire inflation.
Million Mile Truck Tires - Available Today
"Oxygen- the Killer of Tires"
by Lawrence R. Sperberg
All pneumatic tires have suffered from a deterioration starting the day
that tires were invented. That deterioration is chemical oxidation
masquerading under the name of "tire fatigue".
THE ENEMY - OXIDATION
Causing the deterioration are oxygen molecules contained in the inflating
air which is a mixture of gases - nitrogen 78%, oxygen 21%, argon 0.9%, and
miscellaneous O.1%. Tires are designed to be protected from this
deterioration by their liners which are supposed to keep air from
percolating through them into the tire body, which they never do, and by
chemicals called antioxidants or age resisters whose job is to intercept
and neutralize any invading oxygen - which they do until they are
themselves used up, which occurs too soon after a tire enters into service.
So the deterioration spreads. It starts within the tire interior and moves
outward. it first invades and consumes the tire liner. It then ravages the
insulation rubber adjacent the liner. It marches inexorably outward -
because of the pressure differential of the tire inflation on the inside
and the atmospheric pressure on the outside. As the decay moves ever
outward - the oxygen molecules react chemically with the unsaturated double
valence bonds present in all rubbers, causing the rubber molecules to lose
their strength and their elasticity, so that they no longer act as rubbers,
but instead take on the characteristics of a non rigid plastic. The decay
is constantly being fueled by the fresh all too often moist air being
injected into the air chamber to maintain the desired inflation pressure.
How do you get a truck tire to go a million miles? It's simple.
TAKE THE OXYGEN OUT OF THE AIR!
TRUCK TIRE TESTS
A total of 175 truck tires were tested until they were worn down to the
tread wear indicators (TWI). About 125 of these tires wore out without
failing at mileages ranging from 125,000 to 225,000. About 50 of the tires
failed physically at varying mileages generally on the low side. All the
tires had been carefully monitored, measured for tread loss etc., and
inspected at 10,000 mile intervals, a lot of them at 2000 to 3000 mile
intervals. Tire sizes were mostly 11R24.5 & 11-24.5 with a very few 10R20
and 10-20's. About half of the tires had operated over the eastern part of
the United States while the other half had run mostly in the southwestern
part of the U.S.
When the tires were removed from service small samples of tread rubber were
taken from the shoulders of the unfailed tires and from the actual failed
areas of the destructed tires. These specimens were then subjected to the
electron microprobe examination that has been described previously. The
examination was specifically directed at determining oxygen and sulfur
levels which was best accomplished by using IOKV (10000 electron volts)
electron beam And an exposure of 30 seconds.
Both of the figures tell the same story. When a tire lives to wear out, the
oxygen slowly migrates and permeates its way into and through the tire cord
body and finally into the under tread and then into the tread itself. It
takes a long time for an appreciable amount of oxygen to reach the tread
since most of the oxygen gets waylaid along the way by the liner, and then
the cord arid cord insulation compound.
One reason that truck tires can run 250,000 miles with the original tread
while passenger tires can only go 50 to 60,000 miles lies in the relative
bulk of the 2 different tire bodies. The bulkier the body the longer it
takes for the oxygen to work its way into the tread. Unfortunately the
bulkier the body the higher is the heat buildup and the faster is the rate
of oxidation of the available double bonds. Once the tire body is all
oxidized the tire is dead no matter how much tread remains on it. The
thinner the tire body the lower the running temperature and the slower the
rate of oxidation with a correspondingly longer life.
Practically all tire engineers throughout this century attribute the
gradual loss in tire strength to be the result of "fatigue" when in reality
this "fatigue" is nothing more than a slow inexorable oxidation taking
place at the available double bonds of the rubber molecules.
IMPROVED TIRE LIFE
In one experiment involving 54 new 10.00-20 truck tires, 33 were inflated
with nitrogen and 21 were inflated with air. These tires were run side by
side on the same tractor units until they failed or until they wore to the
tread wear indicators. In this case the 54 new truck tires, nitrogen
inflation resulted in 26% more miles being run before tires had to be
removed when wear reached the tread wear indicators.
In the case of the failed tires a smaller percent of nitrogen tires failed
physically (30% vs. 57%) and they gave 48% more miles before failing than
did the air tires. This 48% improvement is due to the tire bodies lasting
longer and not the better wearing properties of the tread which is the
situation with the tires that lived to wear out.
The experiments involving 54 new and 44 used tires running some 7,345,497
tire miles in drive axle service, when viewed in light of the election
microprobe experimental findings presented earlier, depict a clear cut
picture of what nitrogen inflation can do for the transportation industry -
cost wise as well as safety wise.
HOLDING PRESSURE BETTER
Today probably 99% of all tires are tubeless - truck, passenger, giant -
and these tires are inflated with air, and all too frequently with wet air,
i.e. air where the water has not been drained from the compressor tank as
it should be. This moisture laden air (oxygen catalyzed by water) attacks
the paint in the wheel well ultimately penetrating the paint and oxidizing
the iron below it to form iron oxide or rust. Even aluminum is not immune
from rusting, forming aluminum hydroxide, that gives an extremely fine dust
that is difficult to even see inside the tire. The iron oxide rust is
present within the tire in varying sizes ranging from coarse to extremely
fine. Aluminum hydroxide dust is never coarse only extremely fine.
Whenever a tire is checked for its inflation pressure the pressure gauge
requires a small gulp of air to activate the gauge. When the small gulp of
air escapes from the tire the turbulence created picks up the finely
divided rust and the dust enriched gulp of air passes around the open valve
core which has been opened by the tire gauge. When the valve core drops
backward into place after the gauge is removed some of the tiny rust
particles get trapped between the rubber or plastic seal and the metal
housing surrounding the seal.
This results in an extremely slow air leak that all too often escapes
detection by the person gauging the tire and unless a metal valve cap which
has another sealing surface in it is screwed onto the valve stem the tire
will continue to lose air, albeit very slowly. When a larger rust particle
is trapped between the core and housing, the escaping air is easily
recognized so that proper action can then be taken immediately to correct
the problem.
The perennial problem of low tire inflation can be effectively solved by
the simple expedient of using nitrogen to inflate tires. Nitrogen is dry
and contains no moisture. Nitrogen is inert so rust cannot form since there
is neither oxygen nor moisture present to cause oxidation of the wheel.
Copyright 1996 Lawrence R. Sperberg, Probe Forensic and Testing Laboratory,
El Paso, Texas. All rights reserved.
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One company, Generon, is planning to market small, nitrogen generation
systems to the average consumer at a cost of approximately $300 for use in
home garages.
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If you contaminate the nitrogen with even a bit of air during a pressure
adjustment, all nitrogen’s benefits are lost.
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