| |
| NHTSA
RESEARCH: |
Chemical
aging is due to oxygen diffusing through the tire composite and reacting
with the internal components. If the rate at which air diffuses through
the tire is slowed, the rate
of chemical aging will be similarly slowed. (Review the FMVSS 139
for additional information on mechanical aging effects.) |
| |
| AIR
PERMEABILITY TEST PHILOSOPHY |
According
to tire manufacturers: - tires with more expensive, 100% halogenated-butyl
inner liners lose air at a rate of 2.0-2.5% per month (10 lbs per
year @ 35 psi)- tires with
cheaper, blended butyl inner liners lose air at a rate 4.00-5.0% per
month - for the same inner liner compound, a thicker inner liner will
lower the air loss rate - a reduction in air
loss rate, by a factor of 2, may be achievable for some tires. |
| |
| NITROGEN
TEST |
In
on the road tests involving nitrogen inflated truck tires running over 7 million miles, tire failures were reduced by half and tread life increased
by 25% to 30%. The benefits were
repeated in the second tire life after re-treading. These mileage
comparisons were followed by electron microscope analysis which measured
oxygen levels in the tire body and tread of tires inflated with air
and then operated on the road until replaced because of failure or
tread wear. The results were conclusive; oxygen kills tires over time.
Similar tests on automobile tires yielded comparable increases in
tire life. (Reference: Million Mile Truck Tires – Available
Today by Lawrence Sperberg.) |
| |
| NITROGEN
STUDY |
In
a study reported in Rubber and Plastic News by David Coddington of
Exxon Chemical Co. material from tires run for varying periods of
road service and inflated with air was
tested for tear strength. The laboratory findings; strength values
are steadily decreased with increasing service mileage, leveling off
at a value below 50% of original strength. In
lab testing equivalent to less than 40,000 road miles, the relative
strength of oxygen exposed tires declined to under 40% while the material
from tires inflated with nitrogen held
at over 80%. |
| |
| TIRE
DURABILITY TESTING |
Tire
life to failure point in laboratory wheel tests confirmed more than
twice the life for the nitrogen inflated tires. (Reference: "Factors
in Tubeless Radial Tire Durability", Rubber
and Plastic News, August 1993.) |
| |
| GOODYEAR
BULLETIN |
Nitrogen
inflation has advantages in that tires will hold pressure longer using
nitrogen. Nitrogen’s diffusion rate is 25% to 30% lower than
air, significantly reducing tire pressure
loss between inflation checks. The wear rate of under inflated tires is increased
to the point where a tire 10% under inflated will lose approximately
7% of it's service life. On the other
hand, properly inflated tires have less resistance to rolling. (References:
Goodyear Application Bulletin #17 and Bandag Tread Guide, September
1995.) |
| |
| AAA
(American Automobile Association) |
Under
inflated tires can cut fuel economy by as much as 2% per pound of
pressure below the recommended level. Therefore a tire that is just
five pounds below its setting will
consume 10% more fuel. Additionally, tires with low air pressure are
more sluggish in their response to steering input... compromising
your vehicle’s handling. |
