Whats the advantage of filling the tires with nitrogen?
01-08-2005, 06:15 AM
#11
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Tires often contain some amount of liquid water.
The problem with air (mostly oxygen and nitrogen) is that it's normally not just air. More often than not, the "air" in your tires contains liquid water from the air compressor and/or the lubricant used on the bead when the tire was mounted on the wheel. Normally the air (or nitrogen) pressure in a tire increases predictably about 1 psi for every 10 oF of temp. If there's liquid water in the tire (and water is usually present if you're filling the tires with "air"), pressures sky-rocket unpredictably as the water turns to steam.
On the street, there little benefit from using nitrogen; the tires normally don't run hot enough to cause a problem. Nitrogen is strongly recommended for racing where tires often run 200 oF or hotter. On track at Mid-Ohio, the left-front tire on my S8 has hit 240 oF. With a starting cold pressure of 36 psi, I normally expect a 47 psi hot pressure. My tires were filled with (wet) air however, and that LF tire was almost 60 psi. When I let "air" out, I was burned by the steam.
On the street, there little benefit from using nitrogen; the tires normally don't run hot enough to cause a problem. Nitrogen is strongly recommended for racing where tires often run 200 oF or hotter. On track at Mid-Ohio, the left-front tire on my S8 has hit 240 oF. With a starting cold pressure of 36 psi, I normally expect a 47 psi hot pressure. My tires were filled with (wet) air however, and that LF tire was almost 60 psi. When I let "air" out, I was burned by the steam.
01-08-2005, 06:55 AM
#13
I was unaware that N2 somehow escaped PV=nRT
Do tell.
All that time in Chemistry, physics, thermodynmanics (including statistical thermodynamics), wasted. Just damn.
And yes, I'm well aware of deviations from the Ideal Gas Law. At the temperatures and pressures of interest, Boyle's Law works just fine, thanks.
All that time in Chemistry, physics, thermodynmanics (including statistical thermodynamics), wasted. Just damn.
And yes, I'm well aware of deviations from the Ideal Gas Law. At the temperatures and pressures of interest, Boyle's Law works just fine, thanks.
01-08-2005, 08:15 AM
#14
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From Aviation World :
Quote :
Since 1987 in the United States, dry nitrogen gas has been mandatory for inflating aircraft tires mounted on braked wheels of specific transport category aircraft.
The use of nitrogen (or another approved inert gas) is intended to eliminate the possibility that a chemical reaction between atmospheric oxygen and volatile gasses from the inner tire liner will cause an explosion of tire/wheel assemblies.
In fact, Airworthiness Directive 87-08-09 specifies that aircraft tires mounted on braked wheels may not contain more than 5 percent oxygen by volume. Aircraft covered by this AD will have a placard that says "Inflate tires with nitrogen only."
The AD explains various means of compliance under an FAA-approved maintenance program and permits the substitution of air at remote locations that do not have nitrogen, providing that the oxygen content does not exceed 5 percent by volume, or within the next 15 hours of time in service, the tire is purged of air and reinflated with dry nitrogen so that the total oxygen does not exceed 5 percent by volume.
Aside from the safety factor, the use of nitrogen, which does not contain moisture like atmospheric air, also greatly reduces oxidation damage to the interior of the tire.
Since 1987 in the United States, dry nitrogen gas has been mandatory for inflating aircraft tires mounted on braked wheels of specific transport category aircraft.
The use of nitrogen (or another approved inert gas) is intended to eliminate the possibility that a chemical reaction between atmospheric oxygen and volatile gasses from the inner tire liner will cause an explosion of tire/wheel assemblies.
In fact, Airworthiness Directive 87-08-09 specifies that aircraft tires mounted on braked wheels may not contain more than 5 percent oxygen by volume. Aircraft covered by this AD will have a placard that says "Inflate tires with nitrogen only."
The AD explains various means of compliance under an FAA-approved maintenance program and permits the substitution of air at remote locations that do not have nitrogen, providing that the oxygen content does not exceed 5 percent by volume, or within the next 15 hours of time in service, the tire is purged of air and reinflated with dry nitrogen so that the total oxygen does not exceed 5 percent by volume.
Aside from the safety factor, the use of nitrogen, which does not contain moisture like atmospheric air, also greatly reduces oxidation damage to the interior of the tire.
01-08-2005, 08:19 AM
#15
I was going to mention the part about oxidation of the rubber liner on the inside of the tire, BUT
for most of the people here, we do not use the ultra-hard, ultra long mileage life tires and if you are going thru a set of tires every 2-3 years like I do, then that situation isn't likely to be of significance.
01-08-2005, 08:30 AM
#17
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That just ain't true. Our atmosphere is ~80% nitrogen...
plus oxygen, carbon dioxide and hydrogen, all of which obey
"Charles' Law" :
Charles's law states that a gas expands by the same fraction of its original volume with each degree that its temperature rises, and that carbon dioxide, hydrogen, oxygen, and nitrogen all expand at constant rates as their temperatures rise.
"Charles' Law" :
Charles's law states that a gas expands by the same fraction of its original volume with each degree that its temperature rises, and that carbon dioxide, hydrogen, oxygen, and nitrogen all expand at constant rates as their temperatures rise.
01-08-2005, 09:50 AM
#19
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There was a thread about this a few months ago when I had my tires filled with Nitrogen.
I haven't seen any significant benefit and no downside at all. The cost per tire wasn't big issue. As a "mod" it is just another choice that we enthusiasts make. Some of us like K&N air filters and others like one brand of oil or spark plugs. It is just another tweak that likely has no street benefit (like all of these M5 spoilers on street driven A6s). After we discuss the facts, let each driver make his or her choices.