Nitrogen Filled Tires?

I personally think it's a waste of money. First off, air that you pump into the tires naturally has ~78% nitrogen to begin with. The remainder is oxygen and other inert gases. Save your money and use what's free. The real stress on tires is the effect of the outer portion which is subject to the elements.

 

Hey, how about filling them with helium. That should reduce the mass of the car and the rolling friction by a miniscule amount. You might be able get another 0.0001 mpg. :wink:

 

And waste another non-renewable resource?

 

Costco does too. (fill tires . . . not the non-renewable resource thingy.)

Nitrogen IS better for tires. Nitrogen leaks out at a slower rate, does not expand and contract as much with heat and cold, and prevents deterioration on the inside of the tire/wheel due to the lack of oxygen, contaminants and humidity.

All airplanes, at least the jets and commercial variety, use nitrogen in their tires. If a 747 were to land with straight air in the tires they would overpressurize on the first landing and explode or pop the safety plug.

 

A friend of mine that used to work for Air Products told me they had a gas, I think it was a fluorine or sulfur based gas that he used to fill his tires. Once filled with that gas, which was a very large molecule, he would never have to adjust the tire pressure --ever-- as it was too large to permeate through the rubber.

 

The gas was probably not fluorine as fluorine gas is highly reactive. I would also guess that it was not sulfur based as the only ones I can thing of off hand are hydrogen sulfide and sulfur dioxide. Both can be deadly can be highly corrosive. It may have been carbon dioxide.

 

Costco fills tires with nitrogen at no extra charge.

 

Fluorine is highly reactive in certain forms, such as hydrofluoric acid, but very inert in other forms like the refrigerant used in air conditioning. I am fairly certain it was a molecule that had 8 fluorine atoms in it.

 

Yes, that would have been sulfur hexafluoride. I hope this does not become a wide practice because SF6 is one of the most potent destroyers of stratospheric ozone.

DAS, and Tochatihu, tires filled with 78% N2

 

Military aircraft tires have been serviced with N2 for many years. Most tires used on aircraft landing on carriers carry very high pressure. In fact, they are serviced inside a metal cage, separated from the person pumping up the tire. These things have exploded, killing everyone in the area... these are 16 ply tires and are infflated with N2 to hundreds of PSI. A blown tire can mean the loss of an airplane and the people on deck. Nitrogen has proved to be a small edge in safety. Like anti-lock brakes, this looks like a good transfer from aviation to automotive.

 

Here is a good read on this subject. (from google)

http://www.tirelast.com/id5.html

Summary:
Oxygen is an enemy of wheel and rubber. According to a research on trunk tires, Notrogen gives 26% longer life and lower failure rate on tires.

 

So, would they vacuum out the tires first or is a small percentage of regular air OK?...

 

Ooops, I made a mistake. It is not ozone reactive. It is an extremely potent greenhouse gas however. Sometimes I get those two mixed up. Sorry.

 

SF6 is used in high-voltage circuit breakers in electrical power generation and distribution systems. It does not support ionization as readily as air, hence arcing and burning of contacts is minimized. That's an important consideration when dealing with 500 KV and thousands of amperes!

However, for tire applications I would guess its main attribute, as a previous poster noted, is its lower rate of diffusion and leakage, relative to air.

As far as health concerns, despite the assurances of the companies touting their SF6 breakers, I think the jury is still out. There is some anecdotal evidence now surfacing from powerhouses and substations with enclosed breaker galleries -- where the SF6 gas is not readily ventilated or diluted -- that it might not be such a benign substance after all. An issue I am keenly following, since my powerhouse is scheduled to have SF6 breakers retrofitted within the next several years. I remember when Halon fire suppression systems were introduced onboard Navy ships to replace CO2 systems. Yes, it wouldn't kill you as quickly as CO2, but we found out later it was far from harmless. . .

One thing for certain, getting rid of the oxygen in contact with the rubber compounds in our tires is a good thing -- oxygen is quite reactive. Ironically, ozone, which is O3, is even more reactive in concentration. It is not uncommon to have rubber and other susceptible materials degrade in a matter of weeks or at most, months, in the presence of ozone generated by arcing or malfunctioning electrical equipment.

In submarines, this was a problem with some of the equipment that used to be installed, and there were cases of ozone poisoning documented back in the bad old days.

Anyway, enough of my rambling. Interesting topic though!

Steve Zettel
near Libby, MT USA

 

Gee. . .isn't air 78% Nitrogen

 

Yes but atmospheric pressure is about 14.7 psi compared to the 34-44 psi you have in your tires. The rate of reaction with the tire is proportional to the concetration of oxygen so you might expect the reaction to occur at least 2-1/2 to 3 times faster than atmospheric oxygen. Also as the tire heats up damage to the tire would accelerate. Nitrogen is probably a good idea.

 

[font=Comic Sans MS:95ac6f968e]Has anybody experienced premature tire failure from using air in their tires? I didn't think so. Might you get longer tire life with a nitrogen inflated tire? Possibly. Will the tread, exposed to the ravages of air and pavement, wear off first? Again, probably.[/font:95ac6f968e]

 

If I am not mistaken, the air pressure we measure (32-44psi) is in relative to the outside air pressure. That means, when you read 42psi from your tire meter, it is actually 14.7+42=56.7psi. In other words, at 42 psi reading, the oxygen density is about 4X that of our atmosphere at sea level. Just to clarify.

 

Nitrogen filled truck tires may last longer and be less problematic than air-filled ones, but keep in mind that our passenger tires last about 1/3 as long (mileage-wise) and the air pressure is also about 1/3 as high. The benefit of having pure nitrogen in our tires deminishs greatly. In other words, I won't pay $$$ to have people fill my tires with nitrogen.