Inflate Your Tires With Nitrogen, Pollute Less

Does anyone happen to know of a website/locator where one can find stations that sport these in the US? Very interesting indeed, and I go through tires too quickly as it is.

J

Obvious marketing gimmick. Air is mainly Nitrogen btw. Tire pressure should be checked weekly because temperature changes will affect it.

There is a good article that explains more about this:

http://www.popularmechanics.com/automotive/sub_coll_leno/1302951.html?page=2&c=y

nonono, if it is "obviously" a marketing gimmick, I want to read about it. Please find me a credible source that explains why.

I understand very well that air is 78% nitrogen, but that still leaves 22% of other things that might leak out faster...

If it made no difference, it would be surprising that technology-obsessed people like NASA, race-car engineers, airplane companies and the military would use it in their tires.

How about the energy required to filter out the O2 from the air and leave nitrogen? Is the 21% of O2 in the tire leaking that fast that it makes more energy sense to remove it? I'm would guess that in terms of total energy this idea is not worth it, but I haven't done the calculations.

I seriously doubt that a few thousands watts of electricity will make a power plant (assuming it's not a clean one) produce more pollution than otherwise (we're talking about a pump that only works for a few minutes each month), or anyway, not enough to offset the benefits of less wear on the tires, a safer car and less emissions and CO2 from the ICE.

I'm not saying you can't get the same benefits from inflating your tires with regular air, it's just that statistically, most people check their tires very rarely (usually only when they are so flat that they can't help but notice) and so if they had been filled with nitrogen, things would have been better. Maybe not for you, but over millions of cars, it could make a pretty big difference.

MGR

If it made no difference, it would be surprising that technology-obsessed people like NASA, race-car engineers, airplane companies and the military would use it in their tires.

I think you are confusing good technology with something that may be good for the planet. A nail gun is good technology and is indispensable to home builders. I however use a hammer as I do not feel I need to spend the money or waste the resources on a full blown nail gun. NASA, race-car engineers air plane companies may use nitrogen in their tires but each of these is an extreme environment with equipment that is replaced or reworked each time it is used.

By the way, the US Navy used regular air to inflate the F-14 and F-18 tires when I was in the Navy. They just topped them off prior to each take off. The force of the landings could cause a tire bead to separate from the rim and let out air anyway. The same is true for your daily driver. As you hit pot holes and take turns at 40 mph (ok maybe that is just me) your tire can momentarily separate from the rim and release air.

yazheirx, aren't we saying the same thing?

I'm not saying that re-inflating your tires regularly wouldn't get you the same result, what I'm saying is that people in general don't do that, so if their tires were deflating more slowly, we'd get lots of benefits (pollution, safety, longer tire life, etc). How best to do that is another question; individuals probably shouldn't own a nitrogen pump, that's overkill. But is gas stations and mechanics had them, that's another story.

If everybody checked tire pressure every week, this would be useless. But since they don't, it could help.

I don't know how much more slowly nitrogen leaks from tires than oxygen or CO2, but I know that the primary advantage of using nitrogen is that it is a far more stable gas than the other two. Nitrogen is used in air-shocks and anything that may be exposed to a wide range of temperatures. N2's fluid properties (viscosity, density) are less effected by a temp change than O2, so that your tire pressure would change less from morning to evening, or from the beginning of your drive to nice and hot on the highway.
This is perfect for race cars because the traction properties of their wheels (tire, air, and rim 'system') will remain more constant around the track as the warm up and cool down at different parts of the track.
This would be useful for us motorists because our tire pressures would remain more constant - ideal for maintaining ideal traction and efficiency pressure level.

Science does not support the claims in this article. Air is 78% nitrogen, 21% oxygen, 1% other stuff. O2 is larger than N2. Both behave as ideal gasses at the temperatures and pressures present in automobile tires. pressure*volume will be proportional to the number of molecules of gas in the tire times the temperature (kelvin).

Aircraft use nitrogen in their tires to reduce fire risk and because of the convenience of using nitrogen bottles to fill the tires.

Race crews use nitrogen because of the convenience of using nitrogen bottles instead of compressors.

Some trucking fleets use nitrogen to extend the life of their tire cores which they have retreaded many times.

The nitrogen generators marketed to garages manage to pull out 50% to 75% of the oxygen, so you will still have 5-10% oxygen in the tire.

Keep those tires topped up to save rolling resistance and increase their life thus saving waste, but nitrogen is probably better for marketing than really saving energy.

http://www.eng-tips.com/viewthread.cfm?qid=120996&page=1 has a long gory discussion on the matter for the soap opera version.

If nitrogen leaks more slowly than regular air, then refilling the tire regularly should have the same end result as the nitrogen would leak more slowly than other gasses that make up normal earth air, and subsequent filling of the tire would replace the relatively more of these other gasses. The net result would be that the percentange of Nirtrogen in the tire would rise to the point that any remaining amount of these other gasses would be negligible. So after several refills, the tire should not need to be refilled so often.

Sometimes simple logic can be applied to determine that certain claims, while even if true, are irrelavent to real life.

I just had a look at that Popular Mechanics link Al posted, and the main reason it gives for using nitrogen is that it won't corrode your wheels the way that air (which contains about 20% oxygen) will. It also makes some claim about how nitrogen maintains its pressure better than air, but I don't believe this claim at all. (P.M. has declined in scientific rigor markedly in the last few years, and this reeks of something written by a journalist who has never even taken a university chemistry course). Furthermore, the idea that it leaks out of tires 30-40% slower sounds pretty absurd given that air is 80% nitrogen, unless we can see some evidence supporting this claim.

Geez Treehugger, how about we at least TRY to post something that is based on real science once in a while. Mmkay?

Why inflate your tire at all? Aren't we all missing the point here since new rubber blends can simulate the same flex as inflation? Here check out Amerytire website and get a free sample!

according to tom and ray of cartalk on npr, the slow diffusion theory is nonsense and the real reason nitrogen is used in extreme environments is because it contains practically no water vapor, whereas ambient air contains an unpredictable and variable amount of water vapor. water vapor expands in your tire as it heats up faster than air (or nitrogen). this makes a race car going at 200 mph more dangerous than it would be with predictable variations in pressure. in regular you and me applications, nitrogen offers no advantage.

High School chemesty will tell you that any ideal gas in a measured volume with the same pressure and temperature will will have exactly the same number of moles of the gas. If you increase the temperature of each of the gases by the same amount the pressure will increase by exactly the same ammount. The equation is pv=nRT.
The use of nitrogren filling is for portability and less costly equipment. Filling with nitrogen almost eliminates the amount of oxygen and water vapour in the tire which can prevent corrosion, but there is so little corrosion occuring already your car would be in the junkyard before thats a problem. Water vapour can create unpredictable pressures in the tire, but the difference is very little and the different temperatures of your tires would make a bigger difference.

I call BS.

At the temperatures/pressures found in _any_ tires, all gases obey the ideal gas laws, and there is nothing unique about N2 vs. air. N2 does NOT exhibit a more consistent pressure across different temperatures.

N2 is used in high altitude aircraft because CO2 freezes at about -57 C and temperatures at 36,000 feet and above are close to that.

N2 isn't appreciably different than 02 (which together make up 99% of air) in size, and therefore doesn't leak through rubber at a significantly different rate, marketing claims notwithstanding. N2 is in fact larger - molecular size is related to molecular weight, and N and O are next to each other on the periodic table, O being very slightly heavier (and not auguments about unsprung weight - that's a non-starter).

N2 is used because it doesn't cause rubber deteriorization through oxidation, and is a convenient source of dry gas (air also has water vapor in it), which can be damaging to rims.

But by far the biggest reason N2 is used in automotive tires is because companies which make/sell N2 inflation equipment market it as beneficial. PT Barnum would be proud.

To the point of this article, I don't buy that pumping air with a simple compressor is more envionmentally friendly than expending energy to not only pressurize, but also extract nitrogen from air.

Oxygen does leak out of tyres faster as any cyclist would attest to. If you replace your tyre, the first fill of air losses pressure within a day or two and needs a top up. This diminishes as previously stated as the "air" in the tube eventually becomes just nitrogen as the oxygen leaks out. This is probably more noticeable on bicycles because the rubber is thinner, the pressure of inflation is higher and the power to overcome the extra friction is easily felt by the operator (not the case for cars).

Corrosion of the rims is more caused by moisture in the air than the oxygen. Steel doesn't rust in dry climates at anything near the rate in moist ones.

I agree with Mike S. Nitrogen gas is a smaller molecule than oxygen gas. Therefore the theory that oxygen leaks out faster than nitrogen is false. Oxygen has an atomic mass of 15.9994 while nitrogen has an atomic mass of 14.0067. Thus, the nitrogen gas molecule (N2) has a mass of 28 while the oxygen gas molecule (O2) has a mass of 32. The post by Sammi claiming that the moisture in the air is what causes the variablility in tire pressure is 100% correct.

Graham's law of effusion of gases states: the relative rates of effusion of two gases through a tube or pathway of equal size is inversely proportional to the square root of the molecular masses of the gases.

Therefore, Nitrogen, being a slightly lighter molecule, theoretically would "deflate" slightly faster than regular air.

Thus the use of Nitrogen in car tires being safer and more earth friendly is most likely bogus. It is likely used in the other applications stated for reasons people have already stated, less oxidation, drier, freezes at lower temperature, etc. The effects of all would be nominal at best in the average automobile.

Maybe a better choice overall would be to inflate tires with Carbon dioxide, which is a heavier molecule than either nitrogen, oxygen or average air. That would keep a limited amount of waste CO2 (greenhouse gas) tied up in people's tires, temporarily removing it from the atmosphere. I'm not sure that it wouldn't increase the oxidation inside the rims however.

Realistically, the best thing you can do is check the pressure regularly.

My vehicle lost pressure in tires constantly. I replaced with nitrogen and it fixed the problem. Worked for me.

I see much merit in the logic that the higher diffusion rate rate of O2 (see G. J. Van Amerongen (1946). "The Permeability of Different Rubbers to Gases and Its Relation to Diffusivity and Solubility". Journal of Applied Physics 17 (11): 972–985) would result in high N2 levels after repeated inflations.

But, if O2 diffuses slower, then O2 would build up and oxidation of the inside of the tire/rim could occur.

The other major issues are pressure fluctuations due to water liquid/vapor, which behaves nonideally across temperatures in found in Chicago (cold winters), water's potential corrosive capability,

Two items argue against water vapor being a problem. The fraction of water vapor in the tire should decrease out after repeated inflations as it diffuses out (presumably water has a faster diffusion rate than N2).

Secondly, most compressors compress the gas to 50+ psi before dispensing it, which will dry out the air as vapor condenses within the condensor. So I'd suggest filling from a high pressure compressor.

While I can't argue with the experience of having leaky tires and NITRONIZING them back to health, my nerdy engineering background does agree with most of the discussion (i.e. Ideal gases chemistry, PV=nRT, water vapor compression, expansion, and corrosion, air flammability).

I just wanted to make one point. . . .

If you are able to keep your tires properly inflated with air, please take the money that you save by not NITRONIZING them and donate it to a worthy cause or just be nice to someone else. I know that this service is highly advertised in the area in which I live, but it is mostly because the tire places bought these expensive machines that they need to justify the costs. If a regular gas station air compressor costs 50 cents and the fancy nitrogen inflation costs a few bucks, buy someone else a cup of coffee instead, I will do the same. I hope that I am behind you in line next time.

N2 is seemingly a better gas for tires but so far I haven't seen true scientific evidence to proof that proves it to be so, or proves it indifferent from normal air. Some of the facts about water vapour affecting the pressure in the tires are false because the gas laws apply to all gases, and the pressure and volume are inversely proportional to each other regardless of the gas.
So take that you people who think that water vapour or O2 affects the tire pressure.

By the way, I'm a high school student.... and I know more than you!!!. except for MGR. I agree with you.

None of this matters cause if nitrogen leaks slower and you have 78% nitrogen in the air then by the time you properly maintain your tires for about 6 months you wil have a high content of nitrogen anyway probably 90% or better so this is just a way to make money from treehuggers.

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If you don't stad for something you'll fall for anything!

The best way to keep tires properly inflated is to buy an air compressor for the garage to make it more convenient to check and inflate the tires. An adequate 120 volt compressor costs only about $100, and it's well worth the cost.

One of the problems with nitrogen inflation is that it makes checking and inflating the tires less convenient, so probably it would be done less often. That alone would outweigh any of the minor advantages that nitrogen might have.

Chemist for 42 years. PV=nRT... that's all there is. I have no idea of what the air/gas permeability of a tire is I'm sure the specs vary more then the size of a molecule size of these two gasses. Also keep in mind the tire is essentially one molecule and not very permeable. Some airplanes will use N2 because it will not support combustion. The variability with race cars would be from moisture in the air not the nitrogen content. You can remove moisture from compressed air by passing it through 3-5 Angstrom molecular sieves... this would cost as much as buying N2. To regenerate the sieves would cost more though. I could go on and on but just use air and check your tires frequently.

All gases expand (almost) the same with temperature. The differences are neglijeable: p V = n R T, no matter what. Nitrogen makes no difference, really, from this perspective.

The nitrogen N2 molecule might be a bit larger than O2 and some other molecules that air contains. If nitrogen migrates out of the tires at a slower rate, guess what? By inflating and than re-inflating the tires with air, in time the nitrogen concentration will increase well over the natural concentration of 78% !! So, you'll get nitroen-inflated tires anyway!

The real benefits of nitrogen-inflated tires might be less inside-tire corosion (due to oxigen, water, etc). Is this really a major problem?

Potentially, there might be a problem with air-inflated tires: when tires inflated in hot, humid summer are used in the winter, as water in that air will condensate inside the tire and the presure will decrease even more than just due to temperature changes acording to the pV =n RT formula.

One is better off (time/money) by just checking the tire pressure periodically, re-inflate or deflate if necessary and don't waste time and money with nitrogen (not to mention the whole pollution thing with purifying nitrogen, packing it, etc, etc.).

As an engineer (EE), I love to see the fallacies people use to extract money from the unknowing.

It's good to se that some people "got" the fallacy of the little molecule vs the big N2 molecule. If you believe the molecule size theory, then you'll eventually have almost pure N2 (after a few refills).

The other marketing fallacy I love is that the better the vacuum cleaner is, the more Amps it uses. The only thing that proves is that the unit is less efficient.

The specification we should be getting for the tire is the permeability of the tire for N2 and O2.

The vacuum cleaner should tell you how much it sucks (no pun intended).

As always, Caveat Emptor...