Is filling tires with nitrogen a gimmick?

Nitrogen composes 78% of the Earth’s atmosphere, so what’s the point of filling your car tires with 100% nitrogen? The elimination of water vapor? I wouldn’t think that O2 or CO2 would be problematic. Or is this all just a lame gimmick?

I can’t imagine any reason why it wouldn’t be a lame gimmick.
If you have any idea what is being claimed, then we can debunk it (or support it, theoretically, but I wouldn’t hold my breath for that outcome)

Filling your tires with nitrogen reduces the mass of your wallet, thereby improving your vehicle’s gas mileage.

Car Talk discusses nitrogen-filled tires
St. Petersberg Times

At my dealership, we would do it for free for any customers that request it. It might cost us $5 a tire to do it, but some customers swear by it. I would think that only a true enthusiast would see the difference.

On a jet airliner, where the brakes are absorbing massive amounts of heat and then radiating it into the tires, filling the tires with nitrogen prevents tire explosions. The rubber outgasses various volatile chemicals, and if oxygen is present inside the tire you can get a chemical explosion. Mexicana Airlines, I think, lost an airliner to this; the tire exploded in the wheelwell, and caused enough damage that the plane went down. Big loss of life.

For a car, meh. I can’t believe that it’s really any sort of improvement over straight air.

I fill my tires with helium. Reduces the weight, really increases the gas mileage.


Actually, I think they do that with Olympic bicycles. When races are decided by thousandths of a second, every little bit helps.

(but I could be remembering wrong)

Air is already over 3/4 nitrogen, so I can’t see it making a noticeable difference for the average consumer. The Car Talk guys say the advantage for racing is due to the water vapor in air which isn’t present in bottled nitrogen. Wouldn’t air with the water vapor removed work almost as well? I suppose bottled nitrogen is already available and relatively cheap.

In a couple of the cites above, it’s mentioned that the nitrogen molecules are larger than those of air so the little buggers can’t sneak out through the tyre walls so easily.
I can remember back in the early 60s when I was being tested for my aircraft board examination that the two points they expected an applicant to make for the advantages of nitrogen over air were better fire resistance and less seepage through the tyre walls.

The first time I saw N2 being advertised for tires the claims were that since there was no oxygen inside the tire, the inside of the tire would not oxidize. Also the water vapor can rust a steel rim, so no water vapor and no oxygen = no rust.
Both of these are good things. Worth money? Probably not. In the case of that tire store this was free with tires purchased.
Was it worth free? Sure.

“Nitrogen molecules being bigger than air” doesn’t make any sense. Two atoms of nitrogen (N[sub]2[/sub]) are both smaller and less massive than two atoms of oxygen (O[sub]2[/sub]). Since those two gases compose 98% of air, removing the O[sub]2[/sub] from the mix would reduce the net size/mass of molecules inside a tire. Correct?

For the same reason, subways which use rubber tires (for example, in Montreal) use nitrogen-filled tires to reduce the chances of a fire inside a tunnel.


I’ve always heard that the nitrogen was used because it was inert and retarded the oxidation and decay of the rubber in the tire.

I belive that there is something too this although I would hesitate to quantify the difference or say that it made economic sense. I do know that a lot of semi-trucks use nitrogen filled tires and I would guess that trucking companies have done the economic calculus.

Anyway check around on Google Scholar for a bunch of cites from the chemical and rubber engineering fields from the 20’s, 30’s, and 40’s. I would say it’s fairly well established that tire rubber and other compounds in tires can indeed be oxidized and its phyical properties change afterwards but I won’t promise that it makes economic sense.

I used nitrogen in my tires when I drove race cars, it doesn’t expand as fast as normal air when heated. With regular air my tire pressure could go up as much as 10 psi during a 25 lap race, with nitrogen it would increase on about 4 psi. Those that race in NASCAR and most other major and minor auto racing use nitrogen in their tires for years. Unless tires are filled in an extremely humid climate, I would no benefit of using nitrogen in regular passenger car tires.

My boss, that knows everyting :rolleyes: Claims that he gets about 10% mileage with nitrogen. :dubious:

Claimed the less leakage, and moisture. :dubious:

We live in a VERY dry climate. Keep your tires aired up and I can’t imagine there’s that kind of a difference, or EVERYONE would do it.

Ummm no boss. My thought is that he got talked into putting it in his tires, for another 5 bucks a tire or so, and he is trying to justify it.

Either that, or he has a corner on the market on the nitrogen supply. :wally

The part of moisture rasies a red, or at least a yellow flag. when you compress moist air the moisture condensates inside the compressor tank, so the air delivered into the tire should be pretty dry already.

No it doesn’t. You need a water separator to use compressed air for painting or sand blasting.

And if you think nitrogen doesn’t do anything consider Mexicana flight 940 that crashed because air was used in place of nitrogen in the tire. If it were up to me 18-wheelers would be required to use it on trailer tires due to the common event of locked brakes. I’ve seen truckers drag a tire down the road until it either catches fire or explodes.

I don’t know if I buy the concept of pressurization but it is certainly more stable than regular air. I’d consider it in SUV’S because of the stress placed on a tire. They always seem to run hotter than smaller cars but that is an anecdotal observation on my part. The $100 per vehicle cost is just rediculous. They give it away free with tire purchase in my area (including refills).

Oxygen molecules are indeed more massive than nitrogen molecules. However, oxygen atoms are smaller than nitrogen atoms The extra attraction of an additional proton-electron pair scrunches the atom even more. In general, atomic radius decreases as you go left to right across a row of the periodic table.

According to Wikipedia, the covalent radius of O[sub]2[/sub] is 73 pm, while for N[sub]2[/sub], it’s 75 pm. (The covalent radius is half the distance between the nuclei of each molecule.) So N[sub]2[/sub] is just a wee bit bigger.

I still say it makes no difference.

I saw an article in “Police Fleet Manager” claiming you should put it in your fleet cars so you’d get less flats, followed by an explanation of all the various moneys you could save including wages, etc.
To my thinking, if the tires need checked that often, make it part of a mandatory process every time the car gets fueled at the end of shift or something…