Yesterday I saw a sticker on the back of a new (Japanese compact) car proclaiming that its tyres were filled with nitrogen. What’s that all about? where would one go for a refill? would the tyres be affected if you filled 'em with regular air?
Some guff about nitrogen in racing tyres.
There are claims it makes the tyre last longer, gives better performance, and is less corrosive. I guess if you filled the tyres with regular air, you wouldn’t get the benefits.
I fill my tyres with a 78% Nitrogen mixture and have never had problems.
This scam (Nitrogen-filled tires) was popular in the USA a few years ago. Tire shops were charging $5 extra per titre to fill with nitrogen!
Of course, if you have the money, nothing is too good!
I’m surpised that dealers are not pushing people to use champagne instead of waterin the radiators!
The World’s Second Best-Selling Commercial Airplane Company, for which I work, recommends that airliner tires be filled with nothing but pure nitrogen.
Air, since it has oxygen in it, will support combustion; there was a nasty accident some years back when a tire (filled with air) exploded in-flight. The airplane had done a lot of taxiing, so the brakes were very hot. The hot tires outgassed (gave off volatile gasses) and the mixture of air and the gasses exploded inside the tire. Sent a big chunk of wheel up through the floor, caused a crash and mucho fatalities.
Well, you don’t say, Pergau!
The USN requires the tires of carrier based aircraft be filled with nitrogen. About 380 psi, if I remember correctly, for a F-14. The high pressure helps keep the tire round when it impacts the deck during landing. Nitrogen is used due to more favorable expansion properties and pressure regulation.
Rocketeer’s point may explain why a car manufacturer would use it.
I’m not a chemist, but if one is aboard, I would appreciate an explanation.
-thanks-
It’s more stable at different temperatures, and isn’t reactive, as the other post said. The space shuttle uses it also:
Why don’t race car drivers use helium, which weighs less than nitrogen, in their tires? It is also unreactive and should be just as predictable.
I don’t think it would be realistic to do so for standard automotive tires because of the extra cost and because helium probably seeps through the tire and connections faster than air or nitrogen.
Professional race teams shouldn’t have to worry about either as they are well funded and don’t expect tire pressure to last for months as does Joe Car Owner.
So, why nitrogen instead of helium?
Nitrogen is preferred in aircraft tyres because it is an inert gas, and as Rocketeer has said, much safer when fire/ or overheating is present. We were also told when I was in training that air seeps through the tyre more readily than Nitrogen.
In the RAF some aircraft also used Nitrogen above the fuel in the tanks as a fire suppressant in war situations.
V
I don’t follow that. Oxygen, the other constituant of air (if we ignore the other 1%) has a mass greater than Nitrogen. So how likely that this escapes faster than Nitrogen alone?
The nitrogen-filled tyre seems to be a marketing scam. Your tyre would be fractionally lighter, and less likely to feed an explosion. But does that make difference to the average car?
Nitrogen is also used in the tires of some rubber-tired subway systems, such as the Montreal Metro. It lessens the danger of fire in a tunnel.
Ed
Ahh, Nitrogen is very reactive. Think of compounds like Nitroglycirn or trinitrotoluene or perhaps Nitric acid.
Yeah, right Rickand water is very reactive, too. Hydrogen and oxygen. Hindenburg. Oxyacetylene.
Personally I never breathe and I never drink water. Too dangerous.
Rick
“Nitro” compounds refer to a functional group containing nitrogen and oxygen bonded together. They are unstable and would like nothing more than to dissociate into gasous nitrogen and oxygen. A little bit of coaxing (heat, a good smack with a hammer), and they will do so. Of course, the newly-released oxygen is now available for further combustion, which in turn releases more oxygen, leading to a very fast chain reaction. Think of explosives as a combination fuel/oxygen source. Nitrogen, on the other hand, is a relatively inert gas that won’t explode no matter how hard you hit it.
As far a physical things like inflating tires, all gasses obey what is called the “ideal gas law,” and a tire filled with air, Nitrogen, or Neon, will all behave the same, at all temperatures.
Futile Gesture has pointed out that the molecular weight of Oxygen is greater than Nitrogen. Since diffusivity is proportional to the reciprocal of the square root of molecular weight, Oxygen should diffuse through the walls of a tire faster than Nitrogen. A whopping 1.07 times faster.
So, the only major difference between air and nitrogen that I can see is that Oxygen is a corrosive gas which supports combustion. Now, you can fill a tire with Nitrogen instead of air, which means that you reduce the risk of ppotential corrosion on the inside, but what about the outside?
Bottom line, you gotta fill your tires with something, and if you’ve got Nitrogen handy, why not?
Oxygen and Hydrogen are very reactive. That’s the reason there’s so much water around. Nitrogen isn’t as volatile, but ir isn’t inert either; if it was, nitrogen compounds wouldn’t exist.
Psst, bizzwire, you mean that nitrogen would diffuse faster than oxygen.
And the Ideal Gas Law is only a good approximation when the gas is far from any phase transition. For any environment a car, airplane, or even the Space Shuttle is likely to be in, this applies perfectly well to nitrogen, oxygen, carbon dioxide, helium, argon, or any combination of those you care to think of (as well as most to many other gasses), but if, say, you were in an extremely low temperature environment, helium would be much closer to ideal than the others.
But the weight saved by using helium would be negligible, even by car-racing standards. True, helium only weighs about about a seventh as much as air (or pure nitrogen), but how much do you think that the air in a tire weighs? I suppose that helium-filled tires might be desireable if even nitrogen wasn’t inert enough for you, but argon would be just as good for those purposes, and much cheaper: Argon is nearly a full percent of the atmosphere, and merely needs to be separated from the other gasses, while helium is mined.
I only know this because I fill fire extinguishers with nitrogen for a living. When I get a flat tire (common on my gravel road), I use dry nitrogen to get going again. Seems I never have to change a tire!
I would estimate that one could fill 100 average tires to 35 lbs pressure off of one 250 lb. tank of nitrogen at 2200 lbs/sq. in., maybe more. That same tank of nitrogen costs me 12.00/tank.
Dry nitrogen is cheap, probably no more than air.
::: Looks at the top of the page:::
Yup, general questions, which IIRC is for Factual answers to questions.
From this site
(bolding mine)
In case you forget what gasses are in group 18, here is a perodic table
Nitrogen is not considered to be an inert gas. That was my point.
Ooops.
Thanks Chronos-got my subscripts backwards.
And another checkmark as regards to the ideal gas law. However, most cars won’t be driven at liquid helium-type environments. Let’s just call it “the pretty darned good gas law.”
Oh, and Rick: I dug this gem out of the link you provided:
Bolding mine.