I just heard two people talk about places that sell tires now putting Nitrogen in the tires rather than compressed air.
What is the deal, air is 78.1% nitrogen to start with?
What are the pros and cons? Is this just a marketing scam in light of the rising gas prices again?
well, i guess if you never check the air in your tires, and the alternative is to fill them with nitrogen that would be OK.
but why not just use air?
you already pointed out ‘air’ is already mostly nitrogen anyway?
hmmmmmmmmmm. the word scam does come to mind. gee, not one thought of hydrogen in tires though!!! 
You’ll see no advantage with nitrogen-filled tires. If the store is giving away free nitrogen, calmly accept it. But if they give you a sales pitch to pay for the option, just say no. Disregard any of the salesmen’s claims, particular about better mpg. It simply isn’t so.
It’s mostly marketing. If someone is willing to inflate your tires with nitrogen for FREE, let them. I would never pay for nitrogen, however, since, as you pointed out, air is mostly nitrogen anyway.
I’ll stick to inflating my tires with 78.1 % nitrogen. That’s close enough for me.
As more and more vehicles are required to have Tire Pressure Monitoring Systems, nitrogen in tires will become more common. While it is true that air comprises of 78.1% nitrogen, it also contains other gasses that are unstable as the tire heats up and cools down. Also, air also contains water vapor.
Pure nitrogen contains no water vapor. That means there’s less of a chance for internal corrosion of alloy wheels which can result in wheel and bead leaks. Pure nitrogen also doesn’t permiate as quickly through small leaks as air does.
So, if the vehicle has a TPMS, there’s a less of a chance of the TPMS warning light coming on when pure nitrogen is used.
Tester
I agree with you completely Tester. To the point answere and very correct.
What is the purity of the nitrogen that they sell? Nothing can be 100% pure without a huge energy expenditure to make it so and then it won’t even be pure.
What do you mean by “gases that are unstable”? What happens to them? Unstable in what sense? Is that damaging to the car or what?
Why doesn’t Nitrogen permeate through small leaks as quickly as air? Nitrogen has a molecular weight of 7 so N_2 had a weight of 14 and Oxygen (20.9% of air) had a molecular weight of 8 so O_2 has a weight of 16. It seems that the oxygen (not to mention CO_2, 0.03% of air, or argon, 0.9% of air, molecular weight of 18) is heavier, probably bigger and would not leak out as easily.
I suspect that the only meaningful difference is the lack of water vapor. Using N2 is probably about the same as using very dry compressed air. Compressed air normally ends up with a fairly high concentration of water vapor.
Due to the covalent bonding and attraction between atoms, the Oxygen, although heavier, is a tighter molecule by about 3% compared to Nitrogen.
The nitrogen may not react with the rubber as much as the oxygen.
http://www.newton.dep.anl.gov/askasci/chem03/chem03741.htm
Also it won’t oxidize the Al mag rims as much.
The water vapor can be up to 4% of air so it is probably the biggest problem and biggest reason to switch to a dry gas to inflate the tires. It is possible that the water vapor is condensing and evaporating (huge heat capacity) as the tire temperature changes.
This nitrogen in the tires was a Porsche thing in the late 70s early 80s nothing new
I really don’t think that there is enough of a difference. I seriously doubt if TPMS would perform any better or worse with it in any measurable or meaningful way.
Everyone here is correct except for Crash’s molecular weights, and I trust that Speed’s molecular size comment was tongue-in-cheek.
The only benefits to nitrogen are:
- It is dry, and water can change state (to liquid or ice) in a tire, dramatically impacting pressure, and
- It is almost completely free of oxygen and ozone, both of which oxidize rubber. Not that this is a real problem for tire life.
Aircraft tires use nitrogen because it is dry, and so that exploding tires tend to extinguish, rather than fan a fire.
Bottom line, nitrogen is better, but not worth paying anything for.
Agreed. I buy tires from a major discount warehouse that runs incredibly astute and respectable tire shops. Except for the silly-looking bright green valve caps that denote nitrogen-filled tires, it’s OK with me. But, I would really prefer to have a choice of valve cap colors!
I think the way to go is fill tires with Xenon. The big Xenon atoms should leak out real slow. Even better would be Radon 222, except it turns into lead after awhile (3.8 day half life)
none makes sense.
the tire carcass is installed onto the rim. then a gas is injected.
the carcass starts out with something in it. (AIR) so how is adding further NO going to be pure?
maybe some validity if the new tire was filled in a complete vaccuumfrom the get go, but this sounds like BS to me.
It’s just a marketing scam, but as long as they don’t charge extra it’s harmless. Air is already about 77% nitrogen.
They’ll tell you that race cars use nitrogen, but their tires as well as the conditions under which they run them are dramatically different from yours and they’re mandated to use nitrogen because it won’t feed a fire.
According to many measurements and due to the strength of attraction of the greater positive charge in the nucleus, the O2 molecule is smaller than the N2 molecule. The permeability law is
Flux out of the tire = Area / Thickness * (partial pressure inside - partial pressure outside) * permeability
the coefficent of permeability for rubber is a function of temperature and gas type.
Nitrogen will leak out slower until the partial pressure on the outside for O2 is greater than in the tire, then O2 will leak into the tire.
Hoyt, the search engine here does not work so well and the fact that the issues are not organized helps very little. So one may expect double postings. It is ironic that your attempt at cuteness could as well be considered annoying. Great to post the link to bring the discussions togehter, however are you any better by trying to be smart? Hard to look from outside the box.
How hard is it to click on “search” and type “nitrogen”? There is no valid excuse.