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Nitrogen for tires..

pierre smith

pierre smith

Well Known Member
A friend of mine told me that he uses nitrogen in his tires because they don't leak down nearly as fast. He said it's because the nitrogen molecules are much larger than air. He also went on to tell me how cheap it is to buy.

Do any of you guys use nitrogen?

Thanks,
 
Niiitroggen!!!

I use nitrogen, put it in these new fangled leak resistant tubes. Have to add the stuff every time I fly! Don't believe it's the nitrogen tho', I never had this problem before I installed these crazy high dollar tubes.
I do believe the nitrogen is a good thing!
 
Well, considering that air is about 80% nitrogen, I'd say we all use nitrogen, at least 80% of it...

Ditto the leak-proof tubes. Michelon Air Stops are my choice. They leak maybe a pound a month, maybe. Not much more $ than cheap tubes either.
 
sprucemoose said:
Well, considering that air is about 80% nitrogen, I'd say we all use nitrogen, at least 80% of it...

Ditto the leak-proof tubes. Michelon Air Stops are my choice. They leak maybe a pound a month, maybe. Not much more $ than cheap tubes either.
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Second the Michelin Air Stops - the tubes I've been using for the last 2-3 years with 78% N2. If your goal is to hold pressure longer, use them. If you want to say you inflate your tires with 99% N2 versus 78% N2, go with the bottled N2.
 
If it really worked....

If the O2 leaked out faster then the N2, as you repeatedly put more AIR in your tire you would be increasing the N2 concentration. After all the O2 would have leaked out and you would be left with only N2 when you started filling.

Kent
 
More ways to spend your money?

The military (and I assume the airlines) uses bottled nitrogen to service tires and oleo struts to very high pressures because it is dryer than air and thus is more corrosion resistant. You don't want parts pressurized to 300 to 1500 psi failing! I doubt the risk is high in our RV's.
 
Nitrogen seems to be the latest fad among car & truck tire dealers. If the reason is because nitrogen is drier than air, than it has to be because cars & trucks run tubeless tires, so wheels are exposed to the gas inside. Anyway, moisture is not an issue in a rubber tube--is it? I don't see how.
 
Air is good enough for me

Pierre,

As a chemist I spent years working with gases. Dry air is 78% nitrogen, 21% oxygen, and 1% argon and other minor components. Nitrogen's only advantage over air is it doesn't react with the rubber and doesn't support combustion. Oxygen will react with rubber slowly and does support combustion, but it does that at a rate so slow we have no reason to worry. You'll wear out the tires long before the reaction will matter. At the speeds we land and the temperatures we develop the use of pure nitrogen is an unnecessary expense. If we regularly produced high temperatures in the tires for long periods as in a race car or very high temps as in heavys and fighter aircraft then the use of pure nitrogen makes sense but not for an RV.

Larry Dickinson
RV-9A 160 hrs
 
Use of nitrogen...

Nitrogen has been used quite a while in racing applications because of it doesn't change pressure quite drastically as the tires heat up, thus you are able to have better control over tire pressure change. Same may apply to using them in cars at today's highway speeds.
I believe the use of nitrogen, especially in high altitude aircraft, is for the same reason, you don't get the drastic pressure changes.
Someone else???
 
I don't know if it is a national thing or not, but the last two sets of car tires I purchased at Costco (in CA) were filled with Nitrogen. They switch your valve caps from black to green to signify the change. The reasons why have already been mentioned, but here is an article explaining Costco's rationale.
 
Gary Bricker

Where can I get the regulator and hose for nitro. I can get the bottle at a local welding supply but they were not sure about the regulator and hose.
 
COSTCO article isn't accurate!

Any knowledgable chemist can tell you that there are statements in the Costco article that are factually incorrect. It is true that rubber is somewhat permeable and gases can leak out through the rubber sidewalls of a tire. However in practice I expect that the most important leak source is either the valve or the failure to seat the bead tightly on an auto tire. Aircraft tires use inner tubes so a leak at the bead can't happen. If you lose air you might want to use the special air retention inner tubes available for aircraft which are especially low in permeablility. The article indicated that oxygen would leak out three to four times as fast as nitrogen. This is just not chemically correct. The molecules are nearly the same size and weight. That means they should diffuse through the slightly porous tire wall at rates that are not very different ( 1.07: 1) with nitrogen the slightly faster. See you basic chemistry text - Graham's Law of Diffusion.

In an auto tire the presence of moisture could promote corrosion of the steel rim. There is no tube in an auto tire normally and the water that could be in air along with the oxygen could cause rust to form on the rim. This is not a problem in aircraft.

The expansion and contraction of nitrogen and oxygen (and all gases for that matter) are the same with temperature.

If you want to spend the money and use nitrogen that is your choice but it is unnecessary.

Larry Dickinson, chemist
RV-9A 160 hours
N95LD with air in the tires
 
Larry D said:
If you want to spend the money and use nitrogen that is your choice but it is unnecessary.

Larry Dickinson, chemist
RV-9A 160 hours
N95LD with air in the tires
Click to expand...

I agree with Larry completely and will continue to use "air" but don't want to discourage anyone that wants to feel good about their tires because they used nitrogen. ;)

How readily available is nitrogen away from your regularly used place of inflation might be one question to consider?

Personally, I find that there are enough maintenance items to worry about on an aircraft and do not want to introduce one more. :)
 
The reason some shops use nitrogen is because it is DRY - moisture promotes bacterial growth on the rubber, which degrades the tube and tire.

Run your air through a dessicant filter, you'll get the same effect.

Fellow Chemist....
 
Hmm, I use nitrogen in struts, but never in tires, seems like waste. Airstop tubes when you wear out the tires will take care of the problem. If you ever had a problem.
 
Costco Article

here is an article explaining Costco's rationale.
Click to expand...
This sort of falls into the category of the New Science by Al Gore.
The media falls for it hook line and sinker and, before you know it, it becomes "fact".
It reminds me of many appropriate sayings I learned as a kid and I would provide attribution to these but have long forgotten the proper source:

"A fool and his money are soon parted"
"There's a fool born every minute"
"No one ever went broke underestimating the intelligence of the public"

-mike
 
Larry D said:
Aircraft tires use inner tubes so a leak at the bead can't happen.
Click to expand...
Not 100% true. Most GA tires are tube-type, but nearly all business/airliner-type aircraft use tubeless tires. Nearly all helicopters with wheeled gear use tubeless tires as well.


Larry D said:
In an auto tire the presence of moisture could promote corrosion of the steel rim. There is no tube in an auto tire normally and the water that could be in air along with the oxygen could cause rust to form on the rim. This is not a problem in aircraft.
Click to expand...
Corrosion on aircraft wheels is a common problem, whether they are tube-type or tubeless, filled with air or nitrogen. Just a matter of where the corrosion occurs...


Larry D said:
The expansion and contraction of nitrogen and oxygen (and all gases for that matter) are the same with temperature.
Click to expand...
I always thought (and had been told numerous times) that nitrogen was more "consistent" re: expansion than air under high temp/pressure. Guess I should've paid more attention in high school chemistry...




Nitrogen is used in aircraft tires because it doesn't support combustion. Very important in the event of a brake fire after a heavyweight landing or RTO, or a wheelwell fire with the gear retracted.

I personally don't see a reason to use nitrogen in RV tires:
- there's plenty of flammable fiberglass surrounding brakes that 99% of builders fill with flammable MIL-H-5606 fluid.
- unless you can get the nitrogen for free, air is cheaper for 99% of owners.
 
Man, this nitrogen thing sounds like magic beans to me. Once and for all, air is mostly nitrogen. Now if dryness is the concern, can't I just use a drier on my compressor line (maybe wait for low humidity days to air up) and get most of it out?
 
Easy

Easy math...Let's see, Small charge for nitrogen vs Air for free.

Sounds like a "no brainer" to me....this ain't rocket science, right Paul?
 
Hwood said:
Sounds like a "no brainer" to me....this ain't rocket science, right Paul?
Click to expand...

Well, I know that we use Nitrogen in the Shuttle's tires....but the Val gets pure, unadulterated (humid) Houston "air" (if you can call it that....) :p
 
The use of Nitrogen for tires is because it is an inert gas that is dryer than the air that comes out of your compressor. We don't worry about the rubber in the tire because it will be replaced long before the moisture breaks down the tire. What we are worried about is the wheel and the bolts that hold the wheel together. The less moisture we can introduce to this area the better... I imagine if you're using a tire with a tube, it really wouldn't matter.
As for the pressure consistency, when I fly from an airport at sea level and land in Denver (let's say), the pressure outside of my tire has changed, there by changing the pressure reading inside of the tire. What kind of gas you use to fill the tire at sea level really doesn't matter...
Bottom line, if you have a tube in your tire, it really doesn't matter what you use. If you have tubeless, you may be better off going with nitrogen... IMHO!
 
0.02 cents FYI

Large planes: Nitrogen is used because its less of a fire hazard. It not only builds less heat (20% cooler), it's non-combustible, does not feed a fire like air/oxygen will. Not a big factor in a RV's small tires. (There was a loss of a B727 in Mexico because they used air to fill the tire, it blew in the wheel well and created a fatal fire.)

Race cars: With Nitrogen the tire temp stays more stable and therefore pressure is more stable.

The other benefits mentioned was drier than air/oxygen and less loss of pressure (leakage is less larger molecule). Also with out the oxidizer (oxygen) it will decay and corrode less.

Nitrogen is far better. NASCAR, NASA Space Shuttle and Jet Aircraft can't be wrong, but air is far more convenient. If I had Nitrogen source I'd use that. Nitrogen of course is not NO2 or Nitrous Oxide. NO2 would make bombs out of your tires.

Here is a site that is selling Nitrogen for tire filling: http://www.innovativebalancing.com/Nitrogen.htm

I remember my old 67 Camaro with steel rally rims got pretty corroded inside. Big fleet operators report tire life increases by 26% and improve fuel economy!

I'd say its more of a benefit for your car than your RV. A Nitrogen filling generator station start at about $5,000. You could go buy (rent) a steel tank and fill it with nitrogen at an industrial supply house that would last a long time.
 
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I have a 1941 9N Ford tractor the rear tires are filled with salt water and air.The tires were replaced in the mid-sixties after 25 years, I now have over 40 years on this set of tires no leaks no problems. So I am not going to worry about a very very small amount of water or oxygen in my small RV tubes.
 
gmcjetpilot said:
The other benefits mentioned was drier than air/oxygen and less loss of pressure (leakage is less larger molecule).
Click to expand...

If this were true, we'd all have pure nitrogen eventually: We fill up with air, the oxygen leaks out, we top up with air, that oxygen leaks out, etc. Proportion of oxygen gets closer to zero each time we fill up.
 
szicree said:
If this were true, we'd all have pure nitrogen eventually: We fill up with air, the oxygen leaks out, we top up with air, that oxygen leaks out, etc. Proportion of oxygen gets closer to zero each time we fill up.
Click to expand...

You're saying it's not true? When was the last time you ran a gas analysis on the contents of your tires?

Not hacking on you - but it's true - to a degree. You won't ever actually get to zero oxygen content, but you'll get lower than atmospheric. The mix will asymptotically approach a value of 9% given enough time (assuming 30 psi tire pressure). Remember, the rubber is not one-way - oxygen (and nitrogen, for that matter) can flow BOTH ways. It's the same principle as a reverse-osmosis water membrane. Higher pressure on one side drives the molecules through the membrane (tube/tire) but some molecules flow easier than others. At some point you reach a partial pressure balance where the partial pressure of oxygen in the tire equals that outside the tire, and diffusion is equal in both directions. The nitrogen inside the tire still has net flow out, since it's all under pressure it's partial pressure way exceeds atmospheric, so you'll keep adding more N2/O2 mix. Common rubber compounds used for tires will eventually produce a mix (given enough time) of 89% nitrogen, ~9% oxygen, and 2+% argon (tends to accumulate) with other trace gases.

If you have leaky tires the O2% will be higher, because you are introducing more oxygen in your "makeup" air, very airtight tires/tubes will be a lower oxygen percentage.

Aircraft (and the space shuttle) that inflate their tires with 100% nitrogen will still have a trace of oxygen in them, due to diffusion INTO the tire from outside air. The partial pressure of atmospheric oxygen is greater than the partial pressure of oxygen in the tire (zero) which results in a net diffusion inflow of oxygen (and argon, CO2, etc etc).
 
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Nice analysis. I never even thought about the inflow, but I wasn't saying it doesn't happen, just that the business about molecule size is a red herring with regard to our application.
 
If it makes you feel better, Size does not matter?

szicree said:
If this were true, we'd all have pure nitrogen eventually: We fill up with air, the oxygen leaks out, we top up with air, that oxygen leaks out, etc. Proportion of oxygen gets closer to zero each time we fill up.
Click to expand...
Well I guess what airguy said. On first blush it seems that your theory that tire/tube would distill the O out of the air might be correct. In theory that is how nitrogen generators work, a membrane.

Yes, I grant you molecule size is probably not the reason, as I said, my bad, but it sounded good to me at the time. However for fun, the size (Atomic radius) of AIR's top three elements are: Oxygen 60 pm; Nitrogen: 65 pm; Argon: 71 pm. I confess total ignorance and apathy. :rolleyes:

In the case of the tire filtering elements, the Helium, Neon and Hydrogen would be the first to pass out of the tire, if your theory or premise where true. There may be a small truth to it. Clearly Hydrogen and Helium are much smaller molecules, but how they are bonded to the 'air' compound and react with rubber may be another issue. I know one tire company sells "low leak" tubes. People report it keeps pressure better. So the 'AIR' DOES get through the rubber. What elements I don't know, probably as the complete compound minus the water and may be the CO2.


However it's a fact 'N' does lose less pressure over time by about a 30% to 40%, compared to "Air". Why, I'll leave that to the chemist but its a fact. I'll buy airguy's explanation, although when it comes to words like osmosis, my eyes glaze over.

The distilling property of rubber to turn "Air" compound into constituent gases is a mystery or probably non-existent. However commercial Nitrogen generators use a filter/membrane, taking regular AIR and extracting the N out, partly based on element size. An example membrane:


(Note: If you read how it works, it uses the size of very small micro tubes and inertia to separate air into its elements. Its a flow through process, unlike a tire where the gas is held under pressure in rubber envelope or membrane if you will. So size does matter? Isn't chemistry fun! - not)​

Does the air pressure in your tire change over time? Yes, but do different elements of the gas compound "Air" escape at different rates, changing the compound? Probably not or not in any significant ratio.

Not withstanding airguy's explanation which I have no reason to disagree with, lets say a tire did leak out by elements, a little; you'll never get to the point it becomes 99% nitrogen. If it where to work like that, you would likely end up with CO2 and water left, not Nitrogen. People do report their mounted tires end up full of water, not withstanding "Tractor-man" (with tires that have 3 inches of rubber). There is something there. Clearly the water is getting in but not getting out, and clearly air is leaking out.

BTW I am not saying Nitrogen or BUST, I use air. But the properties clearly have benefits. I guess a good second place would be DRY air.
 
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Tractor tires are filled with water intentionally, to add wieght to the wheels so they don't slip - many, if not most, tractors have the ability to put more power into the wheels than the wheels can transfer to the ground. Additional weight increases the amount of torque you can apply without spinning the wheels. Salt is commonly added to the water to keep it from freezing - trying to drive a tractor with frozen water in the tires will destroy the tires within seconds. Sometimes you will also see large circular weights attached to the axles just outboard of the main tires - same concept.

Most commercial nitrogen generators operate by adsorption (not ABSorption - there is a chemical difference) - they flow pressurized air through a bed of molecular sieve. The molecular sieve adsorbs the nitrogen preferentially onto it's surface, all other gases flow through. When the pressure is dumped on the chamber containing the seive, the nitrogen is released. For oxygen concentrators, the flow-through air is enriched in oxygen (as the nitrogen is stripped off) and is the product, while the nitrogen purge dumps to vent. For nitrogen generators, the oxygen-enriched flow-through gas is dumped to vent, and the nitrogen purge is the product. Same bed of molecular sieve, same process, slightly different plumbing.
 
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n468ac said:
How about using CO2 for tires??
Click to expand...

Not advised. Any moisture will combine with the carbon dioxide to form carbonic acid, pH of roughly 3.8 - will attack the rubber and the rims.
 
Underwater??

Greg, (re: reverse flow),
Is that why tires on submerged trucks and cars remain inflated for many years? We dove on shipwrecks in Truk lagoon a few years back and the tires on the trucks in the ship's holds still looked inflated.

Thanks,
 
Couldn't say for sure, I don't have any experience with that. It stands to reason that you're looking at two effects, though. First, higher ambient pressure underwater is going to slow the rate of leakage (lower delta-P) through the rubber, so they will stay inflated longer. Second, the trucks are going to be considerably more bouyant in water than in air - so you've got a lot less weight on those tires, allowing them to "look" inflated even at relatively low pressure.

Also - truck tires are usually inflated anywhere from 60 to 100 psi, so they will take longer to bleed down to something that looks "flat" than a standard 30 psi tire inflation, and new rubber most likely will last longer in any case.
 
Way off topic but...HELP

Since all you mechs where talking about nitrogen here....

Where can I buy a high pressure nirtrogen bottle service adapter?

The little 90 degree screw on adapter you attach to High Pressure bottles, its made to hand tighten only?

Need a couple fast.

Thanks
 
You need a high pressure nitrogen regulator, then you can adapt that to whatever hoses/adapters you like. I think HF carries a tire fill kit for this.
 
I

I have the bottle, hose and regulator. I just need that common screw on fitting to hook up to shrader fill valve.

Just can't seem to find one.
 
N2 Won't Support Combustion

I think "jarhead" had it right. Heavy equipment tires use N2 because they get hot and release combustible gasses which combines with the oxygen (if it was air) and explodes. On highway trucks can do the same if they end up underinflated then suddenly light off. Other things such as presence of oils, hydraulic etc, can also autoignite (rapid exothermic oxidation) as pressures are high also. Compression heating during landing in struts, and the like, with hydraulic accumulators etc. Reference diesel compression/combustion.

All the remainder of the N2 "reasons" and "benefits" sounds like an active marketing imagination to sell something, but that is just my opinion. :D

I will be using low leak tubes.
 
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Right on Bill

Let's put a end to this silly idea. The difference between a nitrogen atom and an oxygen atom is one proton and one electron (and maybe a neutron or two). Both form doublet molecules (N2 and O2). There can be NO difference in diffusibility of the two molecules through the rubber. If anything, nitrogen is the smaller of the two atoms. I think the only benefit is the non-oxidative nature of N2
 
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