Nitrogen in Tires

I am very curious about this one too. The only difference I know is that nitrogen will leak faster than air. There were many cases that we would use nitrogen in place of air for pressure decay testing, which gives you a better chance of detecting smaller leaks. What is the real benefit of Nitrogen in your tires?

The last time I fitted new tyres the shop offered to fill it with nitrogen. (no additional charges).

Up to now I did not experience any bad effects.

My gas consumption (3 litre Camry) may have improved slightly but I don't always record the difference between city and open road driving. The tyres feel cooler after a long drive but it may be imagination. As for mileage per tyre - Unable to reply yet.

My honest response would be - small effect if any.

I do not consider it a hoax because I did not spend any additional money.

It may however give the co an edge on their competitors but that cannot be seen as immoral.

"Since air is about 70% nitrogen anyway and the molecular weight of Oxygen and Nitrogen are so close."

What percentage of the compressed air in tyres is pure oxygen? I would assume that there are other elements hanging around, especially if you live in a 3rd world country. I would make the assumption since the air is pumped via compressor and is not pure oxygen (very flamable), there might be a larger weight difference between Nitrogen and Compressed Poluted Air. Or is that 70% you mentioned true regardless of other environmental contaminants? Hmm....

Well you could ask the USAF they put nitrogen in all acft tires. However nitrogen molecules are larger then oxygen and nitrogen does not typically support mosture like oxygen. No mosture less heat transfer maybe, less heat in the rubber maybe less friction. Anyone else want to take a shot at this.

Mike

Article says Nitrogen leaks SLOOOOOOOOOOOOOOOWER than Oxygen, not faster, as stated above. What are the facts? Is the article wrong?

http://www.straightdope.com/columns/070216.html

Excerpt from article:

Most tires are filled with compressed air, which when dry consists of about 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases by volume. Water vapor (humidity) can make up as much as 5 percent of the volume of air under worst-case conditions. Filling your tires with nitrogen mainly does two things: it eliminates moisture, and it replaces skinny oxygen molecules with fat nitrogen molecules, reducing the rate at which compressed gas diffuses through porous tire walls. That means, theoretically at least, that a tire filled with nitrogen retains optimal pressure longer, leading to more uniform tire wear and better gas mileage. The commonly quoted figure is that tires inflated to 32 psi get 3 percent better mileage than at 24 psi.

Ken

I believe the article is wrong. Nitrogen molecules are slightly smaller than oxygen, so pure nitrogen should diffuse very slightly faster than air.

To clear up some other misconceptions:

Nitrogen should hold about the same amount of water as air. The nitrogen is dry because of the way that it is obtained, generated and processed. Air can be dried to the same levels.

Oxygen is not flammable or explosive. It is necessary for combustion.

Tad

Correct me if I am wrong, but when comparing nitrogen and oxygen... they're not molecules technically? And it does look like the atomic radius of oxygen is less than nitrogen... making Nitrogen the larger atom?

I agreet that less moisture would be a good thing. As far as tires losing air slower... That might be worth it if you loss 1 psi a week... but practically... i don't think it's worth it.

Nitrogen and oxygen exist as diatomic molecules at ambient pressures and temperatures (N2 and O2).

I tried to find a molecular size for the molecules, but did not see one in a quick search. The real answer would be experimental results showing diffusion rates, which I did not see either. Radius is pretty theoretical, and experiments give the true answer.

So I can't say for sure that N2 should diffuse faster than O2. However, the common equation for diffusion is that the diffusion rates of two gases are inversely proportional to the square roots of their molecular weights. Using this, N2 would diffuse 7% faster than O2. This may be an oversimplification, as I said.

Given that air is mostly N2 anyway, the main mechanism for pressure loss in tires is not diffusion, and the difference in diffusion is minimal, I would say using N2 to reduce pressure loss is not a valid argument.

Tad

In pressure decay testing of valves (and pressurizing and dunking the valves) I used to manufacture, we have found leaks in valves utilizing Nitrogen, when "Plant Air" found none. Of course, Helium proved to be the best, but MOST costly medium for leak detection.

My understanding of the truckers' advantage comes from exetended life of the of the internal tire structure due to reduced oxidation and lower operating temperatures.

Two reasons for using dry nitrogen. First, racing teams ise it because it is dry. Water in a racing tire turns to steam when the tire gets hot and causes a large pressure change. Not much of an issue for street driving. Second, the electronics in run-flat tire pressure sensors can be destroyed by corrosion if water condenses on them. Dry nitrogen is inexpensive and works. Dry air would work also, but air from a compressor is notoriously wet.

Back to the original question, will it increase gas mileage? NO!

I also have purchased new tires from a major company in Northern California. They filled the tires with nitrogen -- and of course charged me a small amount.

I asked why do I have to pay for this when air has served me well for over 50 years of driving? The response was "Air contains water which causes corrosion of the alloy wheels on new cars".

My truck has steel wheels and there is no visible problem from the air that was used since new 1987. What's with this? Answer "it will help them too" -- So for a couple of bucks I said do it, just get the job done so I can go home.

I know some of my racing buddies, and even a couple of my rock crawling friends, use nitrogen too. I understand that it helps keep a more stable tire pressure and even (minimally) holds lower heat. But i cant really see the benefits of everyday driving, unless its long distance.

Oxygen and water can oxidize (rust) your steel wheels. I know; mine did in just 3 years of Ohio winters. Dry nitrogen won't do this.

I am a Firefighter and we use Nitrogen to pressurize our Dry Chemical Fire Extinquishers for 2 reasons...both have to do with the mositure content in compressed air...1. To prevent corrosion on the inside of the extinquisher,over time rust could flake off and plug the nozzle 2...The mositure could and does cake the Dry Chemical inside making a hard clump that could also plug the nozzle. Removing these 2 negitive factors saves lives because it minimizes an Extinquisher failure and saves money because any corrosion inside means you have to replace the Extinquisher with a new one........Rescue

So, to recap then: Its the moisture of compressed air that nitrogen avoids which prevents corrosion on steel wheels and steam formation in racing tires. Now I have to say that in my 50 + years of car ownership I have never had a wheel rust off from the inside. Granted there was surface rust on some (but not on all) but really didn't impact the integrity of the wheel. I believe that the added mileage claim is based on more stable air pressure (which is in question) but could be obtained with regular maintenance with air.

Thanks all of you for your input.

Yeah, I agree with that. The moisture elimination thing helps reduce the huge pressure increase that will occur when 100C is reached, essential in race cars. Not even air line dryers will not take out all the moisture.

Also, Nitrogen might be lighter than Oxygen but it is much bigger helping prevent leakage.

http://www.straightdope.com/columns/070216.html

http://en.wikipedia.org/wiki/Nitrogen

Two words come to my mind.

1. GIMMICK AND

2. HOAX JUST LIKE YK-2000 where lots of companies spent millions of dollars foolishly and on the other hands many more seasonal companies sprung up, like coal gasification processes in late 70 and early 80s) and made lots of money.

No need to change your tire from air to Nitrogen. Ok, if you consider 3% mileage gain and if you are driving a car with 30 Miles/gal (like I do, A Focus SE) so what did I gain and I will also be paying higher price for Nitrogen as it shall not come free like you get from God's creation, Air. Like some sage said, air is free but without it you can't ride the car (Henry Ford?)

Regards;

Nadeem Butt

07022007

The benefits of nitrogen in tires are more pronounced for large aircraft than for most cars because of the higher pressures (typically 10 - 15 bar). I have read incident reports on aircraft having tires serviced with air, and then taking off with a dragging brake or loading their brakes excessively from a "hot" (higher than recommended touchdown speed) landing. Such tremendous heat buildup in the brakes typically migrates to the tire-seating areas of the wheel rim. The result in one case I'm familiar with was ignition of the tire interior, under that high pressure air (= oxygen-enriched) environment, after the landing gear was retracted, which placed the overheated wheel assembly in close proximity to hydraulic lines and other critical components. The resulting explosion caused damage that almost led to aircraft loss. When serviced properly (with dry nitrogen) tire and wheel may last longer, and the consequences of an overheated wheel are usually less severe, more likely to consist of blowing out the fusible safety plug in the wheel and a ruined tire or, at worst, following a high-brake-energy landing roll, a less aggressive burning of the tire area, perhaps from a brake fire already in progress.

I would like to emphasize one point. Most people currently use standard radial tires. Some moisture in the fill gas won't cause significant damage. Auto manufacturers are delivering select vehicles with run-flat tires (no spare). Run flat tires require a monitoring system to notify the driver if he looses air pressure. The electronic monitoring system mounts inside the tire and can be damaged by condensed water vapor. I personally hope the run-flat tire craze goes away, but if you have them on a vehicle, I suggest you fill your tires with dry gas.

I have read, with interest, the various, often contradictory, replies re nitrogen, oxygen and "air" in tires, (balloons, and permeability thru "rubber").

The units of the following data are: 10 (exp -7)cm (exp 3)/ cm (exp 2)/ cm/ sec

Nitrogen oxygen air

Butyl rubber 0.025 0.098 0.02 Sorry! I can't keep the data columns when I "edit". No N2 data for PU rubber

urethane rubber 0.080 0.05

natural rubber 0.48 1.30 0.67

Hope that helps!

I talked with the guys down the road who built the race car some of you may remember that Kenny Rogers drove in the movie "Six Pack" and after they heard what most of you had to say on the subject, they asked me to reply and tell you guys it's just another Government Cover-Up,,,,,,,,lol