I recently read a thread about filling tires with a mix of nitrogen and oxygen to maintain pressure and increase MPG. I cant find it now, anybody else read this or have any info on the subject?

 

Your question does not make sense. A mix of nitrogen and oxygen is just standard compressed air. Nitrogen makes up 78% of the air around us and oxygen makes up 21%. Some hardcore enthusiasts inflate the tires with 100% pure nitrogen (also called dry air). This is because there no oxygen or hydrogen present. This eliminates having any moisture inside the tire which could lead to internal rusting of the tire.

100% Nitrogen, or dry air, is an inert gas. It is not explosive (like helium) and doesn’t offer any weight reduction or MPG/KPL gains.

 

If you are one of the 85% of Americans who doesn't regularly check tire pressure, you need nitrogen.
We take in nitrogen with every breath. Air is composed of:

• 1% Water Vapor and Other Gases – Escapes up to 250 times faster than Nitrogen
• 21% Oxygen – Escapes 3-4 times faster than Nitrogen
• 78% Nitrogen – The largest molecule in air, dry, non-flammable.

Because of their large size, nitrogen molecules are the least permeable and stay in your tire longer.

It's not about the nitrogen. It's about reducing oxygen, water vapor and other gases.
By reducing the percentage of oxygen, water vapor and other gases in your tires from 22% to 7% or lower, your tires will maintain proper pressure longer than if you use “plain old air.” For example, with 95% nitrogen in your tires, they retain optimal pressure three to four times longer.

Proper tire pressure is a big deal.
Maintain it with nitrogen, and you'll see these three primary benefits:

• Increased Fuel Efficiency – Correct tire pressure keeps the manufacturer's recommended “contact patch” on the road. This lessens the rolling resistance and maximizes fuel efficiency.
• Longer Tire Life – When it comes in contact with other materials, oxygen causes oxidation. Oxidation can make rubber brittle and cause it to lose tensile strength. In addition, at high temperatures and pressures, oxygen reacts and damages inner tire liners and belt packages; nitrogen does not.
• Increased Safety – Under-inflated tires cause 90% of blowouts. Nitrogen provides more reliable pressure for reduced blowout potential.

Other benefits:

• Improved TPMS Performance – If you have a new car, you likely are plagued by a flashing light telling you your tire pressure is low. For example, one woman's light was going off every four to five weeks. After inflating with nitrogen, her light didn't reappear for 53 weeks!
• More Predictable Pressure Fluctuation – NASCAR teams use nitrogen so they can more accurately predict tire pressure fluctuation. Regular compressed air can fluctuate considerably when water vapor is present.
• Longer Rim Life – Rim rust caused by condensation from water vapor and other gases can get caught in valves and create slow leaks in tires. Nitrogen is completely dry, so it eliminates the potential for condensation.

Why not eliminate all oxygen and water vapor?
What's right for me – 95% or 98%?
Numerous studies have proven that nitrogen in tires reduces the volume of gases that escape more quickly and cause damaging oxidation. However, research also has shown that nitrogen purity beyond a certain point does not provide additional benefits. In fact, with a nitrogen purity above 93.4%? in passenger tires, oxygen actually begins to migrate back into the tire. You can get all the benefits of nitrogen with a purity level between 93-98%.

• Bridgestone/Firestone researchers say that 93-95% nitrogen is all you need.
• According to Ford Motor Co., there is no difference between 96% and 99% nitrogen purity.

Who Else Is Using Nitrogen?

• NASCAR - NASCAR teams use nitrogen because it allows them to more accurately predict tire pressure fluctuation. Nitrogen fluctuates with temperature change, but it does so less than when water vapor is present. In addition, higher nitrogen levels eliminate the explosive properties of oxygen (oxygen loses its explosive properties at around 9% or less) NASCAR uses bottled nitrogen for portability. The bottles are delivered to the track by Praxair.
• Commercial Airlines – The Federal Aviation Administration requires nitrogen in aircraft tires because it reduces the potential for water vapor freezing at high altitudes. In addition, airlines such as Boeing use nitrogen membranes or “OBIGGS” on-board inert gas generation systems (OBIGGS) to layer fuel tanks with inert nitrogen. Again, this reduces the potential for explosions. Just imagine if the Pinto had incorporated this technology 30 years ago, we'd still be driving them. Maybe…?
• U.S. Government – NASA and the U.S. military use nitrogen for many of the same reasons it used in commercial aircraft.
• Food Processors and Packagers – Oxygen hastens both the chemical breakdown and microbial spoilage of many foods. Think meat, potato chips, cookies, etc. To help preserve foods longer, processors and packagers often use modified atmosphere packaging (MAP) and controlled atmosphere packaging (CAP) that replaces some or all of the oxygen in the air inside the package with nitrogen.

How is nitrogen separated from other gases in air?
Membranes are the heart of any nitrogen system. Just like a tire, the membranes are permeable. When thousands of these permeable tubes are filled with air at high pressures, smaller molecules leak out while the larger nitrogen molecules travel through the tubes into a holding tank to fill your tires or for other uses.


http://getnitrogen.org

 

Thanks for the chemistry lesson....I knew there was more info out there. Now the question is where do I get that mix? and how do I know thats what I'm really getting if I have to pay for it? I certainly isnt going to damage anything so I want to try it.....

 

I was at Gateway tire a couple weeks ago and noticed they offer the Nitrogen fill. I asked about it and the rep told me that they have a machine which extracts most of the gasses out of the air leaving the Nitrogen. They charge $5 a tire for the service. Not a bad price considering the benefits.

 

A nitrogen fill for your daily driver's tires is a total waste of money. Usually one of 2 things happen to tires:

1). The tread lasts a long time, but the sidewall starts to rot out due to ozone exposure and heat cycling.

2). There's not enough time for the sidewall to rot because the tread is totally gone.

Dry air is important in many applications. Filling up your tires isn't one of them.

If you want clean and dry air, you can install a filter/dryer unit for your air compressor. My experience has been that either my tread wears out within 2 years or the sidewall starts to rot. I've never had tires rot from the inside out due to excessive moisture in the air I used.

 

Whats next?? Draw 20" of vaccume on the tire to remove the air and boil off the moisture (not that you can pull much vaccume on a mounted tire). Then fill with nitrogen??


Just make sure you have relativly dry/oil free air and you are good to go. Nitrogen is not going to hurt anything. But I don't really see the advantages on the street.

The main advantage is what happens to the air over temperature changes. On the track, I can see it. Only because the temperatures the tires run at are so high that on F1, the cars actually ride too low with the tires cold and can scrape. The cars do not achieve proper ride height until the tires are up to temp.

 

Dry air is a different animal. It is your standard air, but it is fully dehumidified to get all the water out of it. aka: DRY air. But it is still air with the nitrogen/oxygen/other mix.

 

Pure nitrogen fill is important in aviation, but for a street cars it is impractical and not needed. First, by just mounting the tire on the rim there will already be oxygen trapped inside the tire, and second, even if you ever did get all the trapped air out, you would only be able to top off with nitrogen, which is not all the common at car shops. So since air is already 78% nitrogen, that 21% oxygen, and 1% inert gases (such as argon) are not going to make any difference in a street car.

 

Tire pressure using regular air changes about 1 psi for every 10*F.

 

Nitrogen in passenger tires is probably more snake oil than anything else.

It is used in Nascar and in other forms of racing because nitrogen filled tires are less affected by differences in heat and humidity. Remember in racing adjustments are often made in very small increments like a 1/2 pound of psi at a time.

Nitrogen is used in long haul situations because it stays in the tire better than normal air. Over time less seeps out.

You may ask how do you get the normal air out of a tire when you want to fill the tire with only nitrogen? In chemistry class i think it is a process called purging. You fill the tire with nitrogen, then you let some out, and you fill it again with nitrogen and you let some out, and you fill it again with nitrogen. You do that several times, and each time the percentage of nitrogen in the tire goes up and the percentage of oxygen and other gases goes down. You get the picture? Pretty soon the amount of Nitrogen will approach 98%.

 

Actually, correct me if I'm wrong, but it seems that "purging" could be already happening on a lesser scale with normal air.
Example: The tire is filled with 78% nitrogen, 21% oxygen. Half the o2 leaks out, leaving about 90% nitrogen, 10% o2. Only about 10% of the total air leaked out, but it was almost all o2. Fill up what was lost with regular air again, and you get about 88% N, 12% o2.

Repeat a few times and you will soon be up into the 90% range.

 

Don't be so quick to downplay the role of snake oil.

Snake oil has been shown to condition the rubber, improve the seal of the tire to the rim, and provide an additional barrier to the nitrogen molecules from permeating the rubber, preventing their escape into the atmosphere.

You may have to milk a few hundred snakes the get the required quanity of oil (the "Enhydris chinensis" or Chinese Water Snake is best), but I think my tires are worth it.

Mark

 

Yes. In general, purging is how you fill a container with a known pure substance while at the same time removing an existing impurity from the container. The process I described is how tires are done.

BTW, if you see a tire with a green cap on the stem, it usually indicates nitrogen was used to fill it.

 

Well, I guess the bottom line (from my original question) is, do I want to spend $20 to find out for myself. I am thinking , YES, I do. If I have a 50 degree temp change one a days drive cross country in the summer, that could change the pressure as much as 5psi. I won't know if its really snake oil unless I sample it... .. . .

 

If my memory is correct, the ideal gas law (PV=nRT) does NOT have any values in it for gas specific constants. R is the gas constant (not depended upon the gas) and n is the number of moles of the gas in the tire (which will change depending on if the fill is N2 or air) which is also a constant (unless you have a tire fill system installed so you can add or remove air/N2 while rolling down the road!).

This leaves us with these variable: PV=T. It doesn't matter what gas you use, the pressure and temperature changes will not be any different.

I CAN see were keeping the O2 out of the tire WOULD be a good thing simply because of the oxidizing effect the O2 will have on the inside of the rubber. You can make a VERY nice rocket motor from a hollow rubber rod and liquid (or even compressed) O2! It does burn. Thankfully, it "burns" very slowly on the inside of our tires.

 

On a motocycle, particularly a racing bike(CBR, GSXR, YZR, etc.), there is a difference, however, a car with 4 wheels and 3,500 lbs., very minimal... Although, every little bit counts.

 

Thats why we are looking to do it for our car. Here in southern Az, 40 degree tempurature swings are normal. Thats close to 5 psi difference which is enough to worry about.

~Mark

 

I currently work at Costco Wholesale in the Tire Center. All of our new tire sale include Nitrogen. Great stuff! While in the Air Force we serviced Aircraft tires with Nitrogen Also. I think it should become a standard in the Auto Industry.

 

Costco Wholesale puts it in for free -easy job with the auto inflators, takes probably all of 20 to 30 minutes depending on the volume of nitrogen required in the tires.