Nitrogen Instead of Air in Tires

Two gases make up 99% of Earth's atmosphere: Nitrogen and Oxygen. Atmospheric composition is relatively stable up to about 80 kilometers above the surface. The remaining 1% is mostly inert Argon (0.93%) plus tiny quantities of other trace gases. Carbon dioxide is present only in small amounts (0.039%). Variable components include water vapor, particulate matter and ozone. Nitrogen is unreactive at normal temperatures.

Filling automobile tires with Nitrogen may make you feel emotionally better, but does nothing for the tires.

Atmospheric composition:

Nitrogen 78.08%
Oxygen 20.94%
CO2 0.03%
Argon 0.093%
Neon 0.0018%
Helium 0.0005%
Krypton trace
Xenon trace
Ozone 0.00006%
Hydrogen 0.00005%

 

Using nitrogen is supposed to help prevent leaking due to the molecule size (so I hear), plus it's not supposed to heat up as quickly in the tire as regular air. Costco will fill your tires with nitrogen, but IIRC it's $10 per tire.

FWIW, it's not something that's on my "gotta do" list of things to change on my Prius.

 

Inflating tires to the correct pressure will do far more to improve MPG and tire life than using nitrogen. Forget the silliness of whether nitrogen will help. Inflate the damn tires properly!

 

Yes, Costco is the one for that.

If you buy tires there (they can get just about any tire), they fill them for free...and continue to do so as many times as you like.

I disagree with the statement that just filling the tires to the correct pressure is better then Nitrogen, as Nitrogen is much more stable and the tire pressure does not have the significant fluctuations as it does with standard air. This would seem to lead to getting both a more consistent ride...and more consistent MPG.

The only problem is that it is a pain to only be able to go to Costco for it...so chances are until I have to get new tires, this is something that is too much trouble for too little gain.

 

This is the best post I found on the subject, and it sums up my opinion. I found it in the thread linked here.

 

As I see it the one BIG problem with filling your tires with nitrogen is that if you're being chased by bad guys and end up going in the water, you won't be able to out-smart SPECTA like James Bond did in that movie.

 

One advantage to N2 in aircraft tires is that Nitrogen will not support fire, which is a risk at the speeds used for landing. This is also true of race cars, which are in much greater danger of setting tires on fire - kind of hard to do in a Prius with traction control.

I suppose much of the interest in using Nitrogen in tires comes from the use of dry Nitrogen in optics and other devices where water vapor will condense and cause fogging. We consumers tend to make funny leaps of logic: if it's good in telescopes, it must be good in tires.

Tom

 

I always thought filling them with Helium would be best for mileage.

 

<div class='quotetop'>QUOTE(qbee42 @ May 4 2006, 09:28 PM) [snapback]249990[/snapback]</div>

What do they use Nitrogen for in optics (telescopes, specifically)?

 

<div class='quotetop'>QUOTE(Tempus @ May 4 2006, 10:28 PM) [snapback]250025[/snapback]</div>

Make the car lighter, and then the NAV Lady would have a high, squeaky voice.

Tom

<div class='quotetop'>QUOTE(Betelgeuse @ May 4 2006, 10:44 PM) [snapback]250036[/snapback]</div>

To drive out moisture. It is used to fill the space between lens elements. When normal air is used, water can condense and fog the inside of the optics. Dry Nitrogen is used to displace the air and keep out moisture. Obviously, this is used only on refractor systems, as most reflector designs are open.

Tom

 

Don't they use Argon to fill those Low-E windows?

Maybe that's what we need.

 

If air is 78% nitrogen am I not already putting 78% nitrogen in the tire?

 

Ideally, you should fill them with a vacuum.
Vacuum has no mass and, therefore uses less energy when accellerating.
It won't build up heat or oxydize your tires or rims.

 

I tried filling them with a vacuum, but I couldn't get the beads to seat. Maybe I should try tubes?

Tom

 

<div class='quotetop'>QUOTE(YBLee @ May 4 2006, 03:26 PM) [snapback]249915[/snapback]</div>

Here's what the American Chemical Society thinks (This is from their Chemical & Engineering newletter):

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C&E News, October 25, 2004:

Pressure rising for nitrogen in tires

The idea that filling your car tires with pure, dry nitrogen is much better for them than using plain old air is getting increased attention. As pointed out by reader James R. Jeitler of North Idaho College and others, tire outlets around the country are offering to replace the air in your car tires with nitrogen for about $5.00 each.

There are a number of rather lofty claims being made about nitrogen in tires. These include that pressure inside nitrogen-filled tires does not rise or fall with temperature changes, that nitrogen leaks out of tires much more slowly than air because the molecules are bigger, that nitrogen is an inert gas, and that moisture and oxygen in air cause corrosion that shortens tire life by 25 to 30%.

Some credence to the idea seems to come from the use of nitrogen in tires of race cars, jet aircraft, and some heavy trucks. Although tire-pressure advantages are mentioned for these vehicles, another reason cited here is that nitrogen will not contribute to combustion in case of a fire around the tires, as the oxygen in air would.

Nitrogen generators are available for filling tires with the gas. At least one company recommends using nitrogen that is at least 98% pure in your tires to prevent rim corrosion and road failures. The nitrogen is generated using a semipermeable membrane system that allows oxygen, carbon dioxide, and water vapor to pass through, concentrating the nitrogen. This concentrated nitrogen can then be put into your tires.

Despite the claims of industry studies demonstrating that these assertions are valid, much of what is promised seems to fly in the face of logic. Reading the literature handed out by one nitrogen promoter, Jeitler said, "I was interested to find out that nitrogen no longer obeys the gas laws that we teach in general chemistry classes, much less Graham's law of effusion."
---

C&E News, November 14, 2005:

Nitrogen claims tiresome

The claims of significant benefits from filling your car's tires with nitrogen instead of plain old air continue to fill the airways. Two alert readers have sent us a short piece aired recently by the local NBC affiliate in Philadelphia on Costco Tire Service Centers advocating nitrogen fill-ups for tires.

Although Newscripts has been covering the nitrogen story for more than a year (C&EN, Oct, 25, 2004, page 88 ), it remains intriguing what people are saying about this practice.

“Nitrogen is four times heavier than oxygen, so those molecules are bigger and won't be able to escape through the small leaks in your tires,†claims a representative of the American Automobile Association with a straight face.

The nitrogen use yields several supposed benefits. Your tires stay inflated longer because “nitrogen is very dry,†and there will be less pressure fluctuation than you get with oxygen, it is claimed. And the moisture in oxygen not only expands and contracts, it can also prematurely corrode your tires, NBC warns.

While water vapor might build up in a tire from filling it with moisture-laden air, the water should escape from tiny leaks just like any gas. Also, of the many tires that this writer has had to buy for many cars over the years, not one has ever had to be replaced because of corrosion of the tire from the inside out.
----

 

Why are they comparing N2 with O2? We would never fill tires with pure oxygen, so the comparison should be N2 against the usual air molecule.

An air molecule should be much larger than either an O2 or N2 molecule: air is a mixture of both, plus the odd other gases.

The air mixture cannot break down under the tire's normal operating conditions; if it did, we'd have free oxygen, nitrogen, and perhaps a few free radicals floating around inside the tire.

So if the standard air molecule is larger than an N2 molecule, it's going to stay inside the tire more readily. Both gases are still going to change pressure with temperature, as others have said.

And this can't be some new-millennium discovery: nitrogen has been available for decades, and I'm sure someone tried this years ago and abandoned it as being of no additional value.

 

<div class='quotetop'>QUOTE(Rick Auricchio @ May 5 2006, 12:51 PM) [snapback]250282[/snapback]</div>

You are correct when you state air is a mixture, but air is not a molecule. There is no such thing as a molecule of air. Thus, air is not bigger than oxygen or nitorogen it is just a mixture of those two and some other gases. The biggest molecule is just which ever component is largest, you don't physically combine them.

 

<div class='quotetop'>QUOTE(Rick Auricchio @ May 5 2006, 12:51 PM) [snapback]250282[/snapback]</div>

We should fill the tires with a mixture of two moles of hydrogen to each mole of oxygen. That way, when combustion does occur, we will get a good bang and a little water vapor. :blink:

Tom