Nitrogen Tire Inflation

What is the Correct Purity for Nitrogen Tire Inflation

There is quite a bit of confusion in the marketplace about what exactly is the proper purity level for a nitrogen filled tire.  It seems the market has moved toward 95% in a passenger tire, and we ship our equipment to meet this demand.  But  Get Nitrogen recommends >93.4% nitrogen, and Parker agrees. Why?  Well, its all about partial pressures, i.e. the pressure which the gas would have if it alone occupied the volume. 

We know the atmosphere is composed of 20.9% oxygen and 78.1% nitrogen.  So, at atmospheric pressure of 14.7 psia, the partial pressure of oxygen equates to 3.07 psi (.209 * 14.7).  Now, consider the 32 psig pressure in the tire, and that same 20.9% oxygen.  At 32 psig in the tire, the partial pressure of oxygen now equates to 9.76 psi (.209 * (32 + 14.7)).  This increased pressure inside the tire pushes the oxygen out, and oxygen is more than willing to leave.  But if you lower the oxygen content in the tire to 6.6% (thus increasing nitrogen to 94.4%), the partial pressure of oxygen is now 3.07 psi (.066 * (32+14.7)).  The partial pressure of oxygen inside the tire is balanced with the partial pressure of oxygen in the atmoshpere, and it will remain in the tire longer. 

So what happens when you increase the purity above 93.4% in a 32 psig tire?  Well, believe it or not, oxgen will begin to leak back into the tire over time.  NHTSA said the same at this year's ITEC, as shown on the last slide of this presentation. 

Download ITEC08PAPER18C1

Are Nitrogen Filled Tires a Scam

Unfortunately, Google tends to auto populate Nitrogen Tire Inflation Scam.  I clicked on a few of the links, and was a bit surprised by the wide variety of people that think nitrogen filled tires are a scam.  There is such a misunderstanding that I thought it may be worthwhile to discuss exactly how benefits are derived from nitrogen inflation.

1.  Nitrogen is not a magic gas.  Nitrogen, per se, does not provide the benefit.  Benefits are yielded from the better pressure retention that nitrogen provides.  Better tire pressure provides better gas mileage and longer tire life.  NHTSA has said so in the past (search this blog for NHTSA if you don't believe me).  Not to mention that proper inflation is safer. 

2.  A tire regularly topped off with air will see performance similar to a nitrogen filled tire.  This is true, assuming the air is dry.  That is a big assumption, because the majority of automotive shops do not have a dryer, or one that works properly.  Even those that do have a dryer still leave a significant amount of moisture (vapor) in the compressed air.  Nitrogen is ultra-dry, so it fluctuates less with temperature buildup during driving.  Bridgestone even said so here.  

3. Nitrogen is non-reactive.  The majority of tire rubber breakdown occurs as oxygen permeates through the sidewall of the tire.  A tire filled with nitrogen effectively halts the aging of the tire.  This means your tire retains its strength throughout the life of the tire.   

4. Maximizing your fuel economy and tire life ARE good for the environment.  So, if these can be accomplished with better pressure retention, then nitrogen filled tires are a green offering.

5. As much as we like to pretend we check our tire pressure regularly, the simple fact is that we dont.  The Rubber Manufacturer's Association (Tire Trade Group) has said that 80% of people don't properly check tire pressure.  Nitrogen, while not eliminating that issue, helps to mitigate its damage. 

6. Air is already 79.1% nitrogen, how is increasing it to 93.5% going to make that much of a difference.  It is important to remember that 79.1% nitrogen is laden with water vapor.  During a typical nitrogen inflation service, that "bad" nitrogen is removed, and replaced with clean, dry nitrogen.  No liquid water to cause rusting.  No oil.  No water vapor to condense out and cause pressure fluctuations.  No pipescale or rust to clog your valve stems.  A benefit for your tires. 

Thats it.  A pro-nitrogen tire guy saying that Nitrogen isnt a magic gas?  That nitrogen isnt the end all to proper tire maintenance.  I have always been of the belief that if the benefits are explained properly, people usually don't have a problem understanding the value of nitrogen.

Why Filling a Tire With Nitrogen is Beneficial - An Unbiased Viewpoint

Modern Tire Dealer, a very reputable tire publication, recently ran this article that explains why nitrogen tire inflation is beneficial to the driver.  The research was conducted by Dr. John Daws, prinicipal at Daws Engineering in Phoenix, Arizona.  This summarizes a lot of the information that we have been touting here on our blog.  This is actually powerful information, considering tire dealers have quite a bit to lose (increased sales) through the increased tire life promoted by filling with nitrogen. 

Tire Nitrogen Inflation Testimonial Video for Fleets

In 2005, Parker Hannifin interviewed some nitrogen filled tire users and put together a video testimonial.  Note the benefits that these users have seen, and how truly impressive they are.  While this video focused on commercial truck users, it is important to note that ordinary, everyday drivers should see similar results.  Commercial trucks are steadfast about tire maintenance, and more attentive than the average driver.  They are seeing these benefits even though their tires were maintained regularly with air.

And remember, the user that states he saw a 0.1 mpg improvement is discussing trucks that typically get around 5.5 mpg (a 2% improvement).

You can view the video here:  Nitrogen Tire Inflation Testimonial Video

Rubber News: "Nitrogen's Time Has Come as a Gas Used to Inflate Tires"

Rubber News is a publication that caters to the tire industry (wow,  who knew rubber was such an important component in the tire making process).  There was an article in their January 11th 2010 edition that touts nitrogen as a safety and performance upgrade.  This is one of the best articles I have seen about nitrogen.  It does not overstate the benefits and warns against doing so.  But the article points out that there are tangible benefits, and that the tire makers should be capitalizing on these benefits.