Mechanics Corner - Nov10
“Nitrogen vs. Compressed Air”
By Mike Godwin
There is a shift in the tire market these days from regular compressed air to pure nitrogen. The question becomes; is filling the tries under my Mustang worth the extra cost? Or is this a gimmick by the tire sales person to get a extra twenty dollars out of the owners pocket?
As we look at this idea of Nitrogen being superior to regular Compressed Air, there are a couple of myths that need to be looked into. Number one is that the Compressed Air modules are smaller than Nitrogen modules. The theory is that the small Compressed Air module escapes from the rubber in the tire while the larger Nitrogen module is trapped inside by the rubber in the tire. There are not enough methods to say, “FALSE!” As will be revealed later in this article, 79 per cent of every breath you take is Nitrogen. Nitrogen is a neutral gas and will not increase in pressure. Another FALSE! Nitrogen is subject to thermal changes as proven by the fact that a product called Liquid Nitrogen used for cooling in many commercial applications is compressed Nitrogen. Compressed to a stage that it becomes a liquid, the inert gas becomes a very cold liquid that requires special handling.
So what is the air we breathe really made up of? Start with 79% Nitrogen gas, followed closely by what keeps us going - 20% Oxygen, then a sparse 0.934% of Argon, and just to poison your system, 0.033% of Carbon Dioxide.
Throw in that deep breath, some other gases that are just hanging around and only measured in Parts Per Million (PPM). These include Neon, Helium, Sulfur Dioxide, Hydrogen Methane, Nitrous Oxide, Xeon, Nitrogen Dioxide and our all time favorite, Carbon Monoxide.
Wow! That is what we are taking in with each breath no matter what our tires are filled with. Of course, if we are breathing this, so is our engine running on the same mixture. Makes one say, to heck with the tires, give me air for me and my poor engine also.
Now to dispel with the idea of if filling our tires with Nitrogen, was such a great idea. One that is frequently heard is that this concept comes to the street straight from the racing community. The theory is, if the big buck racing guys are using this technology, then it is good for the street car also. Wish I was one of the Myth Busters right now because this one is BUSTED again. The idea of filling the pneumatic tire with Nitrogen is very old and from the Aviation Industry. History gives credit to a gentleman from Austria that was working for a French firm of hitting upon the idea of filling a tire with Nitrogen to prevent freezing at altitude. That is a most significant observation, as it allowed pneumatic tires to be developed for the Aviation Industry.
To understand the problems of moisture in a tire, one must understand the principles of compression. A compressor can take in a gas and increase the pressure in a number of methods. A single stage compressor performs this function in one operation. Gas in to increased pressure with a single stroke. Two stage is better as it performs the same operation in two separate stages. First, gas in is increased in pressure a little, then a second stage compresses the gas once more.
The significant advantage of this two-stage process is less moisture no matter what gas is being compressed. Look back at the fact that the atmospheric air has the two gases required to form water. Yes my scientific wonders, H2O is the composition of water. Go figure most gas stations and tire shops are using single stage compressors. Result: a little moisture is sent down the line to your tire every time you add air from one of these sources.
So what are you to do? Let your wallet be your guide, as paying the extra cost per wheel to fill a tire with compressed Nitrogen is not going to net you a great benefit. Maybe a little piece of mind, but fewer flats or loss of inflation pressure are not going to be apparent. As MNW member Scott Robinson recently pointed out at the monthly meeting, nothing beats a tire gauge and a frequent check of your tire pressure, including the spare tire!