Issue link: http://www.e-digitaleditions.com/i/408388
November / December 2014 14 TECHNICAL EDITOR By Karl Wilen In the last 10 years the popularity of using pure nitrogen in tires instead of standard air has grown. While in theory it is a good idea, the end result isn't exactly perfect either. Tire stores have found yet another profit center to make a buck, but it might not be the right thing for your tires. You might have noticed the green valve stem caps when you are at a car show looking at cars, or maybe in the parking lot at work, etc. Green valve stem caps are installed to let the person or technician know that nitrogen has been filled into the tires rather than standard air. The air you breath is the same air that is inflated into your tires through a standard air compressor. When people think of air, they think we are breathing oxygen. Well that is true, but only partially. The mixture of air is 78% nitrogen, 21% oxygen, and the remaining 1% is a various mixture. That's right….78% nitrogen. Now on a nitrogen tire fill, it is accepted that a 93% nitrogen to air ratio is an acceptable fill. After all, it is nearly impossible to get all of the air out of the tire when you go to fill with nitrogen (you can't suck a tire into a vacuum as it is not good for the tire). So you have a 15% increase in nitrogen mixture over standard air. There have been many reasons nitrogen has been pushed in recent years, much of it is hogwash spouted off by shops trying to increase their profit margins (just refer back to the air mixtures we just talked about), but some of it has some value. The #1 thing you hear people spout off about nitrogen is that the molecules are larger, so it will not leak out of tires like regular air does. Well, yes that is true, but if your tire leaks air (it will naturally do so due to permeation of the rubber, let alone other leaks), it will leak nitrogen as well, only reducing leakage by about 1/3rd when compared to standard air. Standard inflation loss (assuming no other leaks) due to permeation through the rubber is accepted to be 1psi per month, so with nitrogen you might have as little as .6 psi loss per month. So while this will help keep your tires inflated a little longer, they will still lose inflation. You still have to check your tire pressures when they are filled with nitrogen on a regular basis, that doesn't change! One advantage of Nitrogen is that it is a dry gas that does not support moisture which can cause corrosion inside your wheels, the tire bead, or the belts in the tire. This moisture can come naturally from the standard air filled in the tires. Some air compressors, like those 25 cent ones at gas stations may not have the proper dryer installed on the air line to prevent moisture Y ou still have to check your tire pressures when they are filled with nitrogen on a regular basis, that does not change! Full of Hot Air NITROGEN VS. AIR