One of the topics that come up often in the RV community is the use of dry nitrogen in tires. That is, using compressed dry nitrogen instead of regular air. Is there an advantage to this that warrants the cost? I think first we have to understand why, and if, nitrogen works better than normal compressed air in an RV tire application.
Normal dry air contains mainly nitrogen to begin with, in fact about 78% by volume. The balance is around 21% oxygen and 1% argon and mixed miscellaneous gases. Moisture, however, is usually present in this air after it has been compressed. For that purpose, air compressors generally employ a dryer in order to reduce this. But, in normal service station tire fill-ups, you can expect an additional product, vapor or humidity, 1 to 5%. The later being the worst case scenario.
Though we can not see them, the air is made up of molecules. Nitrogen molecules are much larger than those of oxygen. This, in its self, serves as a benefit when used to inflate a tire. More on this later.
Over 99% of tires in use today are tubeless. Tubeless tires expose the rim to the gases that support the tire. Over time these gases and vapor can oxidize or rust the rim surfaces. While such internal damage is slight given the wheel’s life span, it can produce micro metallic pieces or dust. There is a remote possibility that this debris may eventually end up in the tire valve seat. This could occur when air is being expelled such as the quick shot of a tire gauge check or if lowering of pressure is required. I addition, moist air causes oxidization and degradation of the rubber inside the tire. This degradation, however, is slow enough probably to never affect the life of an RV tire.
Have you ever wondered why your tires occasionally need a little air top up? Where does that air go, anyway? It is normal and actually passes through the tire body itself. The smaller molecules of the oxygen make there way out far quicker than the larger nitrogen molecules. Now this does not leak at a measureable rate. Pressure reductions are very subtle, resulting in the need to top up every month or so depending on the tire size, pressure and environment. Using 100% dry nitrogen reduces this leak rate equal to only about one third of that of regular air. This, of course, reduces the need to top up the tire pressure substantially.
Nitrogen also offers the added safety benefit of not supporting combustion. For this reason most aircraft tires are nitrogen filled. This was put in place some years ago following a landing gear fire that was amplified by the oxygen contained in an air filled tire. It contributed to the fatal accident that caused the death of 167 people on board. This feature however, offers little benefit to an RV tire application.
Dry nitrogen does not expand at the same rate of the gases of that of regular air, therefore may tend to increase pressure at a lesser heat to pressure ratio. This in itself, may contribute to a better ride throughout the driving temperature cycle. Additionally, the lack of moisture, or water vapor keeps the gases less conductive to heat transmission, thereby running slightly cooler. A fractional more consistent pressure may be experienced which could result in a smoother, or softer, ride.
Nitrogen is much lighter than air. This would reduce the overall weight to an once or so. Definitely there is no advantage found here for an RV.
Nitrogen fills generally cost about $10 per tire. Costco, for one, supplies a free fill, if requested, with any new tires that are purchased and installed at selected stores. Oh, and yes, you can top up nitrogen filled tires with straight air if needed and no nitrogen is available.
So, is going to nitrogen worth the trouble and cost? In my book it may be very questionable for an RV application. The benefits appear very slim. The reduced tire pressure top up may be well worth it for a commercial unit that runs high mileage twelve months a year. This, however, may offer little change to the short seasonal use of the average recreational vehicle.
Bragging rights can be exercised however. When that guy with the Hemi pulls up beside you at a light, you can say “Nice Hemi, I’m running nitro”.
Okay, I know there are many nitrogen users out there. Let’s hear your take.
Just Airing My Thoughts – Lug_Nut – Peter Mercer