Nitrogen in tires is a popular replacement for standard air. Nitrogen is all around us... the air we breathe is 78% nitrogen, 21% oxygen and the rest is small amounts of other gasses. When it comes to tire inflation, nitrogen has many advantages over oxygen. With nitrogen tire inflation, improvements can be noted in a vehicle's handling, fuel efficiency and tire life through better tire pressure retention, improved fuel economy and cooler running tire temperatures.
NASCAR teams use nitrogen because it allows them to more accurately predict tire pressure fluctuation. Nitrogen fluctuates with temperature change, but it does so less than when water vapor is present. In addition, higher nitrogen levels eliminate the explosive properties of oxygen (oxygen loses its explosive properties at around 9% or less).
I thought the idea was to use 100% N2 or as close as possible to 100%?
- It expands less when the tires get hot so you get more consistent tire shape/traction.
- It is also a bigger molecule and therefor less likely to seep out of the tire.
- I have never heard the argument about the explosive properties but that makes sense as well. However, because there is less Oxygen you will not see oxidization on the inside of the tire or wheel.
It is not that expensive but for daily use I would not bother unless it is just really convenient.
First, unless you totally evacuate your tires before filling them, you will only be able to reduce the amount of oxygen and water in them by approximately 2/3 (assuming you fill your tires to approximatley 30 psig = 2 atm) - your tires will be full of air when mounted on the wheels at 0 psig (14.7 psia) and it will take roughly two volumes of N2 to raise their pressure to 30 psig (45 psia). The bad actor in the air is the moisture, not the oxygen,as N2 and O2 both have the same coefficient of thermal expansion (as both behave as ideal gasses at the pressures and temperatures under consideration here). When air is compressed, water vapor in the air comes out of solution and forms liquid water. When it heats up again, in your tire the water vapor evaporates and undergoes a 300 fold change in volume (at STP the volume change is 1000 fold, but it is reduced to 300 fold by virtue of the fact that the air pressure in the tire is 3X that of atmospheric). By virtue of how nitrogen is produced (by air separation) it is inherently moisture free. The problem is you are starting with a tire that is already full of moist air. You can accomplish the same thing by making sure that the shop where you are filling your tires has a properly maintained dryer on their air line. As far as tire life is concerned, you could end up having an inner tire that is pristine while the outside of your tires is toast -- having been attacked by the oxygen in the air, and more importantly the UV in sunlight.
As far as the claim that oxygen is explosive -- this is pure hogwash. Oxygen needs a combustible material in order to undergo a reaction, so unless you fill your tires with a 33%O2/67%H2 mix, there is nothing to worry about. The amount of oxygen surrounding the outside of your tire is infinitely larger than the amount contained within it, and at exactly the same concentration.