Air vs Nitrogen In Your Tires- The Last Thread Ever

Whether at car shows, meets, or forums, the conversation of filling your tires with air vs nitrogen always seems to come up. So, I decided to make the last thread ever about filling your tires with either. Let's jump right in.

While you're reading this, you're breathing in the same ‘air’ that people normally fill their tires with. For this article’s purpose, we’ll call it ‘air’. That air is composed of:

Nitrogen (N2): 78.084%
Oxygen (O2): 20.9476%
Argon (Ar): 0.934%
Carbon Dioxide (CO2): 0.0314%

As you can see, the air that we breathe is made up of numerous gases, including water vapor. The term ‘humidity’ generally refers to the amount of ‘water vapor’ in the atmosphere. Each atmospheric gas has its own vapor pressure (the measure of the number of molecules present at a given temperature). The vapor pressure of water, as you may have guessed, measures the amount of water vapor in the air. Now that this basic knowledge is in the open, we’ll come back to it later.

For starters, nitrogen is less likely to wander through tire rubber than oxygen is. Why is this? Well, tires only appear solid. Microscopically, tires are a bunch of stringy, fishnet-looking molecules. This causes air to escape slowly over time. Nitrogen doesn't expand/contract nearly as much as air, which means that your tire pressures will remain more stable on the long term. This is because nitrogen is much more stable than air. Racers figured out pretty quickly that tires filled with nitrogen rather than air exhibit less pressure change with temperature fluctuations. That means more consistent tire pressure during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important. And though we may not be race-car drivers, we know that a boosted k-series is a race-car for sure.
Right Adm_rsx? :wavey:

Passenger cars can also benefit from the more stable pressures. But there's more – remember the humidity or ‘water vapor’ we spoke about earlier? Well, humidity is a bad thing to have inside a tire. Water, present as a vapor or even a liquid in a tire, causes more of a pressure change with temperature fluctuations than dry air does. It also promotes corrosion of steel or aluminum rims. Now you may be asking yourself, “how is water relevant to a nitrogen discussion?” Any system that delivers pure nitrogen is also going to deliver dry nitrogen. Filling tires with nitrogen involves filling and purging several times in succession, consecutively diluting the concentration of oxygen in the tire. This will also remove any water.

The next question that may arise at this point is, “how can I purge tires of air and fill with nitrogen?” Well, that is a simple answer that you may, unfortunately, be unable to do on your current wheel setup. You’ll need a wheel that has dual valve stem ports. You may have seen then on many wheels over time, or possibly overlooked them because it is such a small visual difference compared to single valve stem port wheels. Check it out:

Enkei RPF-1 Single Valve Port
http://imageshack.us/a/img805/4648/e...erwheelsri.jpg

Enkei NT03 Dual Valve Ports
http://imageshack.us/a/img821/4808/enkeint03.jpg

The purpose of the dual valves is for two reasons: to purge tires of regular air with nitrogen, and to blow out moisture if you've been filling tires on high humidity days (which could affect handling at high speeds if left in there). You would typically keep the valve stem that blows air out at the lowest point of the wheel (closest to the ground) to ensure you get all the water out.

To take this one step further, you may ask what to do if you’re out on the road and need to fill up. What I do is briefly press the tire fill valve with my thumbnail and vent some air. If my thumb gets wet, there's water in the line. Some gas stations don't do a very good job of keeping the humidity out of their air system. To be honest, I don't even like to use a water-based tire mounting lubricant or go to a shop that uses a water-based tire mounting lubricant. And if that’s your only choice, you can let the tire bake in the sun for a couple of hours before seat the bead or air it up. I've heard many stories of dismounted tires that had several quarts of water inside :shocked: This was probably from a compressed air hose that collected water and was never purged properly. This is why you don’t trust shops!

Let’s toss in a little math near the end of the article to further promote brain function (or struggle). Here’s the equation for the combined gas law:

(P1 x V1)/T1 = (P2 x V2)/T2 (temperature in K)

If temperature increases, either pressure or volume (or both) must increase. The important thing is how much they increase. Nitrogen will increase/decrease far less than air will. The primary reason nitrogen is used by the military is because it is inert. It will not promote corrosion and it poses no combustion hazard. Your car may blow a tire, but you won't have to worry about your missiles detonating and creating more of a BOOM. However, the aforementioned facts still remain important and add to their reason for using nitrogen vs. air.

To add some finishing points, your tire pressures will remain more constant with nitrogen, saving you a small amount in fuel and tire-maintenance costs. There will be less moisture inside your tires, meaning less corrosion on your wheels and much less fluctuation of pressure under temperature change. You will not be able to feel any difference in the ride or handling or braking under normal conditions for a daily driver, unless your tire pressures were seriously out of spec and changing to nitrogen brought them back to the proper numbers. And, I made sure to address this aspect last. Many people say “well, air is ~78% nitrogen, so it’s not worth it to pay a little extra when you can use air for free and it’s mostly nitrogen!” Well, to those people I say this: Performance is all relative. You are only as strong as your weakest link. If it is worth it to you, then you probably take your stuff seriously. Just note, you will not be getting "pure nitrogen" in your tire. The industry standard is 93.5% N2 in your tire to realize any benefit. A good nitrogen system will get you around 95% nitrogen. And 95% nitrogen is better than 78%, leaving less room for other crud. Airplanes and jets have been using them in their tires for well over 20 years. And they definitely get put to the test!


Cheers :beer:

Quote:

---

Originally Posted by Spoolin_VTEC

And though we may not be race-car drivers, we know that a boosted k-series is a race-car for sure.
Right Adm_rsx?

:wavey:

---

Damn straight! Lol. :boostedk20:

Nice article man. I had never thought about the use in a race application nor the fact the reason for the dual valve ports.

Great info man. :thumb:

Awesome info right here! +Repped for sure once i'm on a computer. Phenomenal write up