How Much Impact Does Nitrogen Really Have On Your Tires?

If you've read my blog or found me on Facebook or MySpace or various forums, you know that I recently picked up a 07 Corvette, which I love.

One of the things I first noticed was that the tire valve stems had a little "N₂" on them.  This was done to suggest that Nitrogen at one time filled the BFGs.

I wondered if anyone uses Nitrogen in their tires and really how much difference could it make?  When I asked a few guys at my Corvette club Arizona Corvette Enthusiast (ACE), we had lot of "Winter Air and Summer Air" discussions.  It stems from an old joke about a service attendant's response when asked by a customer why there was an extra charge on his bill after he had his tires rotated.  The attendant's answer: "It's for filling them with winter air."

Of course there's no such thing, but Nitrogen is used in tires. Is there really any benefits?

Here is what GM says about the use of Nitrogen in tires:

GM's Position on the Use of nitrogen Gas in Tires (From GM's document #05-03-10-020C: Use of nitrogen Gas in Tires - Apr 27, 2010)

General Motors does not oppose the use of purified nitrogen as an inflation gas for tires. We expect the theoretical benefits to be reduced in practical use due to the lack of an existing infrastructure to continuously facilitate inflating tires with nearly pure nitrogen.... Given those theoretical benefits, practical limitations, and the robust design of GM original equipment TPC tires, the realized benefits to our customer of inflating their tires with purified nitrogen are expected to be minimal.

The Promise of Nitrogen: Under Controlled Conditions 
...The use of nitrogen gas to inflate tires is a technology used in automobile racing. The following benefits under controlled conditions are attributed to nitrogen gas and its unique properties:

• A reduction in the expected loss of Tire Pressure over time.

• A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration.

• A reduction of long term rubber degradation due to a decrease in oxygen concentrations.

Important: These are obtainable performance improvements when relatively pure nitrogen gas is used to inflate tires under controlled conditions.

The Promise of Nitrogen: Real World Use 
Nitrogen inflation can provide some benefit by reducing gas migration (pressure loss) at the molecular level through the tire structure. NHTSA (National Highway Traffic Safety Administration) has stated that the inflation pressure loss of tires can be up to 5% a month..... The actual obtainable benefits of nitrogen vary, based on the physical construction and the materials used in the manufacturing of the tire being inflated.

GM Tire Quality, Technology and Focus of Importance

<section omitted>

Important: Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance.

There you have it directly from the manufacturer. 

Now, NASCAR team uses Nitrogen instead of air to limit the expansion of the tires (less moisture = less expansion).  The average NASCAR's tires average about 200^o F while on the track.  Consider that at sea level water boils 212^o F (higher elevation the temps can be as low as 168^o F).  Without launching into a detailed physics discussion (I work with physicists, I can go on for days!!!)  before the boiling point moisture starts to expand.  On your stove the steam is the result of the escape of the modules during heating; inside a tire there is no escape, at least not at a rate that would reduce the pressure.

So take a highly tuned suspension, moving at 185 plus miles per hour and one tire builds up more pressure, due to higher moisture content.  As little as a half a pound of pressure variance can dramatically change the why the car handles.   

Of course we are talking about the speeds you just don't reach on your way to work, but expansion still has an impact. With the onset of cold weather (hey...37^o is very cold if you live down here in the great Southwest..I'm just saying!!) your street tires are impacted. The cold weather has the opposite effect, as it contracts the moisture and reduces the pressure. Today (12/5) the outside temps was 43^o. Upon firing up my Corvette, the tire pressure sensors showed low pressure in my rear tires.  The left was 24 and right was 25.  I drove the car 1.9 miles to the store and the sensors reported back with 26 and 26 for both, that's only going about 50 miles an hour tops.  Now multiply that by 3 or 4 for racing speeds and you know you are going to have a lot of expansion inside your tires.

Given my experiences and the experiences of the Average Guys I've asked, we've detected no difference for daily driving or when we take our toys to the track.

Thanks for reading and have a great holiday season.

-Tim

Read more from Tim Sweet at Average Guy's Car Restoration, Mods and Racing

Photo Credit: Tim Sweet