Comments on: The Space Shuttle and Commercial Airplanes Use Nitrogen In Their Tires. Should You?

By: Porsche Acronyms Explained | 993C4S: Porsche Cars, Products and LifeStyle

Porsche Acronyms Explained | 993C4S: Porsche Cars, Products and LifeStyle — Mon, 22 Mar 2010 21:40:23 +0000

[...] Porsche Posts Porsche PDK’s Split Personality Porsche Tires: Nitrogen vs Air Porsche Wheels for Sale Understanding N-Spec Approval When Choosing Tires for Your [...]

By: james stanislaw

james stanislaw — Thu, 07 Jan 2010 15:59:40 +0000

sjorry, that should read “…dry N2 changes pressure under increasing temps LESS than humid compressed air.”

By: james stanislaw

james stanislaw — Thu, 07 Jan 2010 15:56:03 +0000

it’s not the gases that create the pressure changes as much as the ambient humidity in compressed air vs dry N2. Racing a 3600 pound car creates pressure changes of compressed air about 15# + whereas with DRY N2, about a 6# increase in hot pressures. Those are facts related to humid compressed air. There is nothing special about N2 as a gas except it is dry from the company that put it in the tank and is less flamable than O2 or we might be talking about compressed dry O2. Anyway, it depends how much variation in tire pressure you are willing to put up with when racing and how much you want to spend to reach the goal (like anything in life), but there is no debate that dry N2 changes pressure under increasing temperature than humid compressed air. As for the inside vs the outside of a tire, the inside is not exposed to UV, wind, sand, dirt, gravel, etc. and should look perfect compared to the outside of the tire.

By: Andy Simpkinson

Andy Simpkinson — Mon, 04 Jan 2010 03:15:07 +0000

I’m of the opinion that Nitrogen for a tire fill is a waste of money even in my race car. The idea that pressure changes are smaller with Nitrogen is also false. The other gases in air, like oxygen, obey the same expansion gas laws that nitrogen obey’s. The only time there could be a greater change would be if there was actual liquid water in the tire. How often have you found water in your tire when you remove it from the rim? Also compare the condition of the rubber on the inside vs the outside the next time you have the tire off the rim. You’ll find the condtion is much better inside even though there was oxygen in there to degrade the rubber. In short there are no advantages to N2 except for the possibility of slower leaking (I doubt this also but don’t have facts to back it up).

-Andy Simpkinson
Spec 911 racer

By: 10 Most Popular Porsche Posts of 2009 | 993C4S: Porsche Cars, Products and LifeStyle

Wed, 30 Dec 2009 23:00:40 +0000

[...] Cameras if You Drive a Porsche 5. Porsche N Spec Approval. Understanding it When Choosing Tires 4. The Space Shuttle and Commercial Airplanes Use Nitrogen In Their Tires. Should You Use it in Your Po… 3. Lego Porsche 911 2. Winterizing and Preparing your Porsche for Storage 1. Jerry Seinfeld’s [...]

By: james stanislaw

james stanislaw — Mon, 28 Dec 2009 18:14:35 +0000

About 3-4 inflations/flushes of nitrogen gets the effect of washing out most of the oxygen and gets the nitrogen closer to 98% instead of ambient 78%. It is true that most of us “racers” use nitrogen in our tires because of the reduction in pressure changes when the tire gets hot on the track. The only trouble is less expense and ease to use a small air compressor for tools and tires at the track than the very large and heavy nitrogen tanks.

By: Walt

Walt — Mon, 28 Dec 2009 17:16:32 +0000

Without evacuating the air in a tire (vacuum pump) there will always be some oxygen in a tire. If you fill and purge the tires several times that will still leave some oxygen. I have no idea if racers vacuum the air out or not but as I see they must or they are not eliminating all oxygen.

By: 993C4S

993C4S — Wed, 23 Dec 2009 22:07:00 +0000

@George,

It seems that there is significant conflicting information regarding the actual “size” of a nitrogen molecules and as many ways to get that measurement as Porsche has options.

Can you point us to any definitive resource? If so, it would be greatly appreciated.

However, I think the one thing that most people agree on, and what we were trying to convey with the part of the article that covers “air leakage”, is exactly what you said above.

Quoting from our post: “[While Nitrogen] can still “permeate” the rubber or leak through, they do it at a much slower rate”

By: George

George — Wed, 23 Dec 2009 13:58:30 +0000

I agree with the points you made in the article on the benefits of nitrogen, except for the first point. A nitrogen molecule is smaller (0.10975 mm) than an oxygen molecule (0.1208 mm). The reason why a nitrogen-filled tire does not lose air is primarily because nitrogen gas is 50% less soluble in natural rubber than oxygen gas, which means that it is less able to be dissolved into the rubber than oxygen. Hence, nitrogen is less permeable and has less pressure loss than oxygen. In addition, by making some not-too-expensive design changes to the inner liner, a tire manufacturer can reduce oxygen pressure loss even more and make it close to the loss experienced with nitrogen gas.

By: 993C4S

993C4S — Wed, 23 Dec 2009 06:00:53 +0000

@George,

I think you hit on the point of the article. Nitrogen makes great sense for those serious about racing and high speed driving events. However, for those of us that simply enjoy a “spirited drive” in our favorite Porsche we can achieve similar results by simply checking the pressure more often.