Comments on: Nitrogen, Myth or Fact

By: Roger Marble

Roger Marble — Tue, 02 Sep 2008 19:07:13 +0000

Thanks Tom
I had forgotten about scuba as I was thinking of the 5′ tall 250 CF 2000psi tanks not your smaller tanks.

By: Tom Warfield

Tom Warfield — Mon, 25 Aug 2008 16:51:10 +0000

Actually, Roger, if you were a scuba diver you would know that “bottles” of air is quite commonplace in that sport.

By: Roger

Roger — Sun, 24 Aug 2008 03:46:20 +0000

Boiling point of water is 212 at sea level or at 14.69 psia or 0 psi gauge.

In a tire operating at 40 psig the boiling point of water is about 286 F.

http://www.engineeringtoolbox.com/boiling-point-water-d_926.html

While the moisture can affect the inflation pressure of a tire it will not turn to steam due to the increased pressure.

Aircraft use Nitrogen for fire safety reasons due to high loads, high speeds and high brake temperatures and the potential for a tire fire where high pressure air can contribute to the fire while Nitrogen will not support combustion of the tire.

Re racing, some current Indy car teams use Nitrogen, it has been reported that some use desicated (dry) air. They have the data so they can calculate and adjust the cold inflation to get the hot inflation they want.

I believe you will find that “bottles” of Nitrogen are readily available and inexpensive but I think you will have some difficulty finding bottles of air, so this is one reason we used N2 in my race team.
We inflated tires and ran our “air” tools while at the track as having a bottle of N2 was much preferable to taking along a gas powered compressor and the N2 was more reliable and we could get more CFM when we needed it while the small compressor just could not keep up.

A tire with 36psi of air will have identical rolling resistance (fuel economy) to a tire with 36 psi of Nitrogen or 36 psi of Argon.

By: hank donaldson

hank donaldson — Tue, 19 Aug 2008 02:06:35 +0000

I think the reason we use nitrogen in tires is to eliminate all of the air which contains moisture.
Moisture plus tire rims equals rust or corrosion the enemy of all metals.
So if we have 99 percent nitrogen and 1 percent air are we going to get rust?
Eventually, yes.
Seems to be an all or nothing deal.
Aircraft require nitrogen in their landing gear struts which just happen to be next to the tires; one cylinder does both.

By: Brad Sears

Brad Sears — Mon, 18 Aug 2008 13:53:55 +0000

Well let me answer a couple of these comments:
Red Rover, my understanding of thermodynamics is that you are correct to a point. The expansion rate occurs after the water has reached the point of vaporization or steam. And I hope that none of our tires get to 212 degrees F. Also as seen in boiler operation it takes a great volume of water to create steam pressure.
Brooker, if you read your comment and the origonal blog you and I are more on the same page than not. As far as wearing my tires out, I check tread depth at least each thousand miles, tire pressure weekly, run my vehicles over my old Bear scuff gage that I kept when I sold my shop at each oil change, and Tommy Knock my tires at every stop when traveling as well as an infra red tire temperature check. What I was getting at was two fold, we were sold a partial bill of goods in years past and with improvements in tires and vehicle engineering we are no longer on the 10,000 schedule for alignment. And lastly I am sorry to add that being a capitalistic society does not excuse not telling the truth.
And a question for Thomas:
How far did you have to drive on low tires to add nitrogen to the tires?

By: Brooker

Brooker — Mon, 18 Aug 2008 13:15:32 +0000

I feel it needs to be said to the people who claim that they are in the business that you should get out of the cave. I see trucks on the road all the time and talked with these drivers and service people for some time, as well and yes i have been in the indusry now for over 30 yrs in many differant postions, from line mechanic to sales to some light engineering to racing. so i am not talking like i do not know. Yes nitrogen dose help in a number of ways and yes it is minimal at best so each of you need to weight it out, yes there is some facts that are being pushed by the fact of money ( marketing) but so is everything else in this country, this is a capialist country. As for the statment from My Sears about not needing a front end alginment well i am glad he likes to drive hanging onto the wheel as it pulls in either direction and also wears out his $100 plus dollor tires.

By: Roger

Roger — Mon, 18 Aug 2008 02:38:31 +0000

Thomas
20psi loss in 3-1/2 months in each tire? Something is wrong unless you didn’t check the tires 24 hours after the initial inflation.
Normally new tires will show a decrease in pressure in the first 24 to 48 hours of 1% to 3%. This is due to tire growth. The increase in volume results in a decrease in pressure.
I would have expected to see something like 5 psi drop.
Keep an eye on your tire inflation and check VERY often. You could have leaky valve or some other problem.

By: Roger

Roger — Mon, 18 Aug 2008 02:33:01 +0000

Some comments from a Tire Engineer.
Do not confuse lower pressure build up (primarily do to dryer inflation gas) with lower heat build up. While I haven’t done a specific test, my personal experience confirms less pressure build with dry N2 in place of air from a compressor. BUT tire heat is a direct function of tire deflection plus tread slippage. If slippage (cornering) is held constant then all we have is increase in heat generation due to more deflection. Lower inflation means more deflection. Dryer inflation medium means less inflation build so it follows that it is entirely possible that the lack of pressure increase could lead to hotter tire operating temperature.

Brad hit the nail on the head when he pointed out that much of the marketing of N2 is based on the fact that tires inflated with N2 lose pressure slower than tires inflated with “air”. Since people don’t check or adjust their inflation then it follows that inflation with N2 and poor maintenance is better than inflating with air and poor maintenance.

If you check your tires at least once a month, or more often, as recommended by tire industry and auto industry, then I don’t see the possibility for inflation with N2 to be measurably different than with air.

I have heard of a test that shows that since the Oxygen “leaks” out faster than the N2 as time goes on and you keep adding air the % N2 does go up a fewe points. You will never get 100% N2 and the best I have heard of is 97% with 4 purges required.

Bottom line. Nothing wrong with using N2 but you still need to check and adjust your inflation at least every month with air or with N2.

By: Stefan

Stefan — Mon, 18 Aug 2008 02:23:20 +0000

I have 2 points to make.
Yes we use nitrogen in aircraft tires but we do it because of the ambient temperature. At altitude the water vapor in the tire will freeze and on landing it could give you an out of round condition.
The second point is actually a question. When you get nitrogen installed in your tires and they are low what do you do? Do you ride on the low tires till you can find nitrogen or do you fill it with air and then dump all the air and refill with nitrogen?
I’m a believer that 20% oxygen is not going to change the dynamics much

By: Thomas Becher

Thomas Becher — Mon, 18 Aug 2008 01:12:42 +0000

in Oct 2007 I had 4 newGoodyear Marathon tires installed by Sam’s
Club. They installed Nitrogen in all 4 at no charge. I didn’t take the fiver out until we left for Arizonia in Mid January. Before leaving I checked the tires. All four were about 45# Sam’s had filled them to 65# Temp or just setting? A 20# loss in 3 1/2 months. I’m glad I didn’t pay xtra for nitrogen.