nitrogen tire fill plus air?

[edhackett]

Nitrogen is used in aircraft tires because the FAA requires the use of an inert gas in the tires. This is so that the fill will not help support combustion if the tire catches fire from an overheated brake. Any inert gas can be used. Nitrogen is used because it is the cheapest, not because of any magical properties beyond not supporting combustion.

Ed

 

[Carbon]

Originally Posted By: edhackett
Nitrogen is used in aircraft tires because the FAA requires the use of an inert gas in the tires. This is so that the fill will not help support combustion if the tire catches fire from an overheated brake. Any inert gas can be used. Nitrogen is used because it is the cheapest, not because of any magical properties beyond not supporting combustion.

Ed


You sound so confident, Ed. What is your belief based on? Did you read a study to that effect, or are you using introspection?

Here is a terrestrial study that looks at the value for long haul trucks: http://www.tc.gc.ca/eng/programs/environment-ecofreight-road-tools-casestudies-drexan-107.htm

While I don't use nitrogen in my tires, that is a cost/benefit/convienience thing. But to say that 2% oxygen in tires has no advantage, other than fire issues, over 30% oxygen is not accurate.

 

[Kestas]

That study, which originates from Drexan Corp, really exalts a lot of benefits to using nitrogen... almost suspiciously exalts it too much.

Could it be that it's because Drexan manufactures nitrogen generating systems used in tire shops?

 

[Carbon]

Originally Posted By: Kestas
That study, which originates from Drexan Corp, really exalts a lot of benefits to using nitrogen... almost suspiciously exalts it too much.

Could it be that it's because Drexan manufactures nitrogen generating systems used in tire shops?

Good point. It did seem to get too strong results beyond what could be expected. Like having drug studies originate from drug companies.

So do you think that edhackett will cite a study that is from an independent source?

 

[Kestas]

I'll let people in the know comment on edhackett's post. It sounds okay from where I'm sitting.

Realize that it's not always fair to ask someone to cite references. For example, I know a lot of stuff that has accumulated in my head over the decades, i.e., from schooling, professional publications, and conversations. I can't always cite the original source from where I learned the stuff.

 

[George Bynum]

Originally Posted By: edhackett
Nitrogen is used in aircraft tires because the FAA requires the use of an inert gas in the tires.
I don't know where the idea that nitrogen is inert comes from ... there are "millions" of nitrogen compounds ... think about the NOx emissions requirements, for one. TNT is a nitrogen compound. Ammonia is a nitrogen compound. Most (all?) fertilizers contain nitrogen compounds. Can you give a reference on the FAA requirement(s)?

 

[CapriRacer]

A couple of thoughts, but first:

http://www.barrystiretech.com/nitrogeninflation.html

That's what I wrote up about nitrogen inflation. 2 points.

1) Lab tests show no difference in rolling resistance. So any fleet that experiences an improvement in fuel economy must be getting it from some place other than the nitrogen itself. Likely suspects: Improved maintenance practices, improved retention of inflation pressure, improved vehicles - and the list could go on.

2) While there aren't any lab tests for tire wear (pretty expensive to run), but there is no reason to believe that just the difference in inflation medium would change tire wear. The mechanisms for tire wear are driven by a lot of things, but because air and nitrogen behave virtually the same, that can NOT be a reason for a wear improvement. So any fleet that experiences a wear improvement likely got that from another source. Like suspects: Improved maintenance practices, improved retention of inflation pressure, generational improvements in the tires - and the list could go on.

I find it supecious that no mention is made of an improvement in pressure retention between pressure checks. I think that means they didn't make any - and if I were running the test, I would [censored] well be SURE that I could document that as that is a MAJOR benefit that is being touted!

Now onto the comments made about Ed's comments:

We can NOT be sure WHY somebody did something - and that includes the FAA. We can verify that aircraft tires are required to be inflated with nitrogen. We can verify they buy nitrogen in 1500 psi bottles. We can verify that aircraft tires are sometimes inflated to 350 psi. We can verify the nitrogen does not support fire.

But we can only guess as to the motivation behind the regulation. Is it just because everyone uses the convenient nitrogen bottles and not a specially built air compressor and that the regulation takes advantage of what is easy to do. I don't know, but it's possible.

It's also possible that the fire issue drove them to adopt a certain way of doing things. But we'll never know unless we can contact someone who was involved with the writing of the regulation.

 

[unDummy]

Like TPMS, nitrogen is just another excuse not to check your tire PSI regularly. I use nitrogen for exactly that reason since I've become lazier with each year that goes by. And, in the northeast, the temperature swings can be drastic. I worry less and don't care to check tire PSI daily because the day's temperature can swing 50f.

http://www.aa1car.com/library/tirepres.htm

Maybe its the quality of my tires, or maybe its the nitrogen, but I don't have to top off my tire's air too frequently. And, I don't mind using my toxic air to pollute my nitrogen filled tires(usually nitrogen filled only at new tire purchase).

The local tire shop here will drain/refill your tires twice when switching to nitrogen. They also offer free top-offs of nitrogen if your pressure is low for the life of that tire(or something like that). Plus, you get free eco-greenie chrome-ish tire valve stem caps with a leaf on it. That gives me brownie points when picking up the hippie-chicks.

I have a glass of 100% beer on the table. You can pour your own glass of 78% beer and the other 22% with bladder drainage. Care to start a thread on which is better?

Now, if I could only get helium. I must be throwing away mega MPG by the excessive weight of the vehicle. Helium would help much. Rumor is that helium leaks right through the tire rubber too quickly. Don't want the tire to look like a couple day old sagging helium balloon. Bummer. I'll have to settle for hydrogen and get some no-smoking signs for 'em.

 

[jhMalibu]

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFinalRule.nsf/0/e18b9cadcf1a66da86256a3100713354!OpenDocument&ExpandSection=-4

Nitrogen gas (N2) doesn't support combustion and can be viewed as "inert" for this purpose.

 

[edhackett]

Thanks for posting the link jhMalibu. I was going to find it and post it.

Here's the important text:



CFR Final Rule

[Federal Register: February 26, 1993 (Volume 58, Number 37)]
[Page 11778]

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. 26147; Amendment No. 25-78]
RIN 2120-AD87
Use of Nitrogen or Other Inert Gas for Tire inflation in Lieu of Air

AGENCY: Federal Aviation Administration, DOT
ACTION: Final Rule
SUMMARY: This amendment to the Federal Aviation Regulations (FAR) requires that an inert gas, such as nitrogen, be used in lieu of air, for inflation of tires on certain transport category airplanes. This action is prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching autoignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion.
EFFECTIVE DATE: This rule becomes effective March 29, 1993.

Ed

 

[Shannow]

Originally Posted By: unDummy

I have a glass of 100% beer on the table. You can pour your own glass of 78% beer and the other 22% with bladder drainage. Care to start a thread on which is better?


[censored] poor analogy IMO.

Both gasses are diatomic, have pretty much the same size, weight (give or take) and leakage rate.

Really, if you believe that N2 is vastly superior, just keep adding air until all of the oxygen has leaked out.

 

[Shannow]

Actually, the really funny thing is that if you were able to eliminate ALL the oxygen inside your tyre, the oxygen from the atmosphere would leak INTO the tyre at around half the rate that your problematic air filled tyre was losing oxygen.

Maybe that's why people feel their tyres stay inflated longer ???

 

[unDummy]

http://blogs.consumerreports.org/.shared...rt_consumer.gif

 

[Shannow]

Guess that the oxygen inleakage must be significant then ?

The pic, you must admit, is pretty light on test parameters...

 

[CapriRacer]

Originally Posted By: edhackett
....... This action is prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching autoignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion.


Ed,

Thanks for that post. I think it is highly unusual for a regulation to give a justification. Most of the one I have seen merely state what is required - nothing more.

 

[Carbon]

Originally Posted By: Shannow
Guess that the oxygen inleakage must be significant then ?

The pic, you must admit, is pretty light on test parameters...
You know a picture that is heavy on test parameters?

Here is some info on the test:
Quote:
Consumer Reports wanted to find out if nitrogen is worth the price, so we purchased a Nitrogen Inflation System and checked out how well the inflation held up over a one year period. We evaluated pairs of 31 tire models of H- and V-speed rated, all-season tires used in our tread wear test from 2006. We filled one tire per model with air and the other with nitrogen. The test was quite simple: fill and set the inflation pressure at room temperature to 30 psi (pounds per square inch); set the tire outdoors for one year; and then recheck the inflation pressure at room temperature after a one year period.

The tires were filled and deflated three times with nitrogen to purge the air out of the tire cavity. We also used an oxygen analyzer to be sure we had 95-percent nitrogen purity in the tire--the claimed purity limit of our nitrogen system, which generates nitrogen gas from ambient air.

We conducted a year long test of the effects of nitrogen in tires and the results show nitrogen does reduce pressure loss over time, but the reduction is only a 1.3 psi difference from air-filled tires. The average loss of air-filled tires was just 3.5 psi from the initial 30 pressure setting. Nitrogen-filled tires lost an average of 2.2 psi from the initial 30 psi setting. More important, all tires lost pressure regardless of the inflation medium, so consumers should check their tires' air pressure routinely. If you decide to have your tires filled with nitrogen, be sure to have them refilled with nitrogen routlinely[sic]. Like air, nitrogen filled tire pressure will drop as seasonal temperatures fall. No evaluation was done to assess the aging claim.

Overall, consumers can use nitrogen and might enjoy the slight improvement in air retention provided, but it's not a substitute for regular inflation checks. For more information on nitrogen and tires, see our FAQs.

 

[George Bynum]

Ed, thanks for the link and extract. I guess they assume something that doesn't support combustion must be inert. I didn't doubt the requirement, just the "inert" part. I deal in industrial hydraulics, and we inflate accumulators almost exclusively with nitrogen, occasionally working with pressures in excess of 5000 psi, but more commonly below 2000 psi.

 

[Carbon]

Originally Posted By: George Bynum
Ed, thanks for the link and extract. I guess they assume something that doesn't support combustion must be inert. I didn't doubt the requirement, just the "inert" part. I deal in industrial hydraulics, and we inflate accumulators almost exclusively with nitrogen, occasionally working with pressures in excess of 5000 psi, but more commonly below 2000 psi.

Inert was not an accurate use of the word. http://education.yahoo.com/reference/dictionary/entry/inert Proteins contain nitrogen, for example. Nitrogen is not readily reactive with tires, as Oxygen is. So for this purpose, it might as well be inert. Argon is actually inert.

 

[edhackett]

From wikipedia definition of inert:

The term inert may also be applied in a relative sense. For example, molecular nitrogen is inert under ordinary conditions, existing as diatomic molecules, N2. The presence of a very strong triple covalent bond in the N2 molecule renders it unreactive under normal circumstances.

I am in fact, right now, breaking apart Ar gas and reacting it with oxygen to form ArO. Inert is surely a relative term.

Ed

 

[unDummy]

http://www.nitrofill.com/documents/Rubber-News-Nitrogen-Tire-Study1.pdf
http://www.getnitrogen.org/pdf/print_art...read%20Life.pdf

How do you increase the age of tires? cook in oven with reduced nitrogen and increase oxygen level?
http://tirenitrogen.typepad.com/techinfo/Ford%20Baldwin%20TireAging%20%232.pdf

With the movement toward 50k-100k+ long life greenie-eco-mpg tires, I would think that those consumers would definitely benefit from reduced tire aging when using nitrogen over air, especially since we can't get tire expiration dates legislated and enforced.

Since I don't buy tires based on how long they last, I never have tires that are more than a couple years old. But, I keep seeing those seriously cracked 5+ year old tires and its scary. There isn't a day during the highway commute that there isn't a car on the side of the road with a tire blow out.

This is no different then comparing a synthetic oil to a mineral oil, or comparing a fast-food burger to a fillet Mignon. To each their own. Draw your own conclusion.

I'm just not finding the anti-nitrogen in tires studies or papers.

Even the Consumer Reports test was a little too inconclusive for me. Not sure if they bead-sealed the tires or if they used new stems & seals.... But, there looks to be some brands that leak too much and I might just avoid.