Nitrogen

[JT1]

Originally Posted By: Kestas
I thought aircraft wheels used nitrogen because you can't get an air compressor to deliver 300 psi like you can from a cylinder of nitrogen. And unlike an air compressor, the cylinder can be brought to the aircraft.


I use nitrogen wherever required but, most of the aircraft I work on only require ~175psi tire pressure, which could easily be supplied by a decent compressor. Around 95% of the time the tires are serviced within the hangar and an air hose is a whole lot lighter and easier to get around than the nitrogen cart.

AFA my car's tires, well, they all get whatever my Husky air compressor kicks out.

 

[Shannow]

Originally Posted By: mpvue
nitrogen is used on aircraft wheels because it won't explode. I used to rebuild aircraft wheels and we had inflation cages; 747 wheels got like 300psi IIRC (it's been awhile), and there are also specs for allowable pressure loss.
anyway, I don't see a need on passenger vehicles, because a car doesn't have the same needs as an aircraft.


Air explodes ????

Hang on while I remove it from my house.

 

[CapriRacer]

Originally Posted By: mpvue
I'm just going by the FAA Airworthiness Directive (AD) that was issued like in '87 I think; I used to be able to quote the AD# when an FAA inspector came around.

http://answers.yahoo.com/question/index?qid=20080526081915AAeLdwN


Thanks for that link. ::gets out soapbox::

Did you see how many people answered that question with false information? This is a problem I am commonly confronted with - and I am sure others have encountered the problem as well.

Amazingly, there were several folks who expressed the answers in ways that correctly characterized the situation. That was unusual.

:uts soapbox away::

 

[cchase]

Helium atoms do not bond together like nitrogen (and oxygen) atoms. Add to that helium atoms being smaller than oxygen or nitrogen atoms and I think you'd have one leaky tire.

 

[Carbon]

Originally Posted By: nleksan
I cannot tell a bit of difference with pure nitrogen in my tires, and this is at the track. No difference in grip, warm up time, braking, handling, or lap times...

I have always wondered about helium though... Maybe a way to lose 0.5lb unsprung weight! Lol


Nitrogen diffuses/leaks slower than oxygen, so you have to fill it less often. If you got the tires filled at each oil change, Nitrogen would have higher pressure remaining at the time you got your oil filled, so you would probably get a tad better mileage with the nitrogen if you top the tires up every six months. Paying $30 for nitrogen is probably not going to get paid back in savings. If you fill your tires more often, and if you don't apply a value to the labor of filling your tires, then gas savings would be much less. If you valued time filling tires highly, N2 could pay off.

Helium would be significantly worse than dry air or N2 in most ways. It costs much more than N2, and it diffuses/leaks much faster than N2 or air. Your lightness thing could be a factor in a race maybe. Also, helium conducts heat well. Maybe it would keep the tires a bit cooler during a high speed race. It would not help tire "warm up time".

 

[nleksan]

Comment about helium was a joke

it wouldn't stay in the tire

 

[SteveSRT8]

Originally Posted By: Carbon

Nitrogen diffuses/leaks slower than oxygen, so you have to fill it less often. If you got the tires filled at each oil change, Nitrogen would have higher pressure remaining at the time you got your oil filled, so you would probably get a tad better mileage with the nitrogen if you top the tires up every six months. Paying $30 for nitrogen is probably not going to get paid back in savings. If you fill your tires more often, and if you don't apply a value to the labor of filling your tires, then gas savings would be much less. If you valued time filling tires highly, N2 could pay off.

Helium would be significantly worse than dry air or N2 in most ways. It costs much more than N2, and it diffuses/leaks much faster than N2 or air. Your lightness thing could be a factor in a race maybe. Also, helium conducts heat well. Maybe it would keep the tires a bit cooler during a high speed race. It would not help tire "warm up time".



No one anywhere has ever proved this ridiculous assertion. It's only 22% more N2 than regular air if it's pure, and that is also unlikely.

I actually have several load range E tires on heavy duty service trucks that NEVER need air. That's right, fill them to the correct pressure and they stay there.

No Nitrogen needed.

 

[DuckRyder]

So is it true it is more temperature stable?

The guys at the dealer tell me the only real reason they got into this stuff was TPMS aggravation and claim it reduces problems with them?

Of course the only car I have around here with TPMS has only come on twice and both times it had a nail in the tire

.

 

[mpvue]

Originally Posted By: Shannow
Originally Posted By: mpvue
nitrogen is used on aircraft wheels because it won't explode. I used to rebuild aircraft wheels and we had inflation cages; 747 wheels got like 300psi IIRC (it's been awhile), and there are also specs for allowable pressure loss.
anyway, I don't see a need on passenger vehicles, because a car doesn't have the same needs as an aircraft.


Air explodes ????

Hang on while I remove it from my house.

I'm sure you're aware of the function of an internal combustion engine, and what happens when air is compressed.

 

[Carbon]

Originally Posted By: SteveSRT8
No one anywhere has ever proved this ridiculous assertion. It's only 22% more N2 than regular air if it's pure, and that is also unlikely.


Which assertion? You deny that N2 diffuses out of tires faster than air? What would you call proof?

Originally Posted By: SteveSRT8

I actually have several load range E tires on heavy duty service trucks that NEVER need air. That's right, fill them to the correct pressure and they stay there.
That's quite the assertion.

 

[edhackett]

CapriRacer, actually none of them got it 100% correct, including the 20+ year AP who states that it must be dry nitrogen.

Here's the actual wording, emphasis mine:
Quote:
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

Preamble Information
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.
FOR FURTHER INFORMATION CONTACT: Robert C. McCracken, Flight Test and Systems Branch, ANM-111, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue Southwest, Renton, Washington 98055-4056: telephone (206) 227-2118.


DuckRyder, all gasess follow the universal gas law. Air from a compressor that does not have a dryer contains water which does cause large pressure swings with temperature. The process used to separate the nitrogen removes water vapor as does a dryer on an air compressor. Dry air and dry nitrogen will respond to temperatures the same.

Ed

 

[Ken2]

Originally Posted By: Kestas
you can't get an air compressor to deliver 300 psi
I've run 450 psi air compressors. Air at that pressure is admitted into the cylinders of big diesel engines to crank them over to start.

 

[edhackett]

SCUBA tanks are filled with up to 3000 psi with air compressors.

Ed

 

[AdamL]

Subaru dealer near my house charged $30 for nitrogen air service!

http://www.subaruoflasvegas.com/specials...1b51db7281834da

Anyway, Costco uses nitrogen for "free" including when you drop by the bays for a top off.

I have a feeling that over the life of a car tire it won't make much difference. And I'd be extremely surprised if a double blind study showed any difference in the driving experience.

Anyway, in regards to the OP's question, it's far more damaging to a tire to run it ten pounds low than use regular air.

 

[pjf]

Consumer Reports, Scientific American and Car Talk are all saying the same thing about nitrogen. Just read one of them:

http://news.consumerreports.org/cars/2007/10/tires-nitrogen-.html
http://www.scientificamerican.com/article.cfm?id=nitrogen-filled-tires-fuel-efficiency
http://www.cartalk.com/content/i-recently-heard-about-filling-tires-nitrogen-gas

 

[George Bynum]

Originally Posted By: Kestas
I thought aircraft wheels used nitrogen because you can't get an air compressor to deliver 300 psi like you can from a cylinder of nitrogen. And unlike an air compressor, the cylinder can be brought to the aircraft.
Cylinders of breathing air are as available as nitrogen at local suppliers. Compressors to get to 300 psi aren't at PepBoys or WalMart, but certainly exist ... as do those to go to 5000 or higher psi. Divers and firefighters use that.

As with many wonderful ways to solve problems, that nitrogen is better than "air" is true ... maybe (my guess) 0.1% better. Experts here have explained that oxygen in air actually will seek equilibrium and diffuse INTO the tire. And the typical nitrogen in tire shops is produced by a "concentrator". 93% is a pretty good level from what I've seen.

 

[A_Harman]

Originally Posted By: mpvue
I'm sure you're aware of the function of an internal combustion engine, and what happens when air is compressed.

Basic lesson in chemistry:

You can't get combustion without oxygen and fuel in the proper concentration. If air exploded just from compressing, air compressors would be impossible to make.

 

[A_Harman]

Originally Posted By: nleksan
Comment about helium was a joke

it wouldn't stay in the tire


But think about the repeat business you'd get filling tires with Helium!

 

[440Magnum]

Originally Posted By: Shannow
Originally Posted By: mpvue
nitrogen is used on aircraft wheels because it won't explode. I used to rebuild aircraft wheels and we had inflation cages; 747 wheels got like 300psi IIRC (it's been awhile), and there are also specs for allowable pressure loss.
anyway, I don't see a need on passenger vehicles, because a car doesn't have the same needs as an aircraft.


Air explodes ????

Hang on while I remove it from my house.



Not exactly. Here's the thing: Rubber (like the inside of the tire) burns- its got a very high energy density as a fuel. You've seen tires burn, I'm sure. They're almost impossible to extinguish once they've caught fire, even in ordinary air at atmospheric pressure. In a pure O2 environment, a simple spark would make a rubber tire go up like a fuel-air bomb, and this is also a risk in hospitals where patients are fed O2 through rubber or plastic hoses- you have to be very careful not to let an ignition source close to those hoses. Available oxygen goes up proportionally to air pressure, so regular AIR at ~300 PSI has as a similar amount of oxygen available for combustion as pure O2 at atmospheric pressure. Is there a chance of a spark INSIDE the aircraft tire? Not likely, but aircraft tires CAN overheat to the auto-ignition temp in a high pressure environment. Why carry around the risk?

 

[HerrStig]

What's the ignition source inside a tire?