gpsman,

while all those things are true, it's also true of compressed air. Tanks can be filled to 3000 psi (I know because I wear one on my back when I scuba dive). They're obviously just as portable and it is also very dry.

I tend to think the reasons for planes using nitrogen is what Pravus Prime said. And they have to use tanks because a compressor would just get you 78% nitrogen.

 

Its been a long time since thermo but

PV=nRT Pressure*Volume = avogadros number * gas constant * Temperature

There is no place in there to put whether you have N or O or whatever... so the pressure should not change based on temperature any more depending on if you have 100%N or 78%N and O for the balance. Thats a fallacy. There might be some truth with water vapor heating up and changing the pressure, but you could always use dry compressed air.... theres no need to go to N2

N2 is more inert and should cause less oxidation inside the tire... however I personally have very little belief that oxidation INSIDE the tire is a major cause of failure or lifetime issues on passenger vehicles... The tire oxidizes on the outside all the time and that would seem to be just as bad. There just isn't enough heat buildup I would think.

I've always beleived (but I don't know where it came from) that the reason planes and NASCAR uses nitrogen in their tires is to prevent heat damage in the tires BUT THOSE TIRES GET INCREDIBLY HOT compared to a passenger tire!!! Its not even close! When they pull off a NASCAR tire the thing is usually nearly smoking and for a plane when they hit the brakes (they use thrust reversers as well) they get HOT.

Another point is that supposedly the N2 stays in the tire better becuase it is larger... its two picometers different.... N2's bonding radius is 75pm and O2's is 73pm I suppose its possible but its only 2.7% larger so supposedly that 2.7% makes a difference when it makes up less than 22% of the gas in the tire. (there are other impurities in there but in very small amounts) If this was true we should see our tires slowly deflate over time. In between the times of a tire rotation I've never seen my tires loose significant air pressure at all unless I had a leak. Besides every 5000miles you top them off (if you aren't checking them regularly like you should be)

Personally.... I think its a marketing gimmick to bilk people out of their cash. there are magnets that "align the fuel molecules" entering your engine to improve combustion I've heard about, all kinds of additives.... I recall reading they've been tested by the government and not ONE has ever shown an improvement in fuel usage (they were also shown on a mythbusters episode if you consider that more definitive)... I really suspect we a talking a similiar thing here. I've never seen any of the tire ads around here ever publish any data to back up their claims.

But it shoudn't hurt anything so someone can give it a try and report back.

 

Sorry to be such a geek, but the "n" is the amount of gas in moles and the R is the constant.

 

This would be a very lonely board without us geeks....I mean you geeks. I'm not a geek. I own two hybrids because it's good for the environment. Yeah, that's it......

 

I knew that..... Its been years since thermo, but I still knew that and I don't know why I wrote different.

As Homer says.... doooooh..

 

You can't spell gEEk with out EE and that would be me (tragically).

 

It has been generally accepted that nitrogen filled objects.....my background is inflatable boats......fluctuate less in pressure from temperature changes than air filled ones. It's an issue here in that lots of inflatables ride on boat tops in the sun, and then get dumped into 30 degree water....and you don't want a soft tube between you and the cold water, so to speak.

Tire pressure would be slightly more constant using nitrogen. Not much, and not critical for "normal" hiway use. NASCAR runs everything at the absolute edge of destruction, so obviously, avoiding fluctuation is worth it to them. The key is that tires would stay more constant at the "right" pressure.....whatever that is.

Expect only very slight changes.....but maybe enough to see.

 

ROFL I'm going to have to remember your comment Nitramjr. Yup two hybrids, not a geek *hides his EE degree*

 

Ever hear of Placebo? People with Nitrogen filled tires get 1-3 MPG better because they THINK they should, and hence, sub-conciously drive a little more gently.

Again, for the last time, then I'll butt out....

Nitrogen ( from an industrial supply ) has 0% water vapor.
Air from an air compressor may have several percent water vapor.
It is the water vapor that affects pressure changes, not the gas of choice.
Some professional air-compressor systems also dry the air.
The one in your garage from Sears probably does not.
Car tires have a pretty small volume, so you'll have close to zero water vapor.

I guess I can lead a horse to water, but can't force him to drink.
Putting premium air in your tires ( 100% N ) is like putting premium gas in your car built specifically for regular 87 Octane. A WASTE OF MONEY!

( if you can get it for FREE, I say go for it, otherwise, no )

There are special cases for Nitrogen tires, as there are special cases for 93 Octane. Your FEH is NOT one of those cases. Period.
- John

 

Wow, John, this topic really hit a nerve, huh? I look forward to starting more of these threads that get your blood pressure up, lol.


BTW, my compressor is not from Sears