Nitrogen filled tires, Is it worth it?

[enollava]

Unless it is free, I wouldn't do it. If you are worried about moisture in your tires it is time for you to buy a desiccator for your air compressor. If not, then just use regular air.

[CoreyB]

It doesnt matter if you remove the moisture present in your air line, as long as you have air compressed it will add moisture with a temperature change.

[Turbo Powered]

Mostly correct info in this thread so far, except Oxygen does NOT contain water moisture. Oxygen is a gas, just as nitrogen is gas, just as water vapor is a gas (water in gaseous form).

It IS true that the compressed air you would fill your tires with from a gas station, contains more water vapor than the nitrogen that is used to fill tires. Note that the nitrogen used for filling tires for consumers is not high purity (>99%) nitrogen, and still has a little bit of oxygen (couple percent) and some water vapor in it. I believe the nitrogen used for racing tires is all high purity (>99.999% nitrogen), contaning VERY low levels of oxygen and water vapor (meassured in ppm - parts per million).

I'm a mechanical engineer and used to work for the company that originally promoted this, including the engineers that developed and support the technology, air separation (PSA - pressure swing absorption and VSA - vacuum swing absorption).

It's not a scam in that most people do not check their tire pressure often enough, and nitrogen filled tires will drop their pressure slower, simply because nitrogen molecules are larger than oxygen molecules. As said, unless you race or never check your pressures, you don't need it. There is also the side benefit of not having as much oxygen inside the tire causing oxidation of the rubber. Some tire dealers are offering it free when you buy tires from them. If you can get it free, why not? There's no downside. I would never pay for it though. Consumer Reports also essentially gave it a thumbs down.

FYI, when I could get high purity nitrogen for free, I never bothered using it.

PS I'm not really sure why people in this thread are talking about water/moisture, it really doesn't have anything to do with the main principles going on.

Edit: Removed my comment, not true: "less pressure variation with temperature".

[AdamVR4]

...and as said, less pressure variation with temperature.

This doesn't make any sense to me, as a fellow ME. The ideal gas law is applicable to both air and nitrogen, is it not?

[Broch]

end of thread

Oxygen has water moisture in it.

Nitrogen does not.

Is it worth it? No. Not unless it's free. People should be checking their tire pressures between tire rotations... at the very least between seasons. Tires last their entire lives with straight air... so Nitrogen is useless unless you're racing with a LOT of heat being generated.

[eblank8]

This doesn't make any sense to me, as a fellow ME. The ideal gas law is applicable to both air and nitrogen, is it not?

Since when do gases act like ideal gases in real life? Almost never, unless they are 100% monotonic at either high or low temps. That said, air is not monotonic. Pure Nitrogen would be, but as stated before, the nitrogen used to fill your tires is not pure.

[Alex3000gt]

Assuming ideal gas, the R values cancel anyway, and the change in pressure is purely a function of the change in temperature.

PV=mRT. Same mass, Same volume, Same R values. Say T1 is 80F and T2=0F

P1/P2*V1/V2=m1/m2*R1/R2*T1/T2

P1/P2=T1/T2..converting to Rankine: 80+460=540 Rankine. 0+460=460 Rankine.

P2/P1=T2/T1 = 460/540= .852 or 85.2%

P1/P2 or the change in tire pressure when the temperature drops 80F, means that your tires will have about 85% of the pressure they had before. Nitrogen or not. You are all suckers if you pay for that stuff. R (gas contant) values cancel, it's in the math.

[AdamVR4]

Alex, you may be right. I try not to clutter my brain with stuff like this, and unfortunately my meticulously kept school notes and books are all at work.

There are gas constants for Air and Nitrogen. Delta Pressure = Density * Gas Constant (unique to air or N) * Delta Temp... If I had access to a temperature-density curve for Nitrogen I would have already finished an excel spread sheet comparing the two.

I don't care if I'm right or wrong. I hope that eblank takes the time to research the usefulness and accuracy of the ideal gas law. There's a reason it's been used by engineers for ~200 years now...

[Turbo Powered]

This doesn't make any sense to me, as a fellow ME. The ideal gas law is applicable to both air and nitrogen, is it not?

Lol, I wondered if I was going to get called out on this or not. I honestly was too lazy to pull out a book to check on this, thought I remembered the comment as being true, said about racing applications. Both you and Alex are right, there shouldn't be any difference in pressure variation from temperature. Yes, the ideal gas law isn't perfect, but it's pretty damn good. And yes, air is a mixture of many gases, and it's not monotonic at the temperatures tires see. However, I'd be willing to bet that the difference in pressure variation from temperature between air and nitrogen is so small that it's very difficult, if not impossible to measure without extremely expensive instrumentation. Certainly it's so small, it is NOT a factor/benefit to use nitrogen. I edited my post with this correction.

[UTRacerX9]

The fastest Stealth in the world has never used Nitrogen filled tires that I'm aware of, and I don't think the few 3S owners out there who have track prepped cars and are active autocrossers use it either, so if there was an outstanding performance benefit, I'm sure they would have looked into it.