So, Ken are you saying flat and underinflated are the same thing? Because if the nitrogen in air doesn't leak out, the tires shouldn't deflate more than 22% when filled the first time, then after everything but the nitrogen leaks out and they are re-filled with air, they would be 95% nitrogen, so the most they should leak down would be 5% (about 1.5 psi off of 32 psi).

I don't check my tires as often as I should, but I'd say virtually all of my low-pressure problems have been due to punctures (jobsites...), bad valves, bad beads and the like. Why? Because all my tires on a given vehicle are the same brand and model, and it's usually only 1 or 2 tires that are low. And, if I find some low, they will always be the ones that are low the next time I check. Oh, there is one more cause of low pressure--fall/winter weather and the ensuing temperature drops will cause low pressure, too. pV=nRT, you know.

Jason

 

People on this site must love to argue. Even if you take a simple, common sense, easily proven statement like, "Nitrogen molecules are larger than oxygen molecules so air-filled tires will leak faster," people will still find something to argue over and nitpick.

Just amazing.

You must have magic tires that never leak air. It's the only reasonable explanation, because if your tires are low, it CAN'T be because air molecules have escaped. Never mind that this is proven to occur with every tire, automotive or otherwise, that has ever been manufactured on this planet.

 

Cut the bickering about this topic; if you want to spend the few extra $ to get nitrogen in your tires, go ahead. It seems crazy to get into this deep of a discussion over someone who asked for information. Simple logic would suggest that if your tires are filled with nitrogen, which does not lose tire pressure, the tires would be properly inflated all the time giving optimum performance both on tread life and gas mileage.

 

Okay, no more arguing. Let me ask a question then.

When the tires are filled with the N2 at Cosco, do they completely evacuate the tires first? If not then wouldn't you still have approximately 1/3 or 1/4 of the volume of the air in the tires being atmospheric? So you'd still have roughly 5-7% of the air in the tires being other than straight N2. Right?

And regarding the study Consumer Reports did, I believe they may have said that N2 in tires is only effective on Toyotas and Nissans and that it would have no effect on tires installed on American made cars...

 

The only place we have that does nitrogen fills charges $25.00 for 4. I refuse to pay that since I have my own air compressor.

 

You're right, I forgot about the effect of the higher pressure on the boiling point.

The race car I work on runs tire pressures of about 20 PSI gauge. That shows a boiling point of about 225F. We routinely see tire temps above that.

 

Well, since we're not arguing any more, then it's okay to bring in common sense and logic.

Now that right there is funny, I don't care who y'are.

Jason

 

The places around here who put nitrogen in the tires use a machine that first purges all the air in the tires and then pumps nitrogen in. Cost is about $25 for four tires, and lifetime replacement should you get a flat.

 

Hmm...let's see, my location is Indiana, so that means through the year, I typically see anywhere from -10ºF to 95ºF. That's a pretty big temp swing--one that will greatly affect the pressure in the tires. If you actually read what I wrote, you would see that I was trying to get Ken to clarify what he was saying. I didn't start out with, "Ken, you're wrong," or anything of the sort, merely relaying my experience, which is that my tire pressures stay pretty consistent. With 4 tires of the same brand, if I check them after 2 months in the same season, I can usually expect 2 to be at the pressure they were originally, one a few pounds low, and one quite a bit low. The two that are low will be low the next time I check, too, and by about the same. I've always been able to track that lowness to a bad bead or a nail, etc. Heck, once in a great while I get 4 good tires that, come springtime, I have to let air out so that they're not over-pressured.

Now, go back and read what I (and someone else originally brought up) wrote about air being 78% nitrogen, and how if that doesn't leak out, but the 20+% of oxygen does, you should be left with a tire that is "low", but not "flat". Now, if you re-fill that "low" tire with compressed air (78% nitrogen/20+%oxygen), you'll be at about 95% nitrogen. What I'm doing here is carrying the pro-nitrogen folks' statements to their logical conclusions, and I don't believe that to be a big stretch.

Andy, as far as I'm concerned, you're the one being argumentative--before that, I think there was a good discussion going on. Heck, I'm a painting contractor. You think I've never been nit-picked? I could tell stories...

There's no nit-picking in this thread--just some details of the science behind the debate getting hashed out. You know, variety is the spice of life and all that. Mark just pointed out that I'm right on a point and agreed with me, which confirmed the moisture part--racers see tire temps that would boil water, I, as a civvie, don't. Even on the hottest days, I've always been able to hold a hand to my tires, even ones that are somewhat low and have a lot of sidewall flex going on. Okay, so I'll concede that there may be a benefit to using nitrogen in racing applications, but I don't think that any of us here are challenging that--just challenging that there's a real benefit to using nitrogen in civilian tires for normal driving.

Jason

 

I'd be curious to see how they purge the tire without either sucking it totally flat or overpressuring it to the point where the beads unseat...

And, yes, I am wearing my skepticism on my sleeves here...

Jason

 

LOL!

"We evaluated pairs of 31 tire models of H- and V-speed rated, all-season tires used in our tread wear test from 2006."

 

Its usually done by having the tire deflated enough to have most of the air gone but not lose its bead, and inflated with nitrogen a total of 3 times (sometimes more, sometimes less, depending on the nitrogen readout). Some places can get 99% or better nitrogen (depending on their equipment).

 

Andy, I think you're completely wrong about this... And now I'm going to tell you exactly why I think that in excruciating detail...

 

YouTube - Monty Python - Argument Clinic

A classic.

 

No, it's not.

Jason