The Missus gets scammed.......

[Trans_23]

Four tires for my F-150 cost $800 last year. I would have jumped for joy getting them for $700. BTW, the place I bought mine from offered nitrogen for $5 a tire. I too wondered how they got all the air out before they put the nitro in.

 

[jmig]

One atmosphere is appx. 14.7 psi, so inflating to even 45 psi with nitrogen still leaves close to 25% air unless the space inside the tire is purged first. Give them this fact and then ask them to justify the cost. If they say they purged the tires, ask them to explain the process.

Not really Tom. Air pressure is measured in psig or "gauge" versus psia or "absolute." In gauge 14.7 is 0. So the 45 lbs gauge is really 59.7 lbs absolute pressure.

Also, consider air is almost 70% Nitrogen. So the small amount of oxygen in the tire at atmosphere is only 21% Oxygen. So your actual O2 content is more like 6.8%. (14.7/45= 32.6% X .21= 6.8%)

Still, I think it is B.S. to charge $45 for nitrogen in tires. Like you, I fail to see the benefits.

 

[Roadburner440]

There is no way to get all of the air out of the tire or "purge" as is being asked. For you to create a vacuum inside of the tire would mean the bead would get broken from the rim. As far as the nitrogen itself goes I am schooled in this on aircraft so will give backround straight from the Navy's aircraft tire/wheel manual.

The reason that aircraft tires are serviced with nitrogen is not because of their heating/cooling properties but rather the lack of water vapor. This prevents the water vapor in the tire from freezing at altitude, and piercing the tire upon landing. In tubless aircraft tires (like you find on most cars as well) the rim is vented (where you see little green dots on the outside of the tire) because Nitrogen naturally permeates rubber. Without said green dots to vent the nitrogen out of the ply's you could get pockets of nitrogen between them causes blowouts once the sidewall is weakened enough.

In cars the only practical use and excuse I see for Nitrogen is in auto racing. Such as NASCAR/F1 and such where you need to be able to predict that the tires will heat up in X amount of time to X pressure, and so on.. When we just got our Trailblaze to replace the GMC we had the Acura dealer tried selling us this stuff, and I must tell you the presentation they give is impressive.. You do not have to check the tire pressure for a year (their claim), and even went as far as telling me that a Nitrogen molecule is bigger than regular air.. Me of course servicing aircraft tires for a living when I came back with all of the above facts (as well as the stuff about regular air being 80% Nitrogen) they really did not know what to say. All I know is that if this stuff did not leak out of rubber we would not have the inspections, and stuff on the aircraft we do. Cause if it flies you check the pressure daily, and if it doesn't fly there is an actual conditional to check the tire pressure every 7 days... So if this stuff was good for 1 whole year like they said I can save a lot of work on my part. Just makes me mad when they try to rip people off like this... Same with that Autobutler detailing junk. Now keep in mind this is my opinion based on the facts I know through my own training.. If anyone does have scientific evidence to the contrary I'd be interested to see it. As long as you keep your tires serviced to the proper pressure though it will not matter if you have nitrogen or air though.

 

[CADFather]

The Nitrogen vs. Atmosphere for tire inflation comes up every so often on the motorcycle forums I belong to. From some of the arguments I've seen there regarding it's usage in racing I gather Nitrogen doesn't expand as much as air as it heats up so the tire pressures remain relatively constant and predictable. That's all fine and well for racing but not really relevant for street use. The other selling point that the proponents use is less frequent need to add air to the tire or even to check the pressure. Now I don't know about you guys and your ground vehicles of choice but my car and truck tires get checked at least once a week and along with all the fluids every time fuel is added. My bike tires get checked for air and damage everyday before I leave on it. Anal yes, but I only have 1* (one Asterisk) and the tires are the only (hopefully) contact point with the road that I have.

I guess it comes down to whether you can justify the expense of having those little green caps or not, I don't think I could give up my little chrome skull caps, though. Oh, and I litterlly just bought 4 10 ply tires for the back of the wifes 1-ton Ford for $25 bucks right before I logged on the forum. They were takeoffs from a buddies shop that does four wheel drive conversions and came off a brand new F-350 that is getting new swampers, . Go, ME.

CAD

 

[Willy]

Maybe in more populated areas, but around here in rural, in the sticks Tennessee if your tires are low on pressure, the only thing that's available to put in them is compressed air.

 

[stuartcox]

I put helium in mine...so I can really fly!

 

[Wing_Z]

Meh.
I bet when you go racing around corners, they squeal in a funny little Donald Duck voice...

 

[Tom Clayton]

John, here's the math in my head... Equal pressure in the tire (zero psi) is one atmosphere. 15psi should then roughly double the mass of air inside the tire, or two atmospheres. So at 45 psi, you've roughly quadupled the total mass of air. Granted, with the total of gasses not nitrogen, you then end up with 25% of 22%, or 5.5% other than Nitrogen. Deflate the tire and reinflate it back to 45psi, and you reduce that by another 75% with each cycle.

But if the average tire sales man knows that, they're overqualified for their job!

 

[jmig]

John, here's the math in my head... Equal pressure in the tire (zero psi) is one atmosphere. 15psi should then roughly double the mass of air inside the tire, or two atmospheres. So at 45 psi, you've roughly quadupled the total mass of air. Granted, with the total of gasses not nitrogen, you then end up with 25% of 22%, or 5.5% other than Nitrogen. Deflate the tire and reinflate it back to 45psi, and you reduce that by another 75% with each cycle.

But if the average tire sales man knows that, they're overqualified for their job!

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