Yesterday I was at the Toyota dealer for a few minutes and I noticed they are now advertising Nitrogen filled tires in the service department.

Their claims in the ad:

"Nitrogen filled tires get better gas mileage! Extend the life of your tires! Maintain pressure longer!"

While I know some of that is true to a certain extent, I was curious to know if any other members are using Nitrogen in their tires, and if so, what is your experience with them?

I might consider doing this myself if the benefits are obvious.

 

Oof, this issue keeps coming up. Air is already roughly 80% nitrogen, 20% oxygen, plus tiny amounts of a few trace gases. So if you could fill a tire with just nitrogen all you would be doing is removing the 20% oxygen to get from 80% nitrogen to 100%. Doubtful if there would be any real advantage, other than to get rid of oxygen which is reactive and supports oxidation and combustion in some scenarios.

But taking a tire at "0" psi and pumping it up to say 42psi with nitrogen would not get you to 100% nitrogen. "0" psi is actually 14psi because that's atmospheric pressure. So you are taking 1 volume of 20% oxygen and adding 3 volumes of 0% (3x14 = 42) and end up with 5% oxygen. The only way to get it to 0% oxygen would be to pull a vacuum on the tire, and that would probably suck the beads off the rim and let air in.

I don't see the point.

 

The reason for going all nitrogen is because of your standard air pumps that you find at gas stations. Check out the amount of moisture in the air. This moisture causes can cause a bigger differnce in PSI as the tire heats up. If you could eliminate all the moisture (and there are pumps that do just that) being pumped into your tire, there would be no need for going the nitrogen route.

 

I agree that having moisture in your tires could cause problems such as corrosion of the rims,etc. But having water molecules in there in a vapor form in place of some of the nitrogen or oxygen molecules should not cause more rapid pressure rise as the temps increase (the gas law PV=NRT). However if you had water in there as a liquid that vaporized as temp increased perhaps. But the higher pressure in a tire would elevate the boiling temp of water so you would have to get above 212 degrees F, which might be rather hot for a tire?

Also, simply letting the tires down to 0 and refilling with dry nitrogen would not remove liquid water that is already there. You'd have to take the tire off the rim, dry rim and tire, refill and purge several times with nitrogen. Do they do this?

Refilling with moist air from service station lines probably isn't ideal. But you're simply topping off, adding only a small portion of the total air that is in the tire, which reduces the amount of moisture you're introducing into the tire.

 

What about using standard air pumps that most people use to cap off their tire pressure?

 

If you mean the ones that run off AC or the cigarette lighter socket, might be drier than the ones at service stations. I'm going to get one of the cigarette lighter ones because I'm in a condo and we have no AC power in our carports (other than lights at night). Anybody have one they recdommend?

 

I was just pointing out the main reason for going nitrogen. Not that I buy into that arguement. In fact i don't use nitrogen to fill my tires. I use the standard pump with moisture and all... Just keep in mind you will see a bigger psi change from cold to hot then you would with a pure nitrogen filled tire.

Having a certain psi at a certain tire temp comes into play in a racing environment. For everything else, it's meaningless.

 

The boiling point is just the temperature at which the vapor pressure of the substance is equal to the pressure of the surroundings. You can still get a phase change (water going to vapor) in a tire without reaching the boiling point.

 

Of course, there is always a vapor pressure above a liquid. What would the vapor pressure of water be at typical street tire operating temps and pressures?
Also worth thinking about: as the pressure in a tire rises, the temperature should fall at a given load, speed, and ambient temp because there will be less flexing, correct?

 

just bought a campbell/housfield (sp?) manual foot pump at the local WM for about $10. small/light, capacity ok (~15 pumps/psi on my HCH2) and the analog gage is within a couple of psi.