Nitrogen in tires????

IMHO, a total waste of money. Definitely not needed in automobile tires.

snipped-for-privacy@nosam.org wrote in news: snipped-for-privacy@4ax.com:

It is, basically.

Air is already 78% nitrogen. The machines that distill nitrogen from the air to make the stuff that goes in your tires are capable of about 95% purity.

But to actually get 95% nitrogen inside your tires, you'd have to deflate and re-inflate several times, refilling with with 95% nitrogen each time, in order to even approach 95% finished nitrogen in the tire. You have to do that in order to evacuate the remaining regular air.

It won't be enough just to deflate then refill once with nitrogen (which is what the garage is likely to do). Do that and you're going to end up with about 85% nitrogen, hardly worth the effort.

Nitrogen is intended for race cars and airplanes. Road cars derive no benefit at all.

more than half =)

I wouldn't pay for it. If they use nitrogen free of charge then OK.

It barely cost a few bucks to have nitrogen put in your tires and dealerships do not do that. It probablly is not even cost effective for any company to fill the tires with nitrogen.

With that said, it does work.

snipped-for-privacy@nosam.org wrote in news: snipped-for-privacy@4ax.com:

See what Click and Clack have to say about nitrogen:

"Go Mavs" wrote in news:oEvRi.10753$2o1.6284@trnddc03:

Define "does work".

Well, I live in Texas. In the middle of the humid hot summers, the tires expand fairly quickly in a short amount of time. All I can tell you is that I know people who sware by it. I have never done it though. I usually just wait near the oil bay for about 15 min while the tires cool and then they fill them to the suggested amount while changing my oil.

"Does work" could mean minimal for a smaller vehicle. I could not tell you. All I know is that the more the nitrogen then the less it will deflate.

Also, there is a big difference between 85% nitrogen and 80% nitrogen... Almost as much of a difference between having a 98.8 temp and 102 temp.

Like the other guys, I would not pay for it unless I was driving a 350 or something. However, if they make it a free service then I am much more likely to go where they offer it as a free service.

Ain't no such thing as a free lunch.

If they put nitrogen in your tires, you pay for it. Maybe it won't be a line item on your bill but the cost will be included in shop overhead and billed to the customer as part of the labor rate or parts markup.

Jack

Perhaps! But, if the cost of getting my oil changed at 4 places is 22 bucks, then I am going to go to the one that offers me more services for the same price. I know there are always hidden cost and its stuffed away in the cost of the bill and competing cost are always inflating. With that said, might as well take it if it is not killing my wallet.

The theory behind using nitrogen in tires is that since it does not expand and vary tire pressure as much as the air from the atmosphere does, and the process of distilling nitrogen from the atmosphere also removes the moisture, which can also contribute to tire pressure variance. Also, nitrogen is supposed to leak more slowly than regular air.

These attributes serve a purpose in race car and aircraft tires, but for passenger vehicle use, as Tegger pointed out, the concentration of nitrogen is not 100%, and so the benefits are not as great. Also, since all tires leak over time, you have to go back to a facility that has a nitrogen generator instead of using a home compressor or going to one of the thousands of places that do not offer nitrogen fill for tires.

I would not pay extra to have my tires filled with nitrogen.

1. It's hype to suck in ignorant consumers.
2. It creates a dependency. Pure nitrogen isn't as widely available as regular air, so those customers may return more often to their tire dealer and provide the dealer with more opportunities to sell them new tires or maintenance services.

"Go Mavs" wrote in news:rNyRi.15087$fm1.7629@trnddc01:

Not to any practical degree.

In practical terms nitrogen is useless for a road car. Period.

It should be noted that most non-jet, non-pressurized aircraft use plain 'ol compressed air in the tires. The tires on my plane, filled with compressed air, are subject to a good amount of stress. They go from

0-75 in only a few feet every time I land. They also get very hot fast from brake heat in short field landings, and when dragged sideways during crosswind landings when the *ahem* pilot lands in a bit of a crab.

Nitrogen is reserved for the guys flying @ 38,000 feet, where it's -50F.

B A R R Y wrote in news:yhHRi.6785$ snipped-for-privacy@newssvr22.news.prodigy.net:

And for the Space Shuttle, whose tires are inflated to something like

325 psi.

My point all along was that nitrogen is meant for extreme situations. Road cars are not subject to those extremes, hence derive no benefit from nitrogen.

Net is - moisture in "air" contributes to unpredictable pressure increases in racing tires. To avoid moisture, race teams use bottled nitrogen. Dry air would work as well, but race teams already have bottled nitrogen handy, so they use that (at least in NASCAR, the tire changing air wrenches are run off bottled nitrogen). The "unpredictable" range of pressure increase do to moisture in the air is in the tenths of a pound. Nobody I know is that careful when inflating the tires of their road vehicles. If they are, then they must check them every time they get in the car with a calibrated digital pressure meter (not a cheap one). Using pure nitrogen has some theoretical advantages, but the advantages are so insignificant as to be meaningless for automobile use compared to ordinary air (which is already 78% Nitrogen).

The chief beneficiary of installing nitrogen in tires are the companies that make the nitrogen generating equipment and the tire stores who either sell it as an extra cost service, or use it as a gimmick to get you to buy from their store. When you buy tires from stores that claim to use "pure" nitrogen, I suspect that what is actually in your tires when you leave the store is no better than 90% nitrogen.

Ed

I'm with ya'!

A funny side to this for road cars is how much liquid water ends up in the when mounted by many retail "tire mechanics".

I dont have nitrogen in my tires and wont be paying for it. But I just have a follow up question. Most of the time, tire wear and MPG is affected by tire pressure. We have tire gauges to measure pressure maybe for a slow leak and especially now cold weather is coming in. I remember reading that a 10 F drop in temp is equal to 1 psi drop in tire pressure, is this an urban legend?!?. Summer reached 90F-100 and now cold morning where I live is the 50s. That is 4-5 psi drop.

No urban legend. Air is not a true ideal gas, but at normal human livable temperatures the ideal gas law is a reasonable approximation of what happens as you heat and cool air. The ideal gas law is written as: PV=nRT where

P= pressure V=volume n=number of moles (a measure of the number of molecules) R=gas constant (for air at normal human temperatures, assume it is a constant - it isn't really, but close for our purposes) T=temperature (you have to use an absolute temperature scale Rankine or Kelvin)

For a tire files with air, we can assume V, n and R are constants. Therefore it follows that:

P1/T1 = nR/V = P2/T2 or this can be simplified as

P1/T1 = P2/T2 or P2 = (P1*T2/T1). Therefore if T2 decreases, so will P2.

Assume you have tires inflated to 35 degrees at 100 degrees F. 100F =

560 degrees Rankine (in Ranking, zero is at "absolute 0," not some arbitrary point) 50 degrees F = 510 degrees Rankine

If the pressure at 100 degrees F was 35 psi, the pressure at 50 degrees F will be approximately P2 = 35*510/560 = 32 psi.

The presence of water vapor will screw up this calculation, since at normal human survivable temperatures, water vapor is very far from an ideal gas. On the other hand, water vapor is a very small percentage of the air in most tires. The effects are usually minimal but if you had a lot of water vapor in the tires at 100 F, then the pressure might drop by 4 or 5 psi instead of 3 psi. This is trivial for road tires, but not race tires (as previously discussed). Most tire stores use reasonably dry air (all you need is a water separator to get rid of most of the water), so this is not a big issue.

Ed