Filling Tires with Nitrogen at home?

[4LowLocked]

I have read the benefits of filling your tires with Nitrogen (improved wear, mileage, pressure consistency, temp) so I am considering this for my truck when I replace the tires soon as it could really help out in the cold winter temps and hot humid summer temps we get here on Ontario Canada

My question is though since there seems to be one MAJOR draw back. If I am planning on Airing down and then need to air up on my way home, is there a kit that will allow you do refill on your own? Or will I constantly have to fill up with regular air, then go to a refilling stating (my local Toyota dealer offers this) to get the nitrogen put back in?

[Robinhood4x4]

You realize the air you're breathing is already 80% nitrogen, right? The nitrogen thing is a myth perpetuated by people trying to sell you something. There is nothing inherently different about N2 that will significantly improve wear, mileage, or temperature.

All you have to do is make sure your tires are at the proper pressure and you gain all the "advantages" of nitrogen, but for free.

[BruceTS]

You realize the air you're breathing is already 80% nitrogen, right? The nitrogen thing is a myth perpetuated by people trying to sell you something. There is nothing inherently different about N2 that will significantly improve wear, mileage, or temperature.

All you have to do is make sure your tires are at the proper pressure and you gain all the "advantages" of nitrogen, but for free.


X2

[AxleIke]

x2.

that "nitrogen is better" is a total scam, and is complete bullcrap. Nitrogen is good in shocks.

As for on board systems to get gas to go in tires, CO2 is far superior to N2 as for the same 20lb tank, you get MANY more fills out of a CO2 systems than nitrogen. Or you can just get an air pump.

[AxleIke]

I guess that makes mine x3

[xonetruthcrewx]

I have a 76cu. ft. bottle of nitrogen in my truck as my on board air system. I get the nitrogen from work for free. That is the only reason i use it. Otherwise i would use a compressor and regular old air. Nitrogen definitely has its benefits though. For one, it cant be beat at the track. I use nitrogen in all my vehicles including my Gixxer 1000. At the track i never have to worry about my tire pressures which are very important. There is no difference between cold and hot tire temps with nitrogen. Check it once and be done with it. The air up times are also awesome with my setup. I can air up all 4 tires from 18lbs to 40lbs in like 3 minutes. Its great.

[Robinhood4x4]

Centuries of science says that all gases change pressure with a change of temperature. That's a fact that cannot be disputed.

Nitrogen is also an inert gas at all temperatures, not just "extreme" ones.

I will concede that it does something. N2 will purge out most of the moisture in the air. The moisture can cause larger fluctuations in pressure than just the fact that you're using N2. Depending on how good your air dryer is on your compressor (or if you even have one) it can do the same thing or close enough for daily driver work.

[MTL_4runner]

Nitrogen is an inert gas at extreme temperatures. It doesn't increase in pressure or decrease in pressure at extreme temps. Thats why it is used in tires that go fast. It is also used at high altitude and cold regions for pneumatics. To say it is a wise tale or a scam is ridiculous. At our low speeds as in crawlers, it is not as much an issue. To someone maintaining high speeds or in different climates it is very important.


Steve is right, no gasses are exempt from the basic laws of physics which govern the behavior of all gasses when exposed to variations in temps or volumes. Nitrogen was originally use in aircraft tires due the fact it is inert and if the tires did catch on fire, the gas filling the tire would not suddenly create a fireball as the tire ruptured. Most of the other claims are unfounded and in general filling your tires with nitrogen does not benefit your or the environment.

[BruceTS]

Nitrogen is an inert gas at extreme temperatures. It doesn't increase in pressure or decrease in pressure at extreme temps. Thats why it is used in tires that go fast. It is also used at high altitude and cold regions for pneumatics. To say it is a wise tale or a scam is ridiculous :rofl:. At our low speeds as in crawlers, it is not as much an issue. To someone maintaining high speeds or in different climates it is very important.



Basic physics of gases states that the volume pressure and temperature of gases is determinted by the equation: PV = nRT, where

P = Pressure
V = Volume
n = number of moles of gas (moles is a certain number fo molecules)
R = Universal Gas Constant (same for all gases)
T = Temperature (on an absolute scale such as Kelvin)

n does not change for gas in a closed system (such as a tire with no leaks) and R does not change at at (it is a universal constant)

So, for any closed system, the amount a gas expands or contracts (i.e., the volume) is directly variable with temperature and inversely variable with pressure. It doesn't matter whether you have air, pure oxygen, pure nitrogen or poo gas. If you have a fixed amount in a closed vessel, the volume changes by exactly the same amount.


The main benefit to nitrogen, it has no water content. Water, flashing to steam as the tires heat up, can cause a noticeable change in tire pressure. But this is only a factor in car tires that will see a dramatic change in temperature, something most daily drivers won't see. We used nitrogen in our race cars mainly for convenience. We used nitrogen to operate our modified impact wrenches that ran at 150psi to change tires, hard to get a compressor to keep up, so it became a standard to fill tires or operate anything else that would have used compressed air.

Besides you'd need to evacuate the tire completely to remove all moisture and trace gasses, if you think your gonna get a fill of pure nitrogen. Then you have to take under consideration that when you get a tire change they use soappy water to seat the bead, so filling the tire with nitrogen is useless, unless you dry the inside out first.

[BruceTS]

Oh, there are plenty of benefits: (1) Cool fluorescent green valve stem caps (assuming your nitrogen vendor has any marketing savvy), which will look sharp with your spinning wheel covers. (2) Bragging rights. OK, you were behind the curve with cell phones, iPods, thong underwear, etc. Nitrogen in tires is relatively new to the mass market. Now's your chance. (3) Reduced fire danger next time you land your space shuttle or commercial aircraft, and tell me you won't sleep better knowing that.

Most tires are filled with compressed air, which when dry consists of about 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases by volume. Water vapor (humidity) can make up as much as 5 percent of the volume of air under worst-case conditions. Filling your tires with nitrogen mainly does two things: it eliminates moisture, and it replaces skinny oxygen molecules with fat nitrogen molecules, reducing the rate at which compressed gas diffuses through porous tire walls. That means, theoretically at least, that a tire filled with nitrogen retains optimal pressure longer, leading to more uniform tire wear and better gas mileage. The commonly quoted figure is that tires inflated to 32 psi get 3 percent better mileage than at 24 psi.

Does nitrogen make any practical difference? You couldn't prove it by me. I found no scientific tests showing that nitrogen-filled tires stayed inflated longer than average under normal conditions. A car-buff buddy was sure it worked but conceded he had only anecdotal evidence that it did.

As for moisture, changes in humidity affect tire performance two ways. First, the density of humid air fluctuates more with temperature than that of dry air, so removing humidity can keep your tire pressure more consistent, especially when the temperature climbs over 100 degrees Fahrenheit. That may be a legitimate concern in Formula One racing, but it's not much of an issue if you're just tooling around town.

Humidity can also be a factor in wheel maintenance — since pure nitrogen doesn't have moisture in it, supposedly your wheels won't rust as quickly, which could lead to improved wheel performance and air sealing. The question is, how big a problem is wheel rust these days? According to a few tire and wheel shops we contacted, not very. Seriously rusted wheels are uncommon in typical steel-wheeled cars, and many high-performance cars have alloy wheels that don't rust at all. One exception is work vehicles such as dump trucks, which are exposed to a much harsher environment.

Another claim I've seen is that since nitrogen is slightly lighter than air, you'll save weight and get better performance. However, we're talking about a weight difference of less than 4 percent of the gas in the tire — in other words, a difference of less than an ounce for most vehicles. A possibly more realistic benefit is that nitrogen is largely inert chemically at low (i.e., normal) temperatures, so it won't attack the rubber in your tires like oxygen does. Oxygen attack is something both the National Highway Traffic Safety Administration and Ford Research have studied, and can be a problem for tires used for a long time or in rough conditions.

More important, nitrogen doesn't support combustion, which is one reason aircraft and the space shuttle use nitrogen in their tires. The wisdom of this precaution was brought home by the crash of Mexicana Airlines flight 940 on March 31, 1986. Shortly after the Boeing 727 took off from Mexico City en route to Puerto Vallarta, an overheated landing-gear brake caused a tire improperly filled with air instead of nitrogen to overheat as well and explode, rupturing fuel and hydraulic lines. The ensuing fire and crash killed 167 passengers and crew. However, unless your driving habits are of the X-treme variety, the chances of your tires catching fire anytime soon are slim.

Overall, filling up with nitrogen won't hurt and may provide some minimal benefit. Is it worth it? If you go to some place like Costco that does it for free with new tires, sure, why not? Elsewhere, though, I've seen prices quoted as high as $10 per tire, which is way more than I'd pay. Rather than shell out for nitrogen, you'd be better off just checking and adjusting your tire pressure regularly, something the NHTSA says less than 60 percent of U.S. motorists actually do.



this sums it up quite well........

[AxleIke]

I don't know how many people here, use it on a daily basis.

I do.

I use liquid nitrogen every day in my job, as well as gaseous nitrogen, along with a great many other gasses.

The OP is not some race specialized engineer trying to squeeze a few 10ths of a second out of his car to win, he is an average driver talking about a 4runner.

So, for his use, and the vast majority of the rest of the members here, paying for nitrogen in his tires is a total scam.

CO2 costs about 15 bucks a fill, and is far superior because of its ability to fill more tires than nitrogen, and, with the exception of engine driven compressors, can reach higher pressures than air compressors, so seating beads, and running air tools is possible, making it the ideal OBA system.


I could care less about the science, but for its use

Sounds like your employers care a great deal about the science. As they should.

[BruceTS]

This looks like a resurfacing of a trend I learned about in general chemistry. Apparently some years ago busineseswere trying to sell this kind of stuff on two claims: one, that nitrogen filled tired deflate at a slower rate, and two, that in an accident, a punctured tire filled with nitrogen is safer somehow than normal air (something to do with fires). What I learned in chemistry is that both of these claims are bogus. Total marketing bullshit preying on the ignorance of the usual consumer. Now it appears these same people have reared their heads again, using different claims. Some facts first of all. Air is already about 78% nitrogen and 20% oxygen by volume (http://en.wikipedia.org/wiki/Air). Thus the company is offering what looks like a replacement of most of the oxygen molecules with nitrogen. At 2% oxygen content you have ten times less oxygen per volume than normal air.

Now to address these new claims. First, they cite facts about the bad things that happen if you don't keep your tires inflated properly. All of the benefits of proper tire inflation can be achieved with normal air. Secondly, if my education serves me well, the claim that "With PurigeN98, tires hold their pressure longer." is incorrect due to the law of effusion of gases. In fact, as rate of effusion is inversely proportional to the mass of the gas molecule (lighter molecules escape faster than heavier ones), and that nitrogen is lighter than oxygen, the tire may deflate even faster with PurigeN98 than when compared to normal air. This is of course assuming that any channels through which the gases may escape is large enough to permit either nitrogen or oxygen.

Thirdly, and I'll concede this point partially, they claim your tires will oxidize slower if you use their product. Now obviously we are talking about the oxidation of the interior of the tire surface, as the exterior is still in contact with normal air. This is were my knowledge halts my opinion. I have not taken any chemistry courses that would cover the oxidatin of rubbers. It is true that such a thing happens, as we all know, old rubber gets hard. I am assuming this is due to the oxidation of the polymer in some way. This obviously could contribute to the degredation of your tires. But, as one who tends to keep his tires properly inflated, I must say from firsthand experience that properly inflated tires will become dangerously threadbare before they fall apart from internal or external oxidation.

In conclusion, find a gas station who has free compressed air, keep your tires properly inflated, and don't waste money on this hype.

(sorry this was so long, but I hate seeing companies pull this kind of stuff on the unsuspecting consumer)

[Robinhood4x4]

I use it everyday too. Back in the semiconductor industry with liquid nitrogen and now gas form in the aerospace industry. Plus, I know the science behind it.

[BruceTS]

I wonder if MythBusters has done this test yet? I guess I'll go suggest it at their website

Edit* this was already done on MythBusters and was BUSTED!

[AxleIke]

LOL.

Good posting.

People always try to argue science. They never win.

[mastacox]

Jeez guys, it's obvious that N2 has magic properties that helps balance your car's Chi.

... Billy Mays here for Nitro-Air- the rare lab-created gas makes your tires last 50x longer and gives your car that extra "pep"!

http://members.cox.net/yiotisshop/main/Billy_Mays.jpg

[YotaFun]

Jeez guys, it's obvious that N2 has magic properties that helps balance your car's Chi.

... Billy Mays here for Nitro-Air- the rare lab-created gas makes your tires last 50x longer and gives your car that extra "pep"!

http://members.cox.net/yiotisshop/main/Billy_Mays.jpg


LMAO!!!! Good One!

[4LowLocked]

Thanks for the feedback guys! I was still sitting on the middle of the fence without much knowledge of the issue (Chemistry wasnt my strong point in school - Im a graphics artist)

Looks like even with our crazy fluctuating temps here - I will be sticking with the good ol' fashion pay my quarter at the pumps

[bamachem]

It's Bogus, but hey, I'm a Chemical Engineer, what do I know??? :D

It's bogus for the every-day application.

Look at the heat capacity of Nitrogen, Oxygen and Air (~80% N2 and ~20% O2).

Cp (heat capacity) of Nitrogen Gas at 300*K is 1.040 (kJ/kgK)
Cp (heat capacity) of Oxygen Gas at 300*K is 0.918 (kJ/kgK)

The difference in the heat capacity is a whopping 0.122 (kJ/kgK) or less than 12% between the two pure gases.

Now, consider that air is ~80% N2 and ~20% O2. When doing the math you can see that the decrease in heat capacity of the gas filling the tire is only 2.3% less if you had air when compared to pure nitrogen. 2.3%. Therefore, it would be safe to deduce that Nitrogen would be slightly cooler for the same specific amount of energy input into a closed system (the tire/wheel in a closed environment). However, remember that the amount of energy input into the "system" of a tire/wheel when driving is continuous. The actual sensible temperature of the "system" will depend on the rate of heat into the system (friction from the tires/brakes, conduction w/ the road, radiant heat from the engine & nearby rotors/calipers, etc) and the rate of heat dissipation out of the system (heat transfer to the surrounding air as well as contact with any water, etc). Let's say you put X amount of heat into a tire filled with air and it reached Y temp. It will take you 1.023*X of energy (2.3% more) to get the tire filled with nitrogen to the same temperature, but since you have a pretty-much endless source of heat energy to put into the system, then the temp will eventually be the exact same for the same external conditions. The tires simply do NOT run "cooler" with nitrogen than with air.

PV=nRT (neglecting compressibility factors since they are essentially equal for air & nitrogen)

So, PV=nRT and since n*R is constant and V is almost constant w/ pressure since your tires don't expand in volume by a significant amount, then P1/T1 = P2/T2 making them a direct proportion.

In other words, for a change from 30*F to 80*F, your tires will change about 10% in pressure (have to use absolute pressures & temperatures - PSIA, NOT PSIG, and *R NOT *F). For a 35PSIG tire at 80*F, you would be at about 32PSIG at 30*F.


When going from 30*F to 80*F, the pressure inside a tire will change less than 10%, so from a very cold morning to warm driving temperatures, you will see a decrease of less than 3.5 PSIG for a tire initially inflated to 35PSIG at the warm temp. A tire filled with nitrogen would decrease in pressure by 2.3% less. Here's the hard numbers:

P1/T1 = P2/T2 therefore,

(P1/T1)*T2 = P2

(49.7 PSIA / 539.67 *R) * (489.67 *R) = P2
45.09 PSIA = 30.40 PSIG = P2

So, If you have a tire filled with Air at 35 PSI on your tire gauge at 80*F and it gets cold, then the tire pressure will be 30.4 PSI on the same gauge at 30*F. The difference measured will be 4.6 PSI. Since nitrogen has a higher heat capacity, it will contract ever-so-slightly less - 2.3% less, remember.

4.6 PSI * 0.977 = 4.49 PSI

with air, you will be at 30.4 PSIG and with nitrogen, you will be at 30.5 PSIG.

ONE-TENTH OF A PSI DIFFERENCE. WHOOPIE.


links:

http://blogs.consumerreports.org/cars/2007/10/tires-nitrogen-.html

http://articles.moneycentral.msn.com/SavingandDebt/SaveonaCar/NitrogenTireBenefitsSeemOverblown.aspx

http://www.straightdope.com/columns/070216.html

[AxleIke]

LOL.

I'm pretty sure 4runnerchevy is having fun with everyone.

There is no way he'd be serious about his posts, hopefully everyone gets the joke, as this is actually turning into good tech, helping spread knowledge about this scam. I'd hate to see it degenerate into a pissing match over a couple of sarcastic posts.

[xonetruthcrewx]

I agree that for everyday use, its not worth it. I use it for everyday use, but i get it for free. Where it is well worth it is on the track like i mentioned earlier. I sit there with my Nitrogen filled tires and never have to adjust my pressure. I watch everytone else constantly adjusting their pressures after each session. I remember a track day in my Audi. After one hard session my tires had increased 12psi. Thats huge. That kind of pressure change will cause major problems with traction on the track. If i had been running Nitrogen, it wouldnt have happened. This is my real world experience with Nitrogen vs. Air.

[bamachem]

Seriously, I agree that with 100+ degree tire temp changes, every little bit helps, but for every-day use and at ~$10 per tire - its a scam on the average consumer, which includes all applications of offroading.

Also, we're not going to piss on your parade here if you have an opinion and express it within the bounds of our rules - that's not how this place works.

It just sucks that we don't have a way of detecting sarcasm on these boards... I can't believe I fell for your bullshit!!! :D

[Robinhood4x4]

But this thread does have great tech that people in the future will find.

[RobG]

Any idea what temp a track tire gets too? 200F+?

The only thing that makes sense to me is they are converting the water to gas giving a large volume change and resulting pressure increase. Bottled N2 is very dry compared to standard compressed air (no dryer) so little to no water.

Street tires probably don't get nearly as hot so you don't see much difference there.

Is that possible?

[BruceTS]

Almost forgot we ran bleeder valves on our wheels to vent off excessive pressure when the tires heated up. I know bleeder valves are banned for use in the NASCAR cup series, mainly because after a tire cools, the pressure drop can cause more problems......OH wait did I say pressure drop? That's right, even with nitrogen filled tires, all NASCAR teams experience this..... What do I know? a simple search will yeild a wealth of information on pressure change in tires in all forms of racing.

I'll bet you won't notice a difference in a tire that is filled with nitrogen vs one filled from a SCUBA tank.

[Robinhood4x4]

The only thing that makes sense to me is they are converting the water to gas giving a large volume change and resulting pressure increase. Bottled N2 is very dry compared to standard compressed air (no dryer) so little to no water.

Is that possible?


Yes, that's what happening.

[bamachem]

here's another point of view.

we all know air is 80% nitrogen and 20% oxygen.

if nitrogen won't leak thru the rubber but oxygen will - as claimed by all the pro-nitrogen people - then wouldn't it make sense that you would eventually end up with all-nitrogen in your tire by filling with air anyway?

think about it.

lets say a tire holds 5 cuft of volume to make the math easier.

initial fill is 4cuft of nitrogen and 1cuft of oxygen.

tire leaks down, supposedly via osmosis thru the rubber. since the nitrogen proponents say that nitrogen doesn't leak down like air, then what's leaving the tire must be oxygen, by simple deduction using their logic, correct?

now, let's say you lost 1/2 cuft of oxygen and now you have the original nitrogen and have to add 1/2 cuft of air.

now you have 4.4 cuft of nitrogen and 0.6 cuft of air.

tire leaks down over time again. we loose half the oxygen.

now you have to add 0.3 cuft of air. at that point, you have 4.64 cuft of nitrogen and 0.36 cuft of oxygen.

leak down half of the oxygen again...

you get the point. you get to 99% nitrogen pretty quick...

http://4rnr.net/tire1.jpg

[BruceTS]

The funniest thing about this myth is the claim of rubber deterioration. It's so silly how some people will believe almost anything. If you have ever looked inside a tire after it's been removed, they usually look brand new. Now how can this be? Duh the outside of the tire is exposed to more harmful effects than the inside will ever see. BTW if you think air is that bad on pressure change, check out the radical changes CO2 with temperature differences. OMG maybe we should have CO2 banned, since it's also a greenhouse gase and every time we use the stuff we are contributing to Global Warming :rofl: :rofl: :rofl: :rofl:

[bamachem]

i did some more reading and found some interesting info. it turns out that DRY air and nitrogen have very similar properties as i've been stating so far. however, when you add moisture to the air, the properties change dramatically. when you factor in thermal expansion of water vapor, increase in vapor pressure, as well as changing any condensed liquid to a vapor (~50X expansion in volume for a given mass at constant pressure), then you can see that the culprit is water vapor and not the use of nitrogen itself.

for everyday driving, it's still 99.9% overkill and really isn't economically sustaining considering that it costs as much as $10/tire. however, if you have access to dry compressed air or nitrogen for cheap/free, then you might as well use it.

here's what i found:

1. when comparing nitrogen gas and moisture-laden air, are pressures more constant with temperature changes? YES, nitrogen is better, and in extreme cases, considerably better. however, the same results could be attained by using dry compressed air instead of nitrogen. moisture is the culprit in the pressure differential, NOT the use of either nitrogen or air.

2. does a tire filled with air leak down faster than a tire filled with nitrogen? YES, but if you continue to refill a tire with air, then the oxygen will eventually diffuse, leaving highly-concentrated nitrogen behind. however this does NOT have the same effect as filling with dry nitrogen since the moisture is still present and, therefore, pressure fluxuations will still be the same as a tire filled with moisture-laden air.

3. do tires filled with nitrogen run cooler? No. Not directly via the use of nitrogen, anyway. Since they don't leak down as fast, they would statistically be operating at more-optimal pressure, resulting in less chance of overheating due to excessive friction - usually caused by underinflation.

4. do tires last longer when filled with nitrogen compared to air? Technically, Yes. Practically, NO. The rubber will not oxidize as fast when you fill with pure nitrogen, however, the chances of you owning a tire long enough for it to oxidize from the inside out before it either wears out, gets dry-rotted from UV/sun exposure is pretty slim. Today's tires are made from some pretty advanced compounds, and unless you plan on driving on a set for 10+ years, then you really shouldn't worry about (or buy into) the "lasting longer" jargan. However, if you look at it from a wear standpoint, with more consistent pressure on the inside, it's more likely to get a more even wear pattern, thereby leading to the possibility of eeeeking a few more miles out of a set.




http://getnitrogen.org/pdf/APTechLetter111804.pdf

1. Why does oxygen migrate out of tires quicker than nitrogen?
2. Why does nitrogen not expand and contract as much as air?

Answers:

1. Oxygen migrates out quicker than nitrogen, because:

a. Permeability coefficients measured for oxygen, P O2 , are higher than the values for nitrogen, P N2 , in all known rubbers (elastomers), including those typical of tires. The ratio of the permeability coefficients, P O2 divided by P N2 , is between 3 and 4 depending on the particular rubber. This means that oxygen permeates 3 to 4 times faster through rubber than does nitrogen, other conditions being equal;

b. oxygen is a smaller molecule than nitrogen (as determined by a wide variety of measurements of molecular size); this is true despite the fact that molecular weight of O2 (32) is greater than that of N2 (28), which might suggest that oxygen is larger than nitrogen;

c. relative permeabilities for oxygen and nitrogen are dominated by the difference in size of the molecules.

2. There is no significant difference in expansion and contraction characteristics of nitrogen, compared to air, when moisture is absent.

a. Expansion or contraction of either air or nitrogen occurs to very similar extent, in response to changes in temperature, in the commonly encountered range of temperatures and pressures relevant to discussion of tire inflation.

b. There is no practical difference as long as the gases are dry, with respect to the effect of temperature on pressure in an essentially fixed volume container, such as in a tire.

c. Water is usually present in the case for conventional compressed air. At lower temperatures, as a liquid, water occupies very little volume. However, as temperature increases, liquid water vaporizes to become a gas and its volume expands, causing total pressure to be higher in the tire, than would be the case with dry gas. Thus, the presence of water in a tire contributes to pressure variations as temperatures change.
Please find attached several pages of more detailed information. I provide a Summary, explaining in plain language several factors at play in tires, comparing using Nitrogen to using conventional compressed air. In Appendix, I provide more detailed technical information drawn from credible literature sources.

If I may be of further assistance, please contact me or our Sales/Marketing Specialists, Bill Phelps and Phil Powell in St. Louis.

M. Keith Murphy, PhD
Air Products Research Associate
(314) 995-3434
murphymk@apci.com





Summary - Nitrogen compared to conventional compressed air for tire inflation

Benefits:

1. Maintain proper tire pressure longer with Nitrogen than with compressed air

2. Reduced degradation of rubber’s mechanical properties caused by oxidation, in the absence of oxygen, using Nitrogen

Composition differences between membrane-generated Nitrogen and conventional compressed air:

Oxygen and moisture are almost completely removed from air by the membrane.

Explanations for the benefits of using membrane-generated Nitrogen compared to compressed air for tire inflation

1. Better inflation pressure maintenance using Nitrogen:

Nitrogen permeation through the rubber is much slower than oxygen permeation.
Measured permeability in all known rubbers is faster for O2 compared to N2,
by factors ranging from 2.4 to 4.7, depending on the rubber.
Permeability of gases is generally faster in some rubbers than in other rubbers, but
all rubbers permeate O2 faster than N2 by a ratio of about 3 to 4.
Oxygen permeates faster because it is a smaller molecule than is nitrogen.
Thus, any tire filled to proper pressure will hold that pressure longer,
if the higher permeability component (O2) is not in the tire in the first place.

2. Reduced oxidative degradation of rubber, because oxygen is absent, using Nitrogen:

according to J. D. Baldwin, et.al., (Ford Motor Co.), in “Passenger tires inflated with nitrogen age slower”, Rubber & Plastics News, pp. 14-19, Sept. 20, 2004
Oxygen chemically reacts with rubber, causing the rubber’s mechanical properties to degrade.
Nitrogen does not react with rubber. If oxygen is absent or present at much lower concentration, rubber mechanical properties are more stable over time.

Do tires run cooler?:

Tire run temperature is influenced by many factors, including:

Proper inflation
Rolling resistance
Road conditions
Speed
Outside environment temperature
Vehicle load
Temperature influences gas pressure.


Heating a gas in a fixed volume container increases gas pressure (P1/T1 = nR/V = P2/T2)
and cooling decreases gas pressure. For example,

a truck tire filled to 100 psig at 60F, increases in pressure to ~118 psig at 140F;
a car tire filled to 30 psig at 60F will increase in pressure to ~ 37 psig at 140F.

For temperatures and pressures near common experience, air, or O2 or N2, all behave very similarly in this respect. Thus, there is no significant difference in pressure changes, comparing air and N2, due to gas temperature effects alone (that is, as long as either gas is “dry”).

Water, however, can exist as liquid or as vapor (i.e., a gas) and water changes from liquid to vapor over the relevant range of temperatures. The “vapor pressure” of water is very sensitive to temperature, increasing from 0.26 psi at 60F to 2.89 psi at 140F.

If there is liquid water in the tire at 60F, as does occur with conventional compressed air, water’s vapor pressure contributes a small additional amount to pressure at 140F. If dry air or dry N2 is used to fill the tire, the effect of water on pressure is eliminated. Tire heating will be greater, if proper inflation pressure in not maintained.

Over time, a tire filled with air, will loose pressure faster, due to faster permeation of O2.
This will contribute to under-inflation of the tire, absent frequent pressure checks. Under-inflation may contribute to excessive mechanical flexing of the tire, which will contribute to additional road resistance and frictional heating. Thus, improper inflation is a principle contributor to excessive tire heating. Nitrogen helps better maintain proper tire inflation pressure, compared to compressed air.

Do tires wear longer?

Tire wear is influenced by many factors:

Proper inflation pressure (see above discussion)
Rubber’s mechanical properties are more stable, if oxygen is not present.


http://www.4rnr.net/tirechart1.jpg


http://www.4rnr.net/tirechart2.jpg