My girlfriends dad recently had his motorhome tires replaced and they put Nitrogen in the tires. All they could tell him was it was the new thing. I know they put nitrogen in shocks to help eliminate the sponginess feeling. Is there a real benefit to putting it in tires?

Nitrogen stays cooler and is less conductive than air, so you don't over pressure the tires while they are hot. I think nitrogen is more dense than regular air as well, so maybe that may be the reason why they remove the spongy feeling?

This is interesting. I'm sure I would just add air for pressure adjusts but it would be nice to have the tires more consistent.

How is...K, Now I'm looking for a periodic table; what is the size a nitrogen molecule?..... Wondering if it will take longer to permeate the rubber and leaks so your pressure stays where you put it.

I'm not buying it now. Our atmosphere is 78% nitrogen. Filling tires with 100% can't be significantly better than the normal 78%.

EDIT: This is a hot topic for some RV folks. My conclusion is dry air is a really good thing. Nitrogen probably falls into the 1% improvement category useful to high end racers etc but not worth my effort.

My understanding is that the claimed advantages of nitrogen is that it is dry and relatively inert, so it will not react with the inner liner of the tire, or the wheel, over time.

Also, it is claimed that leak down is slower with nitrogen.

I have no personal experience with it.

Thanks for the replies.

We use nitrogen on aircraft tires since it stays pretty much the same pressure hot. I think you could end up with the same leakdown because they service the aircraft tires every night. Although, that is a huge weight difference. Also, you don't get condensation from compressed nitrogen like you do with normal air. That COULD cause a slight out of balance with the tire, but I don't see that as a problem since the little bit of water would just spread out in the tire. (kinda like the balancers that go inside big tires) Unless you were to buy a tank of nitrogen I think it would be a pain in the butt to get it.

Friend from work showed me the video of his dad. He was filling up at a gas station and was approached by this guy selling helium for tires so my friend’s dad bought some.
Then the guy pointed to the van with the camera in it and says smile your on candid camera

O my!

I fill tires with nitrogen because I happen to always have it around for my business (recharging fire extinguishers). It's inert and doesn't fluxuate with temps as much. However, I don't think it's worth buying a tank just for tires. The tank itself costs $200-$250 and the fills are around $40.

And the final answer is....

Yes, N2 would be dry. So would any other inert gas, or even air, if you filled the tires in February when the dew point is super low (for those of us in the frickin cold belt that is). Compressed air you would get at any service station in the summer could be loaded with water.

They are also claiming that N2 doesn't diffuse out of the tire as quickly as air. Dunno about that. I'd have to see some data.

Also, I'm not yet buying the "expands and contracts less" claim. Sounds like hooey. PV=nRT. There are slight correction factors to the ideal gas law, of course, but they're typically small. I think the major reason behind that claim is the lack of water always condensing and expanding depending on temperature.

I'll do some more reading, but everything I've read so far is marketing mumbo jumbo and not science.

Running nitrogen is common practice is race car tires. Nitrogen does not have the moisture content in it that regular compressed air does. If they were really doing something new they would have filled them with Argon(sp?). I was told that is the new thing they are expermenting with in the Nextel Cup circut.

Unless you suck all the air out of the tire before you put in the nitrogen how are you going to get the condensation out of there to begin with?

Nitrogen is lighter than air, it reduces your reciprocating mass when put in tires, resulting in lower ET's at the track. Helium does not work as well, N20 even works better but is too pricey. That along with titanium muffler bearings and running pure alchohol in the driveshaft cooling system is an old drag racers trick..

Man I shouldn't let all my secrets out..

Really, circle track racers have been using nitrogen forever. You put it in the tire when you first mount it.

It keeps out moisture and expands/contracts less.

Just a tiny item but when everybody else is doing it, you have to. 10-15 of those tiny little items add up. Difference between checkered flag and being the first looser.

Unless you suck all the air out of the tire before you put in the nitrogen how are you going to get the condensation out of there to begin with?

:exactly:

Unless you're anal-retentive and you pull a vacuum, backfill, re-purge, etc....

:rolleyes:

It .... expands/contracts less.


Wrong!

Tell me why.

Running nitrogen is common practice is race car tires. Nitrogen does not have the moisture content in it that regular compressed air does. If they were really doing something new they would have filled them with Argon(sp?). I was told that is the new thing they are expermenting with in the Nextel Cup circut.

Argon? Why not Krypton? :D

Unobtainium Hexaflouride, anyone? Gorealfastium?

):h

Wrong!

Tell me why.

I have no idea why. Probally because of lees moisture.

Alls I know is I pitted on a superstock car for 2 years. ( Colorado National Speedway J.R. DAVIS #44 his son Luke had a car that I helped with as well.)


All cars used nitrogen. Every now and then a mishap would accur where air was used. You could tell a difference. We measured tires religously. The car was set up with a very specific tire diameter on each tire. We measure every single time that car came off the track. We checked pressure,diamater and surface temparature. It got to be freakin anal if you ask me.

Anyways it does make a difference in how much they grow when heat is added. Nitrogen tires stay more consistant.

I have no idea why. Probally because of lees moisture.


I think that's the correct answer. Dry air would work the same.

Nitrogen has been a standard in Winston cup for many years now.

Basically the pressure gain with temperature increase is much less with Nitrogen than compressed air. So, if stabalizing the circumference of your tire and/or maintaining a given pressure over a wide range of temperatures is of a concern, then Nitrogen is for you. :D

Nitrogen has been a standard in Winston cup for many years now.

Basically the pressure gain with temperature increase is much less with Nitrogen than compressed air. So, if stabalizing the circumference of your tire and/or maintaining a given pressure over a wide range of temperatures is of a concern, then Nitrogen is for you. :D

Yeah, everyone is quoting this everywhere. I know, I'm a Nascar fan myself.

The problem is, the reasoning is urban legend. The water in the compressed air is the killer.

The 80% nitrogen + 20% oxygen (roughly) mixture expands EXACTLY the same as pure nitrogen.

C'mon people, has high school chemistry been that long ago?

):h

Argon? Why not Krypton? :D

Unobtainium Hexaflouride, anyone? Gorealfastium?

):h

Probably illegal in CA.Censored

Might also harm the endangered white spotted teetsie fly.

The key is the total absence of moisture in nitrogen......... When it is processed, all the mositure is removed. The moisture in normal compressed air in the tire is what causes the tire to expand more in the tire, than if you could pull all the moisture out of it.

If you could pull 100% of the moisture out of the compressed air, you would have the same benefits of running nitrogen in your tires. But without some very expensive equipment hooked up to your air compressor (and I don't mean that little "dryer" on your air line), you can't do it. So it is a whole lot cheaper to buy the nitrogen.

Plus the nitrogen bottles carries about 8 to 12 thousand PSI, so you can fill a bunch of tires off one of those bottles. They also make a great souce to power your air tools when you don't have power to run your air compressor at the track. I think that is what the NASCAR teams run their impact wrenches off of when they are changing tires.

Might also harm the endangered white spotted teetsie fly.

:lol:

The key is the total absence of moisture in nitrogen......... When it is processed, all the mositure is removed. The moisture in normal compressed air in the tire is what causes the tire to expand more in the tire, than if you could pull all the moisture out of it.

If you could pull 100% of the moisture out of the compressed air, you would have the same benefits of running nitrogen in your tires. But without some very expensive equipment hooked up to your air compressor (and I don't mean that little "dryer" on your air line), you can't do it. So it is a whole lot cheaper to buy the nitrogen.

Plus the nitrogen bottles carries about 8 to 12 thousand PSI, so you can fill a bunch of tires off one of those bottles. They also make a great souce to power your air tools when you don't have power to run your air compressor at the track. I think that is what the NASCAR teams run their impact wrenches off of when they are changing tires.

:exactly:

Although I'd add that the same process (liquefaction) used to purify almost all the gases has the same end result - so pure, dry carbon dioxide and pure, dry argon would give the same results. So would 'synthetic air' made from pure, dry nitrogen and oxygen. Dry Fart Gas would work as well :D

There is nothing "magical" about nitrogen itself. Most of the properties of the gases are similar, with hydrogen and helium being the notable exceptions with vastly higher diffusivities and thermal conductivities.

If diffusivity through rubber is any factor at all in maintaining pressure, then the larger gas atoms (like argon, krypton, and xenon) would be expensive alternatives.

Searay, ever buy a impact gun? Ever see the instructions explicitly saying you shouldn't hook it to a compressed bottle? ):h

Nitrogen has been a standard in Winston cup for many years now.

:D

I wouldnt believe anything anybody says that is stuckin the past...its NEXTEL Cup.

:muahaha: :muahaha: :muahaha:

Argon? Why not Krypton? :D

Unobtainium Hexaflouride, anyone? Gorealfastium?

):h

Last summer I know that there was some teams testing it Argon in the tires. Was more consistent than Nitrogen and had less pressure build. I think that the cost is what is keeping nitrogen the norm.

Theory has to meet the race track at some point. I've used dry compressed air out of a bottle from a welding supply company and dry Nitrogen. When my circle track Goodyear Eagles got hot, (200 degrees) the Nitrogen tires gained less air pressure than the ones filled with dry compressed air. :confused:

We were using Nitrogen in the Nascar "Winston" West circuit in 1989. I have to believe "Cup" (Winston or Nextel) was doing it before then.:D

how much less, Trip?

When in doubt do some research.

Basically every single gas on earth has it's own specific density or weight.

The heavy gasses expand less then light gasses when exposed to the same amount of heat.

So pure Nitrogen is heavyer then normal atmosphere and will expand less when exposed to heat.

Helium is a light gass and expands alot.

how much less, Trip?

5 psi on a 71" circumference tire.:(

Trip, gimme your starting and ending pressures, I'm working on figuring it out.

I'll assume your start temps are what, 80F?

When in doubt do some research.

Basically every single gas on earth has it's own specific density or weight.

The heavy gasses expand less then light gasses when exposed to the same amount of heat.

So pure Nitrogen is heavyer then normal atmosphere and will expand less when exposed to heat.

Helium is a light gass and expands alot.

):h Bronco, I don't know what you're smokin' when you're doing your research....but the heavy / light thing is baloney.

Nitrogen IS out atmosphere! C'Mon, man!

):h Bronco, I don't know what you're smokin' when you're doing your research....but the heavy / light thing is baloney.

Nitrogen IS out atmosphere! C'Mon, man!

You need to put your chemistry skills to something other than LSD or THC and get some facts together. ITs true, prove me wrong. :lol:

Man, I knew I should have brought my p-chem textbook to work today. I am an analytical chemist and thinking about p-chem makes my head hurt, but I just don't think there is that much difference in the thermal expansion of nitrogen vs. dry air. Like has been mentioned already, air is already 80% nitrogen. I can't believe oxygen has that much different expansion properties from nitrogen, as the molecules are very similar. CO2 might be a little different story, but its concentration is low enough in "normal" air that I can't see it making much difference.

Now throw water vapor into the mix and you have a different story. I wouldn't always trust "dry" air from a welding supply shop, as it usually still has some moisture in it. I wish I still was at my last job, as we used zero-grade air (less than something like 0.001 ppm moisture) and ultra high purity nitrogen for the GC's. Those would be good sources to try to accurately measure expansion differences.

If you want to get really dry air for your tires, it is easy to make a pretty effective moisture trap. You just need to cool the air enough that the water will freeze out. In a pinch, I have used an ethanol/ice slurry in a cooler with a coil of 3/4" copper pipe in it. As the air flows through the pipe, the cold surroundings freeze the moisture out of the air so it collects on the walls. Of course eventually it will freeze enough to block the flow, so you have to take the coils out and thaw/drain them occasionally. If your air is relatively dry to start out with (i.e. using a line drier in front of this set up), you get pretty good performance.

Found an engineering forum that was discussing the same thing. Looks like for once I agree with a bunch of engineers.

http://www.eng-tips.com/viewthread.cfm?qid=120996&page=1

You need to put your chemistry skills to something other than LSD or THC and get some facts together. ITs true, prove me wrong. :lol:

Don't worry, Bronc, I will :D just gimme a few days.

I'm thinking this might be really easy to evaluate on my own truck....I have most of the stuff necessary except a high sensitivity pressure transducer...

The tech stuff I'm looking into discusses the nonlinear behavior of gases and more detailed equations of state. Van der Waals equations, compressibility constants, virial coefficients, that kind of thing.

sounds like nitrogen might be a fine substitute when your tires get real hot, and you're spending sponsorship money.

i don't have any data and have not even looked for any, but i have a suspicion that nascar tires get a bit hotter than our truck tires.

even if i had a sub 12 second truck, i would think real hard before spending $40 to pressure my tires.

just my .02... but maybe this type of thinking is *why* i don't have a < 12 second truck.

The tech stuff I'm looking into discusses the nonlinear behavior of gases and more detailed equations of state. Van der Waals equations, compressibility constants, virial coefficients, that kind of thing.

If you are going to get that technical about it, you are going to have a difficult time accounting for all the variables. Even the interaction between the "rubber" molecules would have to be considered. It would be somewhat easy to empirically determine the difference with a tire on a test stand, but to try to calculate it would be a nightmare.

1. PV=nRT. Nitrogen will expand or rise in pressure the same as air for a given delta T...period. I don't know what is meant by "sponginess", but I can assure you...the tire does not know what is colliding with it's walls, exerting pressure. Forget about non-idealities, they're microscopic for air, and are hardly any different for nitrogen vs. oxygen anyway, as both are dipolar molecules anyway.

2. Compressed air is dry. The compressor pressurizes the air to like 125 psig, then it cools in the tank. Water often condenses out. That's why compressors have drain valves (you do drain your compressor don't you?). When the air is depressured into the tire, the relative humidity drops with the decrease in pressure...and drops further when the tire heats. If you have water in your tire, it's because you filled it with a water hose.

3. Nitrogen weighs 28, Oxygen is 32. The average for air is about 29. Small molecules travel faster for the same energy (temperature). That's why light gasses leak faster through a given leak. A nitrogen filled tire will leak down faster if there's a leak...but not by much.

4. If the tire has no mechanical leaks, then nitrogen diffuses through the rubber more slowly, since it's less soluble in the rubber.

5. Aircraft use nitrogen to save weight. They have BIG tires under HIGH pressure (like 200 psig) and lots of 'em. Nitrogen saves a few pounds, which saves lots of fuel. Heluim would save a bunch more weight, but would also leak like crazy, nitrogen is an economical compromise.

6. A few years ago Shell tried marketing nitrogen at some retail outlets' tire filling stations. The logic was that it would diffuse more slowly through rubber, keep tires inflated and save energy. Nobody bought and they dropped it. Tires have a layer of halobutyl rubber on the inside (if it's tubeless) to keep air from diffusing through. It works great, and the loss rate is very slow unless there's a mechanical leak.

1. PV=nRT. Nitrogen will expand or rise in pressure the same as air for a given delta T...period. I don't know what is meant by "sponginess", but I can assure you...the tire does not know what is colliding with it's walls, exerting pressure. Forget about non-idealities, they're microscopic for air, and are hardly any different for nitrogen vs. oxygen anyway, as both are dipolar molecules anyway.

2. Compressed air is dry. The compressor pressurizes the air to like 125 psig, then it cools in the tank. Water often condenses out. That's why compressors have drain valves (you do drain your compressor don't you?). When the air is depressured into the tire, the relative humidity drops with the decrease in pressure...and drops further when the tire heats. If you have water in your tire, it's because you filled it with a water hose.

3. Nitrogen weighs 28, Oxygen is 32. The average for air is about 29. Small molecules travel faster for the same energy (temperature). That's why light gasses leak faster through a given leak. A nitrogen filled tire will leak down faster if there's a leak...but not by much.

4. If the tire has no mechanical leaks, then nitrogen diffuses through the rubber more slowly, since it's less soluble in the rubber.

5. Aircraft use nitrogen to save weight. They have BIG tires under HIGH pressure (like 200 psig) and lots of 'em. Nitrogen saves a few pounds, which saves lots of fuel. Heluim would save a bunch more weight, but would also leak like crazy, nitrogen is an economical compromise.

6. A few years ago Shell tried marketing nitrogen at some retail outlets' tire filling stations. The logic was that it would diffuse more slowly through rubber, keep tires inflated and save energy. Nobody bought and they dropped it. Tires have a layer of halobutyl rubber on the inside (if it's tubeless) to keep air from diffusing through. It works great, and the loss rate is very slow unless there's a mechanical leak.

So basically the average user won't know any different whether there is air in the tire vs Nitrogen. I guess #4 would be the only benefit and not much of a benefit at that due to the tire's makeup (#6).

Wow, that's a lot of inaccuracies in one post, maybe a record.

1. Yes PV=nRT, I learned that one in high school too. But, there is a little more to it than that. Yes dry air and dry nitrogen are very similar, but the differences aren't quite as trivial as you imply. Add moisture into the mix and you can throw that equation out the window.

2. I don't know where you get your compressed air, but what comes out of my tank sure isn't dry. Maybe if you live in Phoenix that would be the case, but in the midwest in spring and summer, compressed air is not dry. If there is no moisture in my compressed air, I wonder why my fittings were corroded before I bought my drier. Speaking of drier, I wonder why water collects in it if the air is dry going through it. Maybe there is a new route to water synthesis I haven't heard of...

3. I am not sure what role atomic weights play in this argument, but they have little to do with this. I looked up the radii of the two molecules earlier and they were almost exactly the same. O2 was actually a bit larger than N2 due to the triple bond of dinitrogen while dioxygen has a double bond, but there isn't a lot of difference.

4. Can't comment on the solubility of nitrogen in rubber, never heard of that before.

5. Actually the main reason airliners use nitrogen because it doesn't promote combustion should a brake or tire catch on fire. Nitrogen's density is 1.25 kg/m3 while dry air is approximately 1.2 kg/m3 at 25C and 100 kPa of pressure. Of course moisture would increase the density.

All this being said, I think we do agree that nitrogen is a waste of money. I just like to have the facts laid out, though.

Yeah for the normal guy nitrogen is a waste of energy.

The class of circle track I was involved with was very competitve. The cars were inspected and teched regularly. The all weighed the same and had the same transmissions and engines.

So all cars were within about 5HP and the same exact weight. You could play with rear gears and suspension setup but that was about it. Same tires same everything!

So the little tricks and tips that we used were unfreakin real. Like I said 10-15 little tricks adds up. Nitrogen was just one of many.

Ultimently it came down to driver skill and how big his nuts were.

I would like to see some formulas and laws to prove or disprove the expansion charectreisitcs of Nitrogen. I found a few articles but they would just stir up a **** storm.

2. I don't know where you get your compressed air, but what comes out of my tank sure isn't dry. Maybe if you live in Phoenix that would be the case, but in the midwest in spring and summer, compressed air is not dry. If there is no moisture in my compressed air, I wonder why my fittings were corroded before I bought my drier. Speaking of drier, I wonder why water collects in it if the air is dry going through it. Maybe there is a new route to water synthesis I haven't heard of...

3. I am not sure what role atomic weights play in this argument, but they have little to do with this. I looked up the radii of the two molecules earlier and they were almost exactly the same. O2 was actually a bit larger than N2 due to the triple bond of dinitrogen while dioxygen has a double bond, but there isn't a lot of difference.


Let me explain how compressors can dry air...

Water exerts its vapor pressure as a function of temperature. On a humid day, the compressor raises the pressure of ambient air, and heats it. The water stays as a vapor due to the high temperature. In the tank it cools (if you give it time). Water still will exert the same vapor pressure once it cools back down. But, since the pressure is several times higher, the resulting mole fraction of water (for saturation) is less. If there was enough water to start with, it will condense.

If there is a water phase in the tank then the air in there is at 100% relative humidity. The reverse happens when the pressure drops. The air becomes sub-saturated. The water content is not zero, but it is at less then 100% relative humidity..that's what I meant by dry....water will not condense. Maybe if you filled the tire in Houston at 100F then drove to the south pole, you might get a few drops. Even then it would be less mass than a couple pebbles caught in the tread.

Air driers are useful if the compressed air does not get cooled before it's delivered, or if it will go into an air-drive which cools the air as it expands. Then yes, you can get condensation. If you push a compressor to the point where it is delivering warm air, then yes you could get condensation in the lines and corrosion.

The rate of a leak through a small hole, at a given P and T depends on average molecular velocity, not size. Lighter molecules are moving faster at a given temperature, so they leak faster.

As for the expansion issue, all I can really say is, take a thermodynamics class.

for what its worth aircraft use it because its stable at various altitudes, because all air has some moisture, tires would lose bead seal at high altitude, probably where tire companys tell racers, but psi increases in racing tires as they warm up, but controlled due to lack of water vapor which could not be controlled.

Trip, gimme your starting and ending pressures, I'm working on figuring it out.

I'll assume your start temps are what, 80F?

Start: 22psi at 80-90F
End Nitrogen: 25psi at 200F-220F
End Compressed Air: 30+ at 200F-220F

Every effort was made to remove the moisture from the inflation medium using this: http://www.intercomp-racing.com/detail.cfm?ItemID=239

Plus the nitrogen bottles carries about 8 to 12 thousand PSI, so you can fill a bunch of tires off one of those bottles. They also make a great souce to power your air tools when you don't have power to run your air compressor at the track. I think that is what the NASCAR teams run their impact wrenches off of when they are changing tires.[/QUOTE]

A full nitrogen cylinder has between 2000 to 2400 PSI.

All of this in the name of consistancy. Compressed air varies in it's makeup too much from place to place and altitude to altitude if you really need to be anal. Like when your going 200 MPH and turning left a lot.

Nitrogen is cheap and plentiful source of dry gas. Anyone know its thermal coefficient?