nitrogen tire pressure

[04GoatInMass]

did you guys hear about the new way if filling your tires.i read that they use nitrogen to fill tire pressure instead of air.now all i need is a place that does it.heres the link i read it at
http://www.irtools.com/products/nitrogen/

also heres a bit of info on it

Better air pressure retention. The single biggest reason for tire failure is lack of maintenance of tire pressure. In fact, 54 percent of all vehicles on the road have low tire pressure. Oxygen in compressed air can permeate the tire wall reducing tire pressure. With nitrogen, diffusion is 30 to 40 percent slower than oxygen. As a result, nitrogen maintains tire pressure longer than ambient air.


Enhanced fuel economy. Maintaining tire pressure can boost fuel economy by as much as 6 percent. Nitrogen disperses heat more quickly than ambient air. By restraining the heat in the tire and reducing rolling resistance, you get better fuel economy.


Longer tread life. With quicker heat dispersion, you get a cooler running tire which helps extend tread life and reduce tire failure. Nitrogen also prevents oxidation which can not only lead to tread separation and belt failure but, when combined with moisture, corrode rims. In fact, moisture can result in rust flakes that can fall into the valve stem, block the valve and cause under-pressurization. It can even cause the valve stem itself to rust.


Slow chemical aging. Filling a tire with nitrogen also significantly slows the chemical aging process of the tire’s rubber components. This leads to fewer catastrophic failures like blowouts. Slower aging lengthens tire core life, which yields extra retreads and lower fleet costs.

[bser01]

i smell gimick regular air is over 70% nitrogen anyway

[04GoatInMass]

i smell gimick regular air is over 70% nitrogen anyway

what makes you say such when nitrogen is filtered out threw hollow-fiber membranes.i dont know about 70% nitrogen i believe its alot lower of a number

[TriflowM5+M3]

there was a thread on this in the O/T section in the last week or so...

[Rob@WretchedMS]

It's not a gimmick, it does work. But the cost of the equipment is very high.

[04GoatInMass]

there was a thread on this in the O/T section in the last week or so...
sorry for repost then but i did a search and didnt come up with anything

It's not a gimmick, it does work. But the cost of the equipment is very high.

if it works why not release it to the public.id pay the cost if it means saving gas and tread life

[Rob@WretchedMS]

sorry for repost then but i did a search and didnt come up with anything



if it works why not release it to the public.id pay the cost if it means saving gas and tread life

would you pay $40 for air? it's available to the public, just need to find someone that wants to spend 5k on a system

[license-2-drill]

It only works for idiots who never check their tire pressure.

[04GoatInMass]

i smell gimick regular air is over 70% nitrogen anyway

sorry i rephrase that its actually higher 79% of air is nitogen

[04GoatInMass]

It only works for idiots who never check their tire pressure.

why would you be an idiot in saving gas and tread life.


well $40 is a bit high

[GOGOGTO]

I had my tires with nitrogen and it didn't make any difference. And your tires will still gain and lose air pressure. It seems to just be for people that refuse to check their tires every now and then...

[04GoatInMass]

I done my tires with nitrogen and it make any difference.
:confused: are you saying yes it made a difference or it didnt yes it says you will lose air but at a lower rate then reg compressed air

[Rob@WretchedMS]

Seriously, it works, no BS. I wouldn't invest in it though. High end cars, and I fairly sure that planes use Nitrogen in them just for these reasons.

It's not just about checking your pressure, it's about the pressure staying the same as the tire heats and cools,

[license-2-drill]

why would you be an idiot in saving gas and tread life.


well $40 is a bit high


The whole gimmick is it preserves tire life and proper tire pressure gives you better gas mileage which is true but you can easily do this by just checking your tire pressure monthly...Basically this would be a good solution from the factory for non-car people that NEVER check their tire pressure so therefore they get worse gas mileage. Maybe you would see a little better mileage from the tires heating up and it mainting the pressure better but I doubt it would be much

[GOGOGTO]

:confused: are you saying yes it made a difference or it didnt yes it says you will lose air but at a lower rate then reg compressed air

fixed !!!!!

[GOGOGTO]

The whole gimmick is it preserves tire life and proper tire pressure gives you better gas mileage which is true but you can easily do this by just checking your tire pressure monthly...Basically this would be a good solution from the factory for non-car people that NEVER check their tire pressure so therefore they get worse gas mileage. Maybe you would see a little better mileage from the tires heating up and it mainting the pressure better but I doubt it would be much

+1 ^^^^^^

[s/c'd cav]

Seriously, it works, no BS. I wouldn't invest in it though. High end cars, and I fairly sure that planes use Nitrogen in them just for these reasons.

It's not just about checking your pressure, it's about the pressure staying the same as the tire heats and cools,[/B]

#1 reasons right there

[04GoatInMass]

#1 reasons right there

+1 as for this is the true reason to do it

[GOGOGTO]

#1 reasons right there

We know what it does , we are saying that for a daily driver it's a waste of money . If they fill them for free I would get it done ,I'm just not paying for it...IMO... When mine were done they still lost some pressure

[04GoatInMass]

We know what it does , we are saying that for a daily driver it's a waste of money . If they fill them for free I would get it done ,I'm just not paying for it...IMO... When mine were done they still lost some pressure

well everyone has their own opinon as to what to do to their own car.all i was trying to acomplish was to show people there was a different system out there to prolong tire life and yes save a little bit of gas money,for those who use the goat as a daily driver any little bit helps.yes i agree $40 as stated above is a bit high to pay for it when you can just fill with air for free,but if say it was $10 i would do it in a heart beat.its not all about being lazy and checking tire pressure im sure we all do that quite offten but by using nitrogen to fill kinda gives you a better piece of mind knowing your air is more likely to be at the same psi as it was when you first filled it as well.

[GOGOGTO]

well everyone has their own opinon as to what to do to their own car.all i was trying to acomplish was to show people there was a different system out there to prolong tire life and yes save a little bit of gas money,for those who use the goat as a daily driver any little bit helps.yes i agree $40 as stated above is a bit high to pay for it when you can just fill with air for free,but if say it was $10 i would do it in a heart beat.its not all about being lazy and checking tire pressure im sure we all do that quite offten but by using nitrogen to fill kinda gives you a better piece of mind knowing your air is more likely to be at the same psi as it was when you first filled it as well.

I agree, it does work some and if it was free or cheap I would do it again but everyone wants too much money to fill them...

[04GoatInMass]

I agree, it does work some and if it was free or cheap I would do it again but everyone wants too much money to fill them...

what they get you for it

[GOGOGTO]

what they get you for it

At the GOODYEAR place they done it for free because they mounted and balanced my tires and wheels.

[04GoatInMass]

I agree, it does work some and if it was free or cheap I would do it again but everyone wants too much money to fill them...

At the GOODYEAR place they done it for free because they mounted and balanced my tires and wheels.

ok 1 quote you say if it was free and then you say on another that it was free.....which is it?

[Rob@WretchedMS]

I had my tires with nitrogen and it didn't make any difference. And your tires will still gain and lose air pressure. It seems to just be for people that refuse to check their tires every now and then...

I'm guessing they didn't do it then....

Nitrogen doesn't expand, Oxygen does. If your pressure changed, you have oxygen in them and not pure nitrogen.

[Ironmancan]

Some tire places I've seen give you the option. Did some home work on this a while back the 1st time I saw it (approx 2yrs ago). Benefit does not out weight the PITA factor.

[Rob@WretchedMS]

Some tire places I've seen give you the option. Did some home work on this a while back the 1st time I saw it (approx 2yrs ago). Benefit does not out weight the PITA factor.

agreed

[Lothar]

I thought the nitrogen fill also kept out moisture which was supposed to be good for some reason or another?

[GOGOGTO]

ok 1 quote you say if it was free and then you say on another that it was free.....which is it?

Yea ? It was done for free the first time and when I checked them and they were low, I took them back up there and they wanted to charge me for it. I said to them " when it was done you guys said that the tires would not drop in air pressure and they did. Why should I pay for a fill up ?" The guys at goodyear said that it helps the pressure stay up ,it's not garanteed. I was there when they filled them ,they have a tank of nitrogen. I'm not sure if it makes a difference because of our temps. in Florida...

[04GoatInMass]

Some tire places I've seen give you the option. Did some home work on this a while back the 1st time I saw it (approx 2yrs ago). Benefit does not out weight the PITA factor.

call me a noob but whats pita factor?

[GOGOGTO]

I'm guessing they didn't do it then....

Nitrogen doesn't expand, Oxygen does. If your pressure changed, you have oxygen in them and not pure nitrogen.

They all dropped, none of them expanded...

[Ironmancan]

Lol, Pain in the a$$...

[04GoatInMass]

Yea ? It was done for free the first time and when I checked them and they were low, I took them back up there and they wanted to charge me for it. I said to them " when it was done you guys said that the tires would not drop in air pressure and they did. Why should I pay for a fill up ?" The guys at goodyear said that it helps the pressure stay up ,it's not garanteed. I was there when they filled them ,they have a tank of nitrogen. I'm not sure if it makes a difference because of our temps. in Florida...

ok to get back to my orignal question ,what were they going to charge you?

[04GoatInMass]

Lol, Pain in the a$$...

lmao wow do i feel stupid now:banghead:

[GOGOGTO]

ok to get back to my orignal question ,what were they going to charge you?

I don't know what they wanted to fill them completely but they wanted $20.00 to add some...

[Kanding]

I'm guessing they didn't do it then....

Nitrogen doesn't expand, Oxygen does. If your pressure changed, you have oxygen in them and not pure nitrogen.

Doesn't the pressure of O2 increase proportionally with regard to temperature just as N2 (as per PV=nRT), or is there some chemistry that I'm missing? I think you are referring to the water vapor in the air rather than the oxygen. My understanding is the nitrogen fills are more 'pure' than atmospheric air in that they have less water vapor, and are thus less prone to thermal expansion.

[dms]

Nitrogen instead of air is a really good thing for performance. However, the reaon I never got into it, is what if a customer has nitorgen air, then drives and gets a nail and they are not close to you. NNow you will have variations in air pressure side to side, and potential law suits are there.

Plus not all nitorgen systems are equal. First class systems are really pricy.

mike

[robo282]

Most dealers are putting in nitrogen in all 2007 vehicles.

[my06gto]

A total waste of time. nitrogen dosnt expand at the same rate of air. (learned all about it in aircraft mech. school) woopdee do. its total overkill. it would be like checking your coolants PH. you dont need to do it.

they use nitrogen in aircraft tires because the have to. does your car go thousands of feet in the air.... nope. unless your lazy to bust out a pressure gauge every once in a while and want to waste money go for it.

sorry for the bluntness im kinda in a bad mood.

[dms]

A total waste of time. nitrogen dosnt expand at the same rate of air. (learned all about it in aircraft mech. school) woopdee do. its total overkill. it would be like checking your coolants PH. you dont need to do it.

they use nitrogen in aircraft tires because the have to. does your car go thousands of feet in the air.... nope. unless your lazy to bust out a pressure gauge every once in a while and want to waste money go for it.

sorry for the bluntness im kinda in a bad mood.

I think one of the good reasons for using nitrogen is in fact it does not expand with temperatures, is a denser as well. It is also the reason I never did it. If somone is on a trip and picks up a nail, and has to have it fixed, then regualr air installed, now you will have unequal tire pressures side to side, thus potential uneven brakes. Then there is the cost of exchanging the air to nitrogen again.

mike

[jjsams21]

We know what it does , we are saying that for a daily driver it's a waste of money . If they fill them for free I would get it done ,I'm just not paying for it...IMO... When mine were done they still lost some pressure


Exactly!! I'm a mechanic and we have a local chain shop that advertises Nitrogen for better fuel economy. Every car that I check the tires on from them (the put a stupid green washer arount the valve stem) has low tire pressure. They dont't stop a tire from leaking air, they just prevent a minute loss of pressure from temperature. They charge $5.00 per tire to fill them, but their mechanics don't clean the corrosion from the wheels, so they leak around the bead anyways. What a waste of money. Regular air has been fine since the invention of tires, so if you're not racing in NASCAR and heating up the tires, don't waste the money!

[ron2215]

call me a noob but whats pita factor?

PITA = Pain In The A**

[04GoatInMass]

PITA = Pain In The A**

just a tad bit late on that one

[Ret NYCPD]

Recently at a Chevy Dealer looking at several trucks ......... salesmen said the tires have Nitrogen ......... asked question where would I go if I need to add tire pressure.......... his response, any new car dealer is supposed to add necessary pressure........... and if not near any dealers...... you could add reg. air........... he didn't mention anything about there being a charge (cost) to add nitrogen air pressue............ since I didn't bite on the truck, wonder what the real story is.......... free or a fee?

[#1HotRod]

ran with nitrogen for awhile while living in Germany. filled at mounting. thought it was a good idea, thought it would reduce pressure fluctuations during extended high-speed driving. german tire stores offered it. monitoring pressures regularily during operations indicated it didn't work so well in execution, and gas stations didn't have nitrogen pumps, so ended up using reg'lar ole air.

[foster'sguy]

This has been done to death.......People are either for it or against it.
It works fine for me. Yes, I paid for mine, but the deal I got was, anytime I want the pressure topped up its free. If I get a flat some where and have the tire repaired, the shop that did my Nitro-fill will refill it for free.
I checked the pressure last week and it was the same as it was the week before and has been for the last 3 months.

[LS2Jesse]

I love when this pops up. Lets me flex my engineering muscle.

1. Nitrogen will diffuse faster than oxygen, as nitrogen is a smaller molecule(molecular volume 13.54 ×10-6 m^3/mol for N2 and 17.36 ×10−6 m3/mol for O2 at STP)
2. Themal conductivity: N2 [/W m-1 K-1]: 0.02583; O2 [/W m-1 K-1]: 0.02658, so the essentially conduct heat at the same rate.
3. At the pressures that your tires operate Air and pure Nitrogen with behave as ideal gasses and thus expand and contract identically.
4. Air is 79% N2 by volume.

The main reason that shops offer nitrogen fills, is that they do not have to operate or maintain an air compressor, they simply have a vendor supply them with nitrogen tanks. The economics of scale at work. That and people feel that getting "pure nitrogen" is an added value, I mean who wants to pay for air when you breath it for free? In some of the extreme conditions (such as in areonautics, and high performance driving) the small portion of water vapor present in the air around us is what is going to cause problems, that is why they use nitrogen as opposed to air.

[GTO Captain]

Nitrogen is BS, you cant assure that each tire will be filled equally with nitrogen unless you could evacuate all of the air from said tire which would require a vacume chamber which would fit the tire while on the rim and then which could be filled with nitrogen and then have nitrogen added to assure proper pressure.

[D-GTO]

you guys are funny LOL ... they have been using nitrogen to fill tires in road racing for eons because it has better temperature stability than compressed air in addition to being able to control to some extent the purity of the gas in the tire. If you run a compressor in an area of high humidity you will invariably have "wetter" air while if you are in an arid enviroment your air will naturally be "drier" which is why for most large compressor installations in industrial environs they are forced to use single and sometimes multi stage air driers to prevent contamination of lines. If you use controlled process compressed gas from a source such as a nitrogen bottle your tire fills will be much more consistent across the board.

In response to the comment that you would need to vacuum the tire out to prevent mixing nitrogen and natural compressed air you are correct ... and there is equipment that does exactly this. Alternatively I have seen people fill their tires with nitrogen and then release the pressure ... refilling and releasing several times to minimize the contamination of the nitrogen in the tire.

Have a good day.

[JoeCiv]

so is it a 100% nitrogen fill? because unless they suck all the air out of the tire first, isnt there going to be air in the tire to start?

[CaptainDan]

I'm guessing they didn't do it then....

Nitrogen doesn't expand, Oxygen does. If your pressure changed, you have oxygen in them and not pure nitrogen.

Nice. So Nitrogen defies the laws of physics. Gotta get me some of that magical stuff!

[GTO Captain]

For the average GTO and most daily driver applications, I just can't see the justification for all the time and money needed to go with a pure nitrogen fill.

[CaptainDan]

you guys are funny LOL ... they have been using nitrogen to fill tires in road racing for eons because it has better temperature stability than compressed air in addition to being able to control to some extent the purity of the gas in the tire. If you run a compressor in an area of high humidity you will invariably have "wetter" air while if you are in an arid enviroment your air will naturally be "drier" which is why for most large compressor installations in industrial environs they are forced to use single and sometimes multi stage air driers to prevent contamination of lines. If you use controlled process compressed gas from a source such as a nitrogen bottle your tire fills will be much more consistent across the board.



Racers (and professional mechanics) use Nitrogen because it's CONVENIENT. Air is already 79 % Nitrogen. But (as you mentioned) it also contains a small amount of moisture. The racer uses air driven tools (impact wrenches, grinders, air chisels, etc). These use compressed air (or Nitrogen) to run them. The large amount of air (with moisture) flowing thru them can corrode the tools or their fittings. So they use Nitrogen. And it's a waste of money to buy and maintain air compressors you don't need when you're already using Nitrogen. Plus in racing, the pit areas have limited space for extra equipment.

Your tires don't see a large amount of air flowing thru them, they just contain a static amount. And that little bit of moisture isn't going to hurt your wheel or tire. Come on, the OUTSIDE of your tire sees a whole lot more moisture than you could possibly get on the inside.

Why have dealerships and tire stores started selling Nitrogen? Because not too many people were willing to pay for "air", which is free for the taking, all around you.

[wolfdogs]

Most dealers are putting in nitrogen in all 2007 vehicles.


:rolleyes: not true what so ever.

[wolfdogs]

you guys are funny LOL ... they have been using nitrogen to fill tires in road racing for eons because it has better temperature stability than compressed air in addition to being able to control to some extent the purity of the gas in the tire. If you run a compressor in an area of high humidity you will invariably have "wetter" air while if you are in an arid enviroment your air will naturally be "drier" which is why for most large compressor installations in industrial environs they are forced to use single and sometimes multi stage air driers to prevent contamination of lines. If you use controlled process compressed gas from a source such as a nitrogen bottle your tire fills will be much more consistent across the board.

In response to the comment that you would need to vacuum the tire out to prevent mixing nitrogen and natural compressed air you are correct ... and there is equipment that does exactly this. Alternatively I have seen people fill their tires with nitrogen and then release the pressure ... refilling and releasing several times to minimize the contamination of the nitrogen in the tire.

Have a good day.

"compressed air" or just plain air does not contaminate nitrogen. and nitrogen fillstations dont "vacuum out your tires" prior to switching over to nitrogen. there is no need to for a normal consumer who uses his car for "normal" activity, complet evacuation of the the tires inner liner chamber to avoid a slight minute amount of any moisture is totally splitting hairs overkill.

and filling with nitrogen and deflating and refilling is not going to purge moisture from the tubless tire. any moisture that is in there will remain attached to the inner linner, nitrogen does not transport moisture.

there are inexspensive filters that have an air chuck on the end that you can attach to an air hose that removes moisture when you fill your tires. there is a nice advantage to not having moisture in the tire. if you get a cut or small split in the inner linner (which is the "tube" of the tubless radial)...the air thats in there "charges" the casing. if you check your tire pressure, it wont vary much...but now air has penetrated the casing, and moisture has been carried to the belt package. over time, this moisture will cause the belts to begin to rust..... if the tire is left on the vehicle long enough, this rust can eat thru the belt and cause a belt seperation .....which leads to a blow out. some rims are more sensitive to moisture than others, and corrosion can start forming in the inside of the rim over time.

[2 year rental]

Seen a lot of opinions, the truth is if u can get it cheap do it, NASCAR & many forms of racing use NITROGEN not only for air pressure stability but also nitrogen filled tires rarely will "blow out" like air filled tires. If you ever watch NASCAR they always have a tire going down, very rarley will they blow out...

[CaptainDan]

Seen a lot of opinions, the truth is if u can get it cheap do it, NASCAR & many forms of racing use NITROGEN not only for air pressure stability but also nitrogen filled tires rarely will "blow out" like air filled tires. If you ever watch NASCAR they always have a tire going down, very rarley will they blow out...

Air filled tires also "blow out" only rarely. If you've seen a tire blow out, you're probably at the movies or watching television, and T J Hooker has just shot out the tire (the car will also flip over several times and ignite a huge fireball).

Air and Nitrogen are both gasses. neither one has any more potential to "blow out" than the other.

[CaptainDan]

Nitrogen is harmless. If you get it for free, who cares. If they want money for it, don't bother.

[GTO Captain]

Now Hydrogen filled tires would be fun!:drink: :bomb: :turbonaug :gr_jest:

[CaptainDan]

I tried filling my tires with Helium, but the exhaust went all high pitched and squeaky. Sounded like Mickey Mouse. Or a Honda.

[CaptainDan]

......In response to the comment that you would need to vacuum the tire out to prevent mixing nitrogen and natural compressed air you are correct ... and there is equipment that does exactly this......

Won't work. If you TRIED to vacuum the tire out, the tire would try to collapse. Now, the tire carcass is way too stiff to completely collapse, but there is no "attachment" at the tire bead to the wheel. The tire would pull away from the wheel, thus breaking the seal.

[wolfdogs]

Air filled tires also "blow out" only rarely. If you've seen a tire blow out, you're probably at the movies or watching television, and T J Hooker has just shot out the tire (the car will also flip over several times and ignite a huge fireball).

Air and Nitrogen are both gasses. neither one has any more potential to "blow out" than the other.

"sudden air loss" is the tire industry term. and it does happen, more often than you think. general public calls it a "blow out"...i think thats what he's refering to.

to quote the Mich. state police: "The rapid deflation of a vehicle tire or “blow-out” can be a common event. Michelin reports approximately 535 fatalities and 23,000 collisions per year due to a tire blowout".

i have a write up ive posted over the years on how to control a blow out if anyone is interested. i attended a week long school in the nevada desert taught by Michelin back in the mid 90's. it was very inlightning.

[CaptainDan]

I certainly didn't mean to imply that a "blowout" can't happen, just that they're rare. In fact most of those aren't because the they "just blew". It's from the tire hitting something, and that the gas inside the tire won't have anything to do with it. Even if a tire does "just blow", it's because of a tire defect, not whatever gas is in it.

[CaptainDan]

Although, if you put Hydrogen in your tires, I guess it really could be a "blowout"

[wolfdogs]

I certainly didn't mean to imply that a "blowout" can't happen, just that they're rare. In fact most of those aren't because the they "just blew". It's from the tire hitting something, and that the gas inside the tire won't have anything to do with it. Even if a tire does "just blow", it's because of a tire defect, not whatever gas is in it.

no, the "gas" does not have anything to do with it...other than its the gas that carries the load, the tire is a pressure vessel so it is under quite a bit of pressure...

casing failures occur all the time, mainly from people running underinflated in high ambients. belt seperation or belt edge seperation is usually the culprit due to the heat build up from being underinflated, allowing the rubber core to begin softening...the belt package begins to squirm in the casing and eventually comes "unglued"....

the rubber on the road you see is not only retreads, that most folks think ...it new tires too......and 89% of it is from tractor trailers running tires underinflated or missmatched duals.

[CaptainDan]

......casing failures occur all the time, mainly from people running underinflated in high ambients.

You are quite correct. That there is the culprit. Underinflation, especially coupled with high outside temps, cause most tire damage. And that can be followed by CAR damage! And people damage! (Ford Explorers on Firestones!)

Keeping your tires properly inflated is a HUGE deal! (and no, Nitrogen doen't stay inflated better than air) For safety, and improved gas mileage.

Fortunately, a lot more cars have tire pressure warning systems nowadays. And soon such systems will be mandated on ALL cars. 2010 I believe.

[appletonrc]

Curtsey of Wikipedia:

Air contains roughly 78% nitrogen, 21% oxygen, 0.97% argon, 0.04% carbon dioxide, and trace amounts of other gases, in addition to water vapor.

FYI.

[jjsams21]

I love when this pops up. Lets me flex my engineering muscle.

1. Nitrogen will diffuse faster than oxygen, as nitrogen is a smaller molecule(molecular volume 13.54 ×10-6 m^3/mol for N2 and 17.36 ×10−6 m3/mol for O2 at STP)
2. Themal conductivity: N2 [/W m-1 K-1]: 0.02583; O2 [/W m-1 K-1]: 0.02658, so the essentially conduct heat at the same rate.
3. At the pressures that your tires operate Air and pure Nitrogen with behave as ideal gasses and thus expand and contract identically.
4. Air is 79% N2 by volume.

The main reason that shops offer nitrogen fills, is that they do not have to operate or maintain an air compressor, they simply have a vendor supply them with nitrogen tanks. The economics of scale at work. That and people feel that getting "pure nitrogen" is an added value, I mean who wants to pay for air when you breath it for free? In some of the extreme conditions (such as in areonautics, and high performance driving) the small portion of water vapor present in the air around us is what is going to cause problems, that is why they use nitrogen as opposed to air.

A coworker of mine races go karts, they go about 60mph. After he switched to nitrogen in those little tires, he said that tires run cooler and the pressure doesn't fluctuate as much. He uses a non contact thermometer and a real expensive racing tire guage. I'm not sure of the exact number differences, but he is one of those guys that does everything to a tee to win. I'm pretty sure all of those racing guys use nitrogen.

[CaptainDan]

Allow me to "expand" upon this a little more.:nono:



"Nitrogen will diffuse faster than oxygen, as nitrogen is a smaller molecule(molecular volume 13.54 ×10-6 m^3/mol for N2 and 17.36 ×10−6 m3/mol for O2 at STP)"

Nitrogen will diffuse faster, means Nitrogen will LEAK OUT FASTER.

[Wallygator]

Since this discussion has gone crazy, here's another crazy idea. If you're worried about temperature affecting tire pressure, why not just fill your tires with water? Water expands and contracts much much much less than air or Nitrogen. Well wait now....water causes corrosion if it slips into the belts and we don't want rusty belts. How about filling your tires with oil? Oil is lighter than water, and doesn't cause corrosion. You won't have to worry about it leaking out through some crazy hairline hole in the bead. Oil is used in hydraulic systems at extremely high pressures because of its resistance to compression. Perfect solution to a rediculous problem.

[CaptainDan]

I was gonna install silicone implants to give my tires that extra sexy "bounce".

[Cosmoso4]

The Air Force has been using nitrogen in airplane tires for along time. I retired in 1992 and they were using it before that. It had alot to do with pressure fluctuation. I remember doing tire pressure tests for weeks at a time on KC-135s and B52s. Check them in the morning, check them at noon, check them in the afternoon. Pressures would fluctuate just sitting on the ground in the sun. After using the nitrogen, the fluctuations varied less or not at all. Expensive, it must be, that machine we used to pump nitrogen weighed a couple tons and had to moved with a truck.

[CaptainDan]

The Air Force has been using nitrogen in airplane tires for along time. I retired in 1992 and they were using it before that. It had alot to do with pressure fluctuation. I remember doing tire pressure tests for weeks at a time on KC-135s and B52s. Check them in the morning, check them at noon, check them in the afternoon. Pressures would fluctuate just sitting on the ground in the sun. After using the nitrogen, the fluctuations varied less or not at all. Expensive, it must be, that machine we used to pump nitrogen weighed a couple tons and had to moved with a truck.

As mentioned in this thread, there are reasons why consumers, race teams, airlines, and the military might choose Nitrogen inflation. It they do it to avoid pressure fluctuation, they are fooling themselves.

Nitrogen is a gas. Air is a gas (mostly Nitrogen!) Both of them, when heated, expand (increasing pressure). I don't care WHAT you put in the tires. If you heat it, it expands. That's very simple physics. If you heat the tires by using them, or by leaving them in the sun, the pressure increases.

And the molecular differences between air and pure Nitrogen are so miniscule that NO differences in pressure are detectable.

If you (or the Air Force) wants to test this, you certainly can't do it as you described. Outside in the sun? Were these test tires tested the same day, in the same weather, in the same temperature, in the same atmospheric pressure, on the same plane (with the same weight load)? Were there just a few tires tested, or were thousands tested to make up for any potential differences in tires?

And then, of course, if you put Nitrogen into a tire, you've still got some air in it. Unless you fill them while inside a vacuum chamber. And somehow I can't even imagine the US government springing for THAT expense!

[r600]

lol, I could fill my tires with nitrogen for free, I am an avation mech, but it would be such a small change (if any at all) on a daily driver that it isn't worth the effort. If I was tring to break a land speed record yea I might use it.

I would much rather just pay 25 or 50 cents for "free" air, and the convience of getting it at every gas station on the corner.

or buy a small air compressor that plugs in to your cigeratte lighter.

[Cosmoso4]

"If you (or the Air Force) wants to test this, you certainly can't do it as you described. Outside in the sun? Were these test tires tested the same day, in the same weather, in the same temperature, in the same atmospheric pressure, on the same plane (with the same weight load)? Were there just a few tires tested, or were thousands tested to make up for any potential differences in tires?"


I remember testing tire pressures on B52s that were on "alert" status. The problem with air pressure in tires occured because of the inspections required in the AF. As a crew chief, we would normally check tires in the AM, cool temps about 40-50s. Then if an inspector came by later in the day and checked the same exact tires, he would find the air pressure went up. We were only allowed a + or - so many PSI. If the difference was more than allowable, you failed the inspection and had to correct the problem. With the "problem" corrected, the next morning when checking tires, they would be low. We air them up and then in the heat of the day they would be too high. The AF switched to nitrogen to remedy this problem. I believe it worked, they still use it. Now, sure cars don't have 150+ psi tires, so maybe it doesn't pertain to cars. But you can't say it doesn't work. As far as testing tires goes, try this. Inflate all your tires the same, park it overnight so that one side of the car gets the morning sun and the other side is in the shade. Check the tires the next morning and see if there isn't a PSI difference from one side to the other. Did one side lose air overnight? Did the other side gain air overnight? Feel the sidewall of the tires. The sun will raise the tire pressure. I drive a truck for a living, I check tires in the morning and the sun does affect tire pressures by as much as 3 PSI on my truck.

[CaptainDan]

"If you (or the Air Force) wants to test this, you certainly can't do it as you described. Outside in the sun? Were these test tires tested the same day, in the same weather, in the same temperature, in the same atmospheric pressure, on the same plane (with the same weight load)? Were there just a few tires tested, or were thousands tested to make up for any potential differences in tires?"


I remember testing tire pressures on B52s that were on "alert" status. The problem with air pressure in tires occured because of the inspections required in the AF. As a crew chief, we would normally check tires in the AM, cool temps about 40-50s. Then if an inspector came by later in the day and checked the same exact tires, he would find the air pressure went up. We were only allowed a + or - so many PSI. If the difference was more than allowable, you failed the inspection and had to correct the problem. With the "problem" corrected, the next morning when checking tires, they would be low. We air them up and then in the heat of the day they would be too high. The AF switched to nitrogen to remedy this problem. I believe it worked, they still use it. Now, sure cars don't have 150+ psi tires, so maybe it doesn't pertain to cars. But you can't say it doesn't work. As far as testing tires goes, try this. Inflate all your tires the same, park it overnight so that one side of the car gets the morning sun and the other side is in the shade. Check the tires the next morning and see if there isn't a PSI difference from one side to the other. Did one side lose air overnight? Did the other side gain air overnight? Feel the sidewall of the tires. The sun will raise the tire pressure. I drive a truck for a living, I check tires in the morning and the sun does affect tire pressures by as much as 3 PSI on my truck.

Yes, I know, 'tis what I said, the sun will raise the tire pressure. But I gotta say, your inspector sure was a nutjob for blaming you for the sunshine.

[GregKJ]

This is some hillarious reading. I love all of the crap about nitrogen filled tires not changing pressures with temperature. Most of you must believe everything someone tells you without giving it a bit of thought. It is called the First Law of Thermodynamics. It sounds like CaptainDan and LS2Jesse (maybe a couple others) are the only people that know anything about this.

Airplane tires are mostly pure rubber, which oxygen will cause to degrade over time. So in that application, it does make sense.

For our GTO applications, we'll see no benefit in using nitrogen. Our tires are mostly synthetic rubber. And I don't know about you, but I bet my tires will only last two years, so oxygen degredation is not an issue anyway.

Check your tire pressures.

[Grey Goat]

Ok guys, I'm gonna have to do an experiment this weekend. My tires are full of Nitrogen and I have my own tank setup. I'll let the nitrogen out of one rear tire and fill it with good 'ole air straight out of my compressor. I will then confirm both rear tires are exactly the same pressure (one air, one Nitrogen) and then go for a "spirited" drive at night and check the pressures a few times during my ride. This confirm the question of expansion under heat load.

I will shoot for Saturday night, go ahead and post up your thoughts on what the results will be and we'll see in a few days!

PS: Nitrogen is actually very cheap, refilling my 250cf cylinder is around $9.00 and will fill about 65 tires!

[Grey Goat]

The results are in...

The conditions: One tire filled with Nitrogen the other with air - both holding exactly 30 psi. Ambient temperature is 55* Fahrenheit.

I went for a 20 minute drive with speeds of 65 - 90 MPH, all freeway driving.

The results: After my drive both tires were EXACTLY 32 psi!

So, in my little test it would appear that the expansion rate of Nitrogen and air are the same - the true test will be to do this in the summer time when we experience greater temperature swings here in Arizona.

[ashippen]

Ok, I will add my two cents on the topic. The benefits of nitrogen are irrefutable. It stabilizes the tire’s inflation pressure, which subsequently improves the vehicle’s handling, fuel efficiency, and the tire life. Nitrogen is as safe as air, but the molecule is approximately 3 to 4 times larger, which is where most of the benefits are derived from. However, this is assuming it is not diluted with air or “topped” off with air. In my opinion, a lot of people make the false assumption putting nitrogen in their tires it is end all of checking your pressure. The Rubber Manufactures Association (RMA) even said “depending on nitrogen alone to reduce the requirements got inflation maintenance may, in fact, lead to underflated operation, which may result in premature failure.”

In short, check your pressure monthly like normal because the benefits are under the assumption that the tire has no defects or damage.

One last note, try to check which systems the company is using, i.e. Branick Nitrogen systems have a range depending on the machine. I believe it is 95-99.9% nitrogen.

[CaptainDan]

Ok, I will add my two cents on the topic. The benefits of nitrogen are irrefutable. It stabilizes the tire’s inflation pressure, which subsequently improves the vehicle’s handling, fuel efficiency, and the tire life. Nitrogen is as safe as air, but the molecule is approximately 3 to 4 times larger, which is where most of the benefits are derived from.

Flunk Physics and Chemistry?

When you drive your car, the flexing of the tire heats it. When you heat something, air or Nitrogen or ANYTHING, it expands. That's pressure fluctuation. Air and Nitrogen will vary their pressures virtually identically.

Nitrogen Molecules (N2) are NOT 3 to 4 times larger than the molecules that make up air (which, by the way, happens to be 79% Nitrogen molecules anyways). Oxygen (20something%) molecules (O2) are very much the same size as Nitrogen molecules, and the CO2 molecules in air are quite a bit LARGER than the Nitrogen molecules. The other molecules that make up air occur in very, very small quantities, and are generally larger than Nitrogen too. So, if anything, Nitrogen would leak out faster than air.

[ashippen]

So are you just pulling this out of your ass, or can you show some proof other than Wikipedia where any idiot can blog? I have several companies and goverment agencies that I can cite. RMA and Branick were two I named above.

FYI
78% Nitrogen
21% Oxygen (I guess I should have said 20 something instead)
1% other gasses in very small amounts

[GregKJ]

Ok, I will add my two cents on the topic. The benefits of nitrogen are irrefutable. It stabilizes the tire’s inflation pressure, which subsequently improves the vehicle’s handling, fuel efficiency, and the tire life. Nitrogen is as safe as air, but the molecule is approximately 3 to 4 times larger, which is where most of the benefits are derived from...

So are you just pulling this out of your ass, or can you show some proof other than a Nitrogen sales website?

[CaptainDan]

So are you just pulling this out of your ass, or can you show some proof other than Wikipedia where any idiot can blog? I have several companies and goverment agencies that I can cite. RMA and Branick were two I named above.

FYI
78% Nitrogen
21% Oxygen (I guess I should have said 20 something instead)
1% other gasses in very small amounts

How many Physics and Chemistry textbooks can you fit up your ass? 'Cause you're gonna need room for ALL of them. Not to mention Newtons books on Thermodynamics, and he wrote in BIG letters. Double spaced too, I believe.

You want to know something that really is "irrefutable"? Nitrogen does NOT defy the laws of physics. And I'm sorry if you don't agree, but any source (usually a gas supplier or tire store that is trying to SELL me Nitrogen) that claims these "magical" properties for their products is quite "refutable".

[ashippen]

I am not going to bother replying to any more responses because obviously I can not convince you and the naysayers. You can have the final word. Funny thing is how you interpret what I wrote because I never said nitrogen defies the laws of physics. Could be wrong, but isn’t nitrogen a chemical compound? I am very aware that many companies are trying to sell you something. However, Costco Wholesales puts nitrogen in member's tires for free. You don't have to even purchase their tires (the Costco I go to). I simply said nitrogen offers additional benefits over compressed air. You attacked me and put words in my mouth. You still have not reference any sources. Also, their are laws in the United States against false advertisement, so you should lead the way and sue them.

Below are a few sources that promote the use of nitrogen:

Rubber Manufacturers Association is the national trade association for the rubber products industry. They don't sell nitrogen. They recommend using it, but say that it is still necessary to check the pressure.

Tire Business a newspaper had an article titled "N2 inflation gamble a good move".

Goodyear, Michelin, and Bridgestone (and their subsidiaries) have issues bulletins saying they support the use of nitrogen.

Costco Wholesale, NASA, Ingersoll Rand, all use nitrogen.

Finally, math has always been my weakest subject, and I am not that great at science either. However, if you try this simple equation I am sure you will see what I am getting at 21 x 4? Damn it, I guess I should have said 3.7 times larger.

[GRAVE DIGGER]

Ok well honeslty I did not read this whole post but I work for Costco and happen to be the supervisor of the tire center, first we will not fill your tires with nitrogen for free unless the tires were purchased from Costco, in fact Costco will not touch your vehicle unless the tires were purchased there. Nitrogen in fact does work very well but you still must check your pressure monthly. It is not fix-a-flat! I am sure that air is 70% nitrogen 29% oxygen and 1% other gases.
Basicly what i have learned the greatest advantage of nitrogen is that it does not hold moisture as much as pure air helping to prevent corrosion and pressure change. Nitrogen will change pressure up to 2 or 3psi were pure air will change up to 7-9psi. As far as the 20 minute drive test i believe that both air and nitrogen will not change pressure untill driven over 50 miles at speeds over 55mph.Basicly nitrogen will benefit most people who drive many miles daily, due to the heat and cars that are rarley driven, due to it not losing pressure over time (great for spares).
Anyways thats my .02

[swmn]

I love when this pops up. Lets me flex my engineering muscle.



Thank you LS2Jesse, and a few others for factual data.

As a scuba diver, Oxygen and Nitrogen both behave 'close enough' to the ideal gas law to ignore the very minute differences in temperature/volume/pressure fluctuatuions presented by pure oxygen and pure nitrogen.

I am certified to dive gas mixes anywhere between 40% O2 and 21% O2. My tanks are rated from 2250psi to 3500 psi. Anywhere inside those parameters, say 23% O2 at 3,000psi (207 atmospheres), oxygen and nitrogen both are 'close enough' to the ideal gas law (PV=nRT) for me to treat them as ideal gasses, at the limit, and live to tell about it. Actually, I have done this numerous times.

I don't fill my scuba tanks at Exxon for two physiologic reasons. Breathing oil vapors is very bad, and so is carbon monoxide.

Moving on to tires, the major difference between pure gasses and 'compressed air' at the corner Texaco is impurities, mostly water. Any water in the tires, from my perspective, is likely to flash to steam as the tires heat up, dramatically changing the 'n' (n= number of gas molecules) portion of PV=nRT, and therefore changing the 'P=pressure' inside the tires.

You could fill your tires with pure oxygen and enjoy an immediate sensation very similar, I think, to filling your tires with pure nitrogen. Remember the Guy-Lassac curve and google is your friend.

Over time of course, the rubber inside in your tires will oxidize faster if you fill the tires with pure oxygen.

One inexpensive alternative, if you are certified to get scuba tanks filled:

Pay for the nitrogen fill up front as the tires are installed to minimize the water inside the tire. Have the shop fill them to the absolute max on the sidewall. Run them long enough to get them good and hot. Let half the pressure (and half the water vapor) out of the tire. Refill the tires from a scuba tank, the water content regs for scuba fills are very strict. You want Grade E, E+ or better for your scuba air fills, essentailly no detectable water.

One typical "Aluminum 80" holds enough Grade E air to run this cycle, gosh, somewhere between 3 and 4 times at all four corners, so if you get the nitrogen install on a day with 50% relative humidity and fill from 0 psig to 35psig with N2, you are at ~16.67% relative, you can run the water content of the tires down to 2.08% relative. 80cf of Grade E runs about 6 dollars.

M2c,
S

[Kerno]

If the air you're breathing is not about 78 percent nitrogen and 21 percent oxygen, you must live on a different planet.

Filling your tires with nitrogen also lightens your car because your wallet is lighter.

[Konnie the Goat]

After reading thru this thread of half truths, sales pitches, and a few people who remember their high school physics and chemistry, i am left with the following conclusion. Nitrogen is a waste in 99% of automotive applications. You can believe a maketing hype, or you can look at the science.

Air is not a molecule (or compound), its a mixture. A mixture that is mostly N2 (which is how nitrogen exsists in nature), a little O2 (oxygen), and the rest is trace amounts of H2, Argon, Co2, CO, and H2O vapor.

The USAF guys chimed in with Observations, which are accurate, but the its the reasons they are missing. Our scuba man, SWMN, can chime in to back me up, or make me look some of the other people that have posted here. The mixture of gasses can have different properties than their component gasses. So for aircraft, which see frequent and rapid changes in temperature, pressure of surrounding air, and loads on take off and landing, a consistant mixture of N2, vs the N2/O2 mixture of air, makes it easier to manage the pressure of the tire. For those of us that never leave terra firma, there are gains, or rather benefits to nitrogen. Mainly, you know the exact compsition of the mixture. Air varries. N2 doesnt.

It has nothing to do with bigger molecules, more stable pressure vs tempurature, less leaking, moisture, or interactions with the rubber. Its Just more consistant, youre controlling a variable, and thats the gas mixture. The gains are really no different than airing up all your tires from a deflated state at the same time, off the same compressor. Then you know you are compressing the same air, of the same mixture, under the same conditions. Just like a N2 fill. that is all.

[GregKJ]

Moving on to tires, the major difference between pure gasses and 'compressed air' at the corner Texaco is impurities, mostly water. Any water in the tires, from my perspective, is likely to flash to steam as the tires heat up, dramatically changing the 'n' (n= number of gas molecules) portion of PV=nRT, and therefore changing the 'P=pressure' inside the tires.

I agree with most of what you said, except for this paragraph. There is no way that the water inside your tires is going to flash to steam.

After reading thru this thread of half truths, sales pitches, and a few people who remember their high school physics and chemistry, i am left with the following conclusion. Nitrogen is a waste in 99% of automotive applications. You can believe a maketing hype, or you can look at the science.

Air is not a molecule (or compound), its a mixture. A mixture that is mostly N2 (which is how nitrogen exsists in nature), a little O2 (oxygen), and the rest is trace amounts of H2, Argon, Co2, CO, and H2O vapor.

The USAF guys chimed in with Observations, which are accurate, but the its the reasons they are missing. Our scuba man, SWMN, can chime in to back me up, or make me look some of the other people that have posted here. The mixture of gasses can have different properties than their component gasses. So for aircraft, which see frequent and rapid changes in temperature, pressure of surrounding air, and loads on take off and landing, a consistant mixture of N2, vs the N2/O2 mixture of air, makes it easier to manage the pressure of the tire. For those of us that never leave terra firma, there are gains, or rather benefits to nitrogen. Mainly, you know the exact compsition of the mixture. Air varries. N2 doesnt.

It has nothing to do with bigger molecules, more stable pressure vs tempurature, less leaking, moisture, or interactions with the rubber. Its Just more consistant, youre controlling a variable, and thats the gas mixture. The gains are really no different than airing up all your tires from a deflated state at the same time, off the same compressor. Then you know you are compressing the same air, of the same mixture, under the same conditions. Just like a N2 fill. that is all.

You and I are arguing the same point (that N2 has no benefit in most applications), but your post doesn't make a whole lot of sense to me in a few places. What is the benefit of knowing the exact composition of the mixture if it doesn't provide more stable pressure, less leaking, etc., etc.?

I think that your answer is that all the tires will be filled with the same mixture. That is basically what others have been arguing for the benefits of nitrogen. They are saying that nitrogen and oxygen pressure increases differently when heated, which must be what you're saying also.

I don't agree. If that is not what you're saying, what would the benefit be? Just knowing what is in your tires is no benefit. If someone told me that they put a little extra argon in my left front, I could care less as long at the pressure is correct. LS2Jesse, CaptainDan, and I are saying that the exact composition between tires does not matter. (Or at least I believe that they agree with me.)

Your last paragraph baffles me the most. There are negligible differences in air composition where I live to where you live to where anyone else lives in the US. And there are negligible differences between compressors. Fill my front left tire on a Monday in Texas with air from a Shell station, my front right on Wednesday in South Dakota with air from Texaco, my left and right rear in New York with nitrogen on a Saturday. I could care less.

[Konnie the Goat]

You and I are arguing the same point (that N2 has no benefit in most applications), but your post doesn't make a whole lot of sense to me in a few places. What is the benefit of knowing the exact composition of the mixture if it doesn't provide more stable pressure, less leaking, etc., etc.?

I think that your answer is that all the tires will be filled with the same mixture. That is basically what others have been arguing for the benefits of nitrogen. They are saying that nitrogen and oxygen pressure increases differently when heated, which must be what you're saying also.

I don't agree. If that is not what you're saying, what would the benefit be? Just knowing what is in your tires is no benefit. If someone told me that they put a little extra argon in my left front, I could care less as long at the pressure is correct. LS2Jesse, CaptainDan, and I are saying that the exact composition between tires does not matter. (Or at least I believe that they agree with me.)

Your last paragraph baffles me the most. There are negligible differences in air composition where I live to where you live to where anyone else lives in the US. And there are negligible differences between compressors. Fill my front left tire on a Monday in Texas with air from a Shell station, my front right on Wednesday in South Dakota with air from Texaco, my left and right rear in New York with nitrogen on a Saturday. I could care less.

Im saying that while Oxygen and Nitrogen, the two main elements in Air, have nearly identical wiehgts, volumes per mol at STP, thermal conductance, etc, the variance on the mixture of the two, in combination with the other molecules in the Air mixture leaves room for variance. Which is where pure nitrogen has its advantage.

A small variance in the mix can have unexpected results. Take ethylene glycol and water. Very similar properties for freezeing and boiling, water has better heat transfer, and similar viscosity. But you mix them together in the cooling system of a car, and in combination with the pressure of the system, you get much a much lower freezing point, and much higher boiling point than either fluid alone. Same thing happens with some metal alloys, where they may not chemically bond, but the crystaline structures of the metal molecules may interlace to form a stronger structure than any of the component metals. Such it is with gas mixtures. A mix will have different properties than the component gasses. Air is a mix. And while it is generally uniform, there is always some variance, usually in the water vapor area. And we all know that water has very unique properties.

So N2 is better than Air, for airplanes, manily for reasons that have nothing to with cars. An air plane will experience a wider variation in temps than any car. They can take off at speeds most cars only dream of in Kuwait at 140 deg F. Fly up to 40,000 feet, with ist sub-zero air temps for 14 hours, and touch down safely in a 30 deg F New Jersey, or 70 deg F Florida. They run much larger tires, at much higher pressures than cars. Pressure will affect the way the gas(ses) inside behave. And we'll leave a planes weight load out of this. If a plane had air in its tires, under those conditions, there is a greater chance for problems, due to the variance of the mixture.

As i said, thats N2's advantage. Its not a mixture. As such its easier to predict its behavior. Air is predictable, but only to an extent, its a Mix, and a mix can vary. And you shouldn't fill your tires with O2, because pure O2 tends to be pretty volitile and corrosive. Its a very reactive gas. Hence the use in Nitrous Oxide, N2O. Its an oxidizer. Same component gasses as Air, minus the 1% trace gasses, in a slightly different ratio (2:1 vs 3.7:1), but chemically bonded.

N2 does not really have less thermal expansion potential than air, but its is less likely to, and more expected when it does.

[swmn]

The mixture of gasses can have different properties than their component gasses.

Ooh, Dalton's Law and not ideal gasses.

Here is the Wiki page for Dalton's law: http://en.wikipedia.org/wiki/Dalton's_law

The relevant text, in English:

The total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.

I am going to run a really quick scuba class here. Running from entry level beginer certification through advaced open water and on into nitrox and advanced nitrox classes, you get to ignore the impurities in the atmosphere. 'Air' is 21% O2 and 79% N2. You can ignore the other gasses, at least for now.

I am not certified in tri-mix, but I have a decent familiarty with the material. To go even deeper than I can already go I need to get a tri mix certification so I can have the card I need to get tri-mix fills from dive shops.

So, you are going diving. You have 'air' in your tank. 'Air' is 21% O2 and 79% N2. Your tank is filled to 3,000 psi. Atmospheric temperature on the dive boat is 85°F. Water temperature 33 feet down is 73°.

John Dalton says you have 2370psi worth of Nitrogen in that tank, and 630psi worth of Oxygen.

So you jump off the boat and swim down to 33 feet under water. Everything cools off 12 degrees. Using PV=nRT you could calculate what the Pressure of your tank will be when it cools the 12°, assuming you don't breathe off it while you are waiting. Remember V, the Volume of the tank is not going to change. So anything you change among the n number of gas molecules, R the gas constant or T= temperature will be reflected as a pressure change in the scuba tank.

Obviously scuba tanks do swell a little tiny bit when they get hot or filled to high pressures. Also, tires on cars can vary both the P pressure and V volume as they heat up.

When dealing with strictly Nitrogen, Oxygen (and the impurities we are ignoring), many many people have filled scuba tanks to 4,000 psi and found that N2 and O2 still behave as ideal gasses, PV=nRT.

When you stick Helium into a scuba tank we have a problem.

In the Florida cave diving community, there is a group of maybe 50-100 people who go down like 300 feet below sea level in the fresh water cave systems. To just go down there and pick up a rock is a 4 hour decompression obligation. To swim upstream, following a hydrocarbon trail to pinpoint say a leaking storage tank at some gas station that is entering the water supply can easily turn in to a 14 hour dive.

In the 1950s the US Navy figured out (using test subjects in tip-top physical condition) that breathing 'air' at 165 feet below sea level USNavy seals are so narc'd that they blow up US submarines instead of enemy submarines. A small problem. I am sure you have heard of nitrogen narcosis, we are talking about it now.

Imagine you come home from work on an empty stomach, take a huge water cooled bong hit and do two shots of tequila while you are holding the bong hit in. Exhale. Now you are narced. Only when it happens in the ocean there are wild animals bigger than you that are out hunting because they are hungry.

The Navy also figured out that breathing 'air' 218 feet below sea level causes seizures, and frequently death. This turns out to be Oxygen toxicity.

So how do you get to 300 feet underwater if you are stone cold useless at 165 feet and having a seizure at 218 feet? The answer is helium.

If you fill a tank halfway up with Helium, and then fill the other 'half' with 'air', when you get to 300 feet, the 'equivalent nitrogen depth' is 150 feet, and the 'equivalent oxygen depth' is 150 feet. Got it?

Ok, in Florida caves, about the highest pressure tri-mix (He+O2+N2)fill you are going to find is ~3,000 psi. In Norway and Sweden, about the highest pressure tri-mix fill you will find is about 2500 psi.

Why?

Remember the cooling tank with the lowering pressure back on day one? If you pump tri-mix much higher than those numbers, (there is about a 20% safety marggin built in), the Helium might phase change - liquify - as the mixture cools. So you jump off the boat in Norway with 3,000 psi of tri-mix, forgetting that even 300 feet down Florida's water is warmer than Norway's.

You get to 300 feet down, the He liquified, and whats up. The indiated tank pressure is going to be (Daltons Law) 1500 psi. Because 1/2 of the total n number of molecules in the tank are now liquid, they don't contribute to the total gas pressure indicated on your gauge.

If you take a breath off that tank:

The good news is you are going to be really, really, high because the 'equivalent nitrogen depth' is now 300 feet.

The bad news is you will also be really, really dead, because the 'equivalent oxygen depth' is now 300 feet.

That is the behavior of a not ideal gas.

I still think the primary performance benefit of Nitrogen tire fills is minimal water vapor inside the tire carcass.

[swmn]

Konnie,

I believe ethylene glycol works as a cooling system additive because of the colligative properties of the solution. It was one of about three things I remember from organic chemsitry, as my prof hardly ever talked about cars.

http://en.wikipedia.org/wiki/Colligative

[sloloco]

No gimmick guys, I run nitrogen and it makes a difference. (period)
Props for doing your homework and you won't be dissapointed!
Our local shops up here charge $4 per tire, that's chump change and most spend that on coffee in a week around here?!

[swmn]

No gimmick guys, I run nitrogen and it makes a difference. (period)


Yup. This question comes up a couple times a year. The guys actually running pure nitrogen usually chime in with "can't tell the difference", "can tell the difference when I drive a car with regular air in the tires", or "I really like it and can tell the difference all the time".

Typically more than half the repsondents actually running the stuff fall in the latter two categories. I think there is something to it, but it is probably a very subtle thing to describe.

[GTO 06]

We've been using nitrogen in our race car for years. it's no gimmick.

Morty

[dms]

The use of nitrogen has been an interest of mine for some time. Without a doubt, under correct conditions, nitrogen is a benefit, But I have elected not to sell it for several reasons:
1. A small amount of contamination (normal air) in the tire radically reduces the positive benefit of nitrogen, which is being less corrosive than an oxygen based air, and more stable and consistant tire pressures. Without a doubt, in the racing world it is a great thing to have because of extremes.
a. Nitrogen machines are not made equal! At Sema for 3 years in a row, I have looked at every nitrogen machine on the market. The differences betweeen a machine that can generate 99.5% nitrogen or higher and the normal machines that generate 92-95% nitrogen, which are not worth it, is stagering in price
b. There is no benefit letting the air out of your tires, then filling it up with nitrogen. There is still too much residual oxygen in the air that is left inside. This eliminates the real benifit of nitrogen. To do it correctly, the tire needs to be broken down, and put together using nitrogen. the massive amount of air used to inflate a tire will pretty much purge out most of the normal air. But to do this, you need a seriously large nitrogen setup. The one I looked at that was first class and large enough to handle a custom wheel and tire shop had an initial cost of about $15,000. You can get nitrogen machines for $2.5k to $5k. But in the case of nitrogen generators, you do get what you pay for.

2. So lets say you did buy the hummer cranker nitrogen machine, and used nitrogen to assemble the 305/50R20 tires on a 2006 Denali. Roadtesting, you will find the tire pressures are pretty rock solid stable.Maybe a 1 to 2 psi increase versus a 10psi increase using normal air on a trip on a hot day. So lets take it to the extreme. The Denali owner has a big boat, and a bunch of kist and gear and they go camping in August on a 300 mile trip. Tire pressures are at 35PSI cold, and all is sweeet. But on the way back, they pick up a nail and one of the tires goes flat but not damaged. They find a tire shop that breaks the tire down and installs a patch, fills the tire with normal air to 35PSI and off the familty goes on a long 300 mile trip, loaded, and pulling a boat. It could be perfectly normal for the tire pressure of the normal aired tire to go up 10-15psi, while the nitorgen filled tires only goe up 2 to 3 psi maybe. Now we potentially have a 7 to 12 psi variation in tire pressures. This will cause the tire pressure monitor light to come on. But most concerning is now the unequal tire load and diameter vairiations, including traction. Now the unfortunate family has a tire pressure light on, and a joker pulls out in front of them and they have to make a panick stop. the vehicle now has the potential to be less stable due to the 1 tire being higher pressure. They begin to loose it on the road in a corner, and a accident occurs. Did I mention the owner was a ambulance chasing attorney who has a tire pressure light on? Do you smell lawsuit???
I literally have talked to every nitrogen machine manufacturer out there and have given them this exact scenario. Other than giving the customer a small inflatable nitrogen container for emergency fills ( which I have looked for, but have not found under $100 or so), no one had a solution, and all of them recognized this scenario as legitimate; excpet one manufacturer whose machine had the lowest % of pure nitorgen. I think he was not worried about it because with his machine, there would not be much variation between his nitorgen and normal air.

3. I have tried to find this answer and have been unsuccessful at it. All trutck and passenger car tires have a maximum tire pressure reading on the tire itself. With the tire pressure, it alsow lists the maximum weight load of the tire. The higher the tire pressure, the more load the tire can take. Does the tire and vehicle manufacturer include in their research and certification on vehicle maximum load abilites the tire load increases due to tire pressure increases due to temperatur increases, or is it calcuated with max tire pressure cold? Passenger cars may not be that seriously affected. But if you look at a 3/4 ton truck for example, it makes a big difference. Also, tire pressures make a huge difference in a performance driving situation. Most onwers manuals on performance vehicles will give you a higher than normal tire pre3ssure to inflate to cold if you are "playing"

One thing abut GM, is that they are the most conservative manufacturer out there. They do sell the nitrogen machines thru GM Equipment, and list several good quality ones. Here is a copy of bulletin 05-03-10-020 that they published in December of 2005.

Hope this helps. Wow, this post I think is even longer than SWMNs!!

mike
dms

Subject: Info - Use of Nitrogen Gas in Tires #05-03-10-020 - (12/22/2005)
Models: All 2006 and Prior GM Passenger Cars and Light/Medium Duty Trucks (including Saturn)
2003-2006 HUMMER H2
2006 HUMMER H3
2005-2006 Saab 9-7X

GM's Position on the Use of Nitrogen Gas in Tires

General Motors does not oppose the use of purified nitrogen as an inflation gas for tires. We expect the theoretical benefits to be reduced in practical use due to the lack of an existing infrastructure to continuously facilitate inflating tires with nearly pure nitrogen. Even occasional inflation with compressed atmospheric air will negate many of the theoretical benefits. Given those theoretical benefits, practical limitations, and the robust design of GM original equipment TPC tires, the realized benefits to our customer of inflating their tires with purified nitrogen are expected to be minimal.

The Promise of Nitrogen: Under Controlled Conditions

Recently, nitrogen gas (for use in inflating tires) has become available to the general consumer through some retailers. The use of nitrogen gas to inflate tires is a technology used in automobile racing. The following benefits under controlled conditions are attributed to nitrogen gas and its unique properties:

• A reduction in the expected loss of Tire Pressure over time.
• A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration.
• A reduction of long term rubber degradation due to a decrease in oxygen concentrations.
Important: These are obtainable performance improvements when relatively pure nitrogen gas is used to inflate tires under controlled conditions.
The Promise of Nitrogen: Real World Use

Nitrogen inflation can provide some benefit by reducing gas migration (pressure loss) at the molecular level through the tire structure. NHTSA (National Highway Traffic Safety Administration) has stated that the inflation pressure loss of tires can be up to 5% a month. Nitrogen molecules are larger than oxygen molecules and, therefore, are less prone to "seeping" through the tire casing. The actual obtainable benefits of nitrogen varies, based on the physical construction and the materials used in the manufacturing of the tire being inflated.

Another potential benefit of nitrogen is the reduced oxidation of tire components. Research has demonstrated that oxygen consumed in the oxidation process of the tire primarily comes from the inflation media. Therefore, it is reasonable to assume that oxidation of tire components can be reduced if the tire is inflated with pure nitrogen. However, only very small amounts of oxygen are required to begin the normal oxidation process. Even slight contamination of the tire inflation gas with compressed atmospheric air during normal inflation pressure maintenance, may negate the benefits of using nitrogen.


GM Tire Quality, Technology and Focus of Importance
Since 1972, General Motors has designed tires under the TPC (Tire Performance Criteria) specification system, which includes specific requirements that ensure robust tire performance under normal usage. General Motors works with tire suppliers to design and manufacture original equipment tires for GM vehicles. The GM TPC addresses required performance with respect to both inflation pressure retention, and endurance properties for original equipment tires. The inflation pressure retention requirements address availability of oxygen and oxidation concerns, while endurance requirements ensure the mechanical structure of the tire has sufficient strength. This combination has provided our customers with tires that maintain their structural integrity throughout their useful treadlife under normal operating conditions.

Regardless of the inflation media for tires (atmospheric air or nitrogen), inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance. Maintaining the correct inflation pressure allows the tire to perform as intended by the vehicle manufacturer in many areas, including comfort, fuel economy, stopping distance, cornering, traction, treadwear, and noise. Since the load carrying capability of a tire is related to inflation pressure, proper inflation pressure maintenance is necessary for the tire to support the load imposed by the vehicle without excessive structural degradation.

Important: Regardless of the inflation media for tires (atmospheric air or nitrogen) inflation pressure maintenance of tires is critical for overall tire, and ultimately, vehicle performance.

[My First GTO]

Mike, You Win For The LONGEST Post...Frank

[GregKJ]

I am going to run a really quick scuba class here. Running from entry level beginer certification through advaced open water and on into nitrox and advanced nitrox classes, you get to ignore the impurities in the atmosphere. 'Air' is 21% O2 and 79% N2. You can ignore the other gasses, at least for now.

I am not certified in tri-mix, but I have a decent familiarty with the material. To go even deeper than I can already go I need to get a tri mix certification so I can have the card I need to get tri-mix fills from dive shops.

So, you are going diving. You have 'air' in your tank. 'Air' is 21% O2 and 79% N2. Your tank is filled to 3,000 psi. Atmospheric temperature on the dive boat is 85°F. Water temperature 33 feet down is 73°.

John Dalton says you have 2370psi worth of Nitrogen in that tank, and 630psi worth of Oxygen.

So you jump off the boat and swim down to 33 feet under water. Everything cools off 12 degrees. Using PV=nRT you could calculate what the Pressure of your tank will be when it cools the 12°, assuming you don't breathe off it while you are waiting. Remember V, the Volume of the tank is not going to change. So anything you change among the n number of gas molecules, R the gas constant or T= temperature will be reflected as a pressure change in the scuba tank.

Obviously scuba tanks do swell a little tiny bit when they get hot or filled to high pressures. Also, tires on cars can vary both the P pressure and V volume as they heat up.

When dealing with strictly Nitrogen, Oxygen (and the impurities we are ignoring), many many people have filled scuba tanks to 4,000 psi and found that N2 and O2 still behave as ideal gasses, PV=nRT.

When you stick Helium into a scuba tank we have a problem.

In the Florida cave diving community, there is a group of maybe 50-100 people who go down like 300 feet below sea level in the fresh water cave systems. To just go down there and pick up a rock is a 4 hour decompression obligation. To swim upstream, following a hydrocarbon trail to pinpoint say a leaking storage tank at some gas station that is entering the water supply can easily turn in to a 14 hour dive.

In the 1950s the US Navy figured out (using test subjects in tip-top physical condition) that breathing 'air' at 165 feet below sea level USNavy seals are so narc'd that they blow up US submarines instead of enemy submarines. A small problem. I am sure you have heard of nitrogen narcosis, we are talking about it now.

Imagine you come home from work on an empty stomach, take a huge water cooled bong hit and do two shots of tequila while you are holding the bong hit in. Exhale. Now you are narced. Only when it happens in the ocean there are wild animals bigger than you that are out hunting because they are hungry.

The Navy also figured out that breathing 'air' 218 feet below sea level causes seizures, and frequently death. This turns out to be Oxygen toxicity.

So how do you get to 300 feet underwater if you are stone cold useless at 165 feet and having a seizure at 218 feet? The answer is helium.

If you fill a tank halfway up with Helium, and then fill the other 'half' with 'air', when you get to 300 feet, the 'equivalent nitrogen depth' is 150 feet, and the 'equivalent oxygen depth' is 150 feet. Got it?

Ok, in Florida caves, about the highest pressure tri-mix (He+O2+N2)fill you are going to find is ~3,000 psi. In Norway and Sweden, about the highest pressure tri-mix fill you will find is about 2500 psi.

Why?

Remember the cooling tank with the lowering pressure back on day one? If you pump tri-mix much higher than those numbers, (there is about a 20% safety marggin built in), the Helium might phase change - liquify - as the mixture cools. So you jump off the boat in Norway with 3,000 psi of tri-mix, forgetting that even 300 feet down Florida's water is warmer than Norway's.

You get to 300 feet down, the He liquified, and whats up. The indiated tank pressure is going to be (Daltons Law) 1500 psi. Because 1/2 of the total n number of molecules in the tank are now liquid, they don't contribute to the total gas pressure indicated on your gauge.

If you take a breath off that tank:

The good news is you are going to be really, really, high because the 'equivalent nitrogen depth' is now 300 feet.

The bad news is you will also be really, really dead, because the 'equivalent oxygen depth' is now 300 feet.

That is the behavior of a not ideal gas.

I still think the primary performance benefit of Nitrogen tire fills is minimal water vapor inside the tire carcass.

That's a lot of information that has little to do with tires.

[CaptainDan]

....... Take ethylene glycol and water. Very similar properties for freezeing and boiling, water has better heat transfer, and similar viscosity. .........

Ethylene glycol and water have TREMENDOUSLY different properties for freezing and boiling, and nothing close to similar viscosity. These differences are why they are mixed for engine coolant. (Of course there are other additives put in there too)

Water alone would freeze in the winter.
glycol alone would boil away in the summer.

[mistermike]

I'm guessing they didn't do it then....

Nitrogen doesn't expand, Oxygen does. If your pressure changed, you have oxygen in them and not pure nitrogen.
All gases expand and contract with temperature
http://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html
http://www.engineeringtoolbox.com/gas-density-d_158.html
http://www.engineeringtoolbox.com/compression-expansion-gases-d_605.html
The difference in density and molecular weight between air and nitrogen is almost insignificant.

[swmn]

Subject: Info - Use of Nitrogen Gas in Tires
#05-03-10-020 - (12/22/2005)

Models: All 2006 and Prior GM Passenger Cars

• A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration.




I already got one hand on my slide rule. Does anyone still need to see this derived?

S

[Kanding]

The following benefits under controlled conditions are attributed to nitrogen gas and its unique properties:

• A reduction in the expected loss of Tire Pressure over time.
• A reduction in the variance of Tire Pressures with temperature changes due to reduction of water vapor concentration.
• A reduction of long term rubber degradation due to a decrease in oxygen concentrations.
Important: These are obtainable performance improvements when relatively pure nitrogen gas is used to inflate tires under controlled conditions.



Exactly... reduction of moisture is the main reason for the benefit (if minimal) to the N2 fills.

[City Goat]

I think I need some slide rule action for clarification on this matter.

:judge:

[Rob@WretchedMS]

I think I need some slide rule action for clarification on this matter.

:judge:

How about an abacus.

[swmn]

I think I need some slide rule action for clarification on this matter.

:judge:


OK. I am going down to the garage under my apartment building to measure up some SUV rims and tires.

While I am doing that, you need a minimal familiarity with the concept of "heat of vaporization":

http://en.wikipedia.org/wiki/Latent_heat_of_vapori zation

relevant text:


the molecules in liquid water are held together by relatively strong hydrogen bonds, and its standard enthalpy change of vaporization, 40.8 kJ/mol, is more than five times the energy required to heat the same quantity of water from 0 °C to 100 °C

You also need to understand Kelvin temperatures. The ideal gas law, PV=nRT, uses the Kelvin temperature scale. Zero Celcius is the freezing point of water, where water turns to ice. Zero Kelvin is the freezing point of matter, where molecular motion stops:

http://en.wikipedia.org/wiki/Absolute_zero

And you might as well brush up a little bit on ideal gasses:

http://en.wikipedia.org/wiki/Ideal_gas

releveant text:


An ideal gas or perfect gas is a hypothetical gas consisting of identical particles of zero volume, with no intermolecular forces. Additionally, the constituent atoms or molecules undergo perfectly elastic collisions with the walls of the container. Real gases do not exhibit these exact properties, although the approximation is often good enough to describe real gases. The approximation breaks down at high pressures and low temperatures


also boiling point:

http://en.wikipedia.org/wiki/Boiling_point

relevant text:


Something that should be remembered is that boiling is evidenced by the appearance of bubbles containing vapor from the liquid. [Note: The bubbles that precede real boiling in the pot on the stove are either (formerly) dissolved gas or water vapor forming on the very hot bottom of the pot that will be condensed before it can get to the top of the liquid.] Production of vapor requires energy and thus does not occur without some source of energy


My hypothesis is water inside the tire behaves as a not ideal gas. Mike White gave us some data points, I am going to see how high the relative humidity at the compressor inlet had to be for this to work.

[mcgilbery]

The company my wife works for bought a nitrogen system for their fleet vehicles. The head mechanic is a GTO buff and did mine for free about 5 months ago. I haven't had to go by for a top off but I haven’t put many miles on the car either. One thing that their system did was that it evacuated the tires. It sucked them down until they deformed inward to the rim but it did not break the bead. He then refilled them with N2. He repeated it three times on each tire. I haven’t run them much in the heat so I can’t attest to that part yet. The mechanic says the jury’s out still on value versus expense but he’s definitely having fewer problems.

[swmn]

I had to sleep on this, and I will bump the thread again in a couple years when I get it worked out the long way.

For the short version we can draw some conclusions with the Combined Gas Law and then look at the ideal gas law again, the latter introducing Avogadro's research.

http://en.wikipedia.org/wiki/Gas_laws

Essentially, absolute pressure * volume / absolute temperature now is equal to absolute pressure * volume / absolute temperature later, assuming both an ideal gas and a container that doesn't leak.

So we can start with a 305-50-20 tire mounted to a rim and inflated to 35psig while the ambient temperature is 70°F.

The Volume of gas enclosed by that tire is close enough to 6.0 liters (~370 cubic inches) to move on.

35psig is a relative term, in absolute terms we can convert that to 3.38 atmospheres of ambient pressure, or 3.38ATA.

70°F is a relative term, we can convert that to 294 Kelvin.

So there is our "now" tire, 6 liters of gas at 3.38ATA and 294K. Written 3.38ATA*6l/294K.

So Mike White says if you fill the "now" tire with relatively pure nitrogen that behaves 'like' an ideal gas and run it hard on the street, the pressure will increase from 35psig to 38psig. OK.

Let's go to a gas station just off the interstate real quick. You see three identical SUVs lined up at three pumps. One of them is a local resident, lives two blocks away, his tires are cold and inflated to 35psig with some gas. The second has air filled tires, just drove in from 300 miles out, and his hot pressure is 50psig. The third SUV is road tripping with the second one, but the tires are filled with pure Nitrogen and the hot pressure is 38psig. Can you tell which one is which just by looking at the size of the tires?

NO. I do agree that cold tires, down around freezing, will start to look visibly low. I insist that hot tires between 35-50psig all 'look' about the same to the naked eye. We both know the hotter, higher pressure tire is a 'little' bit bigger than the cold one, but we need some sophisticated gear to prove it. So I am leaving the volume portion of the experiment fixed at 6 liters.

So the hot nitrogen filled tire has a pressure of 38psig, 3.59ATA. Leaving the volume fixed at 6 liters:

3.59ATA*6liters/ __x__K = 3.38ATA * 6 liters / 294K

We conclude the hot nitrogen tire has a temperature of 312K, or 102°F.

That is pretty reasonable. I have yet to see an absolute temperature on my street GTO in excess of 90°F. Racing tires, R-compound rubber, is generally available in 10-15°F increments to provide maximum traction at temperatures between 160°F and 220°F.

Now lets look at the air filled SUV. 50psig is 4.40ATA, so:

4.40ATA * 6 liters / __y__K = 3.38ATA * 6 liters / 294K

y = 382K, or 228°F.

You ought to be able to tell a hot N2 tire from a hot air tire just because the N2 tire is hot like a beach while the air tire is hot like an oven. Can you? NO.

Have you ever walked by a street driven rear tire and felt the warmth on your leg the way you do standing next to a hot radiator, hot cats and a front tire? It doesn't happen.

So looking again at the Ideal gas law, PV=nRT, we already know P, V and T for three cases. R is a constant, for ideal gasses. If we leave the ideal gas law alone, we come up with pascals * cubic meters on both sides of the equal sign. If we calculate (or look up) R for specific gasses, we introduce mass (kilograms) to the right side of the equation and have to introduce mass to the left side to get out of the woods. That is a issue beyond my current capabilities, but it will cancel itself out anyway, and we will be left with a 228°F tire.

What we are looking for is some way to increase the pressure in the tire, without doing anything dramatic to the volume, that gives us a reasonable temperature. The only variable left is 'n',the 'number' of gas molecules in the tire.

Somewhere on the internet I haven't looked yet, someone will find the Gay-Lassac curve for water at 3ATA. It will look "something" like this:


http://www.ls1gto.com/forums/attachment.php?attach mentid=50028&d=1168728760

The vertical axis is the percent of the water that is a gas, a particle of 'n' that contributes to the total pressure inside the tire. The horizontal axis is increasing temperature, left hash is freezing point of water, right hash is boiling point of water. If you integrate the entire area under the curve you should find that 100% of the sample is gaseous at the boiling point. If you integrate the entire area of the curve from the freezing point to the freezing point (nada) you should find zero percent of the water exist as a gas.

The red curve is my best recollection (20 + years) of the G-L curve for water at 1ATA. The yellow zone is roughly the reasonable operating temperature range of street tires. When someone finds the G-L curve for water at 3ATA, it will have the same basic shape, but the values on the axes I didn't bother putting in will be different. Who knows where the yellow zone will end up under the correct curve, but the concept is the same.

Air filled tires have 'some' water in them. As the tire heats, some of the liquid water becomes gaseous. As the tire cools, some of the gaseous water becomes liquid. This changes the 'n' value of the ideal gas equations for the interior of the tire. In short air with 'some' water in it does not behave as an ideal gas inside tires.

EDIT: G-L.jpg replaced with G-Lii. Logically correct curve has two asymptotes and one apex, rather than one asymptote and two apexes as originally drawn.

[mixedxboy]

The second has air filled tires, just drove in from 300 miles out, and his hot pressure is 50psig. The third SUV is road tripping with the second one, but the tires are filled with pure Nitrogen and the hot pressure is 38psig.

interesting. how did you come to this assumption that the air filled tires increased to 50psi whereas the n2 filled increased to 38psi? both SUVs travelled the same trip, and therefore transferred the same amount of kinetic energy to the gas in the tires.

as you mentioned, volume and the number of molecules in the tire are fixed (except for a small percentage of water), and R is a constant. the only variables that can change measurably are pressure and temperature.

over the same 300 mile trip, a specific amount of kinetic energy is transferred to the tires. how is it that the air-filled tires are able to convert so much more of that energy to heat than the nitrogen tires? what did the nitrogen tires do with their excess energy if it was not converted to heat?

interestingly, as you mentioned the water in the tire can absorb that kinetic energy and use it to escape the liquid state into the gaseous state. this slightly increases the number of gas molecules in the tire (n), but it also has a cooling effect on the tire and the other gases in the tire. is it enough to make a difference? well that really depends on the percentage of water in the tire. one thing is for sure, the n2-filled tires aren't using condensation and evaporation to manage their heat/kinetic-energy.

[swmn]

interesting. how did you come to this assumption that the air filled tires increased to 50psi whereas the n2 filled increased to 38psi? both SUVs travelled the same trip, and therefore transferred the same amount of kinetic energy to the gas in the tires.



From post number 97 above, paragraph #5:



It could be perfectly normal for the tire pressure of the normal aired tire to go up 10-15psi, while the nitorgen filled tires only goe up 2 to 3 psi maybe. Now we potentially have a 7 to 12 psi variation in tire pressures.

Mike has a lot of SUV experience, I don't have any. I do have a fair amount of GTO tire experience and my take is Mike's data is probably pretty darn good.

[mixedxboy]

ahhh yes my mistake

anyhow i certainly will defer to you and mike--both much more knowledgeable and experienced than myself, and i agree with both of you that there is not much of a practical benefit to n2 fills, or at least not enough under our operating conditions to justify any extra costs.

my question still stands though--SUV or otherwise--how is it that nitrogen is able to defy the laws of thermodynamics, if the data are in fact accurate?

[swmn]

ahhh yes my mistake

anyhow i certainly will defer to you and mike--both much more knowledgeable and experienced than myself,

Mmm, couple fine points.

With basic science out of the way the rest of my undergrad was biology and liberal arts, I am feeling around in distant receses of old memories here.



and i agree with both of you that there is not much of a practical benefit to n2 fills, or at least not enough under our operating conditions to justify any extra costs.

Sort of to not so much really, it depends, mostly I guess, on how $$$ you got in tires and what you expect from them.

my question still stands though--SUV or otherwise--how is it that nitrogen is able to defy the laws of thermodynamics, if the data are in fact accurate?

My point above is that Nitrogen DOES obey the laws of thermodynamics and "air with a little water in it" also DOES obey the laws of thermodynamics, the latter situation merely includes a variable that can be better controlled.

Imagine all four of your tires have "about the same little bit" of water in them. All four will behave 'about the same' and you might never notice.

Say you get a flat, a patch and a refill, only the refill comes from a fill chuck with visible water actually dripping out of it. I know you have seen them, you don't have to look at many gas station air chucks to find one.

Alternatively, imagine you buy 4 new tires in Portland OR while the relative humidity is 100% and there is water dripping out of the fill chuck but all four tires are the same. Then you get a flat next summer in Tucson, the relative humidity is jack-doodle and the shop just drained the compressors and cleaned the water filter yesterday. Now you got one tire significantly _drier_ than the other three.

In this situation, the tire with the patch (and different water content than the other three tires) is more likely to behave differently enough from the other three for you to notice.

But if you go to the welding supply shop and buy H tanks of Nitrogen (the big ones that come about chest high on a grownup) you got some choices. Probably you will choose to lease a tank, and buy the Nitrogen in the tank.

You could buy "two nine" Nitrogen that is 99% pure, or "four nine" nitrogen that is 99.99% pure. If you are planning to mix up some tri-mix at home to go deep scuba diving you want the "six nine" helium, 99.9999% pure. None of these are going to have water vapor concentrations above 3 to 5 ppm (parts per million), water plus high pressure is very bad for the steel walls of these high pressure tanks.

If you are a certified diver all you got to is go rent a scuba tank and figure out how to get the air out of the tank into the tire. That part is easy.

Starting from scratch you are going to need a 'fill whip'. It will have the correct threads at one end to screw to the tank valve. You'll need a industrial grade pressure regulator. Its a block of metal with a spring valve in it, inlet pressure rating needs to be about 2200 to 2500 psi, a 'full' H tank of N2 will arrive at your garage door with a fill pressure of 2000 to 2200 psi. Outlet pressure on the regulator should be 'about' 90 to 150psi, a rating of "125psi +/- 10%" is fine. You don't need a 'good' or 'expensive' regulator, the point is to not slam your tires with 2000psi of unregulated Nitrogen when you pull the trigger.

From the regulator you needs some flexible hose. Now your fill whip, unless the standards have changed, should fit any nitrogen tank valve; from the big boy H tank all the way down to a blackberry sized tank you could carry on your belt. I like to use about 2 or 3 feet of really high quality hose that should last a while, big fat diameter, with a regular air tool female quick connect on it. Now you are ready. With the big tank chained up in a corner of the garage just connect on a regular old air tool extension hose, put your fill chuck on the extension and wander around the car. Personally I wouldn't run an impact wrench with six nine helium, that is laboratory grade stuff and costs like it, but it is an option. A nitrogen fill whip with a couple hoses and a fill chuck should be doable for under $200.

Your only remaining problem is going to be getting water back out of your tire if you get a flat and a refill at Texxon. Carrying a small tank to keep your tires topped should be no problem. Maybe drive on the spare back to the shop that did your original nitrogen assembly?

[swmn]

Some pyrometry data. Yesterday I drove from Blythe, CA to Deming, NM. Ambient temps were 35dF AM, ~50dF PM. Starting cold pressure on air filled tires was 35psi x4.

At the rest area, mp 321 I-10 in Arizona my tire's temps (surface reading IR pyrometer) all ranged from 75dF (outer band, rear tires) to 90 dF (inner band front tires.

Cruise was set at 75mph all day. CAT certified scale says the car weighs 4480 pounds with 255/255 fuel (100.33% of MGVW on door sticker)

Will possibly upload videos of pyrometer readings to you-tube when I get home. Holed up in Los Cruces, NM waiting for TX to thaw for now.

[swmn]

Neglected to include hot tire pressures in #113 above, not much else to do in Los Cruces. Max hot pressures recorded at 41psi x4. Use any tire volume you like, I could not visibly see a difference in tire size/volume.

Conditions cold 35psi, 6.0liters, 32dF temp.

Hot conditions 41psi, 6.0 liters, "82" dF temp. The actual data is in .wmv files inside my digital camera. I pulled 82dF out of thin air knowing only the inner bands of the fronts reached 90dF and knowing the outer bands of the rears were at 75.

Converting to absolute scales:

Cold = 3.38ATA, 6.0l, 273K. Hot = 3.79 ATA 6.0l, solve for T.

P*V/T = p*V/T

306K hot = 33 degrees C = 91dF. Not.

Punch in 82dF ( 301Kelvin) and solve for T. That doesn't work either, but I am within 2% or so.

If I don't have anything better to do Wednesday (very possible) I will bring my digital camera in to the internet cafe and find a USB port.

I am also going to try to corelate P,V and T for each of my four tires separately on the rest of the trip east. That will be a bit of a trick since my camera stores images to the ram sticks in a non linear fashion, but I'll figure it out.

[IDNTWN2]

Intersting stuff gentlemen. As a chemist and engineer, seeing PV=nRT on a car board made my heart sing!

Bottom line really is that the N2 systems generally produce really dry gas. Therein lies the only real advantage. Dry air can also be obtained. The PP due to water vapor is the real issue in tires. The rest of the discussion, IMHO is largely academic.

If you ever find a need to top up your tires at a service station etc, depress the nipple of the chuck and see if any vapor comes out. If it does, go somewhere else.

Happy Motoring

[cptok]

Intersting stuff gentlemen. As a chemist and engineer, seeing PV=nRT on a car board made my heart sing!

Bottom line really is that the N2 systems generally produce really dry gas. Therein lies the only real advantage. Dry air can also be obtained. The PP due to water vapor is the real issue in tires. The rest of the discussion, IMHO is largely academic.

If you ever find a need to top up your tires at a service station etc, depress the nipple of the chuck and see if any vapor comes out. If it does, go somewhere else.

Happy Motoring

Great post. You must be a very good engineer indeed if the measure of "good" is the ability to take seemingly complex problems and boil them down to the relevant issue(s) and present in straightforward terms.

Interesting (and occasionally wildly entertaining) thread to be sure.... but you are quite correct - "The PP due to water vapor is the real issue in tires" hits the only relevant nail right on the head. Well done.