Don't know. I think the atmosphere is something like 80% nitrogen anyway. Don't know what if anything would be gained by not having any other gases in it. Did you read anything about it?

There is a benefit in filling tires with dry nitrogen. Oxygen is one of the major active ingredients in the environment that reacts with rubber. The speed of chemical action is driven by temperature and concentration. Increase of pressure such as inside a tire increases concentration, and thereby, increases chemical reaction. It seems that eliminating oxygen inside the tire has a benefit.

Since typical nitrogen sources come in pressure bottles and are relatively devoid of moisture, filling a tire from this source eliminates moisture inside the tire. This is another benefit.

Nitrogen is used in almost all race cars. Nitorgen has
larger molecules than normal atmospher, hence it will not leak in a porous aluminium rim where normal air will.
Nitrogen is not subject to temp. changes. It will not lose
5-6 lbs. from summer to winter like air does, and when that happends you can kiss your tires good by a lot sooner because not many people keep a good eye on tire pressure.

"Nitrogen is not subject to temp. changes. It will not lose
5-6 lbs. from summer to winter like air does,. . . ."

A reply to the above statement.

Nitrogen follows the same gas laws as does most other gases in the atmosphere with the exception of those that condense within the temperature range of application, notable for one, water vapor. The formula, (p)(v) = (m)(R)(T) applies to nitrogen and oxygen over a wide range of temperatures, where, P=pressure, v=volume, m=mass, R=a constant, and T=temperature in absolute units (referred to absolute zero).

With some algebraic manupulation, one may arrive at:

(p1/p2)(v1/v2) = T1/T2 where 1 & 2 refers to two different states 1 and 2. Since v1/v2 is nearly one, this leaves us with a prediction formula of (p1/p2)=(T1/T2) where Temperature is expressed in absolute units. To convert deg F to deg R, add 460.

For example, consider a tire filled at 100 def F (560 deg R), then cooled to 32 deg F (492 deg R). The pressure ratio is P1/P2 = 560/492 or about 1.138. The pressure at freezing would be 88% of the pressure at 100 def F. [1/1.138 is about 0.88] If the tire had been inflated to 30 psi at 100 F, it would drop to 26.4 psi at freezing.

Nice calculations. Looks impressive. I'm sure the average
auto owner will read the first line and say, NEXT.
No offence but the usual car owner will not digest this.
Looks good on a resume though.

Makes sense to me, on an absolute scale; not on an economic scale - except for the race vehicle.
Nitrogen gas is NOT cheap.
A man selling his Saab 9-5 on eBay was the user of this gas- and this is the first time I have heard of anyone using nitrogen in their tires.

Nitrogen is an option up here since 04 on the new cars.
Our winters go down to - 48F. and up to 110F. in summer.
We use nitrogen in all new refrigeration installs for
leak testing because the pressure does not change with temp. Put 100 lbs. of air in the line and at the end of the day it will be down to 95 or 90. Now is that a leak
or the air contracting from cooling ? Nitrogen is cheap
up here. 72 c.f. at 3000 lbs. is $27.00 canadian. Nitrogen
is also used in the tires of our police cars, Fire trucks and ambulances. I've used it in my tires for years as an experiment. Works great. ( i get the gas for free, company pays ). Haven't had a low tire in the winter for 3 years.

Well, a man learns something every day..
I never knew these things about the use of nitrogen in tires.
Seems as if the Nitrogen gas fill is but 1 to 2 $$, not bad....

Nitrogen sounds like a great idea , now we just have to get the gas station to dispense it. Think of all the energy saved by their compressors not running to refill the constantly leaking tires

Just another thing. Our Costco stores have nitrogen fill
stations for tires. I have no idea of the cost if any because i have not had a low tire for some time. It looks like a regular gas station air fill station though. I'll
check it out one day and get back to you.

Read some of Goodyear's info. Goodyear tire guys fill race track tires with regular dry air. Some racers will, some don't, replace it with nitrogen.

Goodyear Trucker article... They say its not worth the effort or expense in over the road trucks unless there is some other combustible preventive reasons.

Didn't really dig for auto info, lots of search items showed up, more than I care to look through.

1.5 lbs per month average loss for air naturally through the permeable tire rubber, bead seal, and valve stems in auto's.

If you buy tires at Costco, they fill them with nitrogen and will refill for free as needed. I bought some but have not taken back when need air, since it's kind of a hassle to go in to shop etc. They said you can top off with air, though.

Being that nitrogen generator/refill stations are now reasonably priced, would think all tire installation and repair shops would use nitrogen to lessen the probability of come-backs for slow leak repairs.

Maybe we can drive through the local beer distributor or paint ball store and have tires filled, and have fun doing it !

I've yet to find any reasonable proof or explanation as to how nitrogen in automotive tires has any advantages over air. But I do believe in commerce, and supporting your local economy, so go ahead and buy it.

"Nitrogen is not subject to temp. changes. It will not lose
5-6 lbs. from summer to winter like air does"
"the pressure does not change with temp."

That is utter BS! Nitrogen is a GAS. It has to follow the same laws of physics as any other gas (Boyle's Law). That means that in a closed container, the pressure WILL change with changes in temperature. Anyone who can prove otherwiae is in line for a Nobel Prize.

As for any advantage in extending tire life, most tires wear out from the outside - the tread is gone long before any reactions between the oxygen inside the tire and the rubber make a difference.

Having N2 in tires is not good idea nor is it a bad idea. After reading all the posts on this topic I might as well throw my 2 cents in. I sold industrial/medical/welding/rare & sepcialty gases for over 30 years.That doesn't qulify me as the ultimate expert, but I did get involved in some whacky projects along the way and learned 1 or 2 things.
Gases will expand and contract like any other element when subjected to hot or cold. A simple experiment is heating air and sending it in to a bag ( baloon ). The bag will rise. It will rise much quicker if the ambient air temperture is cold rather than hot. Helium filled ballons will rise to the ceiling in a warm room, but if you put them out in the cold, then they will sink to the floor.
With respect to using N2 in auto tires, there is no real advantage unless if you want to go racing. The tires need to built up a certain amount of heat while racing, and with N2, they will, but they will run a lot cooler than with air. A cold tire is less desirable in a race car due to less grip and traction on the road surface. That is why dragsters have burnouts, Nascar drivers when under yellow caution will weave their cars back and forth to keep heat in the tires. N2 will heat up, compressed air will heat up quicker and retain the heat somewhat longer. A hot tire holds the corners better than a cold one. Enough said or perhaps too much.

Lazygardens. you might want to do some research before your spout off. Nitrogen will go to 0 pressure if liquid
because we pour it form the container to our thermal imaging cameras when checking electrical hot spots. no human lives in that temp. We are mandated by law to use nitrogen for checking leaks in pressurized pipe because it
DOESN'T LOOSE OR GAIN PRESSURE AT NORMAL TEMPS. you know,
the temperatures humans live in. I'll prove it. I use nitrogen all the time. If my tank says 1000 lbs it will be
1000 lbs at -30F. or + 80F. Explain that. My acetyline tank
will say 3/4 at that temp and Full when warmed up. normal
Same as my air tank when i finish a dive. 1000 lbs. in the
water 1200 lbs in the sun. Again, normal Nitrogen doesn't
do that. Nitrogen is used in tires to help stop premature
wear from over and under inflation from temperature changes. You might want to tell Ford, G.M., and chrysler
they are doing it wrong. While your at it stop off at CostCo, too. Nitrogen is dry and is also used to inhibit
moisture. Just one man's opinion.
P.s. ford ,G.M. and chrysler have been doing something wrong but they got on the ball with tires, actually they were told to by the tire companes.

Hmmm, this is going to take some work. There are some pretty big holes in the argument to use nitrogen, holes that never should have been allowed to stay open prior to me calling them to attention here.

From a techs perspective, and unless someone can show me verifiable evidence I'm going to stick with the facts that I can directly observe myself.

Nitrogen leaks slower than "air" ?? This claim trys to tell us that using regular air will result in having to fill your tires more often. To me it appeals to the average consumers tendency to be lazy and not bother checking the tires as often as they should. The facts as I see them are, "Air" is 79% nitrogen, 20% Oxygen, and 1% other. In this thread someone used a spec of a tire loses 1.5lbs per month. Going by the claims made to support the use of nitrogen, if you had a tire that started with 30PSI, and you lose 1.5lbs per month in a years time each tire would be down to approximately 50% of it's original inflation. That simply isn't true in itself, but lets have some fun and say it is. Now since "air" supposedly leaks faster than nitrogen, and air IS 79% nitrogen, then it's only fair to reason, that much more oxygen percentage wise and other gases leaked out than the nitrogen in the air. By definition, you should now have almost pure nitrogen in the tire! How much do any of the supporters of nitrogen want to bet that if you take a one year old tire, that has leaked down 50%, and never been filled has a very consistent ratio of nitrogen to oxygen still inside it as compared to regular air?

Another claimed reason to use it is there will be less corrosion of the wheel, and the tire caseing. Well the only point that we see that has corrosion issues is the contact area between the wheel and the tire. This area gets exposed to both abrasion from the tire moving against the wheel, as well as road salt and dirt from the outside! The center portion of the wheel, which is exposed to the pressurized air is usually pristine for decades. Care to explain that in the face of the claims? As far as the oxygen beng forced into the tire, and causing corrosion, and breakdown I cannot prove that one way or the other. But I do know that there is a barrier layer on the surface of the inside of the tire to "seal" it.

Installing winter tires for a period of time each year also introduces another variable into this equation. If the tires are designed to be so soft, such as a winter tire that they have a lifespan of one, and usually not more than two seasons, whats the benefit if there really is one? Especially when they are being installed and uninstalled in just a matter of months?

Now are there circumstances where filling tires with dry nitrogen has real advantages? Sure, I can see that there is more than just a chance that there is. But I cannot see how any of the ones presented equates to passenger cars. Passenger cars do not fly at 35000 ft. They are not race cars trying to maintain running pressures under extreme driving stresses.

In fact, we have this with race cars. In real racing they inflate the tires so that the pressure change that occurs inside the tire from it heating is what they are targeting. They test, and test and are looking for ways to get a consistent rise in the pressure so that it's predictable to 1/10PSI. Tell me what that has to do with a passenger car, anyone?

Nobody, and I mean nobody worries about the tire pressure beyond it being set within a reasonable range cold on a passenger car. By and large the distance of trip, road speed, and ambient temperatures keep passenger car tires easily within the designed pressure ranges desireable for the average driver no matter what the tire was filled with. (air or pure nitrogen) Assuming that pure nitrogen does influence tire pressure rise, and given the fact that the tire pressure specs on the car's information sticker were established using "air" there should be a different spec to offset the lower pressure rise with the nitrogen. Why don't you see this reported, be it 1/4 or 1/2 PSI? Remember the spec on the car is "cold" and there is an expected rise in tire pressure because of the increased temperature from driving. If the nitrogen does not result in the same rise in pressure, it should start off higher!

OK thats enough for the moment. I firmly feel that this is an interesting debate, but the real focus of where it should be is lost. Try this.

If I want to sell more tires, and try and take the market away from my competitors, I need to out market them in some fashion. Great service has value, that price difference cannot always beat. The small independent shop will win the battle of great service over any big marketer, even they know that. But it may be difficult for the small independent to try and keep pace if the big marketer wins the propaganda battle which IMO is what the debate of pure nitrogen in passenger car tires is. Simply put, I can't take $5000.00 and buy a nitrogen purifier. Being forced to have a cylinder of nitrogen on site also increases my cost of doing business in a way that I cannot just absorb and I have to pass that cost on to my customers in a much more visible fashion than the big marketer. So at this point someone has to convince me that it's justifiable for me to add that expense to my customers that purchase tires and other services from me in order for me to spend the money. Anyone??? Remember, form your portion of the debate to how my selling nitrogen fills will make you, and your neighbor willing to spend more money with me.

"I'll prove it. I use nitrogen all the time. If my tank says 1000 lbs it will be 1000 lbs at -30F. or + 80F. Explain that."

You have a faulty pressure gauge on your tank.

You can't defy the laws of physics.

Pressure/Temperature is a constant for the same volume.

If the pressure is 1000 psi at -30F, the pressure at 80F would be approx. 1300 psi and that's for ANY ideal gas.

Going back to the tire, if you inflate your tire to 30 psi on a -30F day, and then park it in a 80F garage, the pressure will increase to 39 psi (assuming no leakage) whether it be helium, hydrogen, nitrogen, oxygen or any other gas.

All of the above assumes a gaseous state for the applicable temps and pressures as well.

kalining -
Just because I hang out on the decorating boards doesn't mean I'm not a scientist. And nitrogen doesn't get to violate the laws of physics. It's just another gas in the periodic table.
The Gay-Lussac Law says "the pressure of a fixed amount of gas at fixed volume is directly proportional to its temperature in kelvins." This law works because "temperature is a measure of the average kinetic energy of a substance; as the kinetic energy (temperature) of a gas increases, its particles collide with the container walls more rapidly, thereby exerting increased pressure."

I work in an industry that runs on gases - some toxic, some explosive, some neither, and some of it is LN2 (liquid nitrogen) and N2. Let's take your arguments one at a time:

"Nitrogen will go to 0 pressure if liquid because we pour it form the container to our thermal imaging cameras when checking electrical hot spots. no human lives in that temp."

Your gauges must not be very sensitive ... the gauges in a semiconductor facility can measure the temperature in the LN2 tanks - they monitor that pressure VERY CAREFULLY!

"We are mandated by law to use nitrogen for checking leaks in pressurized pipe because it DOESN'T LOOSE OR GAIN PRESSURE AT NORMAL TEMPS."

You use it because IT IS AN INERT GAS THAT DOESN'T SUPPORT COMBUSTION, and it minimizes the risk of explosion if you are pressure-testing lines that will be used for LNG or other flammable things. For the same reason, if there is a problem in the wafer fab machines, valves pop open and we vent N2 at high volume: because we can safely do so and dilute the stuff that goes boom or the stuff that kills people.

"you know, the temperatures humans live in."

Yes, and I work around machines and gas supplies with operating temperatures from way below those temperatures to temperatures and conditions way above where molecules can stay together. And all along the temperature gradient, gases all obey the laws of physics.

"I'll prove it. I use nitrogen all the time. If my tank says 1000 lbs it will be 1000 lbs at -30F. or + 80F. Explain that."

You have a broken regulator? The valve is shut off? Your tank of nitrogen doesn't get to violate the laws of physics!

"My acetyline tank will say 3/4 at that temp and Full when warmed up. Same as my air tank when i finish a dive. 1000 lbs. in the water 1200 lbs in the sun. Again, normal Nitrogen doesn't do that."

You may never have noticed N2 tanks doing that, but I have. They act just like other gas tanks when they warm up.

"Nitrogen is used in tires to help stop premature wear from over and under inflation from temperature changes. You might want to tell Ford, G.M., and chrysler they are doing it wrong. While your at it stop off at CostCo, too. "

Hmmmmmmmm ... $2/fill up versus FREE per fillup. I think there is a profit motive here.

Nitrogen is dry and is also used to inhibit moisture." No, it is not "dry", although it can have the water vapor removed. It doesn't "inhibit moisture" ... because it is a non-reactive gas, it inhibits corrosion and other oxidative reactions.

Here is a link that might be useful: Gay-Lussac's law

Nice try Lazygardens. We use " air " to test gas lines .
We use nitrogen to test refrigeration pipe because the pressure doesn't change from the time you fill it to the time you retest it. Like i said before, explain that.You seem to be reinventing the wheel. Who gives a SH&t about the gas properties in your lab. That information and findings will never be used in the real work a day world. People don't care about the effect of hydro and if it can blow up your T.V. People want to watch T.V. People don't care if the stereo is too loud and could wreck your ears. They want to hear their music. I have updates, I have them in my hand,from tire companies. " If there is a non detectable leak from an aluminium rim or tire, fill the said unit with nitrogen gas " . My nitrogen bottle's regulator is fine. Up in this climate we have to have them certified every 6 months by the govmt. Actually we have to put the gauge directly on the bottle without the regulator. Bottom line. No one does the scientific gas thing. We don't care as long as it does as advertized. bottom line. Nitorgen doesn't loose or gain pressure at temperature changes in NORMAL HUMAN applications. End of
debate. GONE. John G. You supprize me. you should know better and have the same update as me. Anyway the original
post was " Is nitrogen in tires a good idea ? " YES. end of discussion.

I suprise you, and I should know better? Know better than to be skeptical when all of the facts just don't sit exactly square? Sorry, I'm no lemming, when something does not add up for me I stop and ask questions to find out why.

The simplest of which goes back to the tire inflation spec cold. "IF" nitrogen only does not increase in pressure the same air does as the tire temperature rises, then why does a nitrogen inflation not require a higher starting pressure? Thats a very simple question, that since it has been previously unanswered casts the shadow of doubt on the debate for me.

For my take, it sounds impressive. But it has not been proven to be practical for the normal driver as far as I can see.

Search through goodyears site. Lots of stuff there. One thing or point of concern is the air you put in the tires needs to have the moisture removed as that boils/steams, expands & isn't quick to release those btu's.

.The life of a race tire can be as little as 30 seconds on a Top Fuel dragster.

Aviation.... Tire temperatures can rise in excess of 200o F (93o C) above ambient during operation. A temperature change of 5o F (3o C) produces approximately 1 percent pressure change.

Aviation... USE DRY NITROGEN GAS (WHEN REQUIRED)
Nitrogen will not sustain combustion and will reduce degradation of the liner material, casing plies and wheel due to oxidation.

Since you won't believe "science" then let's try a simpler aproach.

Call the people that fill or supply your nitrogen tanks and ask them if nitrogen pressure will increase with temperature. They should know since it is their business. If they say they don't know. Ask them if they can fill your tanks to max pressure on a cold day or if they have to compensate for temperature variation.

Also ask them about storage temps and why they are important.

Let us know what they say because I'm always open to learning new things if I'm wrong.

Thanks MIKIE. JOHN. I can't understand your point. Why would you put in a higher pressure in a nitrogen filled tire than air ? nitrogen doesn't change pressures at NORMAL
temps. Put 30 lbs. of nitrogen in a tire and it will stay
at 30 lbs. I've done it with 12 tires on 3 cars. We weld up new refrigeration piping and fill with nitrogen to 100
pounds in -20F. When the sun comes out, and it gets hot on the roof then, the pressure is still 100 lbs. I've been on
a roof at night at 50F. and done a pressure test with 100
lbs. Back on the same roof in the day at 130F. ambient,still at 100 lbs. Do that with air and i would lose a coil due to swelling or explosion. And oh yah, air is full of moisture. Again, why would you compensate a
nitrogen fill with more pressure than a normal air fill ?
30 lbs is 30 lbs whether it is nitrogen,air,or beer. Maybe
i'm missing something here ? Anyway, nice debate. I'm done.
I've used nitrogen for 37 years. I know what it does for my
trade. It works as advertized. I don't have a lab to find out that glass might be liquid, sand, clear, or hard. I just look through it. It works. Who cares. MACHIEM. Yes.
The guys that fills our bottles fill to the max on the bottles pressure stamp. If it says 3000 lbs. they put in
3000 lbs. Doesn't make any difference whether it is -30F.
or +90F. Figure that out. The only thing that is relavent
is when i get my dive tank filled. If it is not cooled in a
water tank my 3000 lb. fill will be about 2500 lbs. when
cooled to ambient temp. They still charge for 3000 lbs.
Have a nice weekend to all. Again, nice debate. It's been
fun.

Why would you have to compensate tire pressure? Simple.

The tire spec on the door of your car is for the tires when they are "cold". The actual operating pressure of the tires is 1 to 2 PSI higher, and it gets there by the tire heating up during use. Racing where the tires see extreme heating because of stress can raise the pressure 3 to 5 PSI.

Taking the argument at face value, and assuming that the dry nitrogen does not increase pressure like "air" does, and you end up with a tire that is slightly under pressure during warm operation.

So you see it's a simple detail that is not being addressed by the claims. Just like we used to do in Geometry, you take a theory, and then you write a proof. If all of the challenges are true then the theory stands, if one of them are false then the theory is flawed and fails. Without compensation for the lack of pressure increase to the full operating pressure at temperature, the nitrogen claims falter. To me that means someone without full understanding of the entire situation is pushing it for the wrong reasons.

John. you are not knowingly proving my point. A nitrogen
filled tire at a given pressure, you say 30lbs., will stay
at 30 cold and will be 30 if you heat the tire up to where
it almost catches fire, well warm anyway, that is why they use nitrogen. This bedate is now dead. Thanks for your input. There has been some good information thrown around. Thanks to all, again very good information. have a good weekend and i'm sure we will have other "discussions". o:) Got to get to work. Talk to you sometime soon.

No Kalining, I'm not making YOUR point, you are making mine.

The "operating" tire pressure on a particular car is 31.5PSI. The cold tire spec is 30PSI so the expected rise in pressure when the car is running is 1.5PSI to the planned "operating" pressure.

"IF" the dry nitrogen does not change pressure as you claim, then the cold tire spec should be adjusted to the operating expected pressure of 31.5PSI.

Quick note.

Early in december I put new tires on my Explorer. Yesterday I went through my normal routine service I do on it every three thousand miles. This quote "1.5 lbs per month average loss for air naturally through the permeable tire rubber, bead seal, and valve stems in auto's." does not stand up to what I found on all four tires. The pressures where exactly where I had set them 30PSI front, 35PSI rear. BTW I use a precision gage that is accurate to the 1/10 PSI......

Yea, but was the ambient air temp, barometric pressure & tire body temp the same. ;)

New Nitrogen rated tires ?

John, you are doing a h e l l of a lot better than I.
1.5 PSI per month, sometimes 1.5 per week is what I am losing !
Even though some men are having no air loss and others lose as much as i do, an average loss of 1.5 per month is about right..The tires are about 3 years old, maybe 5...I inflate the units using a mix of 79.8 room temperature nitrogen; 18.2 % oxygen; 1.9% water vapor and 0.05% trace gases..The rest comprises of pure unadulterated pollution :-)......

You know of all of the claims made trying to support nitrogen filling, the pressure loss one is the easiest to debunk. If your losing 1.5PSI a month, you have an active leak that could be repaired if you try. Most likely the wheel is corroded where the bead seals, and it should be cleaned, and then painted with a special sealer. This also occurs where the valve stem sticks through the wheel, and it can be sealed the same as the bead can.

BTW as far as temperatures, it's 65 in the shop in December when I filled the tires, and 65 the other day when I checked them...

I just received a JC Whitney catalog ... I need a magnifying glass to read descriptions now so I cant get all the hype, hard to get excited about all the gas saving devices and truck bolt on accessories ;)

Anyhow, they show a small pocket sized CO2 inflator that uses the little pellet gun co2 cartridges. Reason it caught my eye was I had just read saftey data for those co2 cartridges. 180 degrees some ungodly pressures in those can explode them through a block wall. And JC Whitney is stocking glove boxes with them.

"The pressure inside a CO2 cylinder is 835 psig. At 140F, it can be as high as 5,000 psig, which is about 2/3 of the strength of the cartridge itself. At temperatures about 89°F, CO2 cannot exist as a liquid, which means that it has boiled off into a vapor.
A cylinder which has been heated over 180°F will rupture violently with a loud and dangerous burst of energy.
"

They should fill those little cylinders with nitrogen. Apparently you don't have to worry about pressure increases due to temperature...

John ...: .... If your losing 1.5PSI a month, you have an active leak that could be repaired if you try. Most likely the wheel is corroded where the bead seals, and it should be cleaned, and then painted with a special sealer. This also occurs where the valve stem sticks through the wheel, and it can be sealed the same as the bead can.
Some good advice from John

The tires have a controlled leak; it is not economically feasible to do any repair at this time, but I did use some liquid tire repair in one of the leakers which, thus far has worked, but I do not expect miracles, no do I readily accept "mechanics in a can".
But when new tires are fitted, I will supervise and ensure that a sealant is used and that the proper new valves are installed.
I used to install tires at Sears(bias ply!), we only used a soap and probably did not inspect the tires and wheels as well as they should have been...

Whoo Boy!
lots of true and false arguments here!
First, cars. The argument for Dry Nitrogen is just that, "Dry" it is a previously compressed and seperated gas, it has, for all practical purposes, NO moisture in it. So, if you use it EXCLUSIVELY for the LIFETIME of your Wheel, the wheel will be better protected from the effects of moisture and Oxygen. that said, if you use air from a large well maintained air tank, the effects are negligable, the key words there being "well maintained" compressing air seperates out much of the moisture in the air, but not all of it. and if you don't drain and filter out the tank and lines the moisture will find it's way into a tire.
kalining,
as to the reason for using Dry Nitrogen in testing for leaks in refrigerant lines. UM, it is the law. Intentional venting of any refrigerant is illegal... don't you have a CFC certification? the only way pressure will change appreciably in a 100 psi pressure test is if you filled the lines with LIQUID refrigerant to the top, then when the ambient built up to 130degrees, there would be significant pressure increase from the state change...
the reason your gauge stays at 100 all day, is because INSIDE the house the temp is still close to what it was when you filled it.
also at 100psi, the dif in the line would only be 1 or two psi, kinda hard to tell with the gauges we use in refrigerant lines.
refrigerant lines cannot use air for testing, because it would introduce too much moisture into the copper lines and the refrigerant would react with the h2o and form an acid that would destroy the system, also h2o not being a refrigerant will eventually find it's way into the compressor, and it being a liquid will destroy things there too.
that is why we use vaccume pumps to remove MOISTURE from the lines, because removing all gases is near impossible.
nitrogen is itself difficult to get out of the lines, but at least the h2o is not a problem there.
John

Wow. This is amazing.
Mechanical Engineer here.

We frequently perform long term leak tests on long piping runs for the utility company. Most of these runs are above ground, exposed to the elements - full sun in the day, and of course, none at night.

The pipe is pressurized with dry, instrument grade N2, and monitored along with the temperature over several days. Guess what else we need to monitor? You got it....temperature. The pressure moves cyclicly along with the daily temperature change. We monitor the pipe temperature, and we must apply pv=mrt to correct back to a standard temperature, or else we would never know if the pipe was leaking.

I have all of the degrees, data, graphs, plots, equations, and proven theories you could shake a stick at, but I don't think anything is going to change kalining's mind.

Homeant

If I see your tire stems frozen over, you know Nitrogen is cryogenic - approximately minus 300 F, I will walk over and freeze off a wart or 2. The waiting rooms are too long for this simple procedure and co-pays infuriate me. If you see anyone kneeling down by your tires, don't shoot, they are merely being expedient.

Also, you may want to check the temp rating of your tires. Using nitrogen gas may accelerate the degradation of the rubber and/or creat embrittlement. Some metals shatter when dropped after exposure to nitrogen gas.

You're thinking of liquid nitrogen, not gaseous nitrogen.

You can't fill a tire with liquid nitrogen. Well, I guess you could but you better run because it will rapidly explode from the expansion from liquid to gas.

I guess that makes sense since they put it in shocks and struts.

This topic is like saying,"If I put helium in my tires ,the car will be lighter and I will get better gas mileage and be a bit faster from the weght reduction".

you've done it! you found out how to increase mileage. this could solve most world problems. maybe even transcontinental travel without boat or plane. imagine, fill up the tires with helium, float all the way to wherever you are traveling. great. it could even be a way to prevent damaging accidents. I mean, really, if the car has helium in the tires, accidents can't happen, cars would just float away from damaging crashes.

Car manufactorers tried but quit putting helium in tires because they get too squeeky.

Thats a new sales pitch Vstech, Some will buy the nitrogen concept but with the price of fuel everyone will buy the helium filled tires.I split the prophets with you if I can use your sales pitch from above. LMAO

I bet the lawyers would love that slogan!

As an electrician I've used nitrogen to dry out wet incoming service wires ( 500 MCM )that were under water during a flood.Of course I put a meter on them before energizing.
I've also used nitrogen on fire alarm ionization detectors that were causing a problem.
Having said that,what say you about helium in tires?