Nitrogen in tyres

[ratusratus]

Has anyone done this? I would be interested to hear the pros and cons....cheers

[Akzle]

srsly?
Lmgtfy...

[Drew]

There is supposedly less pressure variation due to temperature. The gain being you aren't chewing up tyres while cold before they come up to temp.

Real world on a bike with road tyres ? Probably nothing.

[p.dath]

Has anyone done this? I would be interested to hear the pros and cons....cheers

Nitrogen fills were historical used for two purposes. The first was where there was a risk of fire, such as on fire engines and airplanes, where a tyre blowout could cause any existing fire to be suddenly forced fed with air, and become a much larger or explosive fire. The second use was in heavy vehicles (and by heavy, I mean vehicles exceeding 40 tonnes). It was used in heavy vehicles because the tyre carcass could only dissipate so much heat. Nitrogen dissipates heat “slightly” better than a simple air mix, and when the load is so great (especially as it approaches several hundred tonnes) that couple of extra percent can extend the life of the tyre by reducing overheating.

Some people in racing circles like to use nitrogen in race tyres. I’ve never seen anyone substantiate any benefit of the use of nitrogen in this scenario, and whenever I have spoken to someone in racing who does it, they do so because they feel it doesn’t make them any slower, and that “maybe” it might help. There may be some merit that under racing conditions (where a tyre is under considerable and constant stress) that it may promote greater stability in tyre pressure and improve predictability in a tyre performance.

Some people promote the use of nitrogen to reduce the corrosion of rims. I've spoken to my local tyre guy and asked him when the last time he saw a corroded rim after taking the tyre off. He couldn't remember. Alloys have almost made this an issue of the past.

Nitrogen proponents (e,g. Firestone) the improvements in fuel economy. As far as sticking something into your tyre – the most important factor is tyre pressure. If you have the correct tyre pressure it will make no difference whether you run a 78% nitrogen mix (which is standard air, as we breathe, and as what comes out of a standard air compressor) or a pure nitrogen mix.

Nitrogen proponents often make the statement that tyres leak “air”, and wont leak “nitrogen” because nitrogen molecules are larger, or that the nitrogen leaks slower, and as a result the tyre won’t deflate as rapidly. Nitrogen is normally made using either a chemical reaction (such as the nitrogen you get from places like BOC), or by forcing atmospheric air through a “special” rubber membrane. A normal light commercial tyre is nothing like this purpose built membrane.

But let’s pretend that a normal tyre did actually leak oxygen at such a rate that it was a problem. So that means you inflate your tyre with atmospheric air, and it now contains 78% pure nitrogen. If the nitrogen leakage argument was correct, only 22% of the remaining “air” would leak out. The next time you inflated your tyre the nitrogen content would increase to 95% pure nitrogen. By the next time you inflate the tyre the nitrogen content is basically pure nitrogen. The net result is you end up with your nitrogen fill automatically, without having to do anything special. I have never had a nitrogen proponent respond to this blinding logic.

One area of nitrogen fills that does concern me is the potential reductions in safety. Although tyres may look a simple round black piece of rubber they have incredibly complicated physics behind them, and tyre manufacturers go to a lot of trouble to make their tyres work in a particular manner, and to model how they will function under high stress loads, such as emergency breaking and high power loads.
Changing the density of the fill in the tyre along with the heat distribution properties of the tyres fill are likely to change the ultimate shape of the contact patch of the tyre when placed under heavy loads (such as emergency breaking) [because the greater mass of the nitrogen mix requires more breaking effort causing the tyre to distort differently than it was designed to, combined with the issue of the tyre running cooler – and ultimately at a lower running temperature than it was design too]. Alas I have seen no research on the issue of the safety of nitrogen when used for the wrong purposes – but it’s a pretty big call to assume you know more about the dynamic of a tyre than the company that manufactured it.

[p.dath]

Has anyone done this? I would be interested to hear the pros and cons....cheers

Here is a quick question for you. I know the Police motorcycle highway patrol in Auckland have changed over to using nitrogen fills now - in the interests of fuel economy (which I already call bullshit on).

However none of the officers I have spoken to have been told to change their tyres pressures to compensate for the reduced heat, and they using heavy BMW motorcycles and I do expect them to be placing their tyres under considerable load. The net effect is a potential reduction in traction.

Has the crowd in your area been changed over to Nitrogen, and if so have they been advised to very their tyre pressures to maintain the prior levels of traction they have been accustomed to? I would hate for anyone to learn this lesson the hard way.

[Kickaha]

Here is a quick question for you. I know the Police motorcycle highway patrol in Auckland have changed over to using nitrogen fills now - in the interests of fuel economy (which I already call bullshit on).
The police did their own independent study on using nitrogen over a couple of years or so and have changed their who fleet over, pity they didn't have you to advise them to let them know they're wasting their time

However none of the officers I have spoken to have been told to change their tyres pressures to compensate for the reduced heat, and they using heavy BMW motorcycles and I do expect them to be placing their tyres under considerable load. The net effect is a potential reduction in traction.
Did you realise that potential isn't the same as actual?

Has the crowd in your area been changed over to Nitrogen, and if so have they been advised to very their tyre pressures to maintain the prior levels of traction they have been accustomed to?
I'm not sure why they'd need to, based on real world experince it makes no discernable difference to traction level

[p.dath]

The police did their own independent study on using nitrogen over a couple of years or so and have changed their who fleet over, pity they didn't have you to advise them to let them know they're wasting their time

As I understand it, the use of nitrogen was the result of a tender. Who conducted the "independent" study? The only one I know of is the one being cited by Firestone ("The Get Nitrogen Institute" summary of studies) - which has been well rebuffed. Of the four studies they cite, 2 of them found no savings in fuels for light vehicles ...

I'll say it again, the primary factor in fuel savings is correct tyre inflation, not weather you are using 78% or 98% nitrogen. And once again, if the claim of oxygen leaking out through the rubber was correct you would still end up with pure nitrogen in the tyre without doing anything special.

Now think about the source of the report, the "Get Nitrogen Institute". Does this sound like an "independent" organisation? I don't know who they get there funding from, but it is clear from their marketing they are promoting the use of nitrogen, which means someone is benefiting from all their hard PR and marketing efforts.
If you go an use their web site they offer a "locator" service for tyre dealers selling nitrogen.

I'll put money on it that this "Institute" is funded by a tyre manufacturer, and using it's reports to promote the use of their own dealers, and pretending it is independent.


Did you realise that potential isn't the same as actual?

Well, I did choose the word, so yes, I do realise that. The reason why I said "potential" is because I have never seen or heard of a study that looks at the safety implications of using nitrogen in small vehicles, and it seems reasonable that if you are changing the operating dynamics of a tyre - that it could potentially operate differently.


I'm not sure why they'd need to, based on real world experince it makes no discernable difference to traction level

How did you find this out? So you're saying changing the heating effect and density of fill in the tyre doesn't affect is traction level? You could well be right. I don't know. I do know that tyre temperature does have an effect on traction, so this claim simply sounds wrong. It simply doesn't pass the sanity test. Once again, I could be wrong.

[Kickaha]

Alas I have seen no research on the issue of the safety of nitrogen when used for the wrong purposes – but it’s a pretty big call to assume you know more about the dynamic of a tyre than the company that manufactured it.
You'd think then that if tyre companies are putting nitrogen in tyres then they'd know what they are doing considering it's their own product they're putting it in

As I understand it, the use of nitrogen was the result of a tender.
You understand wrong then, the police did their own tesing "independent" of any tyre company before making the decison to change their fleet over

I'll say it again, the primary factor in fuel savings is correct tyre inflation, not weather you are using 78% or 98% nitrogen. And once again, if the claim of oxygen leaking out through the rubber was correct you would still end up with pure nitrogen in the tyre without doing anything special.
Air filled tyres leak down faster than nitrogen filled, that comes from personal observation using it myself in my own motorcycles and passenger vehicles
Nitrogen will still leak but just at a much lower rate so I doubt you would ever end up with the percentages you claim

[James Deuce]

Vince Martin: 1, p.dath: 0

[Kickaha]

How did you find this out? So you're saying changing the heating effect and density of fill in the tyre doesn't affect is traction level? You could well be right. I don't know. I do know that tyre temperature does have an effect on traction, so this claim simply sounds wrong. It simply doesn't pass the sanity test. Once again, I could be wrong.

It was simple really, I filled my tyres with nitrogen and rode my bike

Are you an engineer or university educated?, you seem to like taking quite simple shit and making it way more complicated than it need to be

On yeah I wear a back protector when I ride too :msn-wink:

[EJK]

Got 5 minutes?

<iframe width="560" height="315" src="//www.youtube.com/embed/kmnZ4-EUbIk" frameborder="0" allowfullscreen></iframe>)

[Mike.Gayner]

This whole nitrogen business is beyond stupid. I can't believe people actually pay good money for some dickhead to fill there tyres with this stuff.

With reference to the points made in the Fifth Gear video above:

Nitrogen gas molecules (N2) are actually smaller than Oxygen gas molecules (O2)
If we were to believe that O2 slowly escapes from our tyres, why not just keep inflating them with air? Eventually all the oxygen will let itself out, no?
How can the "technicians" filling your tyres possibly purge all of the air out?
If water vapour really is the problem, why not use a basic moisture trap on the compressor? How can we be sure there's no water vapour in the N2?


Honestly I haven't seen a marketing scheme are brilliant as N2 since bottled water. Thankfully there's a seemingly endless supply of fucking idiots to keep the industry going.

[Kickaha]

Got 5 minutes?

The most interesting point they made was about moisture content as that's what causes the pressure rise, the filling station they used was a nitrogen compressor so I doubt it was dry unless they had extremely good water traps, if you could use dry air then the pressure rise wouldn't happen either

I'd be interested to see the same test using bottled dry nitrogen and seeing if the result was the same

[Kickaha]

why not use a basic moisture trap on the compressor?
Most compressors in any industry that relies on them do use water traps but it still doesn't make it totally moisture free

[Mike.Gayner]

The most interesting point they made was about moisture content as that's what causes the pressure rise, the filling station they used was a nitrogen compressor so I doubt it was dry unless they had extremely good water traps, if you could use dry air then the pressure rise wouldn't happen either

I'd be interested to see the same test using bottled dry nitrogen and seeing if the result was the same

So what you're saying is that N2 filling at your local tyre shop (why invariably use N2 compressors) will always be a waste of time, and to get any (ostensible) benefit you need bottled N2? If that's the case can we please stop pretending there's any benefit whatsoever to N2 filling?

[p.dath]

Got 5 minutes?

...


That video confirms what I have been saying - there is no point is using nitrogen.

They first mention the argument about oxygen molecules leaking more. As I said,%

[Kickaha]

So I'll stick to my original claim, using nitrogen in light vehicles is an almost pointless expense.
Can you please publish your own test data to back that up :yes:

What about using it in heavy vehicles?
http://www.worktruckonline.com/article/story/2007/09/what-you-should-know-about-nitrogen-filled-tires.aspx

[p.dath]

You'd think then that if tyre companies are putting nitrogen in tyres then they'd know what they are doing considering it's their own product they're putting it in

Or maybe, just maybe, they want to sell more tyres?


Air filled tyres leak down faster than nitrogen filled, that comes from personal observation using it myself in my own motorcycles and passenger vehicles
Nitrogen will still leak but just at a much lower rate so I doubt you would ever end up with the percentages you claim

With plain air, you start with 78% nitrogen in your tyre. Lets say you are correct, and the oxygen leaks out faster. Lets pretend al 22% leaks out, and you refill your tyre with standard air. You're tyre now contains 95.16% nitrogen. Lets pretend the remaining 4.84% oxygen now leaks out, and you re-fill your tyre with already air. The tyre now contains over 96% pure nitrogen.

So even if you accept the normal oxygen leaks out, then you have to acknowledge that eventually both a nitrogen filled tyre and an "air" filled tyre will end up leaking at the same rate - because they effectively both contain the same thing.
You are going to end up with a *very* high concentration of nitrogen in your tyres. There is no point paying to get the same thing, is there?

[p.dath]

It was simple really, I filled my tyres with nitrogen and rode my bike

If you believe oxygen leaks out through you're tyres, then you replaced the nitrogen in your tyres with nitrogen. Do you notice any difference?

[p.dath]

So what you're saying is that N2 filling at your local tyre shop (why invariably use N2 compressors) will always be a waste of time, and to get any (ostensible) benefit you need bottled N2? If that's the case can we please stop pretending there's any benefit whatsoever to N2 filling?

The other kicker is using osmosis to produce Nitrogen and a compressor (as opposed to using bottled Nitrogen like you get from BOC produced from chemical reaction) only produces Nitrogen around 95% pure. If you believe that Oxygen leaks out of your tyre, then the eventual Nitrogen content in the tyre will be *higher* than from the compressor - and you will be *lowering* the nitrogen content in your tyres.

[p.dath]

Can you please publish your own test data to back that up :yes:

Read my first post. It's mostly common sense.


What about using it in heavy vehicles?
http://www.worktruckonline.com/article/story/2007/09/what-you-should-know-about-nitrogen-filled-tires.aspx

I believe there *is* benefit in using Nitrogen in heavy vehicles, particularly those that are considerably over 40 tonne.

[Kickaha]

If you believe oxygen leaks out through you're tyres, then you replaced the nitrogen in your tyres with nitrogen. Do you notice any difference?

None whatsoever, but then I didn't expect there to be

However I no longer have to top my tyres up when ever I go for a ride after the bike sits for a month or two as the pressure stays where I set it, which it didn't do after numerous air fills which sort of fucks that theory up

[p.dath]

None whatsoever, but then I didn't expect there to be

However I no longer have to top my tyres up when ever I go for a ride after the bike sits for a month or two as the pressure stays where I set it, which it didn't do after numerous air fills which sort of fucks that theory up

Perhaps you might like to explain why you think a Nitrogen filled tyre retains it's pressure better after sitting for a month then?

[Mike.Gayner]

None whatsoever, but then I didn't expect there to be

However I no longer have to top my tyres up when ever I go for a ride after the bike sits for a month or two as the pressure stays where I set it, which it didn't do after numerous air fills which sort of fucks that theory up

How can you possibly reconcile that with reality though? If you have air-filled tyres, and you're convinced that the O2 is leaking, then surely you have to accept that "topping up" has left you with a higher N2 concentration? And over time that N2 concentration will get closer and closer to 100%, meaning that you should soon start noticing the apparent leak slowing to a stop.

Honestly the best thing about this whole nitrogen business is that it puts the stupid and the gullible into plain sight for the rest of us.

[Scouse]

There I really no point using N2 in car or motorcycle tyres unless you place the tyres on a vacuum pump for a couple of hours to remove all traces of O2 before you fill with N2.

[James Deuce]

Another Internet win! I have no empirical data but we'll call the guy with both exprience and third party practical and theoretical data an idiot and win the fight!

The Internet is awesome.

[pritch]

Part of my former job was looking after a small fleet of some twenty cars. Firestone made a pitch that I should change them to nitrogen but I wasn't convinced.

There may have been an advantage if the nitrogen maintained its pressure longer because the drivers were mainly female and the pressures would not be checked from one service to the next. I didn't however think that the advantage was such as to justify the additional expenditure.

Having said that, I'm currently running nitrogen in the back tyre of my push bike because I had a puncture and re-inflated the tube with a nitrogen bottle.

The tyre pressures of my motorised conveyances are adjusted cold at home with a bicycle track pump and pressure gauge.

Without some radical advantage nitrogen would just seem too much trouble.

[Mike.Gayner]

That's an important point pritch - most of us (I assume/hope) pump our own tyres at home, which means frequent checks and adjustments if necessary. Having to wait between visits to your local N2 supplier means less frequency of checks and adjustments, which has to be a bad thing. The idea of being too scared to fill my own tyres in case some evil O2 gets in there makes my eyes roll to the back of my head.

[Big Dave]

Use Helium. Tyres are lighter, but they sound funny.

[Kickaha]

Perhaps you might like to explain why you think a Nitrogen filled tyre retains it's pressure better after sitting for a month then?
I dont need to explain it, all I know is with the practical experience I had with it that was what happened, I dont really care why or how

And over time that N2 concentration will get closer and closer to 100%, meaning that you should soon start noticing the apparent leak slowing to a stop.
Doesn't happen, so somewhere that theory is flawed, but you've given me an idea for a test using the nitrogen measuring gadget thingy to see what does happen if I can lay my hands on one

Honestly the best thing about this whole nitrogen business is that it puts the stupid and the gullible into plain sight for the rest of us.
I didn't need a nitrogen thread to work any of that out

There I really no point using N2 in car or motorcycle tyres unless you place the tyres on a vacuum pump for a couple of hours to remove all traces of O2 before you fill with N2.
I think the filling stations fill and purge and fill again

The Internet is awesome.
It's why we loves it so much :love:

That's an important point pritch - most of us (I assume/hope) pump our own tyres at home, which means frequent checks and adjustments if necessary. :lol: what a fucking dreamer

Having to wait between visits to your local N2 supplier means less frequency of checks and adjustments,
You dont need to check and adjust as often so it makes fuck all difference

[Mike.Gayner]

Doesn't happen, so somewhere that theory is flawed, but you've given me an idea for a test using the nitrogen measuring gadget thingy to see what does happen if I can lay my hands on one

Once again, how do you reconcile that with reality?

Not that you have to when you're living in a fantasy world.

[Kickaha]

Once again, how do you reconcile that with reality?

Not that you have to when you're living in a fantasy world.

My practical real world experience is reality, whch is a bit different than you just making shit up on the internet

[SPman]

Vince Martin: 1, p.dath: 0

With a blunt axe?

[Mike.Gayner]

My practical real world experience is reality, whch is a bit different than you just making shit up on the internet

You need still need to reconcile the two points you're making though. You claim the oxygen leaks out of the tyres, but refuse to accept that this leads to a high concentration of N2. How can both of these things be true?

[Motu]

Use Helium. Tyres are lighter, but they sound funny.

I heard that the original Mach III had a helium filled front tyre, it caused a lot of handling problems and quite a few riders were killed...so later models reverted to just air.

I use the green caps for a colour contrast on my bike.

[SMOKEU]

I wouldn't use nitrogen in anything other than a fairly high end racing vehicle.

[AllanB]

Waste of money IMO. Just ride the fucking thing and enjoy it.

[caspernz]

Have used nitrogen in truck tyres for years. Less leak down and longer tyre life, and yup that's using the exact same tyres with air previously and then going to nitrogen at new tyre fit time. Normal service life top ups done with air. Practical experience suggests it works rather well. And note I was a sceptic prior to first hand experience.

Tried it in the car, difference not as marked...but the car feels different driving on nitrogen filled tyres. Using slightly lower pressures to make tyres wear square or flat, and less leak down is the main difference noted. Fuel economy is slightly better, but hard to pin down to exact numbers.

Never tried it on a bike as yet...doubt it offers any tangible advantage on normal road use. But no harm in trying I reckon, just gotta experiment a little with pressures.

[Ntoxcated]

I've got it - the O2 molecules must be holding the door open for the N2 molecules to escape. If the tyre is just N2, they can't get out! Because of this the tyre ends up with a higher O2 ratio thus allowing the N2 to get out quicker. So for best results, flatten your tyre completely before refilling to restore the ratio :niceone:

:bleh: :facepalm:

[Scouse]

I've got it - the O2 molecules must be holding the door open for the N2 molecules to escape. If the tyre is just N2, they can't get out! Because of this the tyre ends up with a higher O2 ratio thus allowing the N2 to get out quicker. So for best results, flatten your tyre completely before refilling to restore the ratio :niceone:

:bleh: :facepalm:Does your brain hurt when you try thinking?

[caseye]

We have run Nitrogen in the Super saloon for about 5 years now, run a separate tank in the truck and all fitting and topping up is done using it. For us the major difference is a complete lack of Tyre pressure expansion/increase, which on really big wide feet is very important it definitely works for us and luckily it is a fully sponsored product so no cost.
Our right rear Tyre lasts nearly twice as long now as it used to simply because having the Tyre entirely filled with nitrogen keeps em cooler and stops them burning off the vital tractiony stuff on the outside.

[The Reibz]

Has anyone here filled their tyres up with Acetylene or LPG? Heard that it extends the tire life by up to 5 million percent...

[bogan]

Has anyone here filled their tyres up with Acetylene or LPG? Heard that it extends the tire life by up to 5 million percent...

Fucking argon master race you pussy!

Supposedly lower leak rate than N2 as well...

[The Reibz]

Fucking argon master race you pussy!

Supposedly lower leak rate than N2 as well...

I have a big bottle or argon up in my shed, argon is a heavy gas though. It has better shielding properties than n2 though. Helium has the best penetration properties for welding but is hard to get, almost as hard as a bottle of wine for under $9.

Has anyone put that in their tyres? Weight savings over standard air would be simply phenomenal...

[bogan]

I have a big bottle or argon up in my shed, argon is a heavy gas though. It has better shielding properties than n2 though. Helium has the best penetration properties for welding but is hard to get, almost as hard as a bottle of wine for under $9.

Has anyone put that in their tyres? Weight savings over standard air would be simply phenomenal...

Helium is a well small molecule, that's fuck off real quick.

Hmmm, gives me an idea though; argon/helium blend. The spin would force the argon out to line the tyre, while the helium sits on the inside against the alloy where it ain't escape.

[Ocean1]

Helium is a well small molecule, that's fuck off real quick.

Hmmm, gives me an idea though; argon/helium blend. The spin would force the argon out to line the tyre, while the helium sits on the inside against the alloy where it ain't escape.

... Until you stopped. And the argon would all sink to the bottom. And when you took off again the wheel would be out of balance.

I know someone who slimes his bike tyres when fitted, it reduces the leak-down issue a fair bit apparently.

[schrodingers cat]

The point about the nitrogen staying in the tyres is correct
Also there is a benefit over the life of a road going tyre from reduced rubber oxidation internally.

'Correct' tyre pressures however is quite a can of worms.
Roughly 6 degrees C of temperature will lead to a pressure charge of 1 psi.
How should I set my pressures when yesterday the temp was a high of 11 deg and today will be 27?

Having done some real time logging of tyre temp/pressure, the rise in a road going application is tiny (hence a start pressure very close to ideal hot pressure recommended by manufacturers).
The greatest variation seems to come from ground temperature and sunlight.
The side facing the sun gets a rise comparative to the shaded side - obviously I'm not talking about a motorcycle now.

Racing is lot simpler. Since you're trying to achieve a target hot pressure nitrogen adds consistency to the gas mix.
Ideal procedure is to bleed and purge 3x to achieve a significant concentration. This also reduces moisture in the tyre.
A lazy tyre fitter slopping soapy water in the tyre creates issues...
For the lucky few, a vacuum purging machine speeds the process.

The reduced cold/hot gain from the dry gas means the start (cold) pressure can be a little higher. This gives the pilot a better feel of stability and reduces load on the carcass as there is more internal support.

Tyre warmers reduce the temperature variation from warm to hot but a whole slew of factors determine what the tyre temperature arrives at.
You might be targeting 110 deg but can you get there (or stay there?)

[pritch]

almost as hard as a bottle of wine for under $9.

Has anyone put that in their tyres?



No, but have poured a lot into the rider. :whistle:

[bogan]

... Until you stopped. And the argon would all sink to the bottom. And when you took off again the wheel would be out of balance.

I know someone who slimes his bike tyres when fitted, it reduces the leak-down issue a fair bit apparently.

Thank you captain obvious, that was the joke :laugh:

I slimed my front tyre when I had a bit of a leaky bead, did the trick, and certainly doesn't handle any different; though it might be interesting to check the balance next time I have it off...

[SMOKEU]

I know someone who slimes his bike tyres when fitted, it reduces the leak-down issue a fair bit apparently.


Thank you captain obvious, that was the joke :laugh:

I slimed my front tyre when I had a bit of a leaky bead, did the trick, and certainly doesn't handle any different; though it might be interesting to check the balance next time I have it off...

Slime is great on push bike tyres, but not on a motorbike due to the increased speeds. It puts the wheels severely out of balance. After adding the suggested amount to my push bike tubes, if I lift a wheel up and spin it, I can feel that it's severely out of balance and the whole bike moves up and down while the wheel is spinning.

[biketimus_prime]

I know some of you will disagree like crazy but here are some practical results and situations I've experienced.

My own car, street driving, all tyres sit at their set pressures all day.
Track days after hard driving, none go about 1 or 2 psi, 3 at most above cold pressure. That is with just filling with dry air at the petrol station. The air will have slight moisture though but nothing that causes unpredictable pressures.
The tyres don't lose much more than 1psi all round if I don't inflate them after a month of driving.

You'd be stupid to nitro fill and drive around for more than a month and just assume your tyres are all at the right pressures- you'll never know if one may be losing air. So advantage of nitro fill meaning less frequent stops for pumping tyres is invalid, you should check often.

On the race cars I worked with (toyota racing series tatuus chassis cars) we only filled the tyres with dry air, small top ups on the fly were done with nitro bottle, but even then a minute or two in the hot sun saw the pressures go up by 2-3psi. Yes on wet days engineers complained about the unpredictable pressures due to damp insides of the new tyres that were fitted, however on dry days they were just fine with no nitrogen.
This is a race class where only suspension, aero and tyres were allowed to be changed. Where the wings were adjusted by a couple of mm because the driver complained of over/understeer to get that precise result. If nitro was so damn important, they'd be using it on every car, every tyre. But no they didn't. Dry air worked just fine and gave predictable pressures constantly.

Nitro is a waste of money for street use tyres and only fussy as hell people would bother with it on race cars, more hassle than anything. If you're that concerned, just make sure you use very dry air.