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Discussion Starter · #1 ·
Can someone recommend where to go to get nitrogen filled?

I understand it needs to be inflated with nitrogen then deflated and then inflated again to make sure all the oxygen is out, I dont want to go to someone who will do a crap job , any recommendations would be great
 

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Compressed air is a really good alternative. Nitrogen fill is just hype.
 

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Discussion Starter · #4 ·
So forget the nitrogen then just go with normal air? So could you confirm what PSI i should have then on the tyres from cold with compressed air, thanks , I thought it was 29psi but seems to be some debate over that.
 

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I'm on non run flats mate so run a little higher than normal. 33psi cold. Can't remember what non's were. Thinking 29??
 

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Yep, 29 psi (200mbar) for RF's and 33 to 35 psi for the squashy alternatives.
 

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I'm new to R35 ownership, previously running Imprezas for many years.
But had this experience only a couple of weeks ago, before a 1400 mile run to Scotland;



Well, I posted on another nitrogen/air thread that I had a all-wheel nitrogen purge & re-fill on the R35 the other day, as I was getting ready for a run.
So I got up the following morning & the GTR had a flat front tyre!
I had to pull it forward onto the drive to get a bit of room, to find the dust cap had a rubber grommet at it's base & it had slightly pressed into the valve & let the tyre down! I think the ATS guy over tightened it! This also resulted in setting off my TPMS sensor, with it informing me visit the main dealer for a TPMS ECU re-set!

So I had to fill the flat with air from my Michelin electric compressor to 32psi, to match the other 3 tyres which have nitrogen!
I'd called Litchfield & they were great & said for me to pop by & they'd re-fill with Nitrogen & clear the ECU warning for the TPMS!

On the way there, which is approx 50 miles of motorway, the 3 nitrogen tyres increased to 34psi occasionally 35psi but the normal air filled tyre that I filled shot up to 40psi occasionally 42psi!!!

So normal air is definitely less stable & subject to thermal increase in psi over nitrogen!

On a side note, I'll also be lowering my nitrogen psi to 31 so it only increases to 33/34psi when running :good:

I have to say a massive thanks to the guys up a Litchfield for their help, saying "no problems, just pop it up"
 

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You are saying a Nitrogen filled tyre went up in pressure by 5%, but your regular air filled tyre on the same car went up in pressure by 20% ?
Same car, same driving?

Considering air is nearly 80% nitrogen that logically means the other 20% that isn't nitrogen is increasing in volume by 500% or something...

I find that hard to believe.
 

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lol.. I find that very hard to believe.. I think your TMPS is tripping out :p

Most people on here are using air not nitrogen.. Last time i was on the track i had 34psi (normal air) and gave the car a nice beating all day long.. Only managed to increase it to about 37psi..
 

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I thought it was a big increase over the nitrogen filled tyres. But I can only go by what the in car tyre pressure monitoring said!
Would've liked to have had the tyre temperatures as well..!!

Edited to add,
Since Litchfield re-set the TPMS warning & re-filled with nitrogen, it has matched the other 3 tyres in pressure perfectly. So the TP sensor must be working as it should!
 

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I thought it was a big increase over the nitrogen filled tyres. But I can only go by what the in car tyre pressure monitoring said!
Would've liked to have had the tyre temperatures as well..!!

Edited to add,
Since Litchfield re-set the TPMS warning & re-filled with nitrogen, it has matched the other 3 tyres in pressure perfectly. So the TP sensor must be working as it should!
Something odd happening there. I'm air only and I can't even get a 2psi cold to hot increase running high a speed over a long trip
 

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Can someone recommend where to go to get nitrogen filled?

I understand it needs to be inflated with nitrogen then deflated and then inflated again to make sure all the oxygen is out, I dont want to go to someone who will do a crap job , any recommendations would be great
Air works, don't get caught up with the hype !:flame:
 

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In my experience, running with normal air instead of nitrogen means the pressure rises by about 1psi more when very hot, i.e. 29 to 34 instead of 29 to 33. Nice gimmick though. Last time I changed the tyres though, I put some ice cubes inside them which resulted in the pressures remaining far more stable now :) Cool tip that ;)
 

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It is quite difficult to explain some of the findings posted using traditional physics, which might suggest there is something else going on. Pressure and temperature in this context are related by the ideal gas law, pV=nRT, where p is the pressure, V is the volume, n is the amount of gas (ie number of molecules), R is the universal gas constant and T is the temperature.
In an average tyre the volume is constant, if there is no leak and the gas is dry n is constant and obviously the universal gas constant is constant. Therefore the pressure is directly proportional to the temperature (in Kelvin). Hence a change from (say) 15 degrees centigrade (287K) to 40 degrees centigrade (313K) should produce a 9% increase in pressure.

It is important to note that a given number of molecules of any gas at a given pressure take up the same volume, so whether you fill your tyres with air, nitrogen, hydrogen or xenon makes no difference.

In the real world, therefore, something else is clearly happening. The biggest variable that is ignored in the above is water vapour, which exists at any temperature below 373K (and above 273K, usually) in equilibrium with liquid water, and as the temperature rises is more inclined to the gas phase - hence 'n' in the equation is not in fact constant if the gas in the tyre is not dry, but increases with temperature too. I would expect adding ice cubes to a tyre would significantly increase the temperature change with heating because of this.
Clearly if you fill your tyre with a compressor you are filling it with air at whatever the ambient humidity happened to be when you filled it. Nitrogen fill comes from a dry cylinder and therefore removes this element of uncertainty.

Another variable is differential diffusion of different gases through the rubber of the tyre. This can change the composition of the air inside the tyre as far as its proportions of oxygen and nitrogen are concerned, but as discussed above apart from slightly affecting the rate of slow tyre deflation through the rubber itself (which is already usually irrelevant) it will have no effect on pressure change with temperature.

So my conclusion from all of that was that nitrogen or dry air makes no difference. Just don't pump your tyres up with a compressor or foot pump when it's raining.

Geek off:runaway:
 

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Does any of you know the tire temp. Cold and hot?

If dry air is used (nitrogen is a good and cheap option for this) the pressure Will romain more stable as the temps rise a lot.
 
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