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Old 02-15-2016, 02:56 PM   #21
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For us nitrogen was no different than air ...... On our camper had to add nitrogen just as air.... in our junk 2011 Subaru had to add air and replace the tires at 32K no difference than air.......... just more cost



Waste of time and money........

It may be a waste of money and time for you but not for everyone, some people like nitrogen.


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Old 02-15-2016, 05:46 PM   #22
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IMO the best part of nitrogen filled tires is the green cap. Haven't lost one yet in my black topped driveway.
X2!!
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Old 02-15-2016, 08:03 PM   #23
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As I understand it the advantage of nitrogen instead of normal compressed air is not in the running of the tire down the road but rather when it is sitting as most TT tires tend to do. Nitrogen tends to leak down less and does not cause the same deterioration of the rubber. Most RV tires time out way before they get any real miles on them. My new TT has nitrogen not sure what I will do when they need to be topped off.
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Old 02-15-2016, 09:59 PM   #24
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IMO, If there's any one single advantage to N2 is the fact that it doesn't increase in pressure as much as air when operating at highway speeds. But it's only 1 or 2 psi. Good clean dry air would be pretty close to N2 IMO. Water from compressor tanks end up in the tire and when compressed and heated, turns into vapor which expands and increases the pressure more than dry air or N2.

I think the reason some call it a ripoff is because some dealers charge over $150 for the option and then 10 to 20 bucks ever time you need to top off.

I use my own air and keep the tank bleed of water and have a water trap installed. N2 is great, it's just not practical for me but it's not the N2 that's a ripoff, it's the people that overcharge for it.
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Old 02-17-2016, 07:41 AM   #25
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If you then fill with a compressor with a vessel , and you want to get as less water in the tire as possible ( wich to my opinion wont be needed) , you best put the pressure in the vessel as high as possible , think 8 barr /120 psi is possible for most, the extra water is condensed and collected at the bottom.
Then the Partial pressure of water is max about 0.3 psi and so 0.3/120 part of total air in compressor , wich is pretty low.
But even if you dont tap off , the air that goes in the tire has that 0.3/120 part= 0.25% amount of watergas.

Then fill up a D-load tire to 65 psi for instance with that compressor.
And % water in tire will be that 0.25%.

Nitrogen is by its production process free of water, and this is because they comprimase it to 200 barr /??psi in the main vessel, and filll the smaller bottles with that .
In the main vessel the water condenses, and Partial pressure of water is the same as when 14.7 psi outside pressure 100% humidity. About 0.3 psi partial pressure of water at 68 degr F.
is a percentage of 0.3/14.7= a good 2% . but in the Nitrogen bottle its 0.3/200= 0.02% so neglectable.
mayby you find even a little liquid water in a Nitrogen bottle at the bottom.
but it wont get into the tire.
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Old 02-17-2016, 08:33 AM   #26
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Thats allot of math, however your figures are based on some given amount of water vapor (which you haven't stated) present in the air being compressed. I like Too Tall's salutation and feel air from a compressor with a drier is better the from one without. I have decided to add air driers to both my shop compressors and if I get a portable for the TT it will also have a drier. As for the nitrogen in the tires now it will be a wait and see.
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Old 02-17-2016, 08:51 AM   #27
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In my calculations I asume the outside air to have an humidity of 100% , wich it never is, so in real live the percentages of water that can come into tires is lower.
These examples must be seen as what is maximally possible.
But the other way around , if you have 50% humidity in the air you put in your vessel of compressor, then at 68 degr F 50% of 0.3 psi Pp H2O= 0.15 psi .
When filled to 8 barr in vessel with this air it becomes 8 X 0.15psi= 1.2 psi and max H2O it can be is still 0.3 psi so 0.9 psi will condense to liquid water, and the air inside the vessel still has 0.3 psi of water as gas in it so still same percentage.
The other way around the outside air should have a humidity of 12.5% to have the effect that nothing condenses when you fill up to 8 barr.

I once found on the internet an spreadsheet with the Partial pressures of water for every temperature.
I myself added a conversion from degr. Celcius to Fahrenheit, and Barr to PSI.
Today made for another topic in other forum a summary and will copy it here.

Degr C/ degr F / bar absolute/psi absolute

..0/..32 /0,006111536/0,0886
.20/..68/0,02338504/0,33917
.40/104/0,073836286/1,07091
.60/140/0,199404156/2,89212
.80/176/0,473892271/6,87324
100/212/1,01347789/14,69928

How to read this.
When having absolute dry gascompound in tire and pressure rises by temperature rising , it can be calculated with the gaslaw.
But when there is enaugh water in the tire to go over to gas , it can only go over to gas until the above given Partial pressure is reached.
So when going from 32 degr F and humidity zero in tire but enaugh water as liquid, and temp rises to 104 degr F , we read 1.07 psi maximum Pp of water so calculated pressure with gas law can only be rised extra by the water with that 1.07 psi.
This 104 degr F is about the average warm inside tire temp when driving about 50m/h.
This extra pressure rising will give a bit lesser deflection so a bit lesser heatproduction of tire, so in the end the tire with enaug water in it will have a bit lower inside tire temp then the for instance Nitrogen filled tire.
For races , where inside tire temp can rise to 90degrC/194F the extra rising would be 10.17 psi by the water in tire.
But at this inside tire temp the rubber gets to hot so damages, but roadcontact is better with dry N2 , and that counts for races, and damage to tire is seen as colateral damage.
Best there would be to find a way to activey cool down the tire , for instance by blowing air over the top of the tire, not the bottom because speed to air there is zero, at the top about 2 times carspeed.
Then inside tire temp can be brougt back to for instance 60 degrC/140 degr F for wich the water can only rise extra 2.89 psi and rubber stays under a sertain temp at wich damage happens.

Now realise that 8 bar in the vessel would mean an absolute pressure of 9 barr in the vessel, what you measure is the overpressure above the outside air.
Take the vessel filled to 8 barr, high up in the mountains, and you would measure higher pressure then 8 barr.
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Old 02-17-2016, 08:58 AM   #28
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Like I say I'll keep my air compressor for now but when I move up to the bigger tires then I'll bite the bullet and run nitrogen but I'll top off my tires myself. It's just each person own preference


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Old 02-17-2016, 09:15 AM   #29
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Jadatis thanks for the technical information you have obviously done some major research.
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Old 02-17-2016, 09:15 AM   #30
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Here are just a few shots of our Flagstaff 26RKS. Two are at American Heritage Campground in Williamsburg, VA , one from Myrtle Beach Travel Park, and the other one is in its parking spot here at home.
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