# Nitrogen In Tires?



## WarningU2 (May 5, 2014)

My 2018 Cruze the tires are filled with nitrogen or so they say. 

What I have been reading, is that the tire pressure should not fluctuate with nitrogen. Is that true? It doesn't appear to be the case for me. 

I've noted (with the sensors on the car), that I can go from 240 kPa to 265 if I am on the highway going 120 km/hr for any length of time. The air temp was -2 C. 

I suspect that the tires are in fact NOT filled with nitrogen. 

Should I take the car back to the dealers and ask them to purge the tires and fill them again? Will they think I'm an idiot? Maybe I should just let a bit (of whatever is in the tires) out when it starts to get warmer?


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## IPhantom (Aug 22, 2017)

Wouldn't bother. I found it is pretty **** useless. With proper wheel setup shouldn't have problems with air either.
Although the air temperature may be consistent, the tire temperature changes of course. Mechanical factors (tire stretch) also contributes to pressure changes. Anything expands or shrinks with these factors. They say though that the tire should not deflate with nitrogen, but again that shouldn't be an issue in any case.


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## dhpnet (Mar 2, 2014)

All gas expands with heat, including nitrogen. Your tire pressure will increase when the tires warm up even with pure nitrogen. Tires warm up when they are used - even if it is cold outside. The difference you noticed with nitrogen in your tires doesn't seem abnormal to me. 

You should always check your tire pressures when the tires are cold (even with nitrogen). A good time to check them is in the morning after the car has been sitting over night. Even a short drive to the gas station can affect the tire pressures. If you fill them when they are warm then they will be under-inflated when they cool. If you have the dealer put nitrogen in the tires, they should also only check the pressure after the tires have cooled. 

Here's a fun video
https://www.youtube.com/watch?v=bCnWvMleVD0


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## GraySkies (Feb 6, 2018)

The reason they use nitrogen in race tires and such, is the nitrogen is usually DRY. The moisture content in normal air is usually high, especially after it has been compressed. That moisture causes the pressure fluctuation with temperature to be much greater. That doesn't mean it won't fluctuate at all with nitrogen, as dhpnet said. It just means it will fluctuate much LESS with nitrogen than with air.


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## ProDigit (Aug 31, 2015)

yeah, sounds like some sales crap.
You could go back for a 'nitrogen refund'. They might actually credit you the $2 it costs to fill up the tires. :/


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## snowwy66 (Nov 5, 2017)

If your tires have green valve caps. Then it's nitrogen. 
Black caps then it's air. 

Nitrogen leaks. Top off with air. In about 18 months you won't be adding air so much. My 14 hyundai had nitrogen. Took 2 years before I didn't have to add air anymore.


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## MP81 (Jul 20, 2015)

I mean, air is mostly nitrogen anyway...


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## Blasirl (Mar 31, 2015)

dhpnet said:


> All gas expands with heat, including nitrogen. Your tire pressure will increase when the tires warm up even with pure nitrogen. Tires warm up when they are used - even if it is cold outside. The difference you noticed with nitrogen in your tires doesn't seem abnormal to me.
> 
> You should always check your tire pressures when the tires are cold (even with nitrogen). A good time to check them is in the morning after the car has been sitting over night. Even a short drive to the gas station can affect the tire pressures. If you fill them when they are warm then they will be under-inflated when they cool. If you have the dealer put nitrogen in the tires, they should also only check the pressure after the tires have cooled.
> 
> ...


SSVBS - yes!!!

EDIT: and don't forget the NASH's!!


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## dhpnet (Mar 2, 2014)

Air is 78% nitrogen. As @GraySkies said, the biggest advantage of the nitrogen filling stations is that they remove the moisture (supposedly they use purified nitrogen, but who knows for sure). You would get the same effect with purified oxygen, but that could be dangerous. Or, you could use dry air that has had the moisture removed. All of that probably has a big effect on race cars where the tires can easily hit 150-200 degrees F and cause problems at 250 MPH, but it doesn't really make that big of a difference for passenger cars. You will still see fluctuations in pressure. You will still lose pressure slowly over time. You won't notice any difference in driving. But, your wallet will be lighter, which could save some MPGs, so that's a bonus.


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## ChevyGuy (Dec 13, 2014)

dhpnet said:


> Air is 78% nitrogen. As @*GraySkies* said, the biggest advantage of the nitrogen filling stations is that they remove the moisture (supposedly they use purified nitrogen, but who knows for sure).


One of the reasons I like to top off with the "free air" at my local tire place. The unit gets it's air from the shop's air system - which I assume has something to help remove moisture. Not super dry, I'm sure. But dryer than some other sources.


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## ChevyGuy (Dec 13, 2014)

dhpnet said:


> A good time to check them is in the morning after the car has been sitting over night.


Just get to it before solar heating of one side kicks in.


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## 17Hatch6MT (Dec 28, 2015)

Compressing air also compresses the water vapor. If you've ever owned a compressor, you may have had to blow out the water from the reservoir periodically. I'd suppose the air coming from the chuck is more or less saturated with moisture at the temperature of the air tank. At least, during spring-summer-fall. But it expands into your tire... down from, what 80 psig (95 psi absolute) to 35 psig (50 psi absolute). Approximately doubling in volume and so relative humidity would be 50% if the tire is at the temp of the air tank. But when it's cold, you'll probably have some water or ice in your tire. And correspondingly less pressure, less than if it was dry air or dry nitrogen.


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## dhpnet (Mar 2, 2014)

17Hatch6MT said:


> Compressing air also compresses the water vapor. If you've ever owned a compressor, you may have had to blow out the water from the reservoir periodically. I'd suppose the air coming from the chuck is more or less saturated with moisture at the temperature of the air tank. At least, during spring-summer-fall. But it expands into your tire... down from, what 80 psig (95 psi absolute) to 35 psig (50 psi absolute). Approximately doubling in volume and so relative humidity would be 50% if the tire is at the temp of the air tank. But when it's cold, you'll probably have some water or ice in your tire. And correspondingly less pressure, less than if it was dry air or dry nitrogen.


True. 

If the air in the tire drops below the dew point then the water could condense inside the tire and could freeze. But, as soon as you start driving and the tires heat up, then the dew point climbs and the relative humidity drops. If it gets hot enough then the water will vaporize again.

Either way, it probably won't make much of a difference in a normal passenger car under normal conditions.


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## snowwy66 (Nov 5, 2017)

Tires only hold 32. 

Compressors have highly pressurized air. Up to 150 or more possibly.


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## WarningU2 (May 5, 2014)

Thanks for the comments folks. I won't worry about the increase in pressure. 

Note: The caps btw are blue with a flat end with an N on them. I was told to put nitrogen in them and was given a little book that explained why it was better. Which turns out their description that pressure does not fluctuate is wrong. The dealership I go to will check your tires and fill them for free.


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## dhpnet (Mar 2, 2014)

WarningU2 said:


> Thanks for the comments folks. I won't worry about the increase in pressure.
> 
> Note: The caps btw are blue with a flat end with an N on them. I was told to put nitrogen in them and was given a little book that explained why it was better. Which turns out their description that pressure does not fluctuate is wrong. The dealership I go to will check your tires and fill them for free.


If they will do it for free then it couldn't hurt. There are some very minor advantages, such as low moisture. It's just not worth the cost that many places charge, or the hassle, in my opinion.


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## BlueTopaz (Aug 25, 2012)

Unless you get Nitrogen for free it is a not worth it. I never noticed a difference when I tried it.


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## Robby (Mar 1, 2013)

OK.....as usual I will get a bit long winded.

Pure Nitrogen in tires is a good thing only IF: It is an aircraft that flies above 10'000 feet. Aircraft tires with regular 'you are breathing it' air will explode above about 15 to 20'000 feet.
Or if it is a car used for racing where you have determined the chassis handles best with each, individual tire at a certain pressure. This way, the tire pressure is at optimum as the race begins and, with the pressure stability of 'PURE' nitrogen, the tire pressure will have hardly changed at the end of the race.......so, the car handles about the same throughout the event.

It is a bad thing in a daily car and the tire manufacturers love it.
Your street car has a label that specifies minimum cold tire pressure. In this case, cold means in the shade after sitting overnight. Sunlight on the sidewall will cause a incorrect reading.
Because it is a cold specification, we all know that as the day and miles pile up the tires operating pressure will raise. Higher pressure means a cooler running tread and carcass and a cooler tread results in longer tread life.
And that, quite simply, is why tire makers like nitrogen. If the tire fails due to underinflation they can blame nitrogen. Obviously it will be running underinflated because the expansion rate of nitrogen is rather low.......so the tire will actually run hot. Also, rolling resistance will remain higher than if filled with air.......I'll speculate that maybe the oil companies like it too, heh heh.
Mind you, these are tiny differences that can be measured over the life of the tires or the car, but there is a difference.

I mentioned Pure Nitrogen.........This is kind of like the difference between a bottle of compressed oxygen for my oxy-acetylene torch and a bottle of compressed oxygen for hospital use......the hospital stuff is pure (and could make torchwork memorable).....mine isn't.

The aircraft and racing industry use Pure Nitrogen......I'll estimate it is like Ivory soap...98% pure.
The stuff the car dealers (and some tire shops) is not so pure and not as expensive (for them, cheaper, for the end user......bend over).
Add to this, simply deflating the tire and re inflating with nitrogen gets you at maybe 60% nitro.
Unless they can squish the tire down the thickness of a sandwich bag once deflated there is still a lot of air, by volume, in that tire.
So, in that case, you are putting nitrogen in a vessel that still has a lot of air to mix in......hence, pressure changes similar to plain ole air.

There is a process that comes with a vacuum machine.......the tire is vacuumed and refilled with nitro a minimum of three times......the Auto X gang might do it four or five.
You are throwing a lot of nitrogen away but this is the only way you can get close to 95% nitrogen content.

I assure you, there are no tire stores or car dealers blowing raw nitrogen into the heavens so you can come close to that perfect fill.

So, bottom line, IMO, Why bother?

Rob


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## Blasirl (Mar 31, 2015)

Just to add my $0.02 worth:

There really is no difference in Hospital grade and Commercial grade Nitrogen other than the color of the tanks and the fact that hospital grade tanks are never hooked up to anything other than hospital systems. When in Kuwait, we needed a large supply of O2 for a major welding job and since it was urgent and we only had a few O2 tanks- and those were mostly empty - we ordered some. 

Well it was going to take forever to come in through the supply channels as they were compressed cylinders. Well, we asked the hospital if there was a way to help us. They told us the fittings and what goes into the tanks was the same, but they were not allowed to hook "dirty" tanks to their system. They did have some extra green tanks and said we could have them provided we marked them as "bad" or something once they were connected to the welder. All we had to do was change our order to the hospital grade tanks to replace them.

I pretty much agree with most everything else Robby said though.


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## Robby (Mar 1, 2013)

Blasirl said:


> Just to add my $0.02 worth:
> 
> There really is no difference in Hospital grade and Commercial grade Nitrogen other than the color of the tanks and the fact that hospital grade tanks are never hooked up to anything other than hospital systems. When in Kuwait, we needed a large supply of O2 for a major welding job and since it was urgent and we only had a few O2 tanks- and those were mostly empty - we ordered some.
> 
> ...


The oxygen story is a good one........I always visualized a four foot oxy-acetylene flame (rosebud size) from a brazing tip (heh heh).

Good story though......necessity is the mother of invention.

Rob


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## gliderdriver (Jan 7, 2018)

Robby said:


> Add to this, simply deflating the tire and re inflating with nitrogen gets you at maybe 60% nitro.


This is not physically possible...air is 78% Nitrogen.


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## Robby (Mar 1, 2013)

gliderdriver said:


> This is not physically possible...air is 78% Nitrogen.


Alright, alright........I'm trying to say 60% of the tires capacity is now inflated with the stuff coming out of the bottle that says nitrogen on the side.

Heh heh..........OK......you crushed my nuts.

Rob


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## dhpnet (Mar 2, 2014)

Robby said:


> Alright, alright........I'm trying to say 60% of the tires capacity is now inflated with the stuff coming out of the bottle that says nitrogen on the side.
> 
> Heh heh..........OK......you crushed my nuts.
> 
> Rob


LOL.

I think your point is good. It would be almost impossible to get a 100% pure fill of nitrogen in the tires. It would require some sort of laboratory setup. 

I think the biggest problem with selling this nitrogen service is that the consumers think they don't need to check their tire pressures as often, and they don't. Or, they knowingly drive around on under-inflated tires because they don't have time to drive to the nitrogen filling station and they don't want to use air. This service creates a huge safety problem. I stay away from cars with green caps on the tires because they are probably under-inflated and at risk for a blowout. 

Anyone thinking about spending money on this service would be better off buying a cheap air compressor. It's much more important to check the pressures frequently (when cold) and keep them properly inflated.


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