Nitrogen in car tires

[Pelican]

Originally Posted by StevieC
I have Nitrogen in my tires from Toyota. I have read that it's supposed to be more consistent in pressure when the wheels heat up during driving. It is also suppose to leak out of the tires less that typical air and it has a benefit that it helps aluminum rims not oxidize as much where the tire seals against the rim because its humidity is controlled and it's a "Dry gas" versus the humidity in the air.
There is a sticker on my windshield that says "Free Nitrogen Top-Up's" from any Toyota dealer at any time.
Whether this actually works I don't know. All my previous vehicles had standard air and had no issues with leakage on Steel or Aluminum rims and we get a ton of salt and moisture here in the winter to oxidize the rims.


I too have nitrogen and I remember reading that because of its larger molecules there is less if one can call it that "seepage" I know that it is better suited for big changes of temperature that's why they use it on airplanes.

 

[ARB1977]

If it's good enough for airplanes, it's good enough for passenger vehicles, lol.

 

[Oildudeny]

stewarts free air for my tires love the fishy air smell - reminds me of something

 

[oliver88]

We use N in the race car tires because the pressure increases less as the slicks get heat in them...for a street car it's a gimmick and waste of $$ in my opinion.

 

[Hall]

Originally Posted by Trav
They had to figure a way to get money out of something everyone uses that cost nothing.

Apparently just justify charging for air because it's a "service" they offer. By "they", I mean 99% of gas stations around here. If you want free air, you better have your own compressor or find a tire shop that offers it or has a hose outside for public use. I know of just one gas station that offers free air anymore. All the rest have a little vending machine that takes credit cards for "air".

 

[BrocLuno]

Most compressors condense the water in the air, that's why they have to drain the tanks periodically. Compressed air has less water than ambient. Maybe not dry, but drier

 

[Nyogtha]

It's still saturated with water at the compressor discharge pressure. Less than ambient as you note, but saturated at whatever the pressure & temperature is at the drain point on the compressor discharge. So inside your tires, it's saturated at the ambient temperature you use that compressed air to fill or top off your tires. Lower temperatures can then cause free water to drop out of solution inside your tires.

Having said that, I've used such compressed air in my automotive tires for decades with no negative consequences. For scuba diving or emergency response / hazardous chemicals handling & exposure SCBA, I use breating gases that have been through scrubbing systrms and dessicants to remove compressor lubricant mists and dramatically lower the dew point. A first stage regulator freeze-up in an IDLH (Immediatey Dangerous to Life and Health) environment, be it liquid water or something else, doesn't lead to good outcomes,.

 

[KJSmith]

From what I remember, they started using nitrogen in cars about the same time tire pressure monitors came about.

If you remember, the first cold spell would set everyone's TPMS into alarm.
Nitrogen in the tires helps eliminate that.

I think that is what got this BS started.


JMHO

 

[bdcardinal]

We had a nitrogen filling station at work for a while. The machine was free to us as long as we sold the caps (insert eye roll emoji). Needless to say I put nitrogen in the tires of my Mustang almost 2 years ago at 35psi and they are still at 35psi.

 

[spk2000]

My motorcycle tires used to need air added every 2-3 weeks. Someone recommended I try Nitrogen and I did and it went 2 years same tires no need to add any. It worked in this case but each case may be dependent on different factors.

 

[CR94]

Lots of misinformation quoted in this thread!

Dry air doesn't change pressure with temperature changes any more than dry nitrogen does.

It's a legitimate (though often exaggerated) claim that nitrogen permeates out through the tire more slowly than oxygen, so pressure loss due to that cause will be slower. However, if you occasionally compensate by adding air, the percentage of nitrogen in the tire will increase, so you eventually end up with a tire full of practically 100% nitrogen, for free! Water vapor permeates out faster than nitrogen, too, so that's mostly a bogus issue.

 

[Ducked]

Originally Posted by CR94
Lots of misinformation quoted in this thread...

....... if you occasionally compensate by adding air, the percentage of nitrogen in the tire will increase, so you eventually end up with a tire full of practically 100% nitrogen, for free!


What would stop the oxygen in the air permeating into the tyre? I think its supposed to work both ways.

 

[Lubener]

Nothing but a sales gimmick.

 

[Nyogtha]

Originally Posted by Ducked
Originally Posted by CR94
Lots of misinformation quoted in this thread...

....... if you occasionally compensate by adding air, the percentage of nitrogen in the tire will increase, so you eventually end up with a tire full of practically 100% nitrogen, for free!


What would stop the oxygen in the air permeating into the tyre? I think its supposed to work both ways.

Pressure gradient

 

[circuitsmith]

Originally Posted by Ducked

What would stop the oxygen in the air permeating into the tyre? I think its supposed to work both ways.


It will work both ways. If the partial pressure of oxygen is lower inside the tire than outside oxygen will diffuse into the tire.

https://en.wikipedia.org/wiki/Partial_pressure

It seems to me carbon dioxide would make for a low seepage tire fill.

 

[edhackett]

Originally Posted by Nyogtha
Originally Posted by Ducked
Originally Posted by CR94
Lots of misinformation quoted in this thread...

....... if you occasionally compensate by adding air, the percentage of nitrogen in the tire will increase, so you eventually end up with a tire full of practically 100% nitrogen, for free!


What would stop the oxygen in the air permeating into the tyre? I think its supposed to work both ways.

Pressure gradient


No. Diffusion takes place at the molecular level and a pressure gradient has no effect. It is driven by the partial pressures only. The migration of gasses across a leak has been demonstrated at a 50,000 psi differential. Individual molecules know nothing of pressure. Any time there is a path for molecules to move, they will. In reference to tires; that means through the rubber, leaky valve core, imperfect bead seal, or wheel porosity. With a nitrogen fill oxygen is happily leaking in and "extra" nitrogen is happily leaking out to equalize the partial pressures of the gasses inside and outside of the tire.

If you're having trouble with the concept of partial pressures, think of them as concentrations. Gases will seek to equalize their concentrations if they can. If there is a permeable barrier or a leak between two concentrations of a gas, the gas will move to equalize the concentration regardless of any pressure differential.

I think that the fact that people see lower leakage is that a nitrogen fill usually comes with replacement of the cheesy plastic valve caps with higher quality ones with an o-ring seal.

Ed

 

[CR94]

Originally Posted by Ducked
What would stop the oxygen in the air permeating into the tyre? I think its supposed to work both ways.


It will, but NET oxygen flow will be outward, because of the higher partial pressure of oxygen in the tire. Which means I admittedly oversimplified when I said nitrogen percentage will increase to "practically 100%." It will increase above the percentage in air, as most (not all) of the oxygen and water vapor permeates out.

Edhackett's answer was good, although more detailed than I assumed you expected.

 

[Traction]

EVENTUALLY the oxygen, and moisture equalize. I've been using 95% nitrogen in a few thousand tires for over 14 years. Yes, it's oversold, but it has some definite advantages over wet air full of oxygen. If you start out with 95% nitrogen, with no water vapor, it will pretty much stay there. Every you top off your tires with wet air , and oxygen, you bring the oxygen and water concentration back up, and it all has to leak out over again. I just checked my new tires I put on a couple of months ago I filled with 95% nitrogen, and they have 5% oxygen, 18% humidity with a dew point of 25 degrees. No more oxygen leaks out at that point, and the moisture level probably slowly goes up, and down a little with the ambient humidity. Not so with air coming out of cheap, hot compressors.

 

[Hootbro]

My wifes then new 2017 Renegade came with Nitrogen filled tires when delivered almost 1 year ago. Only had to finally refill them last weekend. I can say they did not wildly fluctuate with OAT like regular does.

That being said, I would not pay the premium for it going forward but if it was way cheaper or free to be had, I would use it.

 

[jhellwig]

Bought a new Chevy in 2013. Dealer had all the vehicles on their lot filled with nitrogen with the little green caps. The caps they were using sucked and the end popped off of them in about 2weeks letting dust and dirt get in the valve stem. They weren't the right caps for the valves anyways. Gm uses valve stems that have caps that cover all the metal of the stem. The green ones didn't letting the stem corrode.