Running with Nitrogen in the tires

Running with Nitrogen in the tires

We picked up our 85 last Thursday and couldn't be happier. I have run nitrogen in all my vehicles tires for the past five years and been very happy with the performance and tire ware. We life in the California desert with high summer temperatures. Does anyone have any experience with using nitrogen in their model S tires? We have the 19s on the car.

Thank you,

NKYTA | 19 marzo 2014

Bill, use to search the forums. There was at least one thread on nitrogen in the tires. With different viewpoints, of course. ;-)

sule | 19 marzo 2014

:) just try to get your tires NOT filled with mostly Nitrogen. When you find a way to do that, please report your experience in detail ;)

info | 19 marzo 2014

Bill: When my wife, who lives on the East Coast was sold nitrogen for her tires, I hit the roof. I thought it was a big scam. I have a friend who earns his living racing cars and he uses nitrogen and he said that he didn't use it in his personal car. However, in the last five years, I have evolved. First, and most importantly, your car has TPM sensors in each tire. Moisture which reacts with the Oxygen in regular air can cause deterioration of the sensor. It will not happen with N.

I have regular air in my tires and have no plans to use Nitrogen, but if it was readily available and not very expensive, I think it's not a bad thing to do. As a matter of fact, I think it's preferable, especially if you've got a source to re-fill handily. The problem is that if you need to top off tire pressure and the N isn't available, you put in air with 0x and you're no better off than if you used regular air to begin with.

I don't think the N makes much difference in the heat, but if you've been used to using it and you're happy--keep going with it. Couldn't hoit.

jordanrichard | 19 marzo 2014

Nitrogen filled tires will stay at a constant pressure much, much longer than regular air. Air, believe it or not does seep through the rubber in the tires. Nitrogen molecules are larger and won't bleed through. Also, heat/cold doesn't affect nitrogen as it does reg. air. This is why aircraft tires are filled with N. The tires goes from being below freezing at altitude to hitting the runway at 200 mph. The instant heat build up would blow an air filled tire in an instant.

However, N is not available everywhere and where it is, is expensive. They have to use a special machine that evacuates all the air and moisture out of the tires and then replace it with N.

So you have to ask yourself if the cost is worth it. Theoretically since the tires stay at a constant pressure, then that means the rolling resistance remains constant. What does that do for one's range....who knows.

joenanp | 19 marzo 2014

So I do not know, maybe many aircraft use nitrogen today. Certainly not all, and they did not used to use it at all not that long ago. With air, they do not blow in an instant when landing. There are recommended pressures to set aircraft tires before takeoff and these take into account all sorts of things, one of them being landing. Air is 77%ish nitrogen. Difference in thermal effects is minimal. There would be some benefit of N2 with moisture but if dry air is used not even much diff there. N2 filled tires will not stay at a constant press; the range of pressure change for a given temperature range will be smaller than air but not constant.

rfriess | 19 marzo 2014

I fill my tires with 78% Nitrogen. Works fine and is much less expensive that the 100% stuff.

Dramsey | 19 marzo 2014

The pressure of the gas used to inflate a tire varies with temperature, but this variation is the same for all gases. Dry air, pure oxygen, N2, argon, helium, whatever-- it doesn't matter. Fill each tire of your car with a different gas to the same pressure, then raise or lower the temperature, and the pressure in all four tires will match.

(Obvious exceptions for gasses with very small molecules that will gradually diffuse through rubber, gasses with relatively high freezing points, et cetera...)

It's called Boyle's Law, and they used to teach it in school.

Rheumboy | 19 marzo 2014

I filled mine with helium and I can't get Stela off the roof. STELA!!!!!

Sound like Marlon Brando?

AoneOne | 19 marzo 2014

The one exception to Boyle's law that matters in this case is the water in the air. Dry air and nitrogen, as Dramsey said, are affected equally by temperature. If the Nitrogen fill is dryer than the air fill, that could be a measurable, if not practical, difference.

sbeggs | 19 marzo 2014

@Rheumboy, ho, ho, ho!

EssDub | 19 marzo 2014

i filled my old range rover with nitrogen in hopes to improve efficiency a bit. i don't believe it did much -- maybe 12.5 mpg from 12, but as i recall it wasn't expensive either. the dealer put N in all 4 tires for 100 bucks i think, and top offs were always free. i believe this was the service:

i'd be interested to try it out on my mS and see if it has a noticeable effect on range.

mrspaghetti | 19 marzo 2014

@Dramsey +1
@Rheumboy lol

I'd say putting nitrogen in your tire is a scam. If you're worried about corrosion get a compressor with an air dryer.

NKYTA | 19 marzo 2014

Like I said at the top, Bill, some different viewpoints. ;-)

NKYTA | 19 marzo 2014

What I should have said is...YMMV. ;-p

AAviator | 19 marzo 2014

Nitrogen is put in plane tires for one reason only. Fire protection. The Brakes on a normal landing will get as high as 600 degrees C. The carbon brakes in the center of the hub will then heat the metal rim to near or above the flash point of rubber. Aircraft tires are from about 150psi - 200 psi at ambient temp, and the wheel wells are unpressurized.

The flash point of the tires will be reached a lot sooner on the inside of the tire than the outside of the tire if there was O2 inside the tire (around 20 percent in ambient air) under pressure. With no O2, inside the tire the chances of a tire fire are reduced dramatically.

A tire fire in flight is a VERY big deal. There are a lot of very fragile temperature sensitive things routed right next to the tires in the wheel wells.

While I love the idea that Costco puts Nitrogen in our tires when I buy tires from them. Its still bullshit even though I love the green caps.

Furthermore, I believe the reason that tire pressures will drop marginally more than when filled with air, is not that the o2 escapes through pores that the Nitrogen would not escape through. Its that the O2 is lost through chemical reactions (rusting, oxidation of rubber etc...) I'm not 100 percent sure on that, however, so your mileage may vary.


Dramsey | 19 marzo 2014

I have had a fellow earnestly explain to me that oxygen in the air will degrade rubber (true enough) and that using a nitrogen fill would therefore make my tires last longer.

I have been driving for many decades, and have been through a lot of tires. I have worn tires down to the cords over some years; I have destroyed tires at Sears Point (fist-sized chunks of rubber coming off the edges of street tire after an afternoon of hot laps); and I have run tires over objects and curbs that damaged or destroyed the tire.

I have never had a tire fail by rotting from the inside. I would expect that the outside of the tire would rot through first. It seems the nitro sellers have a panoply of pseudoscientific reasons that a nitrogen fill is worth the money. I don't think any of them make any sense.

NKYTA | 19 marzo 2014

@rfriess, clever! :-)

cerjor | 19 marzo 2014

If moisture is the problem, fill your tires in Quartzite AZ. Humidity today was only 2%.

Brian H | 19 marzo 2014

Same amount of H2O in the air as elsewhere; it's just that at 100°+ it could potentially hold so much more!

inverts | 20 marzo 2014

N2 is a scam. If moisture is a concern, fill from a SCUBA tank with air, where during compression most water is removed. But still don't buy it. Or filter the air through some silica gel. But O2 mediated degradation of the rubber or metal over the normal life of a tire makes not an iota of difference, even if you figure in elevated partial pressure. Escape of gas is only an issue with He, maybe H. Pressure variability is physical nonsense.

Next is the issue of purity of the gas. I wonder what grade the car dealer is using. Usually they are specified with the number reflecting the exponent of the impurity. For sputter coating I use 4.8 grade Ar, which means it has 1/10 exp 4.8 impurities, which is fairly pure, maybe not ACS analytical grade, though. I very much doubt that car dealers use that sort of grade.

mclary | 20 marzo 2014

Sounds Explosive!!!

Webcrawler | 20 marzo 2014

I see No difference in "Clean" air vs Nitrogen...

I have a good compressor with a good air dryer on it.... I have never had a Tire/Pressure sensor issue in the past 50 years...

xrayangiodoc | 20 marzo 2014

Nitrogen is element#7 and Oxygen is element#8. The both exist as the bi atomic form (N2 & O2). I doubt that O2 is any smaller than the lighter N2. Consumer Reports does not feel that Nitrogen fills are useful. Just a nice little scam for tire dealers to sell, right next to the gizmos to raise gas mileage, "up to" some absurd amount.

ye | 21 marzo 2014

Apparently, nitrogen does leak out of tires more slowly than oxygen.

I don't think it has any other benefits over dry air.

ZsoZso | 21 marzo 2014

Actually, the size of N2 molecule is a bit smaller than the O2 molecule, because of the stronger triple bond in N2 versus the double bond in O2. The bond length of N2 is 1.098 Å, while the O2 has 1.208 Å length, so N2 is roughly 10% smaller.

For more details see:

AoneOne | 21 marzo 2014

Also, if O2 is more soluble in solid rubber than N2, perhaps due to its greater reactivity, then O2 diffusion will be enhanced.

Facilitated diffusion like this is (as I understand it) an important role of myoglobin in muscles: by increasing the solubility of the oxygen, it increases the rate at which the oxygen diffuses from the capillaries through the muscle cell protoplasm to reach the mitochondria.

robert | 21 marzo 2014

Have been using Nitrogen in all my cars (get it for free) and must report that I find it better than air. No leakage at all, ever.

KevinE | 21 marzo 2014

N2 has been used in aircraft for a long time cuz it's just so darn hard to find a good, portable, air compressor that goes over 300 psi.

@ AAviator, you reminded me of some good times on the flightline. Hot brakes, exploding tires, washdown trucks used to cool them off... Don't remember the planes getting better fuel economy with N2 filled tires though. :-/

Brian H | 22 marzo 2014

They may have while taxiing.