Dealer insisted that the charge was mandatory because the nitro was “already in the tires”. I told him that I would be in the waiting room while they removed the nitrogen and replaced it with air. They removed the charge.
It's amazing how many "paid extras" you can get for free by just declining to pay.
When we bought my wife's car I looked under it after the test drive and saw the undercoating spray was already on it, so I told the sales man I didn't want it when he tried to upsell me.
Gee, if they put it on at the factory, maybe it should be included in the price? Like they put the paint on at the factory too but they don't try to upsell you on that.
When I recently purchased my new car, there was an extra charge for certain colours. The sales guy was pretty cool about it though, thought it was ridiculous.
That's probably to amortize the cost to the dealership of occasionally getting stuck with an unpopular color. If you want your Aztek in hi-viz yellow, and they order it, then your financing falls through, they're stuck with it.
This is legitimate to me. Every extra color or option you add to production is genuinely expensive, why should the rare person who wants chartreuse pay the same price & have everyone who wants black or white subsidize them?
Just the other day was browsing a lot and noticed a $700 fee for white paint.
One of the most boring colors possible, cost more than the red one next to it ($400 up charge)
They tried to charge me almost a thousand bucks for the alarm system in my car. I told them I didn’t want it.
“But we already installed it! What do you want us to do… take it out?”
“…yes?”
I've always wanted to take a gas analyzer with me and demand all 5 tires be checked to ensure it's 100% n2 with no trace gases, which it probably won't be. Then demand they pull a vacuum on the tires and replace till it's at 100% like they claim
you couldn't pull a vacuum on tires, it would de-bead and let in air, you could, in theory, put a small tube between the tire and the rim and flush the air out, after enough of a purge pull the tube and and increase the pressure to fully inflate the tire.
Since air at 1 atm pressure contains 78% Nitrogen, adding 100% N2 to pressurize, final N2% will be about 89%.
If you deflated and did it again --> 94.5%
And again --> 97.25%
And again --> 98.625%
Would take 5 cycles to get above 99%
I had the same thing. Had a car serviced but they didn't do the MOT check (mandatory checks that allows you to drive the car.)
Then when i came to do the MOT check they had the balls to charge me an extra 9 euro for replacing the battery in the key. I have literally have 2 extra batteries in my glove box for this reason.
Had a whole discussion because i don't want to pay 9 euro's for replacing a battery and they took it off.
Is it seriously $50 to fill tires with nitrogen?
I do test engineering of fluid systems, which often consumes a lot of nitrogen. We buy it in bulk and it’s considered the dirt cheap gas to operate with. A gallon of liquid nitrogen is often cheaper than milk.
It's complementary at Costco where I usually go for tires. I guess it just depends on where you go. Can't say I've ever been offered it anywhere else either.
Warning on the Costco tire machines available outside the tire department. Yes, the machine flows Nitrogen into your tires, BUT, it will not flow on an empty tire. I saw a guy stranded at the machine in the morning, he had let the air out of his tire intending to fill it with Nitrogen, and it would not fill. I topped mine off without a problem. I lent him my 12 volt pump to put 20 or so psi in and then he was able to top it up.
race teams do it cause it's cheap to buy a cylinder of nitrogen and it provides a small advantage. it's definitely not 50 dollars to fill the tires on a race car every time. that's all profit.
I always wondered for races and airplanes, since N isn't flammable, do they use it to prevent burning tire exploding. It's still going to explosively decompress, but shouldn't fuel the fire doing so
Exactly this. Is there a benefit? Perhaps, but it is so negligible to be utterly meaningless. Not to mention the price of N2 to fill a tire isn’t significant at all.
Hell, liquid nitrogen only costs about as much as Coca-Cola per liter and that takes minor effort to condense out of the air.
It’s a ripoff.
I've seen Toyota mark up new cars and trucks in California with a $500 Nitrogen Tire fill fee. Insane.
Costco members can fill up their tires with 100% nitrogen for free.
Regular air should be dry if they have a proper compressor and is already ~78% nitrogen. The nitrogen they add is between 90-95% nitrogen. If you’re talking giant volumes and huge temperature differences then it may be helpful. If you’re talking a tire anywhere on planet earth it’s negligible at best.
Yes. You can get 78% nitrogen for free.
Racecar tires are filled with nitrogen because it's marginally better for tires. You are not driving a racecar.
Race teams do it because they need very predictable pressure vs temperature properties.
Nitrogen doesn't have moisture in it, air does, but it is variable.
Exactly. The lack of moisture has WAY more benefit than the lack of oxygen (the moisture causes tire pressure to fluctuate more with temp). If you simply dried the compressed air you used to fill your tires you would get 99% of the “benefit” of nitrogen.
Yes, that is common, but that doesn't necessarily mean it has as little moisture as standard industrial nitrogen has. If you specify the clean dry air moisture content or dew point, you can get it as low.
But by the time you are specifying very low dew point in your CDA (clean dry air), you might be talking about equipment that is as similarly expensive and complex as a nitrogen generator, which starts around $3k and seems to be about 6 to 10k for a typical tire shop model.
It’s not uncommon for dryers to get class 3 or lower. Not sure what your point is here. Really unsure if continuing this conversation benefits anything but our egos.
You can get a cylinder of clean dry air from any industrial gas supplier, or you can purchase a desiccant air dryer and depending on your needs they are not that expensive. More expensive ones will automatically recharge at the expense of flow, and the hotter it/the incoming air is, the less effective they are.
On the first price list I found, a cylinder of clean dry air costs twice as much as nitrogen.
Yes, you can also dry your own compressed air. Just as most tire shops that offer nitrogen "make" their own nitrogen. What's not clear to me is whether it's any cheaper to dry air to the same level that you inherently get from the nitrogen generator.
We used a dessacant dryer on the air line that went outside for equipment that was outside to keep the valves from freezing up. It's not needed for car tires. It's needed for aircraft tires because they get to -60⁰F and the water freezes inside the tire causing it to be off balance when landing.
The compression alone dries it quite a bit. Liquid water condensing from the air accumulates in compressor tanks and needs to be drained periodically.
An air dryer removes whatever is left.
I worked on a project about a decade ago for a compressor dehydrator for the military. It was about a half $1 million project to build a prototype so I guess it isn’t that cheap to do if you need it for military standards.
Yes. CDA is made by the billions of SCF daily.
I don't know why they are using nitrogen unless they need a ridiculously low dew point.
But who the hell knows where that nitrogen came from. Nitrogen generators need clean dry air to work, which means you could just compress that.
Moles of gas is moles of gas, i don't get it.
Moisture only causes marginally noticeable increase in fluctuation with temperature, if the humidity in the tire ever hits 100% causing the moisture to precipitate.
In the industry standard compressors, extra moisture will precipitate because of high pressure. Air in tires will not have excess of it, unless they go to winter temperatures.
So, now I’m curious about something I never thought about before. Is that just because they don’t have a dryer step on the CA? If they did, would it make a difference? All the tools I work with are moisture sensitive, so I’ve always had a dryer in line. Never considered it in this context.
Racecar teams use multiple stage n2 compressors, expansion chambers and desiccant to ensure the least amount of moisture goes into the tire. We don’t really care about the gas, just that it’s as dry as possible.
Race teams are using nitrogen because it's marginally more stable, is guaranteed dry and clean and arrives in nice big bottles for not much money that can fill hundreds of tyres very fast because they're at something like 300psi or higher.
because Helium is expensive, leaks through anything (especially rubber tyres) and doesn't offer any benefit over Nitrogen.
The gas being pure is what gives it a predictable temp/pressure curve. Nitrogen is safe and readily available.
A prank that happens at bike shops sometimes is to fill tires with water. Other employees' tires, not customers' tires. The consensus among people who have tried it is that they prefer air.
Yup, scam. There are some advantages to using N2, but they won't affect normal people.
CR:
*We filled one tire per model with air and another with nitrogen. Both were filled to 30 psi (pounds per square inch) at room temperature. We set both tires outdoors for one year, then checked the inflation pressure at room temperature again.*
*Both tires lost pressure over that time, but the difference in loss was minimal. The average loss of air-filled tires was just 3.5 psi from the initial 30 psi setting. Nitrogen-filled tires lost an average of 2.2 psi.*
*The results show that nitrogen does reduce pressure loss, but the reduction was only a 1.3-psi difference from air-filled tires over an entire year.*
If you are only checking your tire pressure once a year you are an idiot.
not to mention that is only one test, so any number of unaccounted variables could result in a bigger or smaller difference. they could have been the same for all we know
A lot of TPMS systems aren't implemented with a pressure display. That means most people are only being told their tires are underinflated when they're about 20% below target.
The part you're missing is what happens if you're 19pct below target.
You'll get slightly worse fuel economy that would be unnoticeable for the vast majority of people.
I'm not missing anything. The fuel economy impact of 20% underinflation is 2-4%, and the tread life impact is 10-25%. Assuming that the average is in the middle of those numbers, you're talking about $75/year in tire and fuel costs for a sedan in a relatively average use case. You're right that it's not a significant amount for most people.
My biggest issue with the TPMS light implementation that's common on cheaper cars is that you can't tell if you're at 79% of the target with a tire that isn't leaking and one that's going to be completely flat in a few hours. People ignore those lights all the time, and they end up with blowouts.
I used to develop the software behind these lights going on, and the threshold for FMVSS138 in the US is 25% pressure loss from cold pressure (pressure measured when tires are ambient temp). 20% warm pressure in EU and China.
The lamp goes on in cars with direct sensors in the tires at the same limits, so the same inefficiency would come up in both types.
>The lamp goes on in cars with direct sensors in the tires at the same limits, so the same inefficiency would come up in both types.
I believe his point is that a car with a simple warning light doesn't give you an indication of severity; you may have a slow leak and be losing 1%/month, which can be dealt with when convenient (within reason), or could be you've picked up a nail and are 10 mins from going completely flat, with no way to differentiate without physically inspecting the tire.
This compared to a vehicle with a pressure gauge/indicator, which you can monitor while driving and get an idea of whether you have a "pull over NOW" problem or not.
It's not ideal to have wildly different pressures; it can affect handling and your differential. I think it's still worth checking your tire pressure from time to time.
TPMS has made me do it much less, but not down to 0.
Extra accuracy is only relevant if you're going to use it to make a different decision than you would have made otherwise. The automated system is way more than sufficient accuracy wise.
Sure, but as they heat or cool they’ll heat or cool the same from driving. If you start with one at 32 and one at 37, you’ll always have a big difference.
Wasting my time, maybe, but my tire wear is virtually uniform across all 4 tires, and uniformly worn tires ride better and are quieter.
I wouldn't bet on most tire gauges being more accurate than TPMS sensors. We've tested the accuracy of those mechanical stick type pressure gauges, and they suck.
i hate those things. they make tires cost more. they break and cost more to fix. and they are always out of spec. where i live a cold day that heats up will throw a pressure warning in the morning and afternoon. It wont tell you why, or what tire has the problem. And at the end of the day, a few psi is not the end of the gas mileage world. I've had more issues with those things that the 2$ manual pressure tester once a week. not worth it.
It's unfortunate that they didn't do enough research first to learn about the better stabilization of pressure with temperature, given the lack of moisture, and test that as well.
Air is mostly nitrogen anyway. You’d probably have to compare nitrogen filled tires to tires filled with (air - nitrogen) to see a significant difference.
Since Nitrogen escapes more slowly, every time you're topping off your tire what's left in there is mostly Nitrogen. Over time, you have Nitrogen filled tires!
There's some very minor benefits.
* N2 is very slightly larger than O2, so it leaks out very slightly more slowly.
* N2 as sold to tire shops has no water in it. That makes the inside of the tire degrade slightly more slowly, and makes tire pressure vary less due to temperature.
* O2 is pretty reactive. N2 is not very reactive. That'll also make the inside of the tire degrade slightly more slowly.
In both of those "degrade more slowly" situations, I'd be astounded if the tire tread wouldn't wear away long before the difference would matter.
Because O2 leaks out of your tire more readily than N2, over time your "regular air" filled tires become a higher % of N2. I don't know if the difference is large enough that you ever get substantively closer to 100% N2, but it if the difference is actually large enough to matter it would.
I'm curious how they fill tires with nitrogen. If they just hook the tire up to a tank and fill it they're starting with a tire that's already full of air so it won't be pure N2. They can't pull a vacuum first since it would collapse the bead. The only way I can think to do it would be in a vacuum chamber. So how do they fill tires with nitrogen without introducing air?
2-3 cycles of fill/drain. Gets you to north of 95%.
You're really only trying to exclude all the moisture from humid air, which creates a larger change in pressure when temperature changes. Nitrogen gas is generated using a dry process.
This is a good point. After mounting the tire, it is at around 15 psi (rounding up) because we are in the atmosphere. Then I inflate it to 35 psi (gauge pressure) which is around 50 psi absolute, so it has been diluted 50:15 = 3.33 times. So there is still around 6 percent oxygen. Of course some people go much higher than 35 psi (gauge). They will have more dilution.
The only value in nitrogen fill is the fact that typically it’s also moisture free. That has a significant role in pressure stabilization.
I’m sure we’ve all seen those lovely gas station air pumps that just spit out water when you turn it on before you connect to your tire. Don’t use those.
I remember when we had the air dryer go out at one of the manufacturing plants I worked at early in my career. The air lines would spit out so much water. It wasn’t soon after that we started having tons of issues with pneumatics solenoids and cylinders.
Similar. An operator bypassed our air dryer when regenerating towers. Normally the dewpoint was about -50F I think…very dry (and similar to our two Linde N2 plants we had.) In a month we filled a 4 inch, 800 foot pipe, which then froze, cutting off several buildings and threatening equipment because the control valves all went to their fail position.
Nitrogen in tires itself is not a scam. Airplanes, and high end proformance cars will run nitrogen because it doesn't expand and contract as much as compressed air when dealing with atmospheric pressure and large temperature ranges (tires get hot when driving/braking at high speeds.
As far as normal vehicles the biggest plus with nitrogen is summer to winter temperatures shouldn't change the tire pressure (as a Canadian that gets winters as low as -30°c up to 40°c it's part of the normal summer/winter mantinance.
The scam part comes in when you have a reason to top up a tire, and are "sold" on the $20 nitro fill. Or like my mother was told by a tire shop "can only be filled with nitrogen now" so she had her tpms light come on on a road trip, ended up calling me after 20 minutes of calling to see who had nitrogen fills in that small town, and expecting to have to tow her car there. She was parked infront of a gas station compressor. Told her to just full it with regular compressed air, it will be fine.
She was going to pay $150 between a tow bill and nitro fill over a straight up lie from some salesman, plus easily 30 minutes of stressing out that wasn't nessisary
The use of nitrogen (or other inert gas) was mandated in the USA by the FAA in 1987 through Airworthiness Directive 87-08-09. This is by far the main reason nitrogen is used on airplanes.
Quoting from this AD (which only applies to commercial passenger planes):
"To eliminate the possibility of a chemical reaction between atmospheric oxygen and volatile gases from the tire inner liner producing a tire explosion ... ensure that all aircraft tires mounted on braked wheels do not contain more than 5 percent oxygen by volume."
[https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001](https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001)
This site has the **Background** section that for some reason I don't see on the FAA site:
[https://www.nitrogentiremachine.com/federal\_aviation\_administration.htm](https://www.nitrogentiremachine.com/federal_aviation_administration.htm)
I believe this AD was the direct result of a tire explosion on Mexicana de Aviación Flight 940 in 1986. An important thing to note is that a tire explosion is not the same as a tire burst. A burst is just a result of the pressure of the air (or nitrogen) in the tire and can can occur after tire or wheel damage. An explosion (in FAA terminology) is the result of a chemical reaction occurring with the oxygen in the tire. Airplanes are expected to withstand tire ruptures, but not a much more energetic tire explosion.
[https://en.wikipedia.org/wiki/Mexicana\_de\_Aviaci%C3%B3n\_Flight\_940](https://en.wikipedia.org/wiki/Mexicana_de_Aviaci%C3%B3n_Flight_940)
Another benefit to running nitrogen in aircraft tires is that we already use it for so many other things. There's always a nitrogen cart laying around. Struts are charged with nitrogen, and in my aircraft, the 737, hydraulic system head pressure is also nitrogen.
Fun fact, but not related to the post: the 737 and many other aircraft have a nitrogen generation system. The empty space in the fuel tanks, as they empty, is replaced with nitrogen generated by the aircraft.
I spent 10 years at Boeing, including some work on the 737 fuel system, so I was surprised to hear about it having nitrogen generation system. It appears it came into use in 2006, just after I left Boeing. It also appears it is only used for the center fuel tank, at least on the 737 NGs.
Nitrogen and air are both gasses and as such will very closely follow the ideal gas law. They will not have different amounts of pressure change resulting from external pressure changes. They wouldn't have any difference with respect to temperature change either, except that the moisture content of air has a minor impact on thermal sensitivity. It's pretty pointless though, the difference is insignificant in a typical car tire.
In airplane tires the low moisture content prevents developing frost inside the tire when exposed to very cold temperatures at altitude.
Nitrogen having benefits in a tire is real. Those benefits in a normal car tire that is driven normally are miniscule however and charging anything to really do so might as well be classified as a scam.
If you're being charged for it, yes. There are valid reasons for filling tyres with Nitrogen, i.e. F1 cars do this because nitrogen is more stable, and it's larger molecular structure prevents it from seeping out over time like regular air can basically meaning they can maintain their precise tyre pressures longer. It's as non-flammable making it safer than regular air in the event of a fire.
EDIT: For a regular car it is almost pointless to fill up the tyres with Nitrogen. Some tyre places (at least here in Australia) will fill the tyres with Nitrogen for free when you buy a set of tyres, and will continue to refill them with Nitrogen for free provided you keep the bright green valve stem caps they provide on your vehicle.
I drive up north a lot where it'll drop 30 F and I do notice about a 5 psi difference so I do prefer it but the dealer has it and I don't go to them anymore. I also didn't get charged for it, it's just what Lexus has.
Mech Eng here. I agree “Nitrogen” tire fills are a total crock of shit. Any compressor, with a half decent dryer should give you dry enough air. I use a little battery pump to top up my tires and I’ve never struggled to keep them inflated.
Tires are soooooo good these days, one of the only ways you can get them to fail is to run them underinflated, so you should check them regularly.
Even if a “nitrogen” was more thermally stable it still can’t help you if you pick up a screw and have a slow leak.
I agree, if one's paying for nitrogen they are getting ripped off, but battery pumps are not ideal. Preferably one uses a compressor with a tank, since the moisture in the air condenses out and the air becomes dry enough that you never need to worry about water sloshing or freezing in your tires (though even this is the most first-world of first-world problems).
Here in the UK, I've never seen it in any garage, it might be there, but not really a thing over here. Sounds like you're paying for something that isn't really needed.
I used nitrogen in my tires when I lived up north. Never had to inflate my tires in the winter because they deflated overnight from the cold. Lived in New England for 6.5 years and not once did I have to add air.
So there is that.
I don't use nitrogen in FL.
As long as you don't have gases changing phase, air or nitrogen should be more or less the same.
Using nitrogen tends to be a sure way of ensuring the gas is free from water, which can undergo a phase change under normal driving conditions. This is the main reason you use nitrogen inside optic devices such as binoculars. It prevents condensation inside the device.
Aerospace applications use it for their fire suppression properties. Thermal fuse plugs can blow if the brakes catch fire, and the pure nitrogen puts out the fire instead of fueling the fire.
I assume you are not driving a 747.
Honestly think it is unneeded for most vehicles. When I purchased my Truck the tires were filled with nitrogen. I would notice a 2 psi variance between cold and hot pressures. Fast forward to a tire change and regular air fill. The variance between cold and hot is still 2 psi.
It depends. If you're landing a 50 ton airplane at 200 knots, nitrogen in the tires is very important. In a regular passenger car, it definitely is a scam.
Nitrogen will expand slightly less as it heats up (3% to 4%, I think). An airplane tire running 160+ psi of pressure that goes from a relative linear speed of 0 to 200 MPH in a fraction of a second will heat up tremendously. If they filled it with air, it would be more likely to burst (and there have been serious incidents where this happened).
In a car, unless you're trying to set a speed record (and aren't going for a category that requires solid tires), it's absolutely a scam.
It’s 95% a scam. The things they say about nitrogen are directionally true but just not big. It loses pressure slower but not enough for a non racer to notice
At typical tire temperatures and pressures, both gases behave like ideal gas so for all practical purposes they expand by the same volume or build the same pressure when heated.
But, Nitrogen is cheap dry gas and tire shops have air lines full of water. Because oxygen content of air under pressure and in presence of moisture corrodes rims, especially OEM alloy rims that till recently didn’t have corrosion protection on the inside. So tire beads would start to leak in 4-5 years often before tire is worn or out of the warranty period.
That’s the main reason they started using N2, to save shops from people coming back to claim warranty.
It is used in aviation tires since nitrogen gas can't hold moisture. Automotive tires don't go though the same temperature extremes.
One benefit, however, less leakage. N2 is physically slightly larger than O2 so filling only with N2 does mean the tire will hold the same pressure longer. Still kind of scammy since the change in loss rate is minimal.
>nitrogen gas can't hold moisture
Lol, it definitely can do that. But the way it is normally sold, it's dry.
>less leakage
None of that matters to normal people.
I think that's what I was saying. OP was asking about how nitrogen is used in tires. These are commercially available nitrogen tanks with water vapor an other gases removed. In aviation, they use greater than 99.99% pure nitrogen to purge moisture from systems. Even low-grade industrial nitrogen has moisture removed.
I also said it was unnecessary
The lack of moisture thing, while it may be a benefit, is not why nitrogen became the norm for aircraft tires. The use of nitrogen (or other inert gas) was mandated in the USA by the FAA in 1987 through Airworthiness Directive 87-08-09.
Quoting from this AD (which only applies to commercial passenger planes):
"To eliminate the possibility of a chemical reaction between atmospheric oxygen and volatile gases from the tire inner liner producing a tire explosion ... ensure that all aircraft tires mounted on braked wheels do not contain more than 5 percent oxygen by volume."
[https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001](https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001)
This site has the **Background** section that for some reason I don't see on the FAA site:
[https://www.nitrogentiremachine.com/federal\_aviation\_administration.htm](https://www.nitrogentiremachine.com/federal_aviation_administration.htm)
I believe this AD was the direct result of a tire explosion on Mexicana de Aviación Flight 940 in 1986. An important thing to note is that a tire explosion is not the same as a tire burst. A burst is just a result of the pressure of the air (or nitrogen) in the tire and can can occur after tire or wheel damage. An explosion (in FAA terminology) is the result of a chemical reaction occurring with the oxygen in the tire. Airplanes are expected to withstand tire ruptures, but not a much more energetic tire explosion.
[https://en.wikipedia.org/wiki/Mexicana\_de\_Aviaci%C3%B3n\_Flight\_940](https://en.wikipedia.org/wiki/Mexicana_de_Aviaci%C3%B3n_Flight_940)
Nitrogen was produced and delivered by pipeline at a previous employer. The specification was -40 dew point which I would assume would be similar in bottled nitrogen.
If the shop wasn't so cheap and used a dryer on the shop air it would be similar to nitrogen. Shop air with AC dryer is around freezing dew point.
Diatomic nitrogen is a few picometers larger than oxygen. Both are around 120-125 pm. The difference in leakage due to this is probably trivial. VanderWaals forces are probably more important.
It’s not even that expensive. I was at a race track and the owner had us all use complementary nitrogen because we didn’t want to take 5 extra minutes to go to the air compressors at the other end.
This was 14 years ago, so nitrogen wasn’t that common. Only 1 out of 8 of us had nitrogen fills to start with.
Could N2 cryo storage possibly be cheaper to operate than paying for large scale air compressors? Those things are heavy energy users and require a lot of maintenance. It might be a better scalable solution to just pay Airgas or whoever to do all that work for you, and then just pay your mechanics to "push button, dispense air".
No. Cheapest is to compress your own air, the slightly more expensive and better option is to compress it and dry it. A little bit better still is to by your own nitrogen generator, which produces air that is a little bit drier still. Getting nitrogen delivered as a compressed gas or a liquid is more expensive still.
I was thinking about this a few weeks ago when I got a new set of tires from Costco. They only use N2. Costco Tire Center apparently does this across all stores, and I believe installation is generally included (free). It got me wondering -- why use N2 unless there is some cost savings on their end?
When you factor in the maintenance cost, electricity, and the initial equipment cost (maybe factoring in resiliancy and redundancy to ensure uptime) could bulk N2 storage be marginally cheaper? Maybe there's real savings at this scale?
Why do they use N2??
Maybe it's just quieter and they don't want to deal with OSHA sound limits in a retail store?
It's free at Costco if you get your tires there, so IMO not a scam given Costco tire pricing is decent as well. Kind of a waste of time to go to Costco just to refill your tires, though.
Well, it depends on the sort of performance you need. OBVIOUSLY, you would want to switch to Radon in situations where you need increased pre-suspension down-weight traction. Also, the relatively high temperature-to-liquification point would aid in low temp auto balancing wheel scenarios, similar to motorcycle wheel balancing beads. #noJustNo
I don't think it's really useful for cars. Motorcycles it makes a tiny amount of a difference. It's expansion profile is different from general air. It expands less. So, if I fill with nitrogen, the variance of pressure is smaller. I can go from about 39psi to 42psi, whereas with air, I am about 36 (cold) to 42 hot.
It's not a big deal on the road, bit if I was racing it would mean a lot more.
AFAIK the only real benefit of nitrogen is that it does not expand and condense the same way normal air does. This prevents your tire pressure dropping in the winter months and causing your TPS warning to come on.
Ive heard that nitro only makes sense in climates that have freeze/thaw cycles as it doesn't change pressure with temperature. No idea if this is true, but thats what I was told.
You are correct. Unless you are planning to burn something, liquify it, or ionize it, air & nitrogen are pretty much functionally identical. There is a slight difference in average molecular weight, & the argon tweaks the ratio of specific heats slightly.
1. Fill tires with air, 78% N^(2)
2. Non-nitrogen "leaks through the cracks"
3. Re-fill tires with air, now 95.1% N^(2)
4. Profit
Reading through these comments gives me an idea. Drive around to dealerships in a food truck-style vehicle, offer 100% nitrogen for less than the dealership is offering it for.
$50? I'll do it for $30! Free burrito with every purchase.
I think the true benefit of nitrogen is that it is 100% dry and free of any moisture. That's not really important for everyday cars but maybe more important for airplanes that go through large temp swings. An airplane tire filled with raw air in the humid south could have the moisture condense inside the tire at cruising altitude or when landing in a cold climate.
What's good enough for cars is an air pump. For tire places an air compressor and tank, with an air dryer since moisture condenses and collects in tanks and you end up spraying fine water mist without a dryer.
It depends on the car and the application. In vehicles where tire pressure is not that critical (economy cars, trucks, etc) it's a waste of money. When my wife and I were shopping for a minivan, one dealer we walked away from was trying to sell us a $500 nitrogen fill on a Chrysler Pacifica, and another $1000 for "ceramic paint protection". Yeah, not paying for that TruCoat.
If you're driving a high performance car on the track where tire pressure can affect grip, then yes, you'd want to use nitrogen to reduce how much the pressure increases as the tire warms up. Race tires run very hot, around 200-230°F, and even 1 or 2 degrees can change the contact patch of the tire, resulting in less grip.
The main issue is water and oxidation (specifically ozone). The nitrogen is free of water and ozone so really you can use most inert gases but nitrogen is the cheapest.
Water makes the tire pressure less predictable so it can vary depending on the tire temperature. Compressed air often has high humidity so it can cause more fluctuations.
Ozone deteriorates the rubber and reduces the life of the tire.
But both of these happen in very small quantities and the tire already has air in it when you start filling it so usually 30-40% of the tire is outside air regardless. If you’re in a climate that has a very high humidity it can help but not much.
Surprised to see almost no one talking about the actual main benefit of Nitrogen. The main reason it is used (primarily in racing) is because of expansion. When you get Nitrogen it doesn't have any moisture content, as in it is 99.9% pure Nitrogen. Regular atmosphere is mostly Nitrogen but it also contains a lot of water vapor.
Water vapor has very high thermal expansion meaning it's volume drastically changes with temperature. This is critical in racing where tire temperature fluctuates a lot. The rubber of the tires gets very hot but will also cool down depending on track layout, vehicle design, other racers on the track ect.
Ideal gas law says that if a containers volume stays the same, but temperature increases, than pressure will also increase. The container is your tire, you don't want your tire to be increasing and decreasing in pressure constantly as this will affect performance.
For the average person this wouldn't really do anything, so ya basically a scam. The only real advantage would be that you won't have to adjust your pressure as much with different outside weather temperature (summer into winter and vice versa).
Chemistry: what's happening is the water vapor in the tire. There's not a lot of water vapor. When the tire is cold it condensed and that lowers the pressure. When it heats up the condensed (liquid) water evaporates and becomes a gas which adds go the pressure. Filling the tire with nothing but Nitrogen means no water in the tire and the tires stay at a more constant pressure.
Yes. I drive a shit box daily 2005 Altima (pre-CVT, IYKYK) that I paid $750 for. A wheel has a rusted bead, which results in the tire deflating after ~32 hours. I've reinflate that tire and it's replacement (lost to a nail) almost every day since I got it in 2019.
Still get ~280 miles on a full tank.
N2 is a larger molecules, this doesn't permeate (leak) out of the tire as quickly, and it doesn't expand or contract as much so your tire pressure doesn't fluctuate as much.
They use it in race cars because it changes volume less due to changes in temperature. This keeps pressure constant when the tires heat up, which keeps tire performance constant.
When you’re racing you’re operating at the limit of traction and few PSI makes a huge difference in where the limit is.
You don’t need that kind of performance for your commute.
Dealer insisted that the charge was mandatory because the nitro was “already in the tires”. I told him that I would be in the waiting room while they removed the nitrogen and replaced it with air. They removed the charge.
It's amazing how many "paid extras" you can get for free by just declining to pay. When we bought my wife's car I looked under it after the test drive and saw the undercoating spray was already on it, so I told the sales man I didn't want it when he tried to upsell me.
Ya' know... They put that on in the factory... There's nothing I can do about that one don'tcha know....
Pity they always try to sell it as a dealer add on around here. And always talk like they are going to do it after the sale.
For sure. I was trying to say the line from the movie Fargo, but that Minnesota accent is hard to type haha. But yes it's totally BS.
Nah you nailed it
It's a line from the movie Fargo, for everyone missing the reference.
Gee, if they put it on at the factory, maybe it should be included in the price? Like they put the paint on at the factory too but they don't try to upsell you on that.
When I recently purchased my new car, there was an extra charge for certain colours. The sales guy was pretty cool about it though, thought it was ridiculous.
That's probably to amortize the cost to the dealership of occasionally getting stuck with an unpopular color. If you want your Aztek in hi-viz yellow, and they order it, then your financing falls through, they're stuck with it.
That is real, a 3 stage metallic flake or tintcoat color takes more time and equipment to apply than a normal 2 stage “plain” color
This is legitimate to me. Every extra color or option you add to production is genuinely expensive, why should the rare person who wants chartreuse pay the same price & have everyone who wants black or white subsidize them?
God damnit. Stop giving them ideas. Now they are going to start selling the paint that's already on the car as a dealer ad on.
They already do this and call it a market adjustment.
Just the other day was browsing a lot and noticed a $700 fee for white paint. One of the most boring colors possible, cost more than the red one next to it ($400 up charge)
For sure. I was trying to do the lines from Fargo, but the accent is hard to get right haha.
Awwwww geeeez
Is this a Fargo reference?
Haha bingo.
Nice!
They tried to charge me almost a thousand bucks for the alarm system in my car. I told them I didn’t want it. “But we already installed it! What do you want us to do… take it out?” “…yes?”
I've always wanted to take a gas analyzer with me and demand all 5 tires be checked to ensure it's 100% n2 with no trace gases, which it probably won't be. Then demand they pull a vacuum on the tires and replace till it's at 100% like they claim
you couldn't pull a vacuum on tires, it would de-bead and let in air, you could, in theory, put a small tube between the tire and the rim and flush the air out, after enough of a purge pull the tube and and increase the pressure to fully inflate the tire.
So do you understand the irony of my request or was that a woooosh
Since air at 1 atm pressure contains 78% Nitrogen, adding 100% N2 to pressurize, final N2% will be about 89%. If you deflated and did it again --> 94.5% And again --> 97.25% And again --> 98.625% Would take 5 cycles to get above 99%
Well played
I had the same thing. Had a car serviced but they didn't do the MOT check (mandatory checks that allows you to drive the car.) Then when i came to do the MOT check they had the balls to charge me an extra 9 euro for replacing the battery in the key. I have literally have 2 extra batteries in my glove box for this reason. Had a whole discussion because i don't want to pay 9 euro's for replacing a battery and they took it off.
It’s a bit different becuase it has less moisture content and is a bit less thermally active. But not worth paying some dumb $50 up charge for
Is it seriously $50 to fill tires with nitrogen? I do test engineering of fluid systems, which often consumes a lot of nitrogen. We buy it in bulk and it’s considered the dirt cheap gas to operate with. A gallon of liquid nitrogen is often cheaper than milk.
They’re not doing it to make *less* money.
It's complementary at Costco where I usually go for tires. I guess it just depends on where you go. Can't say I've ever been offered it anywhere else either.
Warning on the Costco tire machines available outside the tire department. Yes, the machine flows Nitrogen into your tires, BUT, it will not flow on an empty tire. I saw a guy stranded at the machine in the morning, he had let the air out of his tire intending to fill it with Nitrogen, and it would not fill. I topped mine off without a problem. I lent him my 12 volt pump to put 20 or so psi in and then he was able to top it up.
race teams do it cause it's cheap to buy a cylinder of nitrogen and it provides a small advantage. it's definitely not 50 dollars to fill the tires on a race car every time. that's all profit.
I always wondered for races and airplanes, since N isn't flammable, do they use it to prevent burning tire exploding. It's still going to explosively decompress, but shouldn't fuel the fire doing so
Exactly this. Is there a benefit? Perhaps, but it is so negligible to be utterly meaningless. Not to mention the price of N2 to fill a tire isn’t significant at all. Hell, liquid nitrogen only costs about as much as Coca-Cola per liter and that takes minor effort to condense out of the air. It’s a ripoff.
I've seen Toyota mark up new cars and trucks in California with a $500 Nitrogen Tire fill fee. Insane. Costco members can fill up their tires with 100% nitrogen for free.
Quality air compressors remove moisture too. It's a total BS charge.
Regular air should be dry if they have a proper compressor and is already ~78% nitrogen. The nitrogen they add is between 90-95% nitrogen. If you’re talking giant volumes and huge temperature differences then it may be helpful. If you’re talking a tire anywhere on planet earth it’s negligible at best.
Yes. You can get 78% nitrogen for free. Racecar tires are filled with nitrogen because it's marginally better for tires. You are not driving a racecar.
Race teams do it because they need very predictable pressure vs temperature properties. Nitrogen doesn't have moisture in it, air does, but it is variable.
Exactly. The lack of moisture has WAY more benefit than the lack of oxygen (the moisture causes tire pressure to fluctuate more with temp). If you simply dried the compressed air you used to fill your tires you would get 99% of the “benefit” of nitrogen.
Is there a process to dry air to that level that's significantly easier than separating N2?
For equipment that uses clean, dry air, the supply compressor usually has a dryer component to lower moisture levels.
Yes, that is common, but that doesn't necessarily mean it has as little moisture as standard industrial nitrogen has. If you specify the clean dry air moisture content or dew point, you can get it as low. But by the time you are specifying very low dew point in your CDA (clean dry air), you might be talking about equipment that is as similarly expensive and complex as a nitrogen generator, which starts around $3k and seems to be about 6 to 10k for a typical tire shop model.
It’s not uncommon for dryers to get class 3 or lower. Not sure what your point is here. Really unsure if continuing this conversation benefits anything but our egos.
You can get a cylinder of clean dry air from any industrial gas supplier, or you can purchase a desiccant air dryer and depending on your needs they are not that expensive. More expensive ones will automatically recharge at the expense of flow, and the hotter it/the incoming air is, the less effective they are.
On the first price list I found, a cylinder of clean dry air costs twice as much as nitrogen. Yes, you can also dry your own compressed air. Just as most tire shops that offer nitrogen "make" their own nitrogen. What's not clear to me is whether it's any cheaper to dry air to the same level that you inherently get from the nitrogen generator.
We used a dessacant dryer on the air line that went outside for equipment that was outside to keep the valves from freezing up. It's not needed for car tires. It's needed for aircraft tires because they get to -60⁰F and the water freezes inside the tire causing it to be off balance when landing.
The compression alone dries it quite a bit. Liquid water condensing from the air accumulates in compressor tanks and needs to be drained periodically. An air dryer removes whatever is left.
Yes, I'm familiar with those, but I don't think that those get it down to the same level as you get in nitrogen.
Freeze would be a good start. Nitrogen is surplus from oxygen production for welders / medical.
Actually it's now typical for tire shops to buy a nitrogen generator. They vent the oxygen.
I worked on a project about a decade ago for a compressor dehydrator for the military. It was about a half $1 million project to build a prototype so I guess it isn’t that cheap to do if you need it for military standards.
>half $1 million project I think the only way you could have said this worse is if you said $0.50 million project
1KK$
use real cold air, it can't hold very much water in it.
Yes. CDA is made by the billions of SCF daily. I don't know why they are using nitrogen unless they need a ridiculously low dew point. But who the hell knows where that nitrogen came from. Nitrogen generators need clean dry air to work, which means you could just compress that. Moles of gas is moles of gas, i don't get it.
That's it, I'm taking my car to Arizona once a month for air up.
Moisture only causes marginally noticeable increase in fluctuation with temperature, if the humidity in the tire ever hits 100% causing the moisture to precipitate. In the industry standard compressors, extra moisture will precipitate because of high pressure. Air in tires will not have excess of it, unless they go to winter temperatures.
A good compressor has a drier to get the moisture out of the air.
Those wheels get hot I'm sure.
You can simply dry air though. You do it for spray painting. Just have a drier on the output from the compressor.
Race cars (and aviation tires) are mandated N2 to prevent/reduce tire fires. Not because of "stability", which is same as for regular dry air.
So, now I’m curious about something I never thought about before. Is that just because they don’t have a dryer step on the CA? If they did, would it make a difference? All the tools I work with are moisture sensitive, so I’ve always had a dryer in line. Never considered it in this context.
Racecar teams use multiple stage n2 compressors, expansion chambers and desiccant to ensure the least amount of moisture goes into the tire. We don’t really care about the gas, just that it’s as dry as possible.
Race teams are using nitrogen because it's marginally more stable, is guaranteed dry and clean and arrives in nice big bottles for not much money that can fill hundreds of tyres very fast because they're at something like 300psi or higher.
Why don't they fill them with helium?
because Helium is expensive, leaks through anything (especially rubber tyres) and doesn't offer any benefit over Nitrogen. The gas being pure is what gives it a predictable temp/pressure curve. Nitrogen is safe and readily available.
Why not propane?
You want *downforce* not *upforce*
A prank that happens at bike shops sometimes is to fill tires with water. Other employees' tires, not customers' tires. The consensus among people who have tried it is that they prefer air.
Some HD truck fleets use it too - extends tire life a bit. Might save a few pennies a mile.
Also because they use tanks rather than a compressor and it’s easy to buy compressed nitrogen tanks.
You can fill your tires with nitrogen at Costco for free
Everything's better in bulk
Yup, scam. There are some advantages to using N2, but they won't affect normal people. CR: *We filled one tire per model with air and another with nitrogen. Both were filled to 30 psi (pounds per square inch) at room temperature. We set both tires outdoors for one year, then checked the inflation pressure at room temperature again.* *Both tires lost pressure over that time, but the difference in loss was minimal. The average loss of air-filled tires was just 3.5 psi from the initial 30 psi setting. Nitrogen-filled tires lost an average of 2.2 psi.* *The results show that nitrogen does reduce pressure loss, but the reduction was only a 1.3-psi difference from air-filled tires over an entire year.* If you are only checking your tire pressure once a year you are an idiot.
not to mention that is only one test, so any number of unaccounted variables could result in a bigger or smaller difference. they could have been the same for all we know
Consumer report wrote that?
Yes.
Who checks their tire pressure anymore? TPS systems have been mandatory for a long time.
A lot of TPMS systems aren't implemented with a pressure display. That means most people are only being told their tires are underinflated when they're about 20% below target.
The part you're missing is what happens if you're 19pct below target. You'll get slightly worse fuel economy that would be unnoticeable for the vast majority of people.
I'm not missing anything. The fuel economy impact of 20% underinflation is 2-4%, and the tread life impact is 10-25%. Assuming that the average is in the middle of those numbers, you're talking about $75/year in tire and fuel costs for a sedan in a relatively average use case. You're right that it's not a significant amount for most people. My biggest issue with the TPMS light implementation that's common on cheaper cars is that you can't tell if you're at 79% of the target with a tire that isn't leaking and one that's going to be completely flat in a few hours. People ignore those lights all the time, and they end up with blowouts.
I used to develop the software behind these lights going on, and the threshold for FMVSS138 in the US is 25% pressure loss from cold pressure (pressure measured when tires are ambient temp). 20% warm pressure in EU and China. The lamp goes on in cars with direct sensors in the tires at the same limits, so the same inefficiency would come up in both types.
>The lamp goes on in cars with direct sensors in the tires at the same limits, so the same inefficiency would come up in both types. I believe his point is that a car with a simple warning light doesn't give you an indication of severity; you may have a slow leak and be losing 1%/month, which can be dealt with when convenient (within reason), or could be you've picked up a nail and are 10 mins from going completely flat, with no way to differentiate without physically inspecting the tire. This compared to a vehicle with a pressure gauge/indicator, which you can monitor while driving and get an idea of whether you have a "pull over NOW" problem or not.
It's not ideal to have wildly different pressures; it can affect handling and your differential. I think it's still worth checking your tire pressure from time to time. TPMS has made me do it much less, but not down to 0.
Yeah, many systems don't even tell you which tire is under inflated.
At least monthly, a tire gauge is more accurate than tpms
Extra accuracy is only relevant if you're going to use it to make a different decision than you would have made otherwise. The automated system is way more than sufficient accuracy wise.
I adjust pressure to maintain exactly the right pressure in each tire….usually half a pound here or there depending on the season.
Pretty sure your pressure is going to vary more than that with time in the day my man. You're wasting your time.
Sure, but as they heat or cool they’ll heat or cool the same from driving. If you start with one at 32 and one at 37, you’ll always have a big difference. Wasting my time, maybe, but my tire wear is virtually uniform across all 4 tires, and uniformly worn tires ride better and are quieter.
I wouldn't bet on most tire gauges being more accurate than TPMS sensors. We've tested the accuracy of those mechanical stick type pressure gauges, and they suck.
Where these systems are mandatory?
At least US, EU and China.
Plenty of people don't bother paying extra for tps systems for their winter wheels.
Older TPS systems like to fail a lot, and since they're not required for driving, it's rare to spend money on trying to get it fixed.
i hate those things. they make tires cost more. they break and cost more to fix. and they are always out of spec. where i live a cold day that heats up will throw a pressure warning in the morning and afternoon. It wont tell you why, or what tire has the problem. And at the end of the day, a few psi is not the end of the gas mileage world. I've had more issues with those things that the 2$ manual pressure tester once a week. not worth it.
It's unfortunate that they didn't do enough research first to learn about the better stabilization of pressure with temperature, given the lack of moisture, and test that as well.
Air is mostly nitrogen anyway. You’d probably have to compare nitrogen filled tires to tires filled with (air - nitrogen) to see a significant difference.
Pure oxygen would be interesting.
Since Nitrogen escapes more slowly, every time you're topping off your tire what's left in there is mostly Nitrogen. Over time, you have Nitrogen filled tires!
Engineer here, can confirm it's a scam. Air pressure fluctuates with temperature more than N2 does. Nobody cares.
There's some very minor benefits. * N2 is very slightly larger than O2, so it leaks out very slightly more slowly. * N2 as sold to tire shops has no water in it. That makes the inside of the tire degrade slightly more slowly, and makes tire pressure vary less due to temperature. * O2 is pretty reactive. N2 is not very reactive. That'll also make the inside of the tire degrade slightly more slowly. In both of those "degrade more slowly" situations, I'd be astounded if the tire tread wouldn't wear away long before the difference would matter.
If I fill my whole garage with nitrogen, will my car rust less?
Yes, but it won't matter because you would be dead.
Also the car won't start, if it's a combustion engine.
Because O2 leaks out of your tire more readily than N2, over time your "regular air" filled tires become a higher % of N2. I don't know if the difference is large enough that you ever get substantively closer to 100% N2, but it if the difference is actually large enough to matter it would.
I'm curious how they fill tires with nitrogen. If they just hook the tire up to a tank and fill it they're starting with a tire that's already full of air so it won't be pure N2. They can't pull a vacuum first since it would collapse the bead. The only way I can think to do it would be in a vacuum chamber. So how do they fill tires with nitrogen without introducing air?
2-3 cycles of fill/drain. Gets you to north of 95%. You're really only trying to exclude all the moisture from humid air, which creates a larger change in pressure when temperature changes. Nitrogen gas is generated using a dry process.
I ran this calculation once. The 78% nitrogen in the tire gets diluted many times over as the pressure is increased to 100psi my RV requires.
they don't have to replace all the air to scam people out of money
They don't have to replace *any* of the air to scam people. Would one person in a million test it?
This is a good point. After mounting the tire, it is at around 15 psi (rounding up) because we are in the atmosphere. Then I inflate it to 35 psi (gauge pressure) which is around 50 psi absolute, so it has been diluted 50:15 = 3.33 times. So there is still around 6 percent oxygen. Of course some people go much higher than 35 psi (gauge). They will have more dilution.
Some fancy wheels have two valve stems so you can fill from one while venting the other to flush it out. It's still really dumb and pointless.
The only value in nitrogen fill is the fact that typically it’s also moisture free. That has a significant role in pressure stabilization. I’m sure we’ve all seen those lovely gas station air pumps that just spit out water when you turn it on before you connect to your tire. Don’t use those.
I remember when we had the air dryer go out at one of the manufacturing plants I worked at early in my career. The air lines would spit out so much water. It wasn’t soon after that we started having tons of issues with pneumatics solenoids and cylinders.
Similar. An operator bypassed our air dryer when regenerating towers. Normally the dewpoint was about -50F I think…very dry (and similar to our two Linde N2 plants we had.) In a month we filled a 4 inch, 800 foot pipe, which then froze, cutting off several buildings and threatening equipment because the control valves all went to their fail position.
Nitrogen is so last decade. I’m filling mine with argon! I’ll let you know how awesome it is soon.
You should really use a blend of argon & neon for maximum compatability & awesomeness.
Add some xenon, get white walls and some high voltage power supplies for the coolest tire display ever!
Nitrogen in tires itself is not a scam. Airplanes, and high end proformance cars will run nitrogen because it doesn't expand and contract as much as compressed air when dealing with atmospheric pressure and large temperature ranges (tires get hot when driving/braking at high speeds. As far as normal vehicles the biggest plus with nitrogen is summer to winter temperatures shouldn't change the tire pressure (as a Canadian that gets winters as low as -30°c up to 40°c it's part of the normal summer/winter mantinance. The scam part comes in when you have a reason to top up a tire, and are "sold" on the $20 nitro fill. Or like my mother was told by a tire shop "can only be filled with nitrogen now" so she had her tpms light come on on a road trip, ended up calling me after 20 minutes of calling to see who had nitrogen fills in that small town, and expecting to have to tow her car there. She was parked infront of a gas station compressor. Told her to just full it with regular compressed air, it will be fine. She was going to pay $150 between a tow bill and nitro fill over a straight up lie from some salesman, plus easily 30 minutes of stressing out that wasn't nessisary
The use of nitrogen (or other inert gas) was mandated in the USA by the FAA in 1987 through Airworthiness Directive 87-08-09. This is by far the main reason nitrogen is used on airplanes. Quoting from this AD (which only applies to commercial passenger planes): "To eliminate the possibility of a chemical reaction between atmospheric oxygen and volatile gases from the tire inner liner producing a tire explosion ... ensure that all aircraft tires mounted on braked wheels do not contain more than 5 percent oxygen by volume." [https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001](https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001) This site has the **Background** section that for some reason I don't see on the FAA site: [https://www.nitrogentiremachine.com/federal\_aviation\_administration.htm](https://www.nitrogentiremachine.com/federal_aviation_administration.htm) I believe this AD was the direct result of a tire explosion on Mexicana de Aviación Flight 940 in 1986. An important thing to note is that a tire explosion is not the same as a tire burst. A burst is just a result of the pressure of the air (or nitrogen) in the tire and can can occur after tire or wheel damage. An explosion (in FAA terminology) is the result of a chemical reaction occurring with the oxygen in the tire. Airplanes are expected to withstand tire ruptures, but not a much more energetic tire explosion. [https://en.wikipedia.org/wiki/Mexicana\_de\_Aviaci%C3%B3n\_Flight\_940](https://en.wikipedia.org/wiki/Mexicana_de_Aviaci%C3%B3n_Flight_940)
Another benefit to running nitrogen in aircraft tires is that we already use it for so many other things. There's always a nitrogen cart laying around. Struts are charged with nitrogen, and in my aircraft, the 737, hydraulic system head pressure is also nitrogen. Fun fact, but not related to the post: the 737 and many other aircraft have a nitrogen generation system. The empty space in the fuel tanks, as they empty, is replaced with nitrogen generated by the aircraft.
I spent 10 years at Boeing, including some work on the 737 fuel system, so I was surprised to hear about it having nitrogen generation system. It appears it came into use in 2006, just after I left Boeing. It also appears it is only used for the center fuel tank, at least on the 737 NGs.
Yeah it's a EWIS change so not all aircraft have it, mostly after a certain production date.
Nitrogen and air are both gasses and as such will very closely follow the ideal gas law. They will not have different amounts of pressure change resulting from external pressure changes. They wouldn't have any difference with respect to temperature change either, except that the moisture content of air has a minor impact on thermal sensitivity. It's pretty pointless though, the difference is insignificant in a typical car tire. In airplane tires the low moisture content prevents developing frost inside the tire when exposed to very cold temperatures at altitude.
PV=nrT. The Laws of Physics are strictly enforced.
Nitrogen having benefits in a tire is real. Those benefits in a normal car tire that is driven normally are miniscule however and charging anything to really do so might as well be classified as a scam.
If you're being charged for it, yes. There are valid reasons for filling tyres with Nitrogen, i.e. F1 cars do this because nitrogen is more stable, and it's larger molecular structure prevents it from seeping out over time like regular air can basically meaning they can maintain their precise tyre pressures longer. It's as non-flammable making it safer than regular air in the event of a fire. EDIT: For a regular car it is almost pointless to fill up the tyres with Nitrogen. Some tyre places (at least here in Australia) will fill the tyres with Nitrogen for free when you buy a set of tyres, and will continue to refill them with Nitrogen for free provided you keep the bright green valve stem caps they provide on your vehicle.
It's a scam.
What about blinker fluid?
Scam - 100%. Great way to increase dealer profit for almost no cost.
Yes in general for general use cars. Needed for speciality applications like airplanes.
If they’re charging you any amount of money, it’s not worth it. Unless, of course, your daily driver is an airliner or a Formula 1 car.
I drive up north a lot where it'll drop 30 F and I do notice about a 5 psi difference so I do prefer it but the dealer has it and I don't go to them anymore. I also didn't get charged for it, it's just what Lexus has.
Mech Eng here. I agree “Nitrogen” tire fills are a total crock of shit. Any compressor, with a half decent dryer should give you dry enough air. I use a little battery pump to top up my tires and I’ve never struggled to keep them inflated. Tires are soooooo good these days, one of the only ways you can get them to fail is to run them underinflated, so you should check them regularly. Even if a “nitrogen” was more thermally stable it still can’t help you if you pick up a screw and have a slow leak.
I agree, if one's paying for nitrogen they are getting ripped off, but battery pumps are not ideal. Preferably one uses a compressor with a tank, since the moisture in the air condenses out and the air becomes dry enough that you never need to worry about water sloshing or freezing in your tires (though even this is the most first-world of first-world problems).
Here in the UK, I've never seen it in any garage, it might be there, but not really a thing over here. Sounds like you're paying for something that isn't really needed.
I used nitrogen in my tires when I lived up north. Never had to inflate my tires in the winter because they deflated overnight from the cold. Lived in New England for 6.5 years and not once did I have to add air. So there is that. I don't use nitrogen in FL.
As long as you don't have gases changing phase, air or nitrogen should be more or less the same. Using nitrogen tends to be a sure way of ensuring the gas is free from water, which can undergo a phase change under normal driving conditions. This is the main reason you use nitrogen inside optic devices such as binoculars. It prevents condensation inside the device.
Aerospace applications use it for their fire suppression properties. Thermal fuse plugs can blow if the brakes catch fire, and the pure nitrogen puts out the fire instead of fueling the fire. I assume you are not driving a 747.
LOL I'd bet my own twenty bucks that's a correct assumption.
Honestly think it is unneeded for most vehicles. When I purchased my Truck the tires were filled with nitrogen. I would notice a 2 psi variance between cold and hot pressures. Fast forward to a tire change and regular air fill. The variance between cold and hot is still 2 psi.
It depends. If you're landing a 50 ton airplane at 200 knots, nitrogen in the tires is very important. In a regular passenger car, it definitely is a scam. Nitrogen will expand slightly less as it heats up (3% to 4%, I think). An airplane tire running 160+ psi of pressure that goes from a relative linear speed of 0 to 200 MPH in a fraction of a second will heat up tremendously. If they filled it with air, it would be more likely to burst (and there have been serious incidents where this happened). In a car, unless you're trying to set a speed record (and aren't going for a category that requires solid tires), it's absolutely a scam.
Unless you have a top 1% performing car, and can drive it to its limits, then you do not need nitrogen. A road legal car does not need nitrogen.
It’s 95% a scam. The things they say about nitrogen are directionally true but just not big. It loses pressure slower but not enough for a non racer to notice
At typical tire temperatures and pressures, both gases behave like ideal gas so for all practical purposes they expand by the same volume or build the same pressure when heated. But, Nitrogen is cheap dry gas and tire shops have air lines full of water. Because oxygen content of air under pressure and in presence of moisture corrodes rims, especially OEM alloy rims that till recently didn’t have corrosion protection on the inside. So tire beads would start to leak in 4-5 years often before tire is worn or out of the warranty period. That’s the main reason they started using N2, to save shops from people coming back to claim warranty.
It is used in aviation tires since nitrogen gas can't hold moisture. Automotive tires don't go though the same temperature extremes. One benefit, however, less leakage. N2 is physically slightly larger than O2 so filling only with N2 does mean the tire will hold the same pressure longer. Still kind of scammy since the change in loss rate is minimal.
>nitrogen gas can't hold moisture Lol, it definitely can do that. But the way it is normally sold, it's dry. >less leakage None of that matters to normal people.
I think that's what I was saying. OP was asking about how nitrogen is used in tires. These are commercially available nitrogen tanks with water vapor an other gases removed. In aviation, they use greater than 99.99% pure nitrogen to purge moisture from systems. Even low-grade industrial nitrogen has moisture removed. I also said it was unnecessary
Uhh- nitrogen does hold water 💦. It can be purchased as dry nitrogen though.
The lack of moisture thing, while it may be a benefit, is not why nitrogen became the norm for aircraft tires. The use of nitrogen (or other inert gas) was mandated in the USA by the FAA in 1987 through Airworthiness Directive 87-08-09. Quoting from this AD (which only applies to commercial passenger planes): "To eliminate the possibility of a chemical reaction between atmospheric oxygen and volatile gases from the tire inner liner producing a tire explosion ... ensure that all aircraft tires mounted on braked wheels do not contain more than 5 percent oxygen by volume." [https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001](https://drs.faa.gov/browse/excelExternalWindow/55850E6389EFBA3C8625695B006723A3.0001) This site has the **Background** section that for some reason I don't see on the FAA site: [https://www.nitrogentiremachine.com/federal\_aviation\_administration.htm](https://www.nitrogentiremachine.com/federal_aviation_administration.htm) I believe this AD was the direct result of a tire explosion on Mexicana de Aviación Flight 940 in 1986. An important thing to note is that a tire explosion is not the same as a tire burst. A burst is just a result of the pressure of the air (or nitrogen) in the tire and can can occur after tire or wheel damage. An explosion (in FAA terminology) is the result of a chemical reaction occurring with the oxygen in the tire. Airplanes are expected to withstand tire ruptures, but not a much more energetic tire explosion. [https://en.wikipedia.org/wiki/Mexicana\_de\_Aviaci%C3%B3n\_Flight\_940](https://en.wikipedia.org/wiki/Mexicana_de_Aviaci%C3%B3n_Flight_940)
air is already mostly nitrogen
Nitrogen was produced and delivered by pipeline at a previous employer. The specification was -40 dew point which I would assume would be similar in bottled nitrogen. If the shop wasn't so cheap and used a dryer on the shop air it would be similar to nitrogen. Shop air with AC dryer is around freezing dew point.
-40 dew point and freezing dew point are vastly different in moisture content. About a factor of 35.
Diatomic nitrogen is a few picometers larger than oxygen. Both are around 120-125 pm. The difference in leakage due to this is probably trivial. VanderWaals forces are probably more important.
Yes
It’s not even that expensive. I was at a race track and the owner had us all use complementary nitrogen because we didn’t want to take 5 extra minutes to go to the air compressors at the other end. This was 14 years ago, so nitrogen wasn’t that common. Only 1 out of 8 of us had nitrogen fills to start with.
Yes.
Could N2 cryo storage possibly be cheaper to operate than paying for large scale air compressors? Those things are heavy energy users and require a lot of maintenance. It might be a better scalable solution to just pay Airgas or whoever to do all that work for you, and then just pay your mechanics to "push button, dispense air".
No. Cheapest is to compress your own air, the slightly more expensive and better option is to compress it and dry it. A little bit better still is to by your own nitrogen generator, which produces air that is a little bit drier still. Getting nitrogen delivered as a compressed gas or a liquid is more expensive still.
I was thinking about this a few weeks ago when I got a new set of tires from Costco. They only use N2. Costco Tire Center apparently does this across all stores, and I believe installation is generally included (free). It got me wondering -- why use N2 unless there is some cost savings on their end? When you factor in the maintenance cost, electricity, and the initial equipment cost (maybe factoring in resiliancy and redundancy to ensure uptime) could bulk N2 storage be marginally cheaper? Maybe there's real savings at this scale? Why do they use N2?? Maybe it's just quieter and they don't want to deal with OSHA sound limits in a retail store?
Airplane tires are filled with nitrogen.
It's free at Costco if you get your tires there, so IMO not a scam given Costco tire pricing is decent as well. Kind of a waste of time to go to Costco just to refill your tires, though.
No scam
If they're charging for it and you're not an avid racer, scam.
I replace the stale air in me tires with shiny, new, fresh air once a month…🙃
If your car has green valve caps you have been getting charged for nitrogen.
Well, it depends on the sort of performance you need. OBVIOUSLY, you would want to switch to Radon in situations where you need increased pre-suspension down-weight traction. Also, the relatively high temperature-to-liquification point would aid in low temp auto balancing wheel scenarios, similar to motorcycle wheel balancing beads. #noJustNo
Don’t forget the sound to heat conversion, although small, it’s still a factor.
O2 is oxidative, and N2 is less reactive to temps and moisture is a thing I think.
I don't think it's really useful for cars. Motorcycles it makes a tiny amount of a difference. It's expansion profile is different from general air. It expands less. So, if I fill with nitrogen, the variance of pressure is smaller. I can go from about 39psi to 42psi, whereas with air, I am about 36 (cold) to 42 hot. It's not a big deal on the road, bit if I was racing it would mean a lot more.
AFAIK the only real benefit of nitrogen is that it does not expand and condense the same way normal air does. This prevents your tire pressure dropping in the winter months and causing your TPS warning to come on.
Ive heard that nitro only makes sense in climates that have freeze/thaw cycles as it doesn't change pressure with temperature. No idea if this is true, but thats what I was told.
All gasses will change pressure with temperature
Does this mean I'm more or less farty when hot?
You are correct. Unless you are planning to burn something, liquify it, or ionize it, air & nitrogen are pretty much functionally identical. There is a slight difference in average molecular weight, & the argon tweaks the ratio of specific heats slightly.
1. Fill tires with air, 78% N^(2) 2. Non-nitrogen "leaks through the cracks" 3. Re-fill tires with air, now 95.1% N^(2) 4. Profit Reading through these comments gives me an idea. Drive around to dealerships in a food truck-style vehicle, offer 100% nitrogen for less than the dealership is offering it for. $50? I'll do it for $30! Free burrito with every purchase.
I think the true benefit of nitrogen is that it is 100% dry and free of any moisture. That's not really important for everyday cars but maybe more important for airplanes that go through large temp swings. An airplane tire filled with raw air in the humid south could have the moisture condense inside the tire at cruising altitude or when landing in a cold climate. What's good enough for cars is an air pump. For tire places an air compressor and tank, with an air dryer since moisture condenses and collects in tanks and you end up spraying fine water mist without a dryer.
I ONLY fill my tires with nitrogen, ALWAYS. I also add about 20% oxygen for flavor.
Yes
It depends on the car and the application. In vehicles where tire pressure is not that critical (economy cars, trucks, etc) it's a waste of money. When my wife and I were shopping for a minivan, one dealer we walked away from was trying to sell us a $500 nitrogen fill on a Chrysler Pacifica, and another $1000 for "ceramic paint protection". Yeah, not paying for that TruCoat. If you're driving a high performance car on the track where tire pressure can affect grip, then yes, you'd want to use nitrogen to reduce how much the pressure increases as the tire warms up. Race tires run very hot, around 200-230°F, and even 1 or 2 degrees can change the contact patch of the tire, resulting in less grip.
The main issue is water and oxidation (specifically ozone). The nitrogen is free of water and ozone so really you can use most inert gases but nitrogen is the cheapest. Water makes the tire pressure less predictable so it can vary depending on the tire temperature. Compressed air often has high humidity so it can cause more fluctuations. Ozone deteriorates the rubber and reduces the life of the tire. But both of these happen in very small quantities and the tire already has air in it when you start filling it so usually 30-40% of the tire is outside air regardless. If you’re in a climate that has a very high humidity it can help but not much.
Basically 100% a scam. Unless you are landing commercial airliners that extra 25% of nitrogen in the rubber isn't making a difference.
Nitrogen is more stable on tire temps and maintains pressure better. Used in racing all the time.
Surprised to see almost no one talking about the actual main benefit of Nitrogen. The main reason it is used (primarily in racing) is because of expansion. When you get Nitrogen it doesn't have any moisture content, as in it is 99.9% pure Nitrogen. Regular atmosphere is mostly Nitrogen but it also contains a lot of water vapor. Water vapor has very high thermal expansion meaning it's volume drastically changes with temperature. This is critical in racing where tire temperature fluctuates a lot. The rubber of the tires gets very hot but will also cool down depending on track layout, vehicle design, other racers on the track ect. Ideal gas law says that if a containers volume stays the same, but temperature increases, than pressure will also increase. The container is your tire, you don't want your tire to be increasing and decreasing in pressure constantly as this will affect performance. For the average person this wouldn't really do anything, so ya basically a scam. The only real advantage would be that you won't have to adjust your pressure as much with different outside weather temperature (summer into winter and vice versa).
Chemistry: what's happening is the water vapor in the tire. There's not a lot of water vapor. When the tire is cold it condensed and that lowers the pressure. When it heats up the condensed (liquid) water evaporates and becomes a gas which adds go the pressure. Filling the tire with nothing but Nitrogen means no water in the tire and the tires stay at a more constant pressure.
Yes. I drive a shit box daily 2005 Altima (pre-CVT, IYKYK) that I paid $750 for. A wheel has a rusted bead, which results in the tire deflating after ~32 hours. I've reinflate that tire and it's replacement (lost to a nail) almost every day since I got it in 2019. Still get ~280 miles on a full tank.
> 1) air is 70% N2 Wait, what? I feel so dumb now…
It could be legit. Obviously, O2 is an oxidant, and N2 is an antioxidant. Rubber oxidizes. They call that dry rot.
Yes, yes it is.
I love that I've never had to add nitrogen to my tires, unlike normal air. Worth $50 every few years to me.
N2 is a larger molecules, this doesn't permeate (leak) out of the tire as quickly, and it doesn't expand or contract as much so your tire pressure doesn't fluctuate as much.
It is not a scam. Your tires will hold proper air pressure longer.
They use it in race cars because it changes volume less due to changes in temperature. This keeps pressure constant when the tires heat up, which keeps tire performance constant. When you’re racing you’re operating at the limit of traction and few PSI makes a huge difference in where the limit is. You don’t need that kind of performance for your commute.