Drivers urged to consider nitrogen for tyres
Motorists have been advised to consider using nitrogen the next time they adjust their tyre pressure.
Standard airlines at garages and service stations fill tyres with compressed air, which contains water vapour and can lead to corrosion over time, according to TyreSafe.
Furthermore, the size of oxygen molecules in the gas can also lead to air escaping from the tyre at a fairly rapid rate. Filling tyres with nitrogen is a solution to such problems, TyreSafe claims.
Among the advantages of using the gas are: a slower rate of pressure loss, a more constant pressure level in tyres, improved longevity and reduction in running temperature.
“All in all, the use of nitrogen can mean up to a 25 per cent increase in tyre life and a five per cent reduction in fuel consumption together with a reduction in CO2 emissions, a vitally important consideration in today’s environmental debate,” the safety group said.
The number of garages offering the choice of nitrogen to fill tyres is currently on the increase.
All of the air within a tyre will have to be evacuated at a garage before nitrogen can be inserted, but this can cost as little as £2 per tyre.
Yeah?? Says who ??
May 23rd, 2007 at 8:38 amHi,
Well, i understand rest of the advantage of using nitrogen exluding 25% increase in tire life and 5% reduction on fuel consuption.
Could you please explain the reason for same.
May 24th, 2007 at 4:22 amHello Mr Rawat,
Thanks for your comments.
Normal air contains about 78% nitrogen, 20% oxygen and 2% some other gases by volume. Nitrogen molecules are significantly larger than oxygen molecules which reduces the rate at which compressed gas escapes through the tyre walls; which helps in tyres maintaining their original intended pressure for longer. Correctly inflated tyres transfer the power efficiently to the road track and minimize loss of power generated from the engine. Under-inflated tyres have a greater resistance and friction co-efficient which increases fuel consumption. Under-inflated tires cause 90% of tire blowouts experienced by drivers. Vehicles with under-inflated tyres also require more fuel to maintain the same speed.
Normal compressed air can contain upto 5% water vapour which condenses and causes corrosion to rims and oxidation of tyres. While driving, the tyre becomes hot and the water vapour expands to increase the pressure by upto 7psi which will increase the wear towards the centre of the tyre.
Most performance tyres and race tyres are filled with nitrogen. For over a decade, Formula 1 tyres have been inflated with nitrogen.
Here are the results of an independent test(TyreBayDirect.co.uk) comparing nitrogen inflation with compressed air:
54 truck tyres were used: 33 inflated with nitrogen, 21 with compressed air.
1. Tyres inflated with nitrogen ran 26% more miles before having to be replaced.
2. Tyres inflated with Nitrogen gave 48% more miles before failing.
3. Tyres inflated with nitrogen had a smaller failure percentage than compressed air, 30% compared to 57%.
Lets sum up the benefits of nitrogen:
May 24th, 2007 at 8:14 am1. Better tire pressure retention
2. Improved fuel economy
3. Cooler running tires
4. Removal of oxidation
5. Improved retreadability
6. Elimination of rim rust
7. On-the-road reliability
Availability is the only real problem with inflating with nitrogen.
It’s all very well to tick the N box when having tyres fitted, but will customers then feel they have to return to a fast-fit tyre centre just to check and adjust tyre pressures?
If more fuel forecourts made nitrogen an option (or even standard) for their “air” stations, user acceptance would increase.
May 30th, 2007 at 11:20 pm1. Better tire pressure retention
“Nitrogen molecules are significantly larger than oxygen molecules which reduces the rate at which compressed gas escapes through the tyre walls; which helps in tyres maintaining their original intended pressure for longer.”
Are you suggesting that users can stop doing frequent check of tyre pressures?
I hope the first one the spin off the road due to an undetected slow puncture sues.
There is always some loss of pressure in doing a tyre pressure check. That loss will need topping up before effect of diffusion rate of O2 from tyre could have been detected.
Taken from Michelin pdf document below. “Inflation using nitrogen does not dispense with the need to frequently verify the tyre pressure.”
http://www.michelin.co.uk/uk/document.DocumentRepositoryServlet?codeDocument=784&codeRepository=AUTO_UK&codeRubrique=home
2. Improved fuel economy
You will get that just by doing weekly check of pressure and setting correct pressure for use - should be adjusted for every trip M-way or town, laden/unladen. You can set pressure easily with a electric pump anywhere, have to run to your N2 supplier before every trip if using N2. If you fail to set the pressure then N2 won’t give any benefit.
3. Cooler running tires
As above.
4. Removal of oxidation
I’ve had some alloy rims out on the yard without tyres in all weather for the last year, I can’t see any deterioration. Alloy has an oxide film that prevents corrosion, if you remove it, it re-forms nearly as fast as you can abrade it away. Steel wheels should be painted and the tyre fitter should touch up any scratches he makes.
5. Improved retreadability
?? what. Who uses re-treads on cars? The tyre makers have taught the public that they are not safe and historically have to have lower speed ratings than vehicles top speed. Used lots on trucks.
6. Elimination of rim rust
Teach tyre fitters not gouge and abrade the paint of the rim.
7. On-the-road reliability
Stops you getting nails in the tyre? I think not.
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Q: How has this idiocy come about?
A: People died.
Q: Gasp!! What!? How?
A: CAP 747 GR No. 16 Tyre Bursts In Flight - Inflation Media.
http://www.caa.co.uk/application.aspx?categoryid=33&pagetype=65&applicationid=11&mode=detail&id=1331
Aviation use nitrogen filled tyres as a plane took off with a brake locked up, which overheated the tyre. It set fire to the inner liner, it didn’t blow out straight off but waited until the outside pressure was quite low in high altitude flight. It exploded.
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Monkey see, monkey do.
The automotive idiots got hold of the idea but have got it all wrong.
“All of the air within a tyre will have to be evacuated at a garage before nitrogen can be inserted.”
Dunlop’s aviation fittment guide, requirement is not 100% nitrogen but less than 5% oxygen, which won’t support combustion of liner. Tyre is fitted in open air and inflated using nitrogen, resulting mix has less than 5% oxygen.
http://www.dunlopaircrafttyres.com/tyrecare/dm1172/DM1172.pdf
Also has stuff on how aircraft tyres can’t be used for first 12 hours after fitting until casing has fully stretched, then pressure is topped up and monitored for leaks.
Car tyres will also change pressure in the first few days. Is the first top up free?
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“While driving, the tyre becomes hot and the water vapour expands to increase the pressure by upto 7psi which will increase the wear towards the centre of the tyre.”
N2 expands as well. Both DRY air and N2 expand just the same. Start at 15°C and 32psig (gauge). Absolute pressure is 32 + 14.7 = 46.7psia. Simple “A level” (in my day) gas law applies. P2 = P1 x (T2/T1). Temp is °K = °C+ 273.
Temp°C Pressure (psia) Rise (psi)
60 53.83 7.13
70 55.45 8.75
80 57.69 10.37
90 58.69 11.99
100 60.31 13.61
Normal running temp for road tyres is 80°C. So pressure rise with pure nitrogen is 3.37psi more than quoted objectionable rise of 7psi from sopping wet air.
Garage air lines ***should*** have a functioning drier on them. As it’s expensive to maintain and takes time to open the purge valve on the compressor tank each day many don’t bother and supply wet air. It’s still drier than the atmospheric air as it cools in tank, the pressure makes some water condense. It sits in the bottom of the tank rotting it away. They eventually find out why they should have opened that purge valve each day as it and a load rusty water shoots across the workshop.
Damp air in tyre only holds a small amount of water. Even at 100% relative humidity and 15°C it’s only 10.6 grams water / Kg air. School physics even at A level can’t cope with this mixture as they only deal with expansion of 100% water vapour called steam. You need a mechanical engineering graduate.
At 80°c the pressure rise for a damp water air mix that was 100%RH 15°C when it went in, inflated to 32psi, will be 12psi. About 1.4psi more than the rise using PURE NITROGEN or DRY AIR. It’s not a really significant pressure rise over that due to N2 or DRY AIR alone.
Best not to inflate tyres in the pouring rain. Or fit them with liquid water sloshing around in them.
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Other often used idiocy for use of N2.
“But I do Race or Track days, the tyre pressure is critical and it’s all over the place.”
Stuff the pressure at the track. If you can’t read the tyre wear pattern or feel what it needs, then you need to measure the tread temperature and get it even. Next morning when it’s cooled off you can take a pressure reading and use that to set cold pressure next time you’re at the track.
http://www.elephantracing.com/techtopic/tiretemp.htm
http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=Fluke-track.htm
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June 14th, 2007 at 5:51 pmThe bottom line.
Unless you drive a 100 ton earth mover that has the same tyres fitted for 10 years at a stretch, on site, to steel rims, in a deep puddle it’s not worth bothering with.
“Nitrogen molecules are significantly larger than oxygen molecules which reduces the rate at which compressed gas escapes through the tyre walls; which helps in tyres maintaining their original intended pressure for longer.”
Firstly, Oxygen and Nitrogen are ELEMENTS, not MOLECULES and secondly, Nitrogen has a lower atomic number than oxygen (7 as opposed to
so it is “lighter” or “smaller” (note the quotes). Therefore, any argument about gas escaping through the tyre wall is pure fantasy.
The next part about water vapour is also incorrect. As has already been stated, everything will expand when it gets hotter, not just water vapour. The only difference is that the water vapour may change state. So Nitrogen will add no benefit here.
The bit about evacuating all the air before filling with Nitrogen is not possible unless you fit the tyre in a sealed Nitrogen environment. In the absence of such facilities, you are still going to have water vapour and oxygen in your tyre to some degree.
Then there’s oxidisation. For alloy wheels, this is a none starter. I can envisage possible benefit of reducing the oxidising element (Oxygen) in favour of an inert element (Nitrogen) to reduce the possibility of oxidising reaction taking place (including reaction with the tyre). But, this is just a finger in the air assumption based on my knowledge of the elements involved and I would say the benefit is probably negligible. I certainly don’t think the benefits are worth sitting down and working out!
My 2p worth is to make sure your tyres are correctly inflated on a weekly basis. I am much better at doing this on my bike than my car but it is amazing just how much the ambient temperature effects the pressure. Here in the UK, the temperature can vary widely from day to day. I have seen variations by as much as 4psi simply due to the ambient temperature.
If you are bothered about water vapour, make friends with a scuba diver and fill your tyres from one of their tanks as the amount of water vapour present in diving compressors is strictly controlled.
April 5th, 2008 at 11:11 amAdam:
Nitrogen and Oxygen may be elements, but in the atmosphere they are molecules. Hence O2 and N2 indicating that a nitrogen or oxygen molecule in air is made up of two of the respective elements.
As to their size, that would be difficult to determine without more in-depth knowledge. Nitrogen (N2) has a triple bond whilst oxygen (O2) has a double bond. The stronger bond may indicate that the atoms are pulled closer together but you will also find that atoms with weaker outer shell electron strengths tend to be larger (a nitrogen atom is larger than an oxygen atom - this is true no matter how many protons/neutrons they have).
Peter Hill’s assessment of Nitrogen is a much more thorough and accurate rebuttal.
April 29th, 2008 at 1:44 pm