Punctures.

[Avocet]

I'm still not convinced by this at all! Surely Nitrogen behaves just the same as any other gas (including air - which is mostly nitrogen anyway!) when heated or cooled? I didn't think gases had different coefficients of expansion like metals do.

Sure, I can see that nitrogen is less reactive than air, and that this would be desirable for a car tyre. I can also see that if the gas is commercially produced it will be moisture-free (another good thing). I can even accept that it's less likely tosneak out through the rubber. I really struggle to see how it's going to expand and contract less than air in response to temperature changes though.

 

[snico]

The use of nitrogen for inflating your car tyres is purely a gimmick to extract more money from people.

The everyday driver will not benefit from using nitrogen. Airplanes use Nitrogen because of the extreme temps, freezing vapour and the elimination of a fire risk due to no compressed air

Formula 1 cars use nitrogen because its easier and safer than using compressed air

Garages that offer nitrogen will tell you that it can stop inner corrosion of the tyre, thats not true because tyres are designed so that any corrosion on the steel bands comes from the out tyre and not the inner,

They will also tell you that it helps pressure, thats not the case since nitrogen and air act in the exact same way to temp changes

So if you have paid to have nitrogen filled, you have been ripped off!

 

[gblades]

Thats mostly true but you are comparing nitrogen to dry air. When tyres are inflated normal air us used which contains water vapor. This does cause the tyre pressure to change a lot more with temperature.

As I do scuba diving I might get one of these. The cylinders are filled with dry filtered air so it would be as good as nitrogen.
http://www.divecourses.co.uk/acatalog/Beaver_Aluminium_Tyre_Inflator.html

 

[Mickymoody]

I think there is a mistake over the use of gasses. Nitrogen in tyres, would surely relate to a deflated tyre? Whereas Helium, in tyres, that is commonly used in racing, is err common. Nitrogen heavier than air, a no no... Helium a Yes.

 

[Mickymoody]

Thats mostly true but you are comparing nitrogen to dry air. When tyres are inflated normal air us used which contains water vapor. This does cause the tyre pressure to change a lot more with temperature.

As I do scuba diving I might get one of these. The cylinders are filled with dry filtered air so it would be as good as nitrogen.
http://www.divecourses.co.uk/acatalog/Beaver_Aluminium_Tyre_Inflator.html[/QUOTE]

Am I correct to suggest that the air that you take, at a deeper depth, would be Helium?

 

[gblades]

Yes its called trimix as it contains helium, nitrogen, and oxygen.
As you start going below about the 50M mark normal 21% oxygen starts becoming toxic so you need to use less oxygen. That means a higher nitrogen content and combined with the deeper depth increases the amount of decompression you need to do.

Helium being a smaller molecule is taken up and released from the body much quicker so less decompression time. Would probably be pretty poor to inflate tyres with as I would expect the helium would seep out much more easily. That and the fact it costs about £40 to fill a 12L cylinder (clean dry air is about £6) so a bit more expensive aswell

 

[EddieM]

Nitrogen may be used as it remains at a steady pressure irrespective of temperature - but thats not really necessary on a car.

I would have thought like any gas it obeys Boyles law??

Nitrogen also has a larger molecule thus does not permeate through the butyl liner of the tyre as fast as regular air thus holding pressure longer

Atomic number of N is 7 atomic number of O is eight .... smaller??

 

[Avocet]

Yes, it obeys Boyle's law.

I don't think molecular weights are relevant - Nitrogen is a lighter BUT BULKIER molecule because of the way the bonds between the atoms hold them all together. I don't think there's much in it though.

I think the main advantages are:

(a) the removal of reactive oxygen, and its substitution with something more inert to make the tyre rubber last a bit longer (and, perhaps, the rims too)!
(b) a lower rate of permeability (so you don't have to top your tyres up as often (but when you do, you need to go back to the nitrogen shop)!
(c) removal of water vapour which, I guess, could accelerate corrosion. Not sure about its effects on pressure though?

 

[PJF220]

Can I just point out the obvious here....

When did you last go to a tyre shop because of a puncture and be told 'your tyre has corroded' in nearly 20 years of motoring, I've never had a tyre corrode. I've had tyres that wear down the tread to below the limit, tyres that get nails etc in them and I've got the original tyres still fitted on my 1969 van... and guess what.... still inflated and working fine.

So where does this corrosion issue come in to effect?

 

[Avocet]

Yes, they can. Not "corroded" as such, but they loose their properties with time. The plasticisers leach out of the rubber and they become harder. I think ozone also attacks them quite vigorously, and possibly ultra-violet light. It's not an issue for me because I do a fair few miles and they always wear out long before they deteriorate in any other way. Whether or not filling them with nitrogen helps in that area, I can't say. It's certainly more inert, but as most of the ordinary "air" is nitrogen anyway, and the outside surface of the tyre is in contact with it regardless what you fill the inside with, I'm sceptical, to be honest.

 

[EddieM]

seems so

 

[Burnerman]

I've never seen corrosion on the inside of a tyre or rust on the inside of a rim for that matter....if the tyres are getting on a bit, the side wall and treads crack first anyway, irrespective of what gas they've been filled with!
John

 

[Avocet]

seems so

That's interesting, but the author was:

Dr. Keith Murphy
Air Products and Chemicals, Inc.
Prism Membranes
St. Louis, MO

So while I don't question his knowledge, it's worth remembering who is paying him!