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Nitrogen in tyres and gas struts?

I understand that the original reasoning for changing over to nitrogen in large aircraft tyres was indeed due to the fact that nitrogen is inert. As mentioned above, a dragging brake on a airliner can get rather hot to say in the least. (They have multiple disks and get hot enough to melt and fuse together if you are really ham fisted. I know an example of this when a BA 747-200 made a RTO a few knots before V1, I believe they blew 10 tyres and the brakes fused, while they were sitting at the end of the active runway at Heathrow...)

I'm sure that there are other advantages of nitrogen, again as stated above, but as I have heard the original reasoning was indeed to prevent tyres exploding.

United Kingdom

It would still be subject to the law of partial gas pressures, which raises an interesting question whether you can get transfer from say 15psi to say 50psi, of a gas not present in the 50psi container.

I imagine so, though probably not to a significant amount. The one situation where I've run into this in practical terms is in opthalmic surgery (not something I do myself) where after a vitrectomy, the eyeball is filled with a fluorocarbon gas. You have to keep the pressure low to allow for a later increase in pressure as atmospheric gases are drawn into the eyeball - likely to be of the order of a few tens of mm hG. I haven't managed to find the equations for gaseous osmosis anywhere yet though.

Just seen this here.

Motorsports for tyre inflation – Filling tyres using a Nitrogen gas canister rather than air has many advantages, combatting water vapour issues by displacing the oxygen needed for vapour to form. Nitrogen gas also has a more consistent rate of expansion, which is ideal for motorsport tyres due to the varying temperatures and traction throughout a race track. Nitrogen gas remains at constant pressure despite these affecting factors.

Is that really true? Surely all pure gases obey the same gas laws?

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

Filling tyres using a Nitrogen gas canister rather than air has many advantages, combatting water vapour issues by displacing the oxygen needed for vapour to form. Nitrogen gas also has a more consistent rate of expansion

Pure, unadulterated balderdash.

LKBU (near Prague), Czech Republic

F1 tyres get incredibly hot and need to cool quickly at slower speeds. However too cool and they lose grip.
If you think of it as a layer of melting rubber being laid on the track at high speeds. But you don’t want to be laying down that rubber when not needed as your tyres will wear away quickly.
If nitrogen helps those changes then it will certainly be used in F1.
Roughly the same reasons it is used in the tyres of CAT jets.
Forgot to say nitrogen is more stable than air.

Last Edited by gallois at 07 Aug 06:27
France

Forgot to say nitrogen is more stable than air.

In what way? Air is ~80% nitrogen.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

In what way? Air is ~80% nitrogen.

Yes, but most of the rest is an oxidiser…

ELLX

Sure, but is this really a factor? Bike and car tyres have been done with air since for ever.

AIUI the reason for nitrogen in gas struts is to avoid getting water in there, which is one advantage of cryogenic distillation used to manufacture most industrial gases. Whereas air is just compressed as-is, usually…

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

AIUI the reason for nitrogen in gas struts is to avoid getting water in there, which is one advantage of cryogenic distillation used to manufacture most industrial gases.

Nitrogen in gas struts is used to avoid possibility for oil to combust. Water is more problematic in systems where compressed gas expands like oxygen regulators.

LDZA LDVA, Croatia

Stable in the way that if you put air in a sealed box and then heat the bottom of it you will ceeate a convective flow.
Nitrogen is believed to more follow the rules of thermodynamics in that the heat from the area closest to the heat source transfers itself to the next layer without convection and with even changes in pressure. So the process by which the wheel hub is heated is slower and more spread around the wheel rather than producing hot spots which would weaken the tyre in patches and be more likely to burst.
How much of this is true but it is my understanding of an explanation I received from a Pirelli tyre technician who was part of the crew that provide the tyres for the formula 1 teams.

France
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