Nitrogen for Better Fuel Economy?

[Steve]

I noticed a lot of tyre garages offering Nitrogen to replace the air in tyres claiming to save tyre wear and better fuel economy. Do you think this is pants or pretty good? Anyone ever tried it? Whats your thoughts?

[steve2006]

I think the reasoning behind the claims is because nitrogen is an inert gas and so the tyre pressures shouldn't alter whether the tyre is warn or cold so this should in theory prevent under/over inflation resulting in better wear of the tyre and optimum grip/handling under all driving conditions,vehicle loading and speeds.

Whether it is cost effective in the long run I don't know, is the initial outlay of having the tyres filled with nitrogen going to be recovered over the life of the tyre compared to filling with air by way of the tyres lasting longer?

Air comprises of 78% nitrogen as it stands so would 100% make that much difference?

Also all tyres leak over time through the valve or rim seals hence the need for weekly checks so what do you do then, put in straight air or pay again for the pressure to be topped up with nitrogen.

Apparently this is popular in motor racing especially F1 but when ultimate traction and tyre grip is this important and maybe the difference between winning and losing a race the cost is insignificant to a multi million pound industry.

Also the tyres are scrap after 20 or so laps so this cannot be compared to a normal road car.

All in all I'm sceptical and personally wouldn't bother with nitrogen.

[Parthiban]

<p>I noticed a lot of tyre garages offering Nitrogen to replace the air in tyres claiming to save tyre wear and better fuel economy. Do you think this is pants or pretty good? Anyone ever tried it? Whats your thoughts?</p>

I've got nitrogen in my tyres but don't really pay enough attention to the pressures to see if it's making a real difference.

But the reasoning as above is sound, with no pressure fluctuations with temperature the tyre is always kept at it's optimum inflation. This should aid even tyre wear and keep fuel economy constant.

Wouldn't pay extra for it but I'd rather have it than not if it's not costing me anything :)

[sprinter2012]

Pretty much same as above, its a more stable gas so it won't expand/contract with temperature fluctuation.

Also, the actual particles of nitrogen are substantially bigger (relatively speaking) than normal air so it leaks less.

However I think it would be a pain, because if you needed to top up your tyres at any point you couldn't just use normal air from you local petrol station or it would make it pointless.

But I think its normall only about £1 per tyre for nitrogen filling IIRC

[dave1]

I think the reasoning behind the claims is because nitrogen is an inert gas and so the tyre pressures shouldn't alter whether the tyre is warn or cold so this should in theory prevent under/over inflation resulting in better wear of the tyre and optimum grip/handling under all driving conditions,vehicle loading and speeds.

Would inflating with nitrogen mean that tyre pressures would need to be modified too? I ask because if nitrogen doesn't suffer from alterations in pressure then surely they would need to be inflated to a higher pressure since as your tyres heat up with "normal" air the pressure also increases whereas the pressure would not increase with nitrogen. Also since inflation figures for cars seem to increase with extra weight and/or speed would it still be necessary to increase pressures if driving at over say 100mph?

[sprinter2012]

I think the reasoning behind the claims is because nitrogen is an inert gas and so the tyre pressures shouldn't alter whether the tyre is warn or cold so this should in theory prevent under/over inflation resulting in better wear of the tyre and optimum grip/handling under all driving conditions,vehicle loading and speeds.

Would inflating with nitrogen mean that tyre pressures would need to be modified too? I ask because if nitrogen doesn't suffer from alterations in pressure then surely they would need to be inflated to a higher pressure since as your tyres heat up with "normal" air the pressure also increases whereas the pressure would not increase with nitrogen. Also since inflation figures for cars seem to increase with extra weight and/or speed would it still be necessary to increase pressures if driving at over say 100mph?

Typre pressure should just be exactly what the manufacturer recommends for normal air. When they give pressures they assume they will be filled at 'normal' temperature. i.e. not in blazing sunshine or in snow.

But yes, you would still need to adjust pressures accordingly for high speeds or extra weight in the car as normal.

[dave1]

Typre pressure should just be exactly what the manufacturer recommends for normal air. When they give pressures they assume they will be filled at 'normal' temperature. i.e. not in blazing sunshine or in snow.

But yes, you would still need to adjust pressures accordingly for high speeds or extra weight in the car as normal.

Thanks for that.

The only thing bothering me really was that if I fill my tyres to say 33psi with "cold" tyres and then drive a few miles they might then register, say, 40psi. I assume that this increase would not occur with nitrogen so I would then be running with a lower pressure than with "normal" air? Do the car manufacturers or tyre manufacturers not factor these increases in when laying down their recommendations?

[sprinter2012]

Typre pressure should just be exactly what the manufacturer recommends for normal air. When they give pressures they assume they will be filled at 'normal' temperature. i.e. not in blazing sunshine or in snow.

But yes, you would still need to adjust pressures accordingly for high speeds or extra weight in the car as normal.

Thanks for that.

The only thing bothering me really was that if I fill my tyres to say 33psi with "cold" tyres and then drive a few miles they might then register, say, 40psi. I assume that this increase would not occur with nitrogen so I would then be running with a lower pressure than with "normal" air? Do the car manufacturers or tyre manufacturers not factor these increases in when laying down their recommendations?

I'm sure they do take into account that the tyres will be slightly higher or lower pressure depending on temperature, but the pressure they state is the pressure they would aim for as an ideal average.

How much heat you get in your tyres also depends on things like what sort of driving you do, how many corners you take, road surface and even what brand of tyre you have. So they can't be too specific.

[dave1]

Typre pressure should just be exactly what the manufacturer recommends for normal air. When they give pressures they assume they will be filled at 'normal' temperature. i.e. not in blazing sunshine or in snow.

But yes, you would still need to adjust pressures accordingly for high speeds or extra weight in the car as normal.

Thanks for that.

The only thing bothering me really was that if I fill my tyres to say 33psi with "cold" tyres and then drive a few miles they might then register, say, 40psi. I assume that this increase would not occur with nitrogen so I would then be running with a lower pressure than with "normal" air? Do the car manufacturers or tyre manufacturers not factor these increases in when laying down their recommendations?

I'm sure they do take into account that the tyres will be slightly higher or lower pressure depending on temperature, but the pressure they state is the pressure they would aim for as an ideal average.

How much heat you get in your tyres also depends on things like what sort of driving you do, how many corners you take, road surface and even what brand of tyre you have. So they can't be too specific.

Cheers! I hate being uncertain about things but that seems a pretty reasonable and logical explanation.

[Mike_B]

Pretty much same as above, its a more stable gas so it won't expand/contract with temperature fluctuation.

Also, the actual particles of nitrogen are substantially bigger (relatively speaking) than normal air so it leaks less.

However I think it would be a pain, because if you needed to top up your tyres at any point you couldn't just use normal air from you local petrol station or it would make it pointless.

But I think its normall only about £1 per tyre for nitrogen filling IIRC

Sorry but this is just nonsense...

Firstly, nitrogen expands and contracts with temperature exactly the same as any other gas does - it obeys the same laws of physics as everything else does. So tyre pressure will rise and fall with tyre temperature whether it has air or pure nitrogen. You could fill them with any gas you choose and would see almost exactly the same effect.

Secondly, normal air is 80% nitrogen anyway, and oxygen is of a similar molecular mass and makes up almost all the remaining 20% of 'normal air'. Therefore pressure stability will be pretty much identical.

If there is any benefit, it's the nitrogen is less reactive and doesn't interact with the rubber. Oxygen can and does react with the inside of the tyre and leach through, which effectively reduces pressure over time.

[sprinter2012]

Pretty much same as above, its a more stable gas so it won't expand/contract with temperature fluctuation.

Also, the actual particles of nitrogen are substantially bigger (relatively speaking) than normal air so it leaks less.

However I think it would be a pain, because if you needed to top up your tyres at any point you couldn't just use normal air from you local petrol station or it would make it pointless.

But I think its normall only about £1 per tyre for nitrogen filling IIRC

Sorry but this is just nonsense...

Firstly, nitrogen expands and contracts with temperature exactly the same as any other gas does - it obeys the same laws of physics as everything else does. So tyre pressure will rise and fall with tyre temperature whether it has air or pure nitrogen. You could fill them with any gas you choose and would see almost exactly the same effect.

Secondly, normal air is 80% nitrogen anyway, and oxygen is of a similar molecular mass and makes up almost all the remaining 20% of 'normal air'. Therefore pressure stability will be pretty much identical.

If there is any benefit, it's the nitrogen is less reactive and doesn't interact with the rubber. Oxygen can and does react with the inside of the tyre and leach through, which effectively reduces pressure over time.

What part of what I said is nonsense exactly?

Normal air contains moisture/humidity which affects pressure change more, so using pure nitrogen will stabilise it.

Nitrogen particles are bigger than Oxygen and also inert, so if 20% of air is Oxygen. Using pure Nitrogen should decrease deflation by 20%

Perhaps the only mistake I made was to say that Nitrogen doesn't expand and contract with heat, when infact what I should have said was that it contracts and expands LESS than just air.

However if we're going to get picky, your statment of "You could fill them with any gas you choose and would see almost exactly the same effect" is completely untrue, as the expansion and contraction of gases can be vastly different depending on its structure.