One tyre nitrogen inflated...
Discussion
Think I know the answer to this but I thought I'd check with the masses.
Had a puncture whilst on holiday back in the summer and the garage that repaired it re-inflated the tyre with nitrogen, I didn't notice this until later on when I looked at the invoice.
Now the colder months are upon us it seems like the pressure fluctuation in my other three tyres is causing the flat tyre alarm to get set off on my BMW. When I check the pressures after this event three out of the four tyres are at a significantly lower pressure than the nitrogen filled one despite trying to equalise them a week or so back.
I'm guessing I'm okay to let most of the nitrogen out of the offending tyre and re-inflate with good old air. It's a run-flat so I assume I can let it completely down and refill (excepting the gas that's still in there as the structure of the tyre won't allow for complete deflation). The tyre place were okay about repairing it as it was never actually "run flat" as it was a screw through it causing it to go down slowly and apparently it is actually okay to repair these tyres under those circumstances.
Thanks.
Had a puncture whilst on holiday back in the summer and the garage that repaired it re-inflated the tyre with nitrogen, I didn't notice this until later on when I looked at the invoice.
Now the colder months are upon us it seems like the pressure fluctuation in my other three tyres is causing the flat tyre alarm to get set off on my BMW. When I check the pressures after this event three out of the four tyres are at a significantly lower pressure than the nitrogen filled one despite trying to equalise them a week or so back.
I'm guessing I'm okay to let most of the nitrogen out of the offending tyre and re-inflate with good old air. It's a run-flat so I assume I can let it completely down and refill (excepting the gas that's still in there as the structure of the tyre won't allow for complete deflation). The tyre place were okay about repairing it as it was never actually "run flat" as it was a screw through it causing it to go down slowly and apparently it is actually okay to repair these tyres under those circumstances.
Thanks.
55palfers said:
Interesting.
I pretty sure N2 and air expand / contract at the same rate.
Hadn't really thought about this but thought that was the whole point of filling a tyre with nitrogen. Google seems a bit vague, something about the nitrogen being dry, i.e. no moisture content unlike air, so this helps with temperature fluctuations, also any loss of pressure is slower as nitrogen molecules are bigger.I pretty sure N2 and air expand / contract at the same rate.
Maybe three of my four wheels / tyres have decided to leak?
C0ffin D0dger said:
trying to equalise them a week or so back.
That's a curious choice of words. The goal should be to have all tyres at the right pressure. That almost always means pumping them up as necessary, whereas 'equalise' suggests you may be letting some down. If you're pumping tyres up to the right pressure it should be obvious over time if some tyres are losing pressure faster than the others. If the difference is significant it's unlikely the nitrogen accounts for it.Nitrogen in tyres is a con designed to get owners to take their cars to tyre fitters more often so they can be sold more tyres. That's harmless, but it also discourages people from checking and pumping up the tyres themselves, which is something that should be encouraged not discouraged.
Firstly, you probably just got charged for nitrogen air and got normal air.
Secondly , they probably didn’t check your other tyres pressures after they replaced the one and that’s all your car has picked up
Put all tyre pressures the correct pressure, don’t bother draining the air out of the new one, reset tyre light, that’s it
Secondly , they probably didn’t check your other tyres pressures after they replaced the one and that’s all your car has picked up
Put all tyre pressures the correct pressure, don’t bother draining the air out of the new one, reset tyre light, that’s it
Nitrogen inflation became a thing for trackcars because nitrogen is dry whereas normal air contains moisture which makes it much more susceptible to pressure changes associated with temperature.
But why would you "equalise" the one tyre which is at the right pressure? Surely you should be pumping the other three up?
Edited for a crappy autocorrection
But why would you "equalise" the one tyre which is at the right pressure? Surely you should be pumping the other three up?
Edited for a crappy autocorrection
Edited by Watchman on Wednesday 23 October 18:04
Watchman said:
Nitrogen inflation became a thing for trackcars because nitrogen is dry whereas normal air contains moisture which makes it much more susceptible to pressure changes associated with temperature.
But why would you "equalise" the one tyre which is at the right pressure? Surely you should be point the other three up?
^^^^ This, you have one filled with a dry gas that responds differently & until you have all 4 filled with the same gas & at the correct pressure, they will always respond differently.But why would you "equalise" the one tyre which is at the right pressure? Surely you should be point the other three up?
Fill/drain/fill/drain the odd one several times and set them all right & then see how you get on.
E-bmw said:
Watchman said:
Nitrogen inflation became a thing for trackcars because nitrogen is dry whereas normal air contains moisture which makes it much more susceptible to pressure changes associated with temperature.
But why would you "equalise" the one tyre which is at the right pressure? Surely you should be point the other three up?
^^^^ This, you have one filled with a dry gas that responds differently & until you have all 4 filled with the same gas & at the correct pressure, they will always respond differently.But why would you "equalise" the one tyre which is at the right pressure? Surely you should be point the other three up?
Fill/drain/fill/drain the odd one several times and set them all right & then see how you get on.
Air is 80% nitrogen and so any difference in expansion due to 20% oxygen us minimal. Ditto , the effect of oxygen on perishing the rubber, which is another “benefit”, often quoted.
The outside will be exposed to the 20% oxygen will perish quicker as it has the help of ultra violet in sunlight .
Another sales pitch is nitrogen is a larger molecule than oxygen and so escapes from the valve more slowly. Again BS, it’s about 2% bigger so negligible effect even ignoring the 80%
The problem is air compressors add water the air. Any liquid water will expand massively when it turns to vapour (18g if water will turn into 24 litres of vapour ).
The amount will vary considerably from place to place and will be mainly due to the maintenance of the system.
The outside will be exposed to the 20% oxygen will perish quicker as it has the help of ultra violet in sunlight .
Another sales pitch is nitrogen is a larger molecule than oxygen and so escapes from the valve more slowly. Again BS, it’s about 2% bigger so negligible effect even ignoring the 80%
The problem is air compressors add water the air. Any liquid water will expand massively when it turns to vapour (18g if water will turn into 24 litres of vapour ).
The amount will vary considerably from place to place and will be mainly due to the maintenance of the system.
This is a quibble, I know!
An air compressor does not ADD water to the air. There is water vapour in the air around us, which a change in temperature will cause to fall out as dew, or rain. But an increase in pressure will do the same, and a change from 15 to 100psi will condense quite a lot! We can't see or feel the vapour in the air around us, but become very aware of it when it 'materialises' in our nice clean, dry compressor!
The air that comes out of the compressor is therefore quite dry! Admittedly, the process that produces industrial nitrogen, fractional distilallation produces near water-free gas ( less than 67ppm v/v) but there is very litle in compressed air (less than 50mgs per cubic meter)
John
An air compressor does not ADD water to the air. There is water vapour in the air around us, which a change in temperature will cause to fall out as dew, or rain. But an increase in pressure will do the same, and a change from 15 to 100psi will condense quite a lot! We can't see or feel the vapour in the air around us, but become very aware of it when it 'materialises' in our nice clean, dry compressor!
The air that comes out of the compressor is therefore quite dry! Admittedly, the process that produces industrial nitrogen, fractional distilallation produces near water-free gas ( less than 67ppm v/v) but there is very litle in compressed air (less than 50mgs per cubic meter)
John
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