MG4 in Australia

[ReintjeWA]

Unless they can suck the air out of your tyre first, the percentage increase in nitrogen is very minimal, I’ve always considered it a gimmick from tyre shops.

 

[Tuareg]

I have topped up my tyre pressures only once since I took delivery of my car in February. No leaks, no TPMS warnings, pressure remains stable within a very small range of 0.1 bar depending on standing air temperature.

 

[ozzz]

Unless they can suck the air out of your tyre first, the percentage increase in nitrogen is very minimal, I’ve always considered it a gimmick from tyre shops.

I think nitrogen is what is in airplane tyres and why it’s no gimmick. Today in my area the morning was 3.5°C and lunch time 24°C. At 100 km/h on the freeway would it make a difference?

 

[decrep]

coefficient of expansion difference?????

 

[wattmatters]

3.5c and lunch time 24c at 100 km on freeway would it make a difference?

The Ideal Gas Law says no.
PV = nRT

Same temperature rise contained within the same volume results in the same change in pressure.

Where it can be different is if there is a phase change involved, e.g. water into water vapour. Nitrogen gas is naturally drier than air.

But you are taking on trust that a nitrogen gas filling facility is actually able to fill your tyres with 100% nitrogen. Frankly they are unlikely to do this, the equipment is more than likely not up to snuff and you just have tyres which might be 15% rather than 20% O2.

The longer you have tyres on your car the naturally higher the nitrogen content becomes.

Think what is in Airplane tyres and why

It's used for aircraft tyres for safety because it does help maintain pressure for longer between checks, eliminates water which is bad news at these temperature extremes (these things can be flying in -60°C conditions and landing at 45°C) as well as the higher risk of fires from landing / braking and the combustibility of some of the materials used which are better left without a high pressure blast of oxygen filled air from a tyre blow out.

 

[ReintjeWA]

Think what is in Airplane tyres and why it’s no gimmick today in my area morning was 3.5c and lunch time 24c at 100 km on freeway would it make a difference?

Sure but we’re talking about your local Bob Jane or something, not an airplane…? If you think it will help you do what you do, I’m just saying I don’t believe the marketing around it, not in the case of normal tyre shops anyway.

It would probably make the same difference to have them fill your tyres with dry air, if you’re worried about expansion as temps rise.

 

[ilukey77]

I've been getting the tyre pressure warnings quite a lot in the last few days.

I could possibly put a little extra air in them but the main reason is the ambient temps outside have been quite cold ( we are in the winter months now in Victoria).

So by default the tyres are cold, the pressures are lower, hence the warning. Once they get heat in them, the tyres expand, increase pressure as such and the alerts stop ..

That said a few more psi in them wouldn't hurt. I may do that today.

 

[EVentropy]

Yep, I inflated them all to 260kpa and notifications stopped.

 

[wattmatters]

I normally inflate to 39 psi with my portable compressor. Other day I brought the rear right back up (that's the one which loses pressure first).

Yesterday was a warmer than normal winter day and with a drive to Coffs and back, pressures came up a touch.

They will have dropped back overnight

 

[Corindikev]

260 kPa in Winter when tyres are quite cold will keep the TPMS happy. When it warms up in Spring just return to 250 kPa. I check mine every month or 2, there is no set routine. If I forget the TPMS will remind me.

 

[Tuareg]

My car has been sitting in temps of near to 0°C in winter and now 34°C in summer, no loss of tyre pressure (apaft from 1 smal, top up in 4 months) and no warnings at all.

 

[ozzz]

I've been getting the tyre pressure warnings quite a lot in the last few days.

I could possibly put a little extra air in them but the main reason is the ambient temps outside have been quite cold ( we are in the winter months now in Victoria).

So by default the tyres are cold, the pressures are lower, hence the warning. Once they get heat in them, the tyres expand, increase pressure as such and the alerts stop ..

That said a few more psi in them wouldn't hurt. I may do that today.

That’s the problem big temp difference in same day sometimes 6 hours, so for thirty dollars problems solved.

 

[wattmatters]

That’s the problem big temp difference in same day sometimes 6 hours, so for thirty dollars problems solved.

There is a no difference in temperature induced rise in tyre pressure between air and nitrogen filled tyres in regular passenger vehicles. You've spent $30 to solve a non-existent problem.

 

[T1 Terry]

If oxygen were 21% of the air we breathe, we'd have a lot more energy and ICE vehicle would operate more efficiently ...... You need to be in a forest or sealed green house to get better than 19% oxygen and 78% nitrogen and the rest made up "other gasses"

If the tyre is deflate to equal the pressure outside the tyre, our pressure testing equipment would read 0 psi, but it would actually be 1 bar (14.7psi) at sea level. To achieve 30 psi, the actual pressure would be 3 bar.

Using 19% as the 1 bar pressure oxygen capacity, then another 2 bar of nitrogen, only roughly 6% of the total gas contained inside the tyre is oxygen ..... this will rapidly oxidise with the rubber of the tyre and make its way out through the sidewalls, then next pressure top up with nitrogen will reduce that 6% even further ...... It does work .....

T1 Terry

 

[T1 Terry]

If the tyres were filled with helium, then the valve moved to the lowest position and the tyre deflated removing much of the air, then reinflated with helium ..... would the tyre now be lighter?

T1 Terry

 

[ozzz]

It’s all about size big molecules can’t escape easily, helium don’t make me laugh

 

[wattmatters]

It’s all about size big molecules can’t escape easily

Over time the air in tyres will naturally increase the proportion of nitrogen.

 

[Corindikev]

If oxygen were 21% of the air we breath, we'd have a lot more energy and ICE vehicle would operate more efficiently ...... You need to be in a forest or sealed green house to get better than 19% oxygen and 78% nitrogen and the rest made up "other gasses"

If the tyre is deflate to equal the pressure outside the tyre, our pressure testing equipment would read 0 psi, but it would actually be 1 bar (14.7psi) at sea level. To achieve 30 psi, the actual pressure would be 3 bar.

Using 19% as the 1 bar pressure oxygen capacity, then another 2 bar of nitrogen, only roughly 6% of the total gas contained inside the tyre is oxygen ..... this will rapidly oxidise with the rubber of the tyre and make its way out through the sidewalls, then next pressure top up with nitrogen will reduce that 6% even further ...... It does work .....

T1 Terry

All the sources I have checked say the percentage is 20.9 but even if it was 19%, an extra 1.9% is hardly likely to give you a big energy boost.