[Phaeton]

Got low tire pressure alert today. Stopped and bought a nifty 12v tire inflation system for USD$24.99 that you can digitally set the max PSI and it auto-fills and stops.

After doing each tire to 32 PSI, the TPMS show each tire exactly at 32.2 PSI. I reset the system.

leaving this little inflator in the car for future use.

[nyalpine90]

its normal, just get nitrogen

[E90Fleet]

Originally Posted by nyalpine90

its normal, just get nitrogen

Shouldnt make much if any difference in this kind of temperature related pressure drop going from 78 to around 98% Nitrogen.

[nyalpine90]

Originally Posted by E90Fleet

Shouldnt make much if any difference in this kind of temperature related pressure drop going from 78 to around 98% Nitrogen.

nitrogen is more stable then oxygen.
my wife has nitrogen in her F48, i havent had low tire warning.
On my x4 that doesnt have nitrogen, had low tire warning twice indicating 28 psi on all tires.

[E90Fleet]

Originally Posted by nyalpine90

nitrogen is more stable then oxygen.
my wife has nitrogen in her F48, i havent had low tire warning.
On my x4 that doesnt have nitrogen, had low tire warning twice indicating 28 psi on all tires.

Normal air is around 80% Nitrogen depending on your altitude and the humidity. And around 20% oxygen.

Filling with close to pure Nitrogen has a few small advantages in normal road tires.

1) Nitrogen passes through the road rubber compound a little slower than Oxygen. So you may loose pressure a little slower if you have more Nitrogen, but this is a very slow process.

2) The Nitrogen used to fill tires is generally dry. Meaning it contains little water vapor.
If you fill the tire with air containing a lot of water vapor (like on a very humid day) the vapor may condense into liquid water in the tire when the car has been standing. Now when you drive a long distance and get the tires heated up this water evaporates again into vapor and increases the tire pressure. It will decrease again when the vapor condenses as the tires cool down after you stop for a long period.


This is why some say Nitrogen is "more stable than air"
But it will only be if it is dry. And just filling the tire once with Nitrogen doesn't get rid of all the water vapor inside it. You need to purge it a few times. And tire pressures would still rise with temperature with dry Nitrogen, just not as much.


Both "Nitrogen" and "Air" filled tires will loose pressure when the ambient temperature drops (like in this example). Its basic physics.
Water vapor generally has no effect here, since it would already have been mostly condensed into liquid on previous days ambient temperatures.



Your X4 showing low pressures may be down to many factors like vapor content, seal strength between your type of rims and the tires, tire rubber compound, heating cycles you tires go through, etc etc. High Nitorogen percentage may have a slight effect on how long you go between pressure drops.

But in the example this thread started on ( the drop in ambient temperatures causing a low pressure warning on cold tires) high Nitrogen percentage would have made hardly any difference

[nyalpine90]

[E90Fleet]

Originally Posted by nyalpine90