Not quite sure why nitrogen filling in tires for road use is seen as such an advantage. There seems to be a lot of hype here.

- I agree with the science. The relative size of the molecules does mean that pressure drops slower, for pressure drops other than rim leaks or valve stem leaks. These two are the reason you won't get away from checking your tire pressures, as some claim; you still have two failure modes that can lead to pressure drops.
- Nitrogen expands very similarly to air (which, as is noted above, is mostly nitrogen). Thus, it is not correct to say that tire pressures won't change as nitrogen-filled tires heat up, they certainly will. They just change more predictably. Since not many road drivers are checking pressures at anything other than the cold tire pressure, the predictability is not really an issue on the road.
- There are many claims that not having oxygen inside the tire will slow oxidation of the carcass. Recall that there is more surface area on the outside of the tire than the inside (and last time I checked, there was oxygen on the outside)
- What about the air that is already inside the tire? Do you have a way of purging it? Something like two valve stems? Or, is it filled several times and vented each time?
- Airplane tires face different issues than automotive tires. Factors like extreme cold, extreme altitude.
- Heavy truck tires (particularly on-road long haul fleets) typically plan on several life cycles through retreading. That makes a case for saving the carcass, to get more lives out of it. Not typically an issue on automotive tires.
- Heavy equipment tires are sometimes filled with nitrogen, but then, they are also sometimes filled with calcium chloride. Wouldn't recommend that on the road, but it shows that what is best in one application isn't necessarily the answer for another (unless you want the advantage of all that road-hugging weight)

All of the above is only to show that nitrogen isn't a wonderdrug, there is no magic. It can't hurt, and it may even help a little. It just isn't likely to solve all of the problems that it is being advertised as being a solution for. Personally, I wouldn't pay extra for it, but I wouldn't object to it being used if it wasn't at any additional cost to me.

Most of the variation in tire pressure during a heating cycle comes from the water vapour, not the oxygen. The water vapour also causes issues with rim-bead seals. The single biggest item to check is whether your tire supplier has a drier on the air pressure line. Issues arise from too much water in the line and tank (if there is no drier, has it been drained off recently, ie today?). Nitrogen avoids that issue, but so does properly maintaining the compressed air system.

Just my $0.02.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue