Heres my 2 pence worth on my pet subject.....tyre pressure stability!
Yes, the principle reason that people use Nitrogen is because its free of moisture, the actual gas composition is a secondary issue. When the air temp gets to about 60DegC inside the moisture releases and turns to steam and has the effect of ballooning the tyres.....to use Nitrogen effectively you need to triple fill the tyres and purge out the air and moisture.......un-screw the valves core, fill 3 times with Nitrogen, then as it deflates at the end of the 3rd fill, screw the valve core back in and fill back with Nitrogen. This is whats done in professional motorsport like BTCC, F3 and GT racing, we certainly did it in the BTCC back in 1999-2003 and the car was on the podium and punching above its weight and won class A & B championships........ people also use "dry air" for the reason that its free from moisture.......they both work
I generally find the struggle with tyre temperature balooning is on a warm to hot day (to state the obvious!), I always carry a laser temp gauge in my pocket and measure the floor temp like a hawk, for qualifying it can be 15-20DegC, then my mid-day it can easily be 45DegC in the floor.
no matter what tyre-gas you are using, best advice is get your kart/car on the warm tarmac thats been in the sun-light all day long for about 5-10 minutes before you go on track, and adjust the pressures when you are on the forming-up grid, right up to the last moment that the karts/cars are released on track.......then you will see a lot less balooning during the race and you will be consistently fast......dont be surprised to see the pressures jump up 2-3 psi from when you take the kart/car from the cool shaded garage/awning, onto the warm forming up area.......watch the pressures like a hawk on the forming up area, I also roll the kart forwards to get the other side of the tyre warmed up and stabilized all around the circumference of the tyre......it works for me.
Also, when you set pressures, set them twice, do 2 loops around your kart/car......on the 2nd adjustment I always find our kart tyres have magically increased by 1psi to when I set them 1 minute before.....whereby the tyres appear to relax a bit about 30 seconds after a big deflate down to the required pressure......we are working in the region of 10 to 30psi if that helps