Wrong!
Air is about 78% nitrogen, 21% oxygen, 0.9% argon, 0.1% carbon dioxide.
Specific Heat Capacity is the amount of heat that is needed to raise the temperature of volume of a substance without changing state (Remember you Chem-101 class?)
Air has a specific heat capacity of 1.01 kJ/kg K
Oxygen has a specific heat capacity of 0.91 kJ/kg K
Nitrogen has a specific heat capacity of 1.03 kJ/kg K
Since air has only about 21% oxygen, by using the just nitrogen, the change in capacities are only 0.02 kJ/kg K. Thus Nitrogen fill tires will still expand and contract almost as much as air filled, just a slight difference, immeasurable really.
Generally, 10 degree F in temperature change results in 1 PSI change in tire pressure - Air or Nitrogen.
So why put in Nitrogen?
My reasons for using Nitrogen:
