Originally Posted by
deraltekluge
That's the ideal gas law, and it holds to the extent that the real gases involved approximate "ideal".
I think that the real advantage of dry nitrogen, such as it is, is that nitrogen is nearly inert, and there's no oxygen and no water to degrade the rubber of the tube. So your tubes will last longer...theoretically.
At the temperatures and pressures in bike tires, gases work very much like ideal gases.