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Dry air is about 78% nitrogen, 21% oxygen, 1% other gases, mostly argon. Nitrogen and dry air both behave as ideal gases at these temperatures and pressures. Their physical properties are nearly equal. The only advantage I can see for nitrogen is, it's moisture-free. The residual water vapor coming in with un-dried compressed air must be the source of higher pressure variability in air-inflated tires. Either nitrogen or air will increase in pressure in a hot tire and decrease in a cold tire. No practical measurement of tire pressures at different temperatures could find a difference between nitrogen and dry air. Unless there's something odd going on - like the rubber is adsorbing and desorbing oxygen - but I don't think that's an issue. In short, it's the absence of water vapor that matters, not the 100% nitrogen.
