As has been noted it is the water vapor in common compressed air
that makes it unpredictable for inflation purposes. Note that the
expansion ratio from water (droplets, or liquid) to steam is 1400:1.
When a compressor does its thing on air, the air heats up. Hot air
can hold more moisture than cool air (ever been to New Orleans?).
When you shoot the air into the tires, the air expands, which cools
it off, leading to water condensation inside the tire. See, all the
laws of thermodynamics DO apply. ;=)
As a side note, the tires of the SR71 spy plane are also inflated
with Nitrogen to keep them from exploding!
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