2 thoughts:
On passenger car tires, the difference in pressure between loaded and unloaded is less than a 1/2 a psi (based on actual measurements) - well within measurement tolerances. That's about 1 1/2%, and that would make sense compared to the 4% for aircraft tires, which are more intensely loaded.
ALL tire pressures are "COLD" pressures - except when talking about pressure buildup in service. The MAX pressures listed on the sidewall of tires are COLD pressures and the tire manufacturer factors in the amount of pressure buildup when those are specified (Actually, it's the reverse of that - the tire is designed to withstand those elevated pressures.)
