On the door frame, it says 45 PSI. Is it minimum or maximum one can inflate the MX tires. How much you often do: 44, 45, 46 or 47 while tires are cold? I am to have a trip of 12 hrs driving.
Never put air on cold tires. Always warm. Go for a drive and then check the psi. For me I have it 45. Once I start driving I’ve seen it go to 47. Sometimes 50.
My experience is you always check tires “cold” or prior to driving more than about a mile. Check other sources for conformation.
Page 170 of the Model X Owner's Manual:
Check tire pressures using an accurate pressure gauge when tires are cold. It takes only about one mile (1.6 km) of driving to warm up the tires sufficiently to affect tire pressures. Parking the vehicle in direct sunlight or in hot weather can also affect tire pressures. If you must check warm tires, expect increased pressures. Do not let air out of warm tires in an attempt to match recommended cold tire pressures. A hot tire at or below the recommended cold tire inflation pressure is dangerously under-inflated.
When coolish (never really cold here in the summer), I inflate all tires to 43 psi.
I keep mine between 38 and 43.
45 cold. The X is a very heavy vehicle and underinflating just 3 psi will cause excess wear on the outer edges of the tires. I learned the hard way by keeping my front tires at 41-42 psi and had to replace them at 18,000 miles.