I have a question.

If a tire is rated for a finite load at a given air pressure, how does that rating change as the air pressure changes? I assume it's not linear. That would mean my current tires which I think are about 900 lb. rated more or less @35psi would only be rated for 450 lb. @17.5 psi or as much as 1350 lb. @45psi. Or is the weight rating the maximum allowed at the maximum pressure? Not that it's that critical I suppose, how many car/tire combos out there will exceed the max. weight if the max. pressure is not in the tire?

It would mean I may have been dangerously overloading my tires when they crept down to the 18-19psi range. This obviously applies to my Mirage for safety but I need to know as I'll be pulling a trailer in the spring as much as 50% of the time and I want safety and long tire life together.