Hi,
The tire pressure should always be adjusted to what is given on the door of the vehicle, not on the tire.
Here is a link:
http://www.enjoythedrive.com/content/?id=8748
My own replacement tires on my 2000 Towncar, (bought it used) are not the original tires. The Max on the tire itself is 44 psi. However, the sticker on the door of the car says 32 psi.
I try to keep 32 psi in the tires, when I check them.
That is also the advise given by the tire store where I bought the tires. Tires' tread lasts much longer when using the vehicles' door psi. If using more than that, the inside of the tire tread tends to wear out much faster than the outside tread. PepBoys Tire Centers also suggest the same.