Ramblin':
"...but no where have I ever found a listing for the P225/75 16's that came OEM on my Rodeo and are listed on the door placard..."
Just another example why the placard is important.
"...even my owner's manual states that it should have come with P225/75 15's and not 16's."
If Isuzu can't get it straight, how should we expect folks further down the foodchain to get it right?
"You know I failed to mention that these LT265's are Load Range D tires, if that makes a difference??"
Only if the pressure required exceeds 50 psi.
".... said that I shouldn't run an LT tire below 35psi - is this accurate? "
I tend to use the limits of the load tables as limits for usage. For LT metric tires the lowest pressure listed is 35 psi, so I tend to agree. (For P metric tires, the lower limit is 20 psi, but I think that's too low, so 26 psi is my normal recommendation.)
Why? First, the bead unseating force is greatly controlled by the inflation pressure. Recent vehicle stability tests performed by NHTSA have had beads unseat during the manuevers, so NHTSA has amended the test setup to include tubes.
Second, the amount of stiffness of the tire sidewall is also greatly controlled by inflation pressure. soft sidewalls ride better, but also adversely affect vehicle stability.
Hope this helps.