Comparing 35 in a p and LR D is apples and oranges. With a TPMS system at 35 on a LR D the light would be on. Construction wise the lateral support of the D would be better. Air pressure is no substitute to heavier construction. At the proper inflation of the D at about 40-45 on an F150, it would handle far better in turns. I have no doubt that the p series tire can handle the load at max. It is a question of how it handles it, and in my opinion, not well especially in turns.

 

Actually, higher air pressure capability is what gives a "C" or "D" load range tire it's higher load rating and the heavier construction is to withstand those higher pressures. It is not a case where the more rigid the better, an important part of any tires performance is it's ability to deflect (otherwise we would all be running on rubber-coated, non-pneumatic steel wheels and be in truck heaven). It is desirable to run a tire in the proper load range for the application leaving a good margin to insure the tire is not operating near the edge of it's performance envelope.

Let's look at the facts of the two tires under discussion, both 285/70/17 Goodyear Wrangler Silent Armors:

Maximum Load at various pressures (normalized to LT load values):

-P285/70/17 35 psi-2578 lbs. 40 psi-2578 lbs. 44 psi-2578 lbs.
LT285/70/17 35 psi-2105 lbs. 40 psi-2315 lbs. 45 psi-2510 lbs.

You will note that the "D" load range tire needs to be run well above 45 psi just to match the load capability of the P series tire running only 35 psi. This is because the construction of the LT tire is such that it builds excessive and potentially destructive heat at lower pressures. The carcass construction is not optimized for low pressures and yet most f-150 owners with "D" range tires will naturally run them at 40-45 psi because they are trying to get more deflection from the tires (and frighteningly enough, some will run them even lower than that in an attempt to get more compliance out of them). Higher pressures are only good if there is adequate weight to cause normal deflection and the tires are not optimized for low pressures.

You will also note that even the P285/70/17 are overkill unless you plan to exceed the trucks GVWR by over 2000 lbs. In this case I will agree with you, the "d" load range tire would be superior even though the lighter tire would still be operating within it's design specifications at 35 psi. and would still have 9 psi of reserve pressure to fine-tune the handling for the heavier load. But most of us do not overload our trucks, let alone by that amount, and then expect to be able to drive down the freeway at 80 mph and take corners like it's a sports car. So all most people care about is the traction and handling when the truck is not loaded over it's GVWR and the P285/70/17 have plenty of reserve capacity in this respect.

I understand you admit both of these tires are more than adequate to handle the load but that somehow the LT285/70/17 will go around corners betters. Nothing could be further from the truth on a F-150 because the "D" load range tire will be operating on the bottom edge of the weight it was designed to handle. It's kind of like saying that a 10 ton dump truck will haul a 500 lb. load better than an F-150 because it has heaps of reserve capacity.

The fact is "D" load range tires are not ideal for most F-150 owners. They build more heat and are inefficient while simultaneously providing a harsh un-yeilding ride (and it's laughable that you think they will grip better in the corners than the P series tire under discussion).

What we will agree on is that the P series tires many F-150's are equipped with are cheap crap that cannot be inflated above 35 psi. and they are running at the edge of their design parameters even with light loads.