Hi gang!

I just bought a new set of Firestone Destination A/T's, $567 mounted out the door, what a deal!

I'm running 40psi in these tires to decrease roll resistance, though Ford recommends 35psi (for ride quality I assume). Has anyone else had negative effects running higher psi?

 

The 35 was for your previous tires which were P series tires. What load range are the new tires, and what max pressure?

 

Wow! That was fast.

The new tires are 4 ply P tires with 44psi max presure.

 

I don't have any experience with those, but try the 40 and see how it goes. Those are extra load p Series, where is the old were regular p series with a max of 35. Not sure whether you will have to go up or down (unlikely) at all.
Because you changed load rating, you will not be able to use the door numbers.

 

Sounds kinda high. The center of the tread may start to wear out pretty quick. I always chaulk new tires to make sure the tread will wear evenly. I run my 265/70/17 P Revos at 30 psi. They wear even and the ride is pretty comfy.

 

30 is well below what it should be for an F150. Think Explorer and Firestone. Also your p series tires are not p series extra load or LT tires. One pressure does not fit all unless they are exactly the same load range on the same type vehicle.
Too low a pressure will cause overheating, blowouts and tread separation.

I have yet to see a door sticker for an F150 that has p series tires that doesn't say 34 or 35 psi recommended pressure.