I have the exact same axle ratings as you (3750lbs front, 3850 rear) even though it has the 3.55's. Payload rating as per door sticker is 1540lbs.
With the heavier tires, my payload would be about 1540 lbs.
Wow, that's to low for my tires. I lost about 2 mpg and tire noise and vibration was worse. The truck also was working more like the tire was too flat.
Maybe 55 is higher than I need, but the ride is very good with a bit more stiff. Airing down a bit more will likely still be good but taking some of the stiffness out.
I read a few people who did the chalk test with the 2009 - 2014 F150, and they air between 50 and 55 psi and said the chalk test was right on at those pressure plus had better wear.
I guess it would be nice if I could get a conclusive answer from Discount tire and BFGoodrich but they are so far off from one another.
And I've read that E rated tires require more air pressure for better wear and fuel economy which seem spot on from my limited findings.
Thanks everyone
