Originally Posted by TJC.geotech
You should not run an e-rated tire at 40 psi. They are designed to be inflated to 60~80 psi. Low inflation pressure is the number one reason for tire failure. This is how Ford and Firestone got into so much trouble with the Explorer.
An 18" E-rated tire at 60psi would probably feel very similar to the factory P rated 20" setup. Firm but not harsh.
Going to an LT tire will take some of the sway out of the truck, but you will still be limited to the axle rating of the truck. The axle becomes the weak link and believe me, you do not want to break an axle towing a trailer. Some prudence and common sense is required here.
thanks for the advice. I am assuming that the weight of the tire and wheel combo doesn't have much affect on the towing ability as overall diameter. The weight just hurts my MPG. So would it be safe to assume my plan with the 18" wheel combo (similar overall diameter to OEM) would only hurt a little bit of fuel mileage and most likely no decrease of towing ability (as long as the wheels have the capacity to handle the load of course)?