Tires: Can tire sizes be changed?, foot travel trailer, ford f 250

Question
I have a Ford F-250 short bed 4x4 diesel pickup.  I need the diesel power but only use the pickup for towing a 31 foot travel trailer.  The truck rides rough because it is always empty.  I would like to use passenger vehicle tires to try and get a better ride.  The truck currently has LT 235/85R16 General Ameritrac OEM tires with an E load rating.  I know that the wheel diameter must remain but is there any problem with using a P255/70R16 or even a P265/60R16?  I'm sure that these passenger tires would exceed the load rating of the unloaded pickup.  Secondly, whould this type of change produce the desired results?

Answer
Bruce,

P metric tires are designed for passenger cars and have to be derated so they can be used on regular pickups.  This derating means that you can not go by what is printed for load carrying capacity (the true load carrying capacity for a pickup application is much lower)  This means that P metric tire do not have enough load carrying capacity for a heavy duty truck.  If that were to happen, there is a possibility that the tire could have a load related failure - which sometimes have tragic results.  I can not recommend anyone use a P metric in place of an LT metric - and vice versa.

BTW if you tow, you don't have an unloaded pickup truck.  The trailer adds weight to the rear bumper, which in turn is carried by the tires.

It is unfortunate, but your situation does not lend itself to a soft riding truck except when it is towing.  I suggest you rethink the vehicle situation if the soft ride is that important.