I would like to know if it is better to have an E (10 ply) rated LT tire for towing my travel trailer which has enough tong weight to bring down the bed of my 2006 F150 about 3 inch's when hooked up or if a C (6 ply) rated LT tire will do the job. I only tow the trailer during camping trips in the summer so most of my driving is just normal on road going to and from work. Right now I have the stock OEM P235/70/17 tires and they bulge out at the bottom even without a load.

Thanks,
Greg

 

Load range C should do just fine. They are rated well above your GAWR/GVWR.You just may have to add a bit more air. A LT LRC tire on your truck would normally need about 40psi. A bit more maybe when towing. I would also stay with about the same size, otherwise you would be raising the gear ratio and lowering your tow capacity.
It does sound though that with your tongue weight, you would definitely benefit from a weight distribution hitch.
As far as your OE tires, a P series, I don't like them for a truck, even without towing.

 

When towing, it's always best to go with the overkill. How big is the trailer and what does it weigh?

 

The trailer is 25 ft and weighs about 6900 (dry).

Thanks
Greg

 

You are definitely pushing it with a 150, and will definitely require a weight distribution hitch. The load range C tires will be enough as most I have seen have a load capacity of at least 2400lbs per tire. The F150 doesn't even come close to having a 10k GVW.