I just upgraded to a LT tire on my truck.LT275/65/18. This is stock size for the Lariat. The P rated tires are NOT up to the job! I tow a 34' Trail Bay with my 04 F-150. There are pics in my gallery. The loaded weight/ ready to camp is right at 8300#'s. The truck does great on the flats but does work in the hills. Let the truck do it's job. If you do alot of mountain towing I would suggest staying on the light side... 5000-6000# range. If you're mostly flat land then let er rip. I have a Prodigy brake controller and EZlift WD hitch with friction sway control. I love the Prodigy but dislike the EZlift and friction sway for this length trailer. Equal-i-zer is ordered and should be here this week. The truck tows great. Keep up with your service and I would suggest a gear swap on your truck. I have the 3.73's with a class V hitch. I wouldn't go with any less than that. I do run an Edge programmer and custom Flowmaster setup. The tranny temp is usually right at 190 in the mountains with 100deg days. Flat land it runs right at 170. I cruise at 63 MPH with OD off. Good luck with your search. We love our Trail Bay.

 

As an update I asked Cooper tire about my discover H/T 265/60R18 tires. They stated: "These tires are P Series reinforced rated or extra load tires.
The max carry load for this tire is 2601 lbs, at 50psi." Anyone think these are adequate for towing? If not do you have any reccomendations?

 

I tow a 7,000lb boat on P-rated 285/60R18 performance tires. Their weight rating exceeds what the stock tires were, and I don't really have any issues when towing.

Personally I don't like the hard ride of LT tires.
There may be some advantages to them, but I haven't had any tire issues.

 

Almost all of the "P" rated tires are only 4 ply. They are rated to 35PSI and thats it. LT tires come in 6,8,10,12 ply. THey are coad rated as C,D,E,and F. The higher the capacity, the more air pressure. Load D tires usually run at 50 PSI C range run at 45. This is of course depending on tire width and diameter. My Load E tires size 275/65/18's are rated to 80 PSI. I don't have to run 80. I am running 60 in the rear and 56 in the front. I might bump them just a bit more but not too much. At 75PSI the truck was all over the road! Right now I can drive with one finger on the steering wheel.

 

What is the tounge weight on your boat? I bet it isn't in the 1000# range. My trailer is in the 1000#range and when towing the rear of the truck would walk back and forth on the sidewalls. You can't compare towing a boat to towing an RV. Boats have no frontal area, most do not require a WD hitch nor do they need a sway control. I have towed my father-in-laws Procraft boat. The boat is 4000# the trailer is 2000. I don't even know it's back there. It doesn't even drop the rear of the truck!

 

Thanks again for everyone's insight. I ordered by 4.10's, tires, and a edge evo today. Looking forward to the mods.