Hi Jim,

Been a long time since we have talked. I read in your thread your desire for 37 inch tires. I look at this somewhat differently, as there are other considerations not included in the discussion that are important to long distance trailer towing.
If I did my calculations correctly you have an effective or nominal 3.55 equivalency for a final gear ratio with the 37 inch tires compared to stock. However the tire weight would make a loading or inertia comparison to a higher final axle ratio in terms of torque required to get things in motion. Not so?

You have a engine rpm target in mind and at a certain mph. If that rpm is on the low side of the torque band you may need to apply more fuel which increases exhaust gas and transmission temperatures beyond that which is desirable, especially when in mid-western mountain states. If you need to shift down one gear to change loading, and reduce those 2 temperatures, one might do better with tires of less diameter, better handling, braking, and aerodynamic qualities by reducing truck height.

One of the greatest contributors to fuel economy while towing is driving slower. Doing may put you below that desired rpm if you are geared tall. Pushing the speed up to get into the sweet spot on rpm may be counter productive due to air resistance. If I'm correct, your trailer model is a full 8ft+ wide and many trailers on the road are only 7.5 feet wide, for comparison.
It all adds up.

Another consideration about vehicle gearing and desired road speed is trailer tire specifications. Many trailers come equipped with tires that leave less than 1000 lbs capacity above dry trailer weight. Add H20 (sometimes down the road one ends up with it in all three tanks) plus food, drink and gear and the trailer can be loaded beyond tire ratings very easily. Combine that with temperatures and speed (beyond rating)and tires overheat and fail on the road.

While my discussion isn't answering the question of best tire to buy in that particular size, I believe it constructive to the driving theme of fuel economy and towing and some of the other related considerations of travel trailer efficiency on the road.

Happy Trails,

Marv