If you are serious about switching present tires out, A. Lose the 15" wheels and replace them with 16" or size wheel that fit's your truck. 15" are hard to find in passenger,light truck ,trailer or anything else so they will soon be obsolete. B. Give your truck a new set of LT tires and move old truck tires to trailer. LT tires are tested and approved for much higher standards than trailer tires. C. Buy only domestic tires because overseas mfgrs can't be punished for inferior products so they don't strive to make high quility products.
jaxs, very good post! I agree, mostly because I have done the same in planning as your suggested. However, I ran into a few issues with my trailer that wouldn't allow the suggested change you mentioned. I wanted 16 in wheels on my enclosed trailer, but they won't fit due to height of the wheel pocket. Going to a slightly wider tire was also not a option due to how close of clearance to the inside of the tire/trailer. I thought that maybe I would just go with 14 ply tires, however, besides not being able to find a supplier of 14 ply tires in 15 in range, it also severely overloads the existing rims. My final decision was, when I get ready to start hauling this trailer, I would just order new axles and springs with spacing to allow for the size tire I wanted. Not a cheap venture, but neither is blowing a tire out on the highway if your in the middle of nowhere. (a single tire, got a spare, but multiple blowouts due to a heavy trailer loaded to capacity on already marginal tires, you can't carry enough spares)!
I feel for those who buy new travel trailers, because when I was shopping, every tire on them was severely under rated. The tires would be ok as far as the capacity of the trailer, but once you put a week or months worth of supplies in it, they were right at max, and we all know running tires right at their max rating never works!
Something else worth mentioning on trailers that are used occasionally. Date codes!!! This is especially true on lighter duty tires, because the age of the tire really does matter. 6 years is the approximate lifetime of a standard tire. Most reputable tire shops won't mount a tire (or repair it) after 10 years of age.
If you don't know how to read Date Codes on tires, do an internet search and learn. It could very easily make the difference between a safe trip and sitting on the highway waiting on a tire truck.
David from jax