I am replacing tires every few years but I really dont put a lot of miles on them. I would be surprised if I got more than a couple thousand miles out of them. I have ran the 4.80x12 tires on a couple different boat trailers with similar results so I dont think its the trailer. I have thought about going with a bigger tire and wheel but the fenders are welded on and the trailer is galvanized so Im really not wanting to move the fenders.
Anyone found a tire that they have gotten good mileage out of?