Age is a big factor. I had a "brand new" 16" trailer radial on a spare wheel that was stored inside a trailer or in a garage for about 6-7 years and it looked perfect. When I finally had to use it, the tread peeled like a banana after a couple of thousand miles, It rode on the steel belt for a few miles until I found a place to pull off. Looks like the tread separated from the belts on yours too. I have friends/racers who own a tire store and they change street & trailer tires every 3-4 years regardless of wear.