I have a trailer that the previous owner had put on one 8" tire and one 12" tire. I replaced both with new 12" tire and rim combos. The problem is both tires are worn out after about 5 trips to the lake. There is less than 400 miles on them. One has even worn to the cords in the fabric and went flat in the yard. The axle is attached by 2 U-bolts. The tread was rolled or peeled off from the center of the tire out. What can I check and do to correct this issue?