Ok I went on borrowed time and drove my trailer without a spare. It has 5.3x12 on it. It's a 2 ski trailer. Well I blew a tire the other night and now have had to get smart. I bought two tires of the same size but got C rating vs the B rating that was on it. However, i was wondering if I'd be better served by putting 13" tires on. I tried a 13" trailer tire I had and it fit albeit tightly. Fender wells gave about 1" clearance and the tire had about 3/4 to 1" from the sidewall to the trailer. I am concerned about long hauls and 12" tires. Any thoughts would be greatly appreciated.