Trailer tires usually fail because you are overloading them on weight, or your tires aren't inflated correctly. Tire pressure varies a lot with the air temperature and altitude, so check it often. There is a lot more information about boat trailer tire safety on this blog: http://www.boattrailertires.com/blog/. Another thing to remember, too, is that when one tire blows, the stress on the other tires increases greatly while you are trying to get off the road; and there is a good chance that they were weakened by previous blowouts.
