I had an inner dual go flat my first year (2005) with the 2001 E450. My 29ft coach had decent looking tires on it when I bought it in 2005. I do not remember the brand. I dont know if I was overloaded but the tire likely was underinflated - I say that because I am unsure. I learned after that to pay close attention to tire pressure. At that time we just replaced that one tire and had no more issues for a couple of years. In 2007 I bought 4 Firestone Transforce HT tires for the rear. These are E rated tires which are 10 ply. I was told that this is what is appropriate for this RV. I have had no issues with these tires and they still look great, even the sidewalls. I don't think you need to replace the coach. As others have said, tires can fail and road hazards will always be there.