is it possible for them to rott around the frame under the back bumper
my car underneath is rotted only where the trunk is.... is that bad? and my car also have vibrations coming from the passenger side tire only at high speeds and it makes a thumping noise what could this be
My mother once had her tires changed and they put on one tire that was the wrong size. That was loud and vibrated. I'm not sure that was a thumping noise exactly though.... Are you sure there is nothing stuck on your axle behind the tire? It's possible that it is time for new tires.
However, this is all conjecture as I haven't seen the car. Quite frankly I'd take it to a mechanic. And as the other person said, it is common for cars to rot around the frame. Again, a mechanic could tell you more, such as whether or not it's dangerous to drive your car in that condition.