I would agree on the direction with Boband4. Anything with axle would show wear patterns first, even in 500 miles and you should have handling issues. have you inspected the tread of the blown tires, if axle one edge should rubbed off like an eraser to go out that fast (500 miles). The brake drag is also a item I would check, easy to do yourself. Do you balance your TT tires? You may want to go as far as find a place where they will balance on the TT, the drum/rotor could be out of balance.
Since it is always 1 wheel and so blows so fast, axles (because you can see wear patterns) and tires are not the issue. IMO