i think mine are, my rear tires hit the fender wells alot easier than it use too

struts won't hit your fender walls when they're blown. blown struts give a bad ride. if you have a bad ride on new or decent tires than i'd say your a candidate for new struts. a blown strut will alot of times leak fluid from the top or sides. look for wet spots and feel rub around the strut. if you get anything other than dust on your hands you could be leaking.

i'm guessing you hear a loud whacking sound in the rear of your car and you think it's your struts. the loud whacking is most likely your wheel bearing. they come lose at the top where they connect to the body. when you go out to your car in the back you'll see a big metal bar. it goes from behind your wheel to up under the fender. try to wiggle it from the front of the car to the back. use good force. this shouldn't be lose at all. if it is it will most likeley be causing noise while going over bumps and while braking. this will also give you serious tire wear problems. your ride will get bumpy and start to vibrate more and more as your tires wear.