Go look at the rear fenderwell. Look and see where the bumper meets the fender. Look at how they attach. On my 99 sedan, there is a tab on the rear bumper that kinda juts out and isn't really needed. I could see that my tire was rubbing on it, it had worn some of the tab off. Some people will grind that tab off with a dremel, etc (it's just plastic). If that doesn't help, and it's rubbing on the fender, then your best bet would be to bend or "roll" the inner metal fender lip upwards. Hammer...no. There are a lot of methods out there, even some specialty tools for it. I've personally never done it, but others I know have simply just taken the handle end of a baseball bat, or a metal pipe and just used the tire for leverage and bent the lip upwards. If you are lowered, you'll probably need to jack the car up a bit to get the pipe/bat/whatever in there, but it sounds like you aren't so you won't need to.

If you do it, go slow and see if minor changes help before getting crazy with it.