I have a 1993 pontiac grandam gt 3.3 lt. four months ago I got all 4 new tires and a front end alignment(they said a 4 wheel couldn't be done) but now the back 2 tires are going bauld on the inside. The front two are fine and the front I could see since I have to replace everything. now ihad it check and I know there is shims that are connected to the drum. Could a rear alignment be the problem?