Wheel Rim problems of the 1998 Chevrolet Tahoe

Sometimes when I am driving the steering wheel shakes,I can drive on the same road and it may not. I have had the front end aligned by the chevy dealer in which I bought the Tahoe and also had new tires put on at the same time. It seems like it will go away for awhile and then it comes right back and then I have to have the tires rotated because of bumps forming on the tires and this happens in a very short time. I have had it aligned by 3 different dealers and they say it is in spec and that is all they do. I have just put another set of tires on it and it is starting to do it again. I have been told that there were some bad rims manufactured that year, could that be part of my problem.