I am trying to figure out if you can create backspacing yourself or if it is already set when you buy a rim. I have found plenty of articles on how to determine what back spacing you need, but have not found how backspacing is done.
I have a 91rs with 16inch iroc rims with 245/50/ r16 tires that when i turn somewhat sharp will rub against the inner fender.
They rub in the back of the wheel well towards the compartment of the car. If my car is parked I can turn the wheel and see where it barely touches, but when i drive it actually touches more. Do you think my suspension is sagging too much or do you think my backspacing isn't correct?

 

Yeah, backspacing is already set when you buy a rim. Unless you wanted to un-weld the center from the outer edge, and re-weld the center into the correct position.

Just don't turn the wheel as much... seriously!