Just the front. When the outside edge of the tire moves out, on most Mopars they tend to rub the front bottom fender lip. My 245/50/15 on 15x8 4.5" backspace rims barely fit.
When I tested the Minilite 15x9 with 4 1/8" backspace it flatout hit just turning the wheel parked. The outside edge of the tire in theory should have moved out 1/2 from the 1 inch wider tire and 3/8" from the decrease in backspacing. That's almost a total of 1" compared to the previous rallye rim setup. When I held a L square comparing one side to the other, it confirmed is was about 1" inch out. When you mock it up, when the front tires turns it was a little under 1" closer to front lower fender lip. So I could have just trimmed 1". But I felt I was too close allready. So I went to a 2" fold. Looking back I probably could have got away with 1.25" to 1.5"
Looking from down low right from the side, the 2" fold I made looks pretty aggressive. But on a Cuda the fender rolls in so much that when you stand 10 feet away you don't notice it as much. The closer you get at standing eye level, the less you notice it.
When you run a 17x9 and 5.6 backspacing, you run into the same situation. Read here:
http://www.moparfins.com/CLAIRDAVIS/Cobra_Wheel.htm Clair is only running a 17x8. With a 17x9 and 275/40/17 tire the outside edge will be further out. So