I didn't have to touch the fenders at all.
The 235 is square on an 8" wheel and has a little stretch on a 9" wheel. I'm not sure what look I like better.
I bought mine used from a guy on the forums. He said they were all 18x8 wheels. The tires on the rears were completely shot, so he pulled them off and sent me bare rims for the rears. The fronts had good tread, so he left them on. So before I even got the wheels, I bought a set of the same tires as were on the fronts already (thinking they were all the same size wheels). When I got them, I had the new tires mounted on the wheels and went to put them on the car... It was then I found out that 18x9 + 43 doesn't fit without rubbing on the fronts because I tried to mount the rears on the fronts.
The result is that I have 235/40/18 tires on 8" wide wheels in the front, and the same tire size on 9" wide wheels in the back. I'm going to start a new trend!!!
Check out this thread that I went through a while back. It's pretty funny! Shows how much of a noob I am with wheels/tires as well.
zerothread?id=193125