Depends on your wheel setup. I was able to lay crossmember up front without cutting with a 225/40/18 tire. It did rub a tad, but nothing to damage the tire. I am on stocks right now with 225/60/15 tires and the driver side rubs, but I still left the spalsh shield in.
The rear you are need the rearend narrowed or have a wheel company build your rims with custom backspacing. I have the stocks on there with the 225/60/15 tires and I have to cut the lip off the fender completly. Otherwise they would have cut up my tires. Actually, the pass side did, but I trimmed it a little more and no problems.