True, you can go wider but my 245/35's are perfect on my front 8.5's.

 

what do you guys think about this setup:
8.5 front 225/40/zr18
9.5 rear 275/35/zr18
will the tires rub the fenders in the rear?

 

depends on the tire too, my 245s don't look square on my 8.5, they are a little stretched. I'm running falken 451s, and my next set I'll be installing 255's up front instead

 

I am getting 265/35/18 on my 18x8.5 +35mm soon for my front, I currently have 285/35/18 on my 18x9.5 +35mm. The ride seems normal and more comfortable. It holds more ground. My fender is not rolled or anything. The ride height is stock.