20x8.5 with 245-35-20 tires is what I'm running with no problems. I installed all new front struts and rear shocks prior to getting the rims which I highly reccommend. My car has 190k on the factory suspension so it was overdue for it. Also make sure your rear leveling system works properly with no leaks in the air line.
Other than that you should have no problems. Make sure you get an aligment, you don't want to mess up brand new tires.