I find this page to be very helpful for this. Rim & Tire Size Calculator. Custom Offsets Put in your stock wheels/tires and the ones you want and it will show you what changes. Lower offset is going to move the wheels out. What size tire are you going with? I have 19x8.5's and with a 225, it's the most stretch I'd want to have. I wish I could have got the same wheels in a 7.5" or 8" width, but they don't make them.