I will be changing my tires in a couple of months and have decided to go with the Bridgestone Potenza RE730's. These fell more into my budget. I'm not sure what tire size to go with. I am running on 17" E36 lightweight wheels with 225/40/17 on the fronts and 235/45/17 on the back. These are what came with the car. I was thinking of going with 235/40/17 all around but wanted to get your opinions first. I was also curious as to why the previous owner put different sizes on the front and back. Thanks in advance.