I just called DiscountTire and they told me 225/40-18 for the front and 245/40-18 would be ok for the rear. They don't carry Falken 255's for the rear.
According to them the difference between the two is like 1/3 of an inch. Sorry for all the questions as I just purchased the car. Joe
How have the Falken tires worked out for you? I am talking to Discount Tire about a set for my IS250.