The AMGs all have different size front and rear tires (the technical term for it is "staggered fitment"); the key is to ensure that the overall rolling diameter is the same as compared front to rear. In the case of my C36, it has 225/45-17 tires on the front and 245/40-17 on the rear, and if you do the math you'll find that they're almost exactly the same diameter. Going up in section width the same amount front and rear, say to 235 and 255, does not ensure that you'll maintain that equality of rolling diameter.