Just tapping the automotive knowledge base here about something that just happened to us: My g/f has a 2009 BMW 335i convertible with the sport package. It has staggered wheels/tires -- it has 225/40/18 on the front, and 255/35/18 on the rear. I don't know for sure, but for now, I am assuming all four wheels are the same size. She has been taking it to the local dealer to have her winter/summer wheels/tires swapped each season. This morning before she left on a long trip (about 300 miles each way), I went out to check her tire pressures. The fronts seemed a little high (39 psi) and the rears a little low (38 psi). The fronts should be 35psi and the rears 42psi. Upon further review, apparently the dealer decided to rotate the wheels/tires, and put the rears on the front, and the fronts on the rear. We will deal with the dealer when she gets back in a week, but my really important question, is what are the risks of running this configuration during her trip? Is it unsafe? I understand it may handle differently, but she's not really a driver who will notice. I'm more concerned about her safety and any risks of damage to the car. Thanks.