These types of tires are often refered to as "directional", and if you were to stand back and look at the tire from a few feet, you will see that the tread design makes somewhat of an arrow. This arrow needs to rotate forward for a couple of reasons. One is that when it picks up water, it pushes it out instead of traps it, causing hydroplaning. In addition, many of these types of tires have a more solid shoulder on the out side edge, while the inside may have more voids. This is done as a noise reduction factor. The larger the void of the tread at the casing, the more the road noise. And some of these tires, I recall the contintals and some of the pirelli's, had a softer rubber compound on the outside shoulder as it was supposed to help with cornering. To answer your question, no, it really won't cause any major concerns with the tire rotating backwards. But, it is something you should have turned around as soon as practical. On reason that it is recommended to rotate radial tires front to rear instead of side to side is the way the radial cords lay after a while. When they are turned around to run the other direction, there is a higher risk of them separating. Without knowing your tire shop personel, and knowing the manner in which many of the tire shops operate, one or two of the tires may have been turned on purpose simply because you brought them the labor and not the retail tire business. Sort of like bringing your own steak to a resturaunt and then asking the chef to cook it and subtract the price of the steak from the bill. Don't ask me how I know, just know that I know ; )

Leonard

(Burned out retired tire shop manager)