This is sort of a newbie question yet i cant seem to find an answer anywhere. Anyways, i recently bought new tires and the markings on the side are 205/55/ZR16 W91 . these are W rated tires (so i believe), so what is the Z doing in the side marking? Aswell the UTGQ rating is 280 AA/A, im figuring i can get about 15-20K miles (30 kilometers), seeing as i dont drive overly aggressively. How many miles would you figure I would have gotten with the V rated 340 UTGQ? Sorry for the long post .