My Eibach lowered car had 285s on 20" rears when I bought it. The ride sucked and the tires cost too much to replace. These cars were designed so all the systems work together -- going custom on the wheels and tires adds expense and a high PITA factor for very little reward.

I just went back to stock size rims with stock front tires and 275 rears. The difference in ride quality is phenomenal and no more scraping. If you race, spend the money for a professional setup and you will be happy. If all you do is cruise surface streets, go ahead and spend the dough for the bragging rights. If you're like most people, spend less and have more fun on the freeway. Nobody will dis you for having "only" 275s. See my gallery photos for views of old and new setups.