Go back with the same bolts you are using now if your tires are wearing evenly. If you do this work yourself DO NOT TURN THE HEAD OF THE BOLT!! Turn the nut! The shank of the bolt is not round. It is oblong shaped near its head which fits into a similar shaped slot in the cars frame. Turn only the nut then remove the bolt by pushing it out from the end of the nut. Search for "DIY eccentric bolt install" for more info and pictures.