Going side to side WILL cup the hell out of your tires. Every tire I rotated side to side because the customer is always right came back a few months later with cupping or belt seperation causing a nasty bump in the tire. Side to side was fine for bias ply.
IMO, rotating wears down all 4 tires so you need to purchase 4 at a time instead of 2. On my cars its usually the 2 rear.
