My reg-cab 2wd needed four traffic lanes plus a full-width middle lane to perform a U-turn. So essentially five lanes - how wide is a regular lane, 10ft? This would put me at 50ft diameter, or 25ft radius. I had three things working against me - it's a dually truck, it has a bumper that does not allow the front wheels to turn as much as they could from the factory, and most importantly at the time it had a welded rear differential which makes for a rather severe case of understeer. Dunno if that helps you any...