6. If you don't have turn plates, you can measure on the floor to get exactly twenty degrees of steering, cut a 30-inch piece of 1X6 wood or similar straight, flat piece and lay it against the tire. Mark midway on the wood (15 inches) and line that up with the hub. Mark the floor at the outside corner of each end of the wood. Turn the steering wheel until the ends have moved 53/16 inches and you will have turned the wheel 20 degrees.