Super poke. Like said before it dosnt appear those wheels where ever made in that size. 10.5" is the max I could find you can buy based off the chart on the enkie site. I don't think you'll find many people trying to widen that type of wheel into a 18". I believe he thinks diameter is the same as width. To the op width is the size between the outside and inside lip. Diameter being the face of the circle of the rim. Besides bolt patern another major factor is offset or known as backspacing. If you truly have 18" wide wheels you would definitely want to know that number. It's only very narrow widths that you can take a shot in the dark on offset. Like said with the wrong offset you can hit stuff in the tubs to keep the wheel from going on.
Never liked pokies, flush 'em! Of course that would require a reengineered frame and a narrowed axle, probably tubs since the fat ass tires would likely be 30"+ diameter. Oh My younger days............
Yeah, thin skin and no sense of humor. If you expect straight-up tech go to the factory. Go to a forum and you'll get your answer, and, of course, a little funnin'. Have a chuckle and make a few friends. I always say to put your general location with your question and maybe there'll be someoune around the corner that can lend a hand, but..........