Re-read what Begeezus wrote. You can use any number of wheel and tire size combinations as long as the outside diameter of the tire is about the same. also the wheel should be large enough to clear the front brakes. 18" will clear front brakes on a 2009, possibly 17" but you should have plenty of options with finding an 18".
For outside tire diameter you can look them up for different tire sizes. I just go to Tire Rack's website and pull up the specs on various tires there. They will have a chart with all available sizes for that tire with height, width, load rating and revolutions per mile among other items. You can have a fat tire, skinny tire, smaller wheel with a taller profile, bigger wheel with a shorter profile, whatever as long as the outer diameter is close to your current tires.
