That was one thing that surprised me between the US and Canadian sites ... we seem to get much more information on the Canadian site. The trim I selected gets 20s ... but, as you can see above, they list both 18 and 20 on the Ultimate trim. Personally, I'm a big fan of smaller wheels and taller sidewalls. Lots of reasons - replacement cost is only one. Rim protection is a BIG one if you live anywhere with monster potholes. Doesn't just prevent curb rash! Ever see someone with 20 or 30 series tires nail a pothole and bend a rim? I'll take sidewall EVERY time, unless I'm literally buying a performance car where the smaller sidewalls help with handling. I'm not going racing with a mini-truck!