Hi all, Im very interested in rock crawlers. And I took a step ahead with the purchase of my first crawler - Tamiya CR01. Now theres something bugging me and that is the wheels. I had looked at different threads and forums but i cant find anything that specify the difference between 1.9 and 2.2 wheels. What does they mean by 1.9 or 2.2 wheels? Is it the wall diameter or the tyre thickness. Pardon me for the quest as im a noob in the crawler scene...........