Hello there big wheel people, I have a historical trivia question for you. The first bike I ever rode had fat tires and small rims, but it was a full-sized bike, not a lawn-mower mini-bike. The outer wheel size was similar to a normal trail bike. The bike belonged to my friend Shane's family, and they referred to it as a "Chibby" (my phonetic spelling). It was blue, and had enough power to wheely Shane and I off the back when we were 10 or so & riding two up. The vintage was probably early 1970s. Fender, tank & side covers were metal, not plastic, and the seat was a conventional flat two-person 'loaf of bread' like a 60's or 70's street bike.
In recent years I've tried to figure out what that bike was, and have gotten nowhere. I figure here on this thread, there might be some people with a knowledge of other fat-tired bikes beyond the Yamahas . . . does my limited description ring any bells?
(feel free to PM me if you are stumbling across this post some time long after it was written)