In the mountain bike world, there's really only two modern standards - 650b (also called 27.5in) and 29er's. 26er's were a thing for the longest time, but reall

In the mountain bike world, there's really only two modern standards - 650b (also called 27.5in) and 29er's. 26er's were a thing for the longest time, but really no one makes new bikes in that size anymore. We're mostly riding on wider tires, 2.3 seems to be a rational minimum for real trail riding, and you'll often see widths of 2.6 and beyond (and fat bikes of course go way wider) on both 27.5 and 29in bikes.