Likely just an easy number to move towards. It's not too big (36) but enough of a jump in size to make people think its better. Pure marketing. 29" kind of made sense, it was already the same rim and tire diameter as road bikes, so making that jump for manufactures of wheels and tires, well all they really needed to do was make there 26" wheels and tires on machines they kind of already had. Remember, this was when MTB rims were huge if they were 25mm wide. And when that kind of stalled, they introduced 27.5 as an...