I looked into really fat rims before I settled on the Big Apple balloons. Most of the available rims appeared to be in at best theoretical production, except those made for the unicycle crowd. They have a specialist subgroup, the mountain unicyclists, abbreviated muni. These guys use seriously wide rims, starting at 30mm over the tyre retainer beads, and some use 30in and even 36in diameter rims. All the wide rims that were actually available to buy had lightening holes, and the tube was protected by a tough layer of lightweight plastic on the inside of the rim between the holes and the tube. At a quick glance that could look like a pressed indent in the rim between the spokes.
