Old Iron, the concept behind split rims goes back to early heavy-duty tire construction. The sidewalls were made thick enough that it was difficult, if not impossible to install the tires on conventional drop-center rims. Also, split rims, with their straight center sections, allowed for bigger brake drums to be used without going up a couple of sizes on tire diameter. For instance, my 59 1-ton used 14" brakes on the rear axle, with 18" rims and tires. To use a drop-center rim with those brakes, it would have needed a 20" rim and tire.
There's nothing really dangerous about split-ring rims, IF they're in good condition, and are assembled correctly. They're just terribly unforgiving of incompetence or carelessness.
Jerry
