Split rims represent a piece of automotive history hardly used today. Due to the heavy use of inner tubes to keep tires inflated in early vehicles, well before the days of tubeless tires and solid wheel rims, split rims made it easy for a vehicle owner to pull out a flat tube and replace it on the side of the road. However, these rim types had their flaws, which appeared over time as the vehicles aged.
In a split-rim wheel, the rim that the tire is beaded onto consists of two or more parts. When the tire is deflated the rim nuts can be loosened. The rim halves then separate and come off the tire with a little encouragement from a tire lever tool. Inside the tire and on the rim halves sits the inner tube that keeps the tire inflated; without the inner tube, the air pressure would just squeeze through the halves.
Vintage scooters, such as the Italian Vespa and Lambretta scooters, predominantly used split-rim wheels. This feature made it easy for riders to repair a flat on the side of the road, as long as a new inner tube was available inside the glovebox. However, when such tubes failed, the loss of air tends to be catastrophic and can cause a significant accident if the rider is not paying attention at the handles. Unlike solid rim tires that just leak air out until flat, split-rim tires lose air pressure suddenly.
Large Vehicle Application
Split rims can be found on off-road vehicles, old buses and large construction vehicles as well. Again, the intention is to make it easier for the operator to repair the flat tire out in the open rather than having to bring the vehicle in to a mechanic's tire-rim separator machine. However, such units can be difficult to actually manage repairs and frequently take some serious grunt power and levering to pull the rims off the tires.
Commercial Truck Wheels
Very old commercial trucks from the World War II era also used split rim wheels. The system worked with two halves, but the wheels had a lock circlip-type solid ring that kept the parts together when assembled. The ring had to be removed first when the air pressure was deflated to then get the parts separated. Half-ton, three-quarter ton, and full one-ton trucks were assembled with these wheel systems and corresponding rim sizes.