What I'm refering to as a "2 piece rim" is a rim with a removable ring on the outer lip. Basically you stick a prybar in a groove on the rim and pry the ring off. There's maybe only about 1/8" material on the rim, and in some places not even that much, which hold it all together. The pressure in the tire is what holds everything in place. On a rusty old rig, I think it's a recipe for disaster.
