When I had flat tires in the past, I could not break the tire bead loose from the plastic wheel rim. I took the whole assembly to a tire shop where they broke them loose, but I worried that they were going to break the wheel. This time I tried something a little different.

I made a fixture from three pieces of wood. Two 2x4s were placed side by side and a circle marked whose radius was slightly larger than the wheel rim OD. The inside material was cut away, and the 2x4s were centered and nailed to a backing plate. The tire stem valve was removed and the wheel centered on the fixture with the three clamping bolts still in place. I stood on the wheel with one foot (about 190 pounds) and the bead popped loose from the rim. The wheel was flipped over and the process repeated. Next I removed the wheel clamping bolts and using a large screw driver I was able to continue to slide each tire bead away from the rim and to pop out the wheel half. This process was unbelievably easy compared to my earlier efforts.