The split rims require a special-shaped pry bar to fit a small slot where they join in the center. It's almost impossible to get them to separate without it. No, there's no danger once the air pressure is gone, but the beads still have to be broken down with a tire hammer on both sides before the pieces will separate. If you don't have the right tool, just let the air out and get a professional shop to dismount the tires.
Jerry
