How do I remove the rear wheels from my Honda self-propelled mower?

Taking off the bolt is easy enough. And the front wheels just come
right off. But the rear wheels stay put. They spin around just fine,
but won't pull off. Maybe I'm not applying enough force, not wanting
to hurt anything? I figure it has something to do with the propulsion
unit, but don't know what.
The rear wheel treads have worn down. I want to switch the front and
rear wheels.