Here is a video that I made showing how to break down your riding mower tires and then install inner tubes.
I am sorry for the wind in the opening segment, and also sorry for the video jumping around a bit. It turns out my camera wasn't recording for the vast majority of the job so I had to creatively cut and splice the remainder to get the job done.
Know this. THIS JOB SUCKS.
I did all 4 tires on this mower, and each presented its own challenges. Time and determination is what is required to get it done!