I have a tire half buried in my backyard for beating with the sledgehammer. I was telling this to my brother when I was at his shop, he is a mechanic and gave the tire. One of his customers overheard and asked how it was used. I explained that I use it for conditioning and what not and explained how the tire was set up and so on.
I just got a call from my brother to tell me this guy ended up with 27 stitches in his head and a lump the size of a baseball. It seems he used a tire still on the rim and filled with air, first hit with the hammer caused it to bounce back and hit him right in the forehead.
I guess I assumed he would know enough to use a tire off the rim.