I have a pile of perhaps a hundred used tires. I even have some ~48" diameter tires from a wheel loader.
So far, the only way i have used them is as 'earth bags' to build a half-assed retaining wall. I used a carpet knife to cut the sidewalls 90% of the way around to flip open like a 'lid', then filled them with earth/rocks, stacked the next layer of tires offset from the first, and continued up about 5 layers to make a retaining wall about 3-4ft high along one side of a creek crossing where i placed a 24" diameter culvert pipe. On the other side i built a concrete block retaining wall and poured concrete into the voids to interlock the blocks. Both sides were somewhat experimental and neither side am i really proud of, but my creek crossing has never washed away and it has been traversed by loaded semis so im calling it 'functional'.