I have a large pile of tires that we used in the garden before switching over to concrete blocks. The sidewalls are cut out to make rings for boarders around trees or small raised beds. Some of the rings have been cut and screwed together with others to make larger beds. There are even some tractor tire beds. There are the tire sidewalls in the pile as well.
Shoot me a text and I'll let you know when I'm available for you to come look it over. You can sort through it and take only what you want, I only ask you keep the pile neat and not spread it all over my yard. Gloves recommended and watch out for the screws holding some of the double rings together.