An old tire, some rope or chain, a tall tree -- could anything be simpler? The backyard tire swing has been entertaining kids pretty much since backyards were invented. Here's how to set one up right.
If you don't have a large enough tree, you can retrofit a wooden swing set for either a vertical or a horizontal tire swing.
If possible, find a used beltless light truck tire or old tractor tire (try a junkyard or tire store). Avoid steel-belted tires, whose sharp cords might eventually work their way out of the rubber sheathing.
Drill holes in the bottom of the tire so rainwater can drain.
Choose a healthy hardwood tree such as oak, walnut, sugar maple, ash, or cherry. (Beech, while strong, has delicate roots that resent trampling.) Make sure the branch is straight, forming an L-shape, not a V, against the trunk, and strong -- at least 8 inches in diameter where you attach the swing. It should be 9 to 12 feet off the ground (the higher the branch, the farther you'll swing).
The best way to suspend the tire (for both the swinger and the tree) is with a length of 3/16-inch playground chain. Drill a 12-inch hole through the center of the branch, then insert a 12-inch drop-forged eyebolt through the hole, securing it on top with a washer and two nuts. (If you use rope, choose nylon or Dacron. Polypropylene and hemp don't weather well, and polypropylene can also slip too easily through small hands.)
Drill a 12-inch hole through the top of the tire. Thread a nut, washer, and 3-inch fender washer on another 12-inch eyebolt, slip it through the tire, and thread on another fender washer, washer, and nut. Secure the chain to the two eyebolts with 14-inch quick links.
Spread a circle of mulch or wood chips around the trunk to protect tree roots and cushion falls.