how I used manual tire irons to change a rear tire on my Oliver 77. The tire is 6 ply, 16.9x26. The irons (spoons) I used are one 30" curved and one 24" straight. They're from the 1940's that Dad had and used. I've used the same irons on the 10x24 rears on my AC-B, as well as the fronts and a numbers of other tires. It really isn't that hard to do with typical antique farm tractor tires. The hardest part can be breaking down the beads that may not have been broken in many years.