If you do it right, you’ll be working your glutes, hamstrings, and back - also known as the deadlift muscles. At the end of the movement, when the tire is vertical and you push it over completely, you engage your triceps, biceps, and chest. (Sometimes you can even get a little bit of ab work in there if you keep your belly button pulled in towards your spine as you stand up straight.)
Just be careful. If it’s your first time showing off in front of the other farmers, start with a relatively light tire - one that weighs somewhere around your deadlift range.