What is the average size of a semi truck tire?

Usually, it'll be XXX/75R22.5 or XXX/80R22.5, with "XXX" being 275, 285, or 295. On a 22.5 inch wheel with a 75 aspect ratio, it'll have a diameter of 39.33 inches. With an 80 aspect ratio, it'll have a diameter of 40.45 inches. A 24.5 inch wheel and tire will have a diameter of 41.33 inches with a 75 aspect ratio and a diameter of 42.45 with an 80 aspect ratio.