Divide the total distance by the number of turns to find how far it traveled in one turn, this would give you the circumference of the tire:
125.7 / 16 = 7.85625 feet in one turn.
To find the diameter of a circle divide the circumference by PI:
7.85625 / PI (3.14) = 2.5 feet
1 foot equals 12 inches, multiply total feet by 12 to get inches:
2.5 x 12 = 30 inch diameter.