One scenario where one of the child classes below would be used is when the user needs their robot to drive at a specific speed or drive for a specific distance. Both of those calculations require the circumference of the wheel of the robot.

Example:

from ev3dev2.wheel import EV3Tire

tire = EV3Tire()

# calculate the number of rotations needed to travel forward 500 mm
rotations_for_500mm = 500 / tire.circumference_mm