The rear wheels translate motor's rotation to the movement of the car. If the wheels get damaged or misshapen, they may not allow the motors to move the car and will need to be replaced. The following steps will show how to replace the rear wheels.
Unscrew and remove the 5mm Phillips #0 screw located at the center of the wheel while holding the wheel still.
Slide the wheel off of the axle.
Repeat the previous steps for the other rear wheel.