Step 4: The BeetleBot v2 ( Revisited ) - Motor grip
Same thing with the beetle robot.
The shaft of the motor is the rim and the heatshrink is the tire. Since the robot rests on the shaft of the motor to move around, you will need some grip.
You will need to shrink the heatshrink onto the motor shaft. I use a heat gun but the tip of your soldering iron will do.