Shaft

• The shaft is the portion of the motor that drives the mechanics of your vehicle's transmission. In 540 motors, the shaft is slightly shorter than that of the 550 motor. This allows for the longer length of the 550 motor, and provides more surface area along the shaft for bigger magnets, which generate the energy used by the device.
  
  

Commutator

• The commutator is a cylindrical section of metal mounted to one end of the motor shaft. The commutator is housed within the main body of the motor (called a can) and connects the metal brushes to the rotating armature. The 550 motor has a larger commutator than the 540, which provides more surface area and a stronger connection. This provides greater force, which translates into improved torque.
  
  

Torque

• Torque is the force of rotation; in other words, the motor shaft spins with a certain level of force, and more torque provides quicker rotation and faster vehicle acceleration. A 550 motor has a greater amount of torque than its 540 counterpart, which is why it is usually found in larger vehicles with heavy wheels.
  
  

Magnets

• Any electric motor derives its mechanical force from magnetic fields inside the device. The larger the surface of the magnetic, the stronger the force it exerts on the rotating portion of the motor. Because of their longer length, 550 motors have longer magnets that afford greater mechanical force.