A mid-drive e-bike is an electric bike with a motor attached directly between pedals on the bottom of the bike's bracket. The positioning helps in maintaining a low and central center of gravity.
Mid-drive motors and hub motors are the two most common e-bike designs used in today's electric bicycles. Both have their own set of pros and cons, so deciding which motor is best for you will primarily depend on your demands and which advantages appear to be more helpful.
