Inner and outer Electric Bikes gear shift

Prior to know them, it is necessary to know the concept of the internal gear and the external gear . Simply put outside the transmission gear means mounted on the outside of the Three wheel bikes bicycle exists as a separate part , and the inner gear is hidden in the rear hub represents the concealed parts.
Presented directly outside the outer gear , direct contact with the external space. The speed but hidden inside is not in direct contact with the outside space. Thus, due to the design of outer space becomes larger , have greater speed range , used mountain bike . However, due to exposure and rain , dirt , oil , etc., so care must be regularly cleaned , and do not in the periodic maintenance of the shift , but the shift in the Womens mountain bikes design due to the limited space , so the more limited speed range , typically used in the city the riding light trucks as much.