The present invention relates to an electric propulsion system (1) for a rolling object, comprising a chassis (2) with at least one motorized wheel (3) and at least one non-motorized wheel (4), a handlebar (6), coupling means (5) and drive assist means. The coupling means are intended for gripping, orienting, immobilizing and lifting of at least one wheel (14) of rolling object 13). The drive assist means comprise at least one arm (36) of variable length for varying the distance between the at least one driven wheel (3) and the at least one non-driven wheel (4). The present application also concerns a coupled assembly comprising the electric propulsion system and a method of using the electric propulsion system.