Bicycle operated by transmission device including transmission element rotatably integral with drive wheel and coaxial thereto, and a frame with a front and rear fork; rotatable removable support at the two ends of the arms of each fork, for the hub of a front free wheel and a rear drive wheel respectively, the support including a tie-rod received in a coaxial through-hole made in the hub and in relative holes made at the free end of each arm of the relative fork. The tie-rod, when tensioned by appropriate means, allows holding the relative wheel in position on the corresponding fork. The transmission element supported rotatably by one of the arms of the rear fork. A positive-locking fit rotatably connects the transmission element with the rear wheel hub. The above-mentioned positive-locking fit established when the tie-rod is under tension and nullified when the tie-rod is released.