A bicycle with a rear drive assembly configured to allow pedal boards to be pivotable while moving in an elliptical trajectory and which allows a cyclist to ride in an erect position is disclosed. A front end of each of the pedal boards is pivotably connected to an end of a crank and each of the pedal boards is connected to or integral with a guide rod extending rearwardly from the pedal board. The guide rods are supported by a rear drive assembly comprising a transverse tube that is horizontally connected to a frame of the bicycle. A roller is mounted at each end of the transverse tube. Each roller has a groove which accommodates the cross-section of the guide rod.