The invention relates to an active aerodynamic system (1) for vehicles which comprises a moulded plastics structure (2) arranged to receive movable elements (3; 4) and an actuator (7) off-centre with respect to the structure (2). The system (1) of the invention comprises a force transmission member (5) which connects series of movable elements (3; 4) to each other. The force transmission member (5) also makes it possible to distribute the forces within the system (1).