The invention relates to a combination cylinder including a service brake cylinder as an active service brake with at least one pressure-medium-actuated service brake piston which actuates a brake mechanism via a service brake piston rod, and a spring store brake cylinder as a passive parking brake with a spring store brake piston which is actuated by pressure medium counter to the action of at least one store spring, with the spring store brake piston transmitting the force of the at least one store spring to the service brake piston rod by a force-transmitting gearing in the parking braking situation. The invention provides for the gearing to be designed such that the movements of the spring store brake piston and of the service brake piston rod are coaxial and the force transmission ratio becomes greater with progressive stroke of the spring store brake piston.