Hydrostatic radial piston unit of the cam-lobe type of construction comprising: - a non-rotary, stationary casing comprising a through hole defining a rotational axis of the hydrostatic radial piston unit ; - a cylindrical, rotary casing mounted rotary to the non-rotary, stationary casing in an axial overlapping area in which a front end portion of the non-rotary casing and a rear end portion of the rotary casing overlap such that the rotary casing can rotate relatively to the stationary casing around the rotational axis ; - a park brake mechanism comprising at least two brake discs arranged adjoined in the overlapping area , wherein one brake disc is rotationally fixed to the non-rotary casing and the other brake disc is rotationally fixed to the rotary casing ; - an end cover closing the non-rotary casing on a rear end side of the hydrostatic radial piston unit facing away from the rotary casing , wherein the end cover pre-tensions a disc spring against a disc-shaped brake piston both located in the rear end portion of the stationary casing to generate an axially oriented spring force, characterized in that - a stationary shaft is arranged coaxially with the rotational axis in an internal cavity formed by the stationary casing , the rotary casing , the end cover and a front cover , wherein a cylinder block housed non-rotary in the front end portion of the rotary casing is in torque-proof connection with the stationary shaft , - the rotary casing comprises an internal cam-lobe surface , against which working pistons accommodated in the cylinder block can act; - the axially oriented spring force can be forwarded by the brake piston to at least one brake pin arranged in an axially oriented bore in the stationary casing , in order to press the brake discs against each other when the brake piston on the face opposite to the disc spring is not forced to move towards the end cover . - a non-rotary, stationary casing comprising a through hole defining a rotational axis of the hydrostatic radial piston unit ; - a cylindrical, rotary casing mounted rotary to the non-rotary, stationary casing in an axial overlapping area in which a front end portion of the non-rotary casing and a rear end portion of the rotary casing overlap such that the rotary casing can rotate relatively to the stationary casing around the rotational axis ; - a park brake mechanism comprising at least two brake discs arranged adjoined in the overlapping area , wherein one brake disc is rotationally fixed to the non-rotary casing and the other brake disc is rotationally fixed to the rotary casing ; - an end cover closing the non-rotary casing on a rear end side of the hydrostatic radial piston unit facing away from the rotary casing , wherein the end cover pre-tensions a disc spring against a disc-shaped brake piston both located in the rear end portion of the stationary casing to generate an axially oriented spring force, - a stationary shaft is arranged coaxially with the rotational axis in an internal cavity formed by the stationary casing , the rotary casing , the end cover and a front cover , wherein a cylinder block housed non-rotary in the front end portion of the rotary casing is in torque-proof connection with the stationary shaft , - the rotary casing comprises an internal cam-lobe surface , against which working pistons accommodated in the cylinder block can act; - the axially oriented spring force can be forwarded by the brake piston to at least one brake pin arranged in an axially oriented bore in the stationary casing , in order to press the brake discs against each other when the brake piston on the face opposite to the disc spring is not forced to move towards the end cover . <EOS>