A running gear for a rail vehicle, comprising: - at least a pair of wheel sets (14, 16) comprising a front wheel set and a rear wheel set respectively on a front side and a rear side of a median transverse vertical plane of the running gear, each of the front wheel set and rear wheel set having a left wheel (18L, 20L) and a right wheel (18R, 20R), respectively on a left side and a right side of a median longitudinal vertical plane of the running gear, and - a passive hydraulic wheel set steering system comprising: a front left hydro-mechanical converter assembly for converting motion of the left wheel of the front wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, a front right hydro-mechanical converter assembly for converting motion of the right wheel of the front wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, a rear left hydro-mechanical converter assembly for converting motion of the left wheel of the rear wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, a rear right hydro-mechanical converter assembly for converting motion of the right wheel of the rear wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, wherein the passive hydraulic wheel set steering system further comprises a control valve assembly hydraulically connected to the front left, front right, rear left and rear right hydro-mechanical converter assemblies, the control valve assembly being movable between at least a first position and a second position, wherein the passive hydraulic wheel set steering system is such that in the second position of the control valve assembly, each of the front left and right hydro-mechanical converter assemblies is connected to at least a respective one of the rear left and right hydro-mechanical converter assemblies, caracterised in that the passive hydraulic wheel set steering system is such that in the first position of the control valve assembly the front left and right hydro-mechanical converter assemblies are disconnected from the rear left and right hydro-mechanical converter assemblies, movements of the left and right wheels of the front wheel set towards or away from the median transverse vertical plane are allowed and movements of the left and right wheels of the rear wheel set towards or away from the median transverse vertical plane that are independent from the movements of the left and right wheels of the front wheel set are allowed. - at least a pair of wheel sets (14, 16) comprising a front wheel set and a rear wheel set respectively on a front side and a rear side of a median transverse vertical plane of the running gear, each of the front wheel set and rear wheel set having a left wheel (18L, 20L) and a right wheel (18R, 20R), respectively on a left side and a right side of a median longitudinal vertical plane of the running gear, and - a passive hydraulic wheel set steering system comprising: a front left hydro-mechanical converter assembly for converting motion of the left wheel of the front wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, a front right hydro-mechanical converter assembly for converting motion of the right wheel of the front wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, a rear left hydro-mechanical converter assembly for converting motion of the left wheel of the rear wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, a rear right hydro-mechanical converter assembly for converting motion of the right wheel of the rear wheel set towards and away from the median transverse vertical plane into hydraulic energy and vice versa, wherein the passive hydraulic wheel set steering system further comprises a control valve assembly hydraulically connected to the front left, front right, rear left and rear right hydro-mechanical converter assemblies, the control valve assembly being movable between at least a first position and a second position, wherein the passive hydraulic wheel set steering system is such that in the second position of the control valve assembly, each of the front left and right hydro-mechanical converter assemblies is connected to at least a respective one of the rear left and right hydro-mechanical converter assemblies,