A running gear unit (102; 202; 302; 402) for a rail vehicle, comprising - at least one wheel unit (103.1, 103.2) and - a magnetic circuit device (111; 211; 311; 411) for a magnetic circuit arrangement (112; 212; 312; 412); - said at least one wheel unit (103.1, 103.2) being configured to contact a part of a rail (110.1) of a track to be travelled on with a contact force acting between said at least one wheel unit (103.1, 103.2) and said rail (110.1); - said magnetic circuit arrangement (112; 212; 312; 412) having an activated state and a deactivated state; - said magnetic circuit device (111; 211; 311; 411) being configured to participate in generating, in said activated state, a magnetic flux in a magnetic circuit (113; 213; 313; 413) of said magnetic circuit arrangement (112; 212; 312; 412) to increase said contact force compared to said deactivated state; wherein - said magnetic circuit device (111; 211; 311; 411) is configured such that at least a part of said at least one wheel unit (103.1, 103.2) and said part of said rail (110.1) contacted by said at least one wheel unit (103.1, 103.2), at least in said activated state, forms a part of said magnetic circuit (113; 213; 313; 413); - said magnetic circuit device (111; 211; 311; 411) comprises a magnetic core device (115; 215; 315; 415); - said magnetic core device (115; 215; 315; 415), in said activated state, forms a part of said magnetic circuit (113; 213; 313; 413), - said magnetic core device (115; 215; 315; 415) being configured such that, at least in said activated state, said magnetic core device (115; 215; 315; 415) and said at least one wheel unit (103.1, 103.2) form adjacent parts of said magnetic circuit (113; 213; 313; 413); characterized in that - said magnetic core device (115; 215; 315; 415) comprises a contact unit (115.1; 115.2), said contact unit (115.1; 115.2) being configured to contact, at least in said activated state, a part of said wheel unit (103.1, 103.2) and/or - said magnetic core device (215; 315; 415) is configured such that, in said activated state, said magnetic core device (215; 315; 415) and said part of said rail (110.1) form adjacent parts of said magnetic circuit (213; 313; 413); said magnetic core device (215; 315; 415), in said activated state, contacting said part of said rail (110.1). - at least one wheel unit (103.1, 103.2) and - a magnetic circuit device (111; 211; 311; 411) for a magnetic circuit arrangement (112; 212; 312; 412); - said at least one wheel unit (103.1, 103.2) being configured to contact a part of a rail (110.1) of a track to be travelled on with a contact force acting between said at least one wheel unit (103.1, 103.2) and said rail (110.1); - said magnetic circuit arrangement (112; 212; 312; 412) having an activated state and a deactivated state; - said magnetic circuit device (111; 211; 311; 411) being configured to participate in generating, in said activated state, a magnetic flux in a magnetic circuit (113; 213; 313; 413) of said magnetic circuit arrangement (112; 212; 312; 412) to increase said contact force compared to said deactivated state; wherein - said magnetic circuit device (111; 211; 311; 411) is configured such that at least a part of said at least one wheel unit (103.1, 103.2) and said part of said rail (110.1) contacted by said at least one wheel unit (103.1, 103.2), at least in said activated state, forms a part of said magnetic circuit (113; 213; 313; 413); - said magnetic circuit device (111; 211; 311; 411) comprises a magnetic core device (115; 215; 315; 415); - said magnetic core device (115; 215; 315; 415), in said activated state, forms a part of said magnetic circuit (113; 213; 313; 413), - said magnetic core device (115; 215; 315; 415) being configured such that, at least in said activated state, said magnetic core device (115; 215; 315; 415) and said at least one wheel unit (103.1, 103.2) form adjacent parts of said magnetic circuit (113; 213; 313; 413); - said magnetic core device (115; 215; 315; 415) comprises a contact unit (115.1; 115.2), said contact unit (115.1; 115.2) being configured to contact, at least in said activated state, a part of said wheel unit (103.1, 103.2) - said magnetic core device (215; 315; 415) is configured such that, in said activated state, said magnetic core device (215; 315; 415) and said part of said rail (110.1) form adjacent parts of said magnetic circuit (213; 313; 413); said magnetic core device (215; 315; 415), in said activated state, contacting said part of said rail (110.1).