A system for determining a torque applied between two rotating members (1, 2) about an axis of rotation, said system comprising: - a test body having an internal ring secured in rotation to means for coupling said test body to a first one amongst the members, and an external ring extending around the internal ring while having means for coupling said test body to the second one amongst the members, said rings being concentrically linked around the axis by a deformable structure which is arranged to transmit the torque between the members (1, 2) while enabling an angular displacement between said rings according to the torque applied between said members; - two encoders, respectively an internal one secured in rotation to the internal ring and an external one secured in rotation to the external ring, each of said encoders carrying a track (15a, 16a) capable of emitting a periodic signal representative of the rotational displacement of the corresponding ring (5, 6); - a device for determining the torque comprising a support carrying an internal sensor and an external sensor, each of the sensors (19, 20) comprising a pattern of sensitive elements arranged at a reading distance from the internal or external track to output a signal representative of the angular position of the corresponding encoder (15, 16), said device comprising means for comparing the signals outputted by each of the sensors (19, 20) to determine an angular offset between the rings (5, 6) which depends on the applied torque; - a casing in which the test body, the encoders (15, 16) and the determination device are housed, said casing having an outer wall; said system being characterised in that the outer wall has a cavity forming a compartment in which a subplate is fastened, said subplate being associated with the support by means of a setting screw which is arranged so that the rotation of said screw induces a translation of said support relative to the test body to enable setting of the reading distance of the tracks (15a, 16a) by the respective sensors (19, 20). - a test body having an internal ring secured in rotation to means for coupling said test body to a first one amongst the members, and an external ring extending around the internal ring while having means for coupling said test body to the second one amongst the members, said rings being concentrically linked around the axis by a deformable structure which is arranged to transmit the torque between the members (1, 2) while enabling an angular displacement between said rings according to the torque applied between said members; - two encoders, respectively an internal one secured in rotation to the internal ring and an external one secured in rotation to the external ring, each of said encoders carrying a track (15a, 16a) capable of emitting a periodic signal representative of the rotational displacement of the corresponding ring (5, 6); - a device for determining the torque comprising a support carrying an internal sensor and an external sensor, each of the sensors (19, 20) comprising a pattern of sensitive elements arranged at a reading distance from the internal or external track to output a signal representative of the angular position of the corresponding encoder (15, 16), said device comprising means for comparing the signals outputted by each of the sensors (19, 20) to determine an angular offset between the rings (5, 6) which depends on the applied torque; - a casing in which the test body, the encoders (15, 16) and the determination device are housed, said casing having an outer wall;