Abstract: The present invention relates to a bicycle crank axle torque modulation device (1), comprising a bracket (3) including a spring-bearing assembly (4), wherein each end of the spring (7) thereof is connected to each of the bearings (6) by a connection member (8); an eccentric surface (5) for driving said spring-bearing assembly (4), which is in permanent contact with the bearings (6) of said spring-bearing assembly (4), wherein one of the bracket (3) and the eccentric surface (5) is arranged to be attached to a bicycle frame and the other to be attached to said bicycle crank axle. The invention further relates to a torque tuning process, a kit comprising a crank axle and the modulation device, and to a bike including the same.