A timepiece assembly including a balance spring stud fixed to a plate, and a balance spring wound into coils between an inner end fixed to a collet and an outer end fixed to the balance spring stud. The balance spring stud and/or the collet includes a braking mechanism cooperating with a first coil during accelerations by contraction or expansion of the balance spring higher than set values, to modify a resulting rigidity of the balance spring when the first coil is locally coupled to the braking mechanism, arranged on a first inner lip and a second outer lip included in the balance spring stud and/or in the collet, which includes a first inner lip and a second outer lip each including the braking mechanism.