A method of improving pivoting of a wheel set for a scientific instrument, including an arbor pivoting or oscillating about an axis, in which: static balancing of the wheel set is performed to bring the center of gravity onto the axis; a desired value is determined for resulting unbalance moment of the wheel set about the axis, corresponding to a predetermined divergence between a first principal longitudinal axis of inertia of the wheel set, and the axis; at a predetermined speed about the axis, the resulting unbalance moment is measured with regard to the axis; and an adjustment of the resulting unbalance moment is made within a given determined tolerance with regard to the desired value, and performed by machining both sides of a median plane including the two secondary axes of inertia of the wheel set.