A mirror assembly comprising a disk spring loaded pivot

A pivot assembly between a mirror head and a mirror mounting bracket of a rear vision mirror comprising an aperture and a spigot received in the aperture such that the mirror head can rotate with respect to the mirror mounting bracket and a detent arrangement between the mirror mounting bracket and the mirror head that enables rotation of the mirror head with respect to the mirror mounting bracket from a locked position, where the mirror head is held in a selected position with respect to the mirror mounting bracket, to a disengaged position in which the mirror head is rotated with respect to the mirror mounting bracket and a spring assembly to apply force against the detent arrangement, the spring assembly having a negative spring rate when compressed from a pre-loaded position.