A bearing which includes at least one system for determining an amplitude of pseudo-sinusoidal deformations induced during rotation of a fixed ring within a zone, wherein the system includes four strain gauges spaced equally apart from each other within the zone, a device for measuring four signals based on time variations of a signal emitted by each gauge and for forming two signals for the same angle and amplitude, and a device for computing the time-dependent amplitude A of the zone deformations for calculating an expression such that the amplitude is derived therefrom.