Combined thrust bearing for brake actuators

A ring-shaped thrust bearing extending in an axial direction has an inner surface (50) which includes a first axial groove (54a) in the inner surface (50). The groove (54a) has a first flat wall (70) and a second flat wall (72); and a first principal strain sensor (56a) positioned on the first flat wall (70) of the first axial groove (54a) to measure compression in the axial direction.