Abstract: An extendable exterior rearview mirror assembly includes a mounting bracket, a mirror subassembly, and a support arm which is supported by the mounting bracket. The mirror subassembly is supported by the support arm and is mounted for selective movement along the support arm to one of a plurality of viewing positions. The mirror subassembly includes a housing, a reflective element, and an actuator which supports the reflective element in the housing. The actuator is mounted to the housing by an actuator bracket. The rearview mirror assembly further includes a biasing member which urges the support arm into frictional engagement with the actuator bracket to limit movement of the mirror subassembly along the support arm. In preferred form, the biasing member comprises a plate spring having an undulating cross-section which urges the support arm into frictional engagement with the actuator bracket while absorbing manufacturing tolerances of the actuator bracket and the support arm.