An elevator, comprising: an elevator car ; a drive mechanism connected with the elevator car , the drive mechanism moving with the elevator car in a vertical direction, the drive mechanism including at least one rotatable drive member that is configured to engage a vertical structure near the elevator car , climb along the vertical structure to selectively cause movement of the elevator car , and selectively prevent movement of the elevator car when the at least one rotatable drive member remains in a selected position relative to the vertical structure; a biasing mechanism that urges the at least one rotatable drive member in a direction to engage the vertical structure, the biasing mechanism applying a biasing force based upon a condition of the elevator car , the biasing force changing based upon a change in the condition; wherein the biasing mechanism comprises an actuator that applies the biasing force, and the actuator varies the biasing force based on the change in the condition; characterized in that : the condition comprises a load of the elevator car ; the elevator comprises a sensor that provides an output indicating the load of the elevator car , and a controller that determines the load in the elevator car based on the output of the sensor ; and the actuator is controlled by the controller to change the biasing force for urging the at least one rotatable drive member to engage the vertical structure based on the change in the load in the elevator car . an elevator car ; a drive mechanism connected with the elevator car , the drive mechanism moving with the elevator car in a vertical direction, the drive mechanism including at least one rotatable drive member that is configured to engage a vertical structure near the elevator car , climb along the vertical structure to selectively cause movement of the elevator car , and selectively prevent movement of the elevator car when the at least one rotatable drive member remains in a selected position relative to the vertical structure; engage a vertical structure near the elevator car , climb along the vertical structure to selectively cause movement of the elevator car , and selectively prevent movement of the elevator car when the at least one rotatable drive member remains in a selected position relative to the vertical structure; a biasing mechanism that urges the at least one rotatable drive member in a direction to engage the vertical structure, the biasing mechanism applying a biasing force based upon a condition of the elevator car , the biasing force changing based upon a change in the condition; wherein the biasing mechanism comprises an actuator that applies the biasing force, and the actuator varies the biasing force based on the change in the condition; characterized in that : the condition comprises a load of the elevator car ; the elevator comprises a sensor that provides an output indicating the load of the elevator car , and a controller that determines the load in the elevator car based on the output of the sensor ; and the actuator is controlled by the controller to change the biasing force for urging the at least one rotatable drive member to engage the vertical structure based on the change in the load in the elevator car . <EOS>