A railway car brake system comprising a control device engageable with a predetermined portion of such railway car for compensating braking force in response to a load carried by such railway car. The control device includes a sensor mechanism engageable with a truck bolster or a movable car structure for sensing a vertical position thereof corresponding to a load carried by the railway car. There is a control valve engageable with the sensor mechanism which generates a fluid pressure signal responsive to such load. A pneumatic actuator engageable with a predetermined brake beam disposed on such truck assembly and connected to such control valve. This pneumatic actuator generates a predetermined braking force responsive to the fluid pressure signal and further responsive to the load carried by the railway car as sensed by the sensor mechanism. Such predetermined braking force may be proportionally adjusted to variations in the load carried by the railway car.