An apparatus (10) for turning steerable wheels (12, 14) of a vehicle in response to turning of a steering wheel (18) of the vehicle. The apparatus includes a hydraulic power steering gear, which does not include a rotary valve responsive to a steering input generated by turning of a steering wheel (18). The hydraulic steering gear includes a first chamber (96) for holding hydraulic fluid and a second chamber (98) for holding hydraulic fluid. An increase in fluid pressure in one chamber acts to turn the steerable wheels (12, 14) of the vehicle in one direction and an increase in fluid pressure in the other chamber acts to turn the steerable wheels (12, 14) in a direction opposite the one direction. The apparatus (10) includes a variable flow mechanism (50) for supplying a flow of hydraulic fluid to the first and second chambers (96, 98), which flow varies in dependence upon at least one sensed vehicle condition.