One of the most popular steering systems in modern motor vehicles is the rack and pinion system. The steering rack forms one part of the mechanics of this system. One of the reasons for the system’s popularity is undoubtedly its simplicity. In a typical non-powered steering system a set of rack and pinion gears is enclosed in a metal tube. Each end of the rack protrudes from the ends of the tube. Each end of the steering rack is connected to a rod, known as a tie rod. The pinion is connected to the steering shaft and when the steering wheel is turned it causes the pinion gear to spin, which moves the steering rack transversely. The tie rods on either side of the rack connect to spindles on the car wheels. The transverse movement of the rack thereby causes the wheels to turn right and left according to the direction in which the vehicle is being steered.
In a power steering system the design of the steering rack has one or two variations. A section of the rack is connected to a cylinder with a piston in the centre, which has a fluid port on either side. Hydraulic fluid is provided to either side of the piston, which causes the steering rack to move, producing the power assisted steering.