Steering & Suspension: Steering Systems

Steering principles	Steering systems	Steering systems are designed according to the use requirements of the vehicle. They can be in single or multi-axle designs.
	Principles of steering	The steering system provides control over direction of travel, good manoeuvrability, smooth recovery from turns, and minimum transmission of road shocks.
	Rack-and-pinion steering	Rack-and-pinion type steering gears are used because they are compact and light-weight, give sharp steering response, and light operation.
	Rack-and-pinion steering system	The primary components of the rack and pinion steering system are: rubber bellows, pinion, rack, inner ball joint or socket and tie-rod.
	Recirculating ball & nut steering system	The primary components of the recirculating ball and nut steering system are: pitman arm shaft, idler arm, track rod or center link, tie-rod, tie-rod end and adjustment sleeve.
	Four-wheel steering systems	4-wheel steering can be mechanical or computer controlled. In mechanical systems there is a direct link between the front and rear steering racks. In hydraulic and electric assisted systems the center shaft is replaced either by hydraulic lines, or by electrical connections that are controlled by control valves or computer monitored sensors.

Steering boxes & columns	Steering columns	The steering column is connected to the input shaft by a flexible joint. Some manufacturers fit sensors and control units to the steering column, which provide information to steering control modules as part of an electric assisted or 4-wheel steering system.
	Rack-and-pinion gearbox	The rack-and-pinion steering box has a pinion, connected to the steering column. This pinion runs in mesh with a rack that is connected to the steering tie rods.
	Helix	The helix shape is commonly used as a thread on nuts and bolts, and also for teeth in steering gears, and transmissions.
	Variable ratio steering	With variable ratio steering, as the steering moves away from the straight-ahead position, the ratio, and therefore, the mechanical advantage, increases progressively.
	Worm gearbox	Variations of worm-type steering boxes are worm-and-sector, worm-and-roller, worm-and-nut, and recirculating ball. The steering box gear ratio increases output torque, reducing the effort the driver must apply.
	Power steering	Power steering systems produce assistance that reduces the driver's effort. They are of most benefit during slow cornering and when parking.
	Steering process	When a load is applied to the steering system, the torsion bar twists, causing relative movement of the inner and outer members of the rotary valve. Assistance progressively rises as the torsion bar twist increases.
	Flow-control valve	Power steering pumps have a flow-control valve to vary fluid flow and system pressures. A pressure relief valve prevents excessive pressures developing when the steering is on full-lock.
	Electric power assisted steering	Electric steering is more economical to run, and easier to package and install than conventional hydraulic power steering systems. They are also lighter and more compact than conventional hydraulic systems.
	Basic electric power steering operation	The microprocessor control unit analyzes inputs from the steering sensor as well as the vehicle's speed sensor. The sensor inputs are then compared to determine how much power assist is required.

Steering arms & components	Forward control vehicle steering	Forward-control vehicles mount the steering system forward of the front axle and steering linkage. A drag link connects the Pitman arm to a relay lever, which is connected to the track rod.
	Steering linkages	A steering linkage is a combination of rods and arms that transmit movement of the steering gear to the front wheels, while allowing for wheel movement while the vehicle is in motion.
	Joints	Ball joints are mounted at the outer ends of the control arms and tie-rods. As the suspension deflects, they let the control arms move up and down, and let the wheel and hub assembly turn for steering.
	Bushes/bushings	Bushes, or bushings, act as bearings at suspension fulcrum points, to allow for movement of the component, while maintaining its alignment.

Steering system procedures	Checking & adjusting power steering fluid	The manufacturer has specified an optimum level of the power steering fluid and it is assumed that when the fluid is hot, it will be at this level. If the fluid is cold, it may be at a lower level. The objective of this procedure is to show you how to check and adjust power steering fluid level as necessary.
	Pressure testing a power steering system	Power steering systems can reach a working pressure of over 1,000 pounds per square inch or 6,700Kpa during operation. The objective of this procedure is to show you how to safely pressure test a power steering system. Always follow manufacturers or equipment manufacturers procedure when working on the system.
	Flushing a power steering system	The objective of this procedure is to show you how to flush & bleed a power steering system. When circulating the fluid allow the engine to run for 10 to 15 minutes, turning the steering wheel from lock to lock several times to remove any air trapped in the system and circulate fluid through all parts of the system.
	Inspecting & adjusting an engine drive belt	There are two types of drive belts: V-type and Serpentine type. The objective of this procedure is to show you how to inspect and manually adjust engine accessory drive belts.
	Servicing a steering system	The objective of this procedure is to show you how to check ball joints, lines and linkages according to manufacturer's recommendations. Ensure all rubber bellows or boots that are fitted to steering components are in good condition so that they do not allow contaminants to enter. Communicated any problems to your supervisor.
	Servicing wheel bearings	Wheel bearings are lubricated with grease, which also protects the metal from corrosion and helps conduct heat. The objective of this procedure is to show you how to clean, inspect, and repack non-driving wheel bearings.

Topic group	Topic	Summary