Learn Steering Systems Explained – Manual Steering (Linkage, Gears, Rack & Pinion), Power Steering (Hydraulic & Electric), Electronically Controlled Systems (VES, Active Steering, Steer by Wire) and Key Components

Introduction:

The steering system is one of the most critical vehicle components, serving as the primary interface between driver and machine. Its fundamental purpose is to turn the front wheels and in some cases, the rear wheels to change direction while switching lanes, rounding sharp turns or avoiding roadway obstacles. Few older vehicles had power assist, but today all vehicles have power assist steering. Because these assist systems work in conjunction with manual steering systems, understanding both is essential to grasp how modern steering functions.

The steering system comprises three major subsystems: steering linkage, steering gear, and steering column and wheel. The driver turns the steering wheel, the steering gear transfers that motion to the linkage, and the linkage turns the wheels to control direction. Though many variations exist, these three assemblies are present in all steering systems.

Steering systems have evolved from simple manual mechanisms to sophisticated hydraulic and electronic systems that enhance control and comfort. The three core subsystems: linkage, gear, and column work together to translate driver input into vehicle motion. Power assistance reduced effort and fatigue and electronic control now tailors assistance to vehicle speed, improving both low speed maneuverability and high speed feel. Active steering adds stability by adjusting wheel angles beyond driver commands. Electric systems eliminate hydraulic complexity while enabling customizable feel and continued operation even with the engine off. Though steer by wire remains future technology, it promises further customization and design freedom.

Manual Steering Systems:

Steering Linkage:

The steering linkage is the system of pivots and connecting parts between the steering gear and the steering arms attached to the front or rear wheels. It transfers the gear output shaft’s motion to the steering arms, turning the wheels. The type of front wheel suspension greatly influences steering geometry. Most passenger cars and many light trucks and recreational vehicles have independent front suspension which requires a linkage that tolerates relatively large wheel movement.

Parallelogram Steering Linkage:

Once the most common type on passenger cars, the parallelogram arrangement is now mostly found on larger cars, pickups and large SUVs. It works with recirculating ball steering gears and can be mounted either behind or ahead of the front suspension. This design is often used where engine or chassis components would interfere with linkage operation. It provides good steering and suspension geometry. Road vibrations and impact forces transmitted from the tires cause wear and looseness leading to intermittent changes in toe settings and accelerated tire wear. In a parallelogram linkage, tie rods have ball socket assemblies at each end one end attached to the wheel’s steering arm, the other to the center link. The main components are the pitman arm, idler arm, links and tie rods.

Pitman Arm:

Connects the linkage to the steering column through the steering gear at the column’s base. It transmits motion from the gear to the linkage, moving the linkage left or right to turn the wheels. It also maintains the center link’s height ensuring tie rods remain parallel to control arm movement to avoid unstable toe or bump steer. Toe is a critical alignment factor defining how well the tires point in the vehicle’s direction.

Idler Arm:

Attached to the opposite side of the center link from the pitman arm and to the car frame, supporting the center link at the correct height. A built in pivot permits sideways linkage movement. Some light duty trucks use two idler arms. Idler arms wear more than pitman arms, typically at the swivel point and worn bushings or studs permit excessive vertical movement.

Links:

Called center links or steering links, they control sideways linkage movement to change wheel direction. They also serve as mounting locations for tie‑rods, critical for maintaining correct toe. If not mounted at the proper height, toe becomes unstable, producing toe change or bump steer. Center links and drag links may be used alone or together. Links with stud or bushing ends need periodic inspection, those with open tapers usually only require replacement after damage or excessive tolerance at the idler or pitman arm mounting.

Tie Rods:

These assemblies make the final connections between the linkage and steering knuckles. They consist of inner tie rod ends which connected to the center link, outer tie rod ends which connected to the steering knuckles and adjusting sleeves or bolts that join them and allow length adjustment for correct toe. Tie rods are prone to wear especially if dust boots are damaged, letting dirt and moisture cause rapid failure. A bonded ball stud design without a boot is used on some light duty trucks, an elastomer bushing bonded to the stud provides shock absorption and steering return.

Rack and Pinion Steering Linkage:

Rack and pinion is lighter and has fewer components than parallelogram steering. Tie rods are used similarly, but there is no pitman arm, idler arm or center link. A pinion gear attached to the steering column moves a toothed rack that pushes and pulls the tie rods to change wheel direction, the rack performs the center link’s task. Tie rods are the only linkage parts in this system. Most rack and pinion constructions consist of a tube containing a sliding rack a rod with gear teeth cut along one end and fitted with two balls at the other for track rod attachment. The rack meshes with the pinion at the column end. The two inner tie rod ends attached to the rack are covered by rubber bellows boots that protect against contamination; they connect to outer tie rod ends which attach to steering arms. The housing is fastened at two or three points and can be mounted in front of or behind the suspension. On unibody cars, it may bolt directly to a body panel like a cowl, which must hold the gear correctly and maintain proper relationship between steering and suspension parts. The rack and pinion system combined with MacPherson strut suspension is common in front wheel drive unibody vehicles for weight and space savings. Drivers get greater road feel because of fewer friction points, but that also increases the likelihood of steering complaints and reduces the system’s ability to isolate and dampen vibrations.

Rack:

A toothed bar in a metal housing that maintains correct component height, allowing tie‑rod movement to parallel control arm movement. Its sideways motion pushes or pulls tie‑rods.

Pinion:

A toothed or worm gear at the base of the steering column, turned by the steering wheel. It meshes with the rack teeth, propelling the rack sideways.

Yoke Adjustment:

The rack to pinion lash affects steering harshness, feedback and noise. It is set to manufacturer specifications using an adjustment screw, plug or shim pack on the housing outside at the pinion rack junction.

Tie Rods:

Similar to parallelogram systems they have inner and outer ends and adjusting sleeves. Inner ends are usually spring loaded ball sockets that screw onto the rack ends, preloaded and protected by rubber bellows.

Manual Steering Gear:

The steering gear changes steering wheel rotation into reciprocating motion to move the linkage. Three styles are in use: recirculating ball, worm and roller and rack and pinion.

Recirculating Ball:

Found mostly in larger cars. A sector shaft is supported by needle bearings and a bushing. A ball nut has threads mating to the wormshaft via continuous rows of ball bearings that recirculate through two outside loops. The ball nut has gear teeth on one face that mesh with sector shaft teeth. Turning the wheel rotates the wormshaft, moving the nut up or down, the nut’s teeth move the sector shaft, rotating it and swinging the pitman arm. Two separate ball circuits provide nearly friction free operation. The teeth on the sector shaft and ball nut have an interference fit when wheels are straight ahead to eliminate lash for positive straight line feel. Proper mesh is obtained by an adjusting screw that moves the sector shaft axially. Worm thrust bearing preload set by the adjuster, eliminates end play and prevents free play and wander.

Variable Ratio:

The number of input turns per output turn is the gearbox ratio. Gears can be constant or variable. In variable ratio units, sector teeth have larger center teeth, making steering faster in turns than straight ahead. Variable ratio is normally used only in power steering units.

Worm and Roller:

Similar to recirculating ball but uses a single roller instead of balls and ball nut, reducing internal friction and suiting smaller cars. The linkage typically includes pitman arm, center link, idler arm and two tie rod assemblies functioning the same as parallelogram linkage. The steering shaft rotates the worm gear which engages the roller and turns the roller shaft, moving the pitman arm left or right. The steering gear does not cause vehicle pull or road wheel shimmy.

Steering Wheel and Column:

The steering wheel and column produce the force to turn the gear. The column relays wheel movement to the gear. Major parts include the wheel, covers, universal joints, support brackets and assorted fasteners and seals. In vehicles with a driver’s air bag, the assembly is in the wheel center and must be disarmed before wheel removal.

Designs vary: fixed, telescoping, tilt, manual transmission floor shift and automatic transmission column shift. Tilt columns offer at least five driving positions (two up, two down, center). Both fixed and tilt columns may house turn signal switch, ignition key, lights, horn, wipers and antitheft lock. On automatic vehicles the transmission linkage locks too.

Locking methods include breakaway plastic capsules, inserts or steel balls in a plastic retainer that allow the shaft to roll forward, and collapsible steel mesh or accordion devices. After an accident, the column should be checked for collapse, if collapsed, the collapsed portion must be replaced, even if the column can be pulled back. The steering wheel is held by a bolt or nut.

Steering Damper:

The damper reduces road shock transmitted up the column, found mostly on 4WD vehicles with large tires. It functions like a shock absorber but is mounted horizontally to the linkage one end to the center link, the other to the frame.

Power Steering Systems:

Power steering reduces effort, driver fatigue on long drives and makes low‑speed steering especially parking easier. It is divided into conventional (hydraulic) and nonconventional (electronically controlled electric motor) arrangements. The most common systems are integral piston and power assisted rack and pinion.

Integral Piston System:

This is the most common conventional system. It includes a pump and reservoir, pressure and return hoses and steering gear. The power cylinder and control valve are in the same housing as the steering gear. On some recent models, hydraulic fluid from the pump also actuates the brake booster called the hydro boost system.

Power Assisted Rack and Pinion:

Similar to the integral system, the power cylinder and control valve are in one housing. The rack housing acts as the cylinder and the power piston is part of the rack. The control valve is in the pinion housing, turning the wheel moves the valve, directing pressure to either end of the rack piston. It uses a pressure hose from the pump to the valve and a return line to the reservoir. This system is common on front wheel drive vehicles.

Power Steering Components:

Many manual steering parts (e.g. linkage) are used. Added components provide hydraulic power: pump, flow control and pressure relief valves, reservoir, spool valves and power pistons, hydraulic hoses, and gearbox or assist assembly.

Power Steering Pump:

Develops hydraulic flow to operate the gear. Belt driven from the crankshaft, it provides flow whenever the engine runs, usually mounted near the engine front. The pump assembly includes a reservoir and internal flow control valve, the drive pulley is pressed onto the shaft. Four pump types exist: roller, vane, slipper and gear, all operate similarly. Fluid is stored in the reservoir and routed by hoses, a relief valve controls excessive pressure.

Drive Belts:

Most late model vehicles use a serpentine belt driving all accessories, often with a spring loaded automatic tensioner eliminating periodic adjustments. The smooth backside may drive some components. Older vehicles used V belts. Belt tension is critical, a slipping belt prevents full pump pressure.

Electric Power Steering:

Some vehicles use a 12 or 42 volt electric motor mounted to or in the steering gear, replacing the conventional pump, belts and hoses.

Flow Control and Pressure Relief Valves:

The pressure relief valve controls pump output, needed because engine rpm varies and consistent steering is required from idle to highway speeds. It is positioned in a chamber exposed to outlet pressure on one end and supply hose pressure on the other with a spring at the supply end to maintain balance. Fluid leaving the rotor passes the valve end and is forced through an orifice causing a slight pressure drop holding the valve closed so all flow goes to the steering gear. When engine speed increases, the pump delivers more flow than needed, the difference in pressure across the valve grows until outlet pressure overcomes the combined force of supply pressure and spring pushing the valve down and opening a passage to return excess flow to the pump inlet. A spring and ball inside the valve relieve outlet pressure to prevent damage when the wheel is held against the stops, if pressure reaches a preset level, the ball unseats, creating a greater pressure differential and allowing the valve to open wider returning more flow and holding pressure safe.

Power Steering Gearbox:

Essentially a manual recirculating ball gearbox with hydraulic assist, filled with fluid and using a control valve. In a power rack and pinion, rack movement is hydraulically assisted when the wheel turns, the rotary valve creates a pressure differential on either side of the rack, moving it toward lower pressure and reducing effort. Integral power steering has the spool valve and power piston integrated the spool valve directs pressure to left or right chambers, actuated by a lever or torsion bar. In linkage systems, the control valve connects to the center link and pitman arm; any movement compresses a centering spring and moves the spool, opening ports to direct fluid to one side of the power cylinder piston. The power cylinder attaches to the center link, and its piston shaft attaches to the frame, fluid directed to one side provides assist. Two lines connect the cylinder to the control valve, each acting as supply or return depending on turn direction.

Power Assisted Rack and Pinion:

Components are similar to manual rack and pinion except for the hydraulic control housing. The rack functions as the power piston and the spool valve connects to the pinion. The rack piston is sealed within the housing to form two separate hydraulic chambers for left and right turns. When turning right, the rotary valve creates a pressure differential across the piston, moving the rack toward lower pressure and reducing effort.

Power Steering Hoses:

Their primary purpose is to transmit pressurized fluid from the pump to the gearbox and return it to the reservoir. They also act as reservoirs and dampen sound and vibration. Hoses are reinforced synthetic rubber with metal tubing at connections; pressure side must handle up to 1,500 psi, so rubber to metal connections are crimped. Pressure hoses expand slightly to absorb surges and pulsations. Two internal diameters may be used on the pressure side: the larger at the pump end acts as a reservoir and accumulator; the smaller return hose reduces kickback and maintains backpressure to reduce pump noise. If a single diameter is used, the gearbox performs damping internally. Hoses must withstand temperatures up to 150°C and subzero conditions, with material formulated to resist oil and temperature degradation.

Electronically Controlled Power Steering Systems:

Power steering aims to make low speed steering easy, but higher efforts are desirable at high speeds for better road feel. Electronically controlled power steering (EPS) systems taper hydraulic boost as road speed increases, requiring under 4.4 N effort at low speeds and over 13.2 N at high speeds for improved handling. A rotary valve EPS system consists of the gearbox, pump, pressure hose, and return hose. Fluid flow is controlled by a solenoid valve called the PCV (pressure control valve). The PCV is exposed to spring tension on top and plunger force on the bottom; the plunger slides inside an electromagnet. Varying the electrical current varies the plunger’s upward force against the spring. Current varies with vehicle speed, providing speed matched steering.

Variable Effort Steering (VES):

Used by General Motors, it takes an input from the vehicle speed sensor to the VES controller, which supplies a pulse width modulated voltage to the actuator solenoid in the pump and provides a ground. At low speeds, the controller cycles the solenoid faster for high pump pressure and maximum assist as speed increases, solenoid cycling slows and pump pressure decreases giving better road feel.

Active Steering:

Active steering improves stability by turning the wheels more or less sharply than commanded in certain situations. Through computer programming, it can adjust steering to respond quickly to skid threats and also provide a variable steering ratio with vehicle speed. Current active steering systems are not steer by wire, they still have a mechanical connection. They have an overriding drive in the steering column controlled by an electric motor which is computer controlled. The computer determines if and by how much the steering angle should change. If the system fails, the planetary gear rotates directly with the steering wheel.

Electric/Electronic Rack and Pinion System:

This system replaces the hydraulic pump, hoses and fluid with electronic controls and an electric motor concentric to the rack. It features a DC motor armature with a follow shaft to allow rack passage, rotary motion is transferred to linear rack movement through a ball nut with thrust bearings, with the armature mechanically connected via splines. The system can change motor rotational direction and deliver up to 75 amperes to meet torque requirements higher current means greater rack force. Turn direction is controlled by reversing signal polarity. The field assembly uses permanent ceramic magnets and provides structural integrity. The system monitors steering wheel movement via a sensor on the input shaft, an electronic controller activates the motor for assistance based on directional and load information. These units can be retrofitted. No replacement parts are currently available if the rack fails, replace the entire unit. Unlike conventional power steering, electric/electronic units provide assistance even when the engine stalls because they run off the battery. Steering feel can be adjusted to match driving characteristics from high performance to luxury touring. It also eliminates hydraulic fluid and leaks.

Steer by Wire System:

Steer by wire systems are not yet in production vehicles but are being tested and have appeared on concept cars. They have no steering column or shaft, the system is entirely electronic. A sensor monitors steering wheel turning and sends a signal to a controller, which commands an electric motor in the steering gear, also factoring in inputs like vehicle speed. A small motor attached to the steering wheel mount, controlled by the controller, provides appropriate steering feel for current conditions needed for driver control. Steer by wire allows total customization of steering performance and a constantly variable ratio. Eliminating the column opens interior and engine compartment space, and the system is lighter than conventional steering.