Every Car Steering System Explained | Hydraulic, Electric & Steer-By-Wire

Summary

The video explains how automotive steering systems convert the driver’s steering-wheel movement into changes in the direction of the front wheels. It also describes how power assistance has made steering easier over time.

Steering basics

• Steering systems trade movement distance for force: the steering wheel travels much farther than the road wheels, while gears and levers multiply the driver’s effort.
• The narrator illustrates this with a steering wheel that travels about 5 m around its rim through a full turn from lock to lock, while the tire edge moves about 300 mm.
• Steering geometry angles the inner front wheel more sharply than the outer wheel during a turn because it follows a tighter curve.

Rack-and-pinion steering

Common in modern cars, rack-and-pinion steering uses:

• A pinion gear connected to the steering shaft.
• A toothed rack that moves left or right as the pinion turns.
• Tie rods that transfer rack movement to the steering knuckles and wheels.

For example, turning the wheel clockwise to make a right turn rotates the pinion, moves the rack, and steers the front wheels to the right.

The number of pinion teeth affects steering feel. Fewer teeth generally mean more steering-wheel turns but less effort; more teeth provide a quicker response but require more effort.

The video describes rack-and-pinion steering as efficient, relatively easy to maintain, and precise. It says BMW adopted it early, other European manufacturers followed, and it appeared in U.S. cars with the Ford Pinto in 1974.

Power-assisted rack-and-pinion steering

Many rack-and-pinion systems add a hydraulic cylinder and piston to help move the rack.

A pump supplies pressurized fluid, while a rotary or control valve directs the fluid to the appropriate side of the piston as the driver turns. This assistance reduces steering effort, particularly at low speeds. Some systems adjust the level of assistance according to speed, turning force, or vehicle load.

Older steering designs: worm-and-sector and recirculating ball

Older steering systems include worm-and-sector and screw-and-nut designs.

In recirculating-ball steering, the steering shaft turns a worm gear inside a box. A toothed block transfers that movement to a sector gear, which moves the pitman arm and steering linkage. Small ball bearings circulate between the worm gear and the block to reduce friction and slack.

The video characterizes recirculating-ball steering as durable and suitable for heavy loads, though less precise than rack-and-pinion steering. It remains in use in some trucks and SUVs.

Hydraulic power steering (HPS)

HPS uses an engine-driven pump to pressurize hydraulic fluid. When the driver turns the steering wheel, a control valve directs fluid to one side of a piston in the steering cylinder. The piston helps move the rack, and the fluid returns to the reservoir after the turn.

The system operates continuously and assists in either direction. The video notes that hydraulic assistance depends on the engine-driven pump, so it stops if the engine stops.

Electric power steering (EPS)

EPS replaces the hydraulic pump with an electric motor mounted on the steering rack or steering shaft. Sensors detect the driver’s input, and an electronic control unit (ECU) commands the motor to provide assistance.

Assistance can be adjusted for vehicle speed, vehicle type, and driver preference. The video presents EPS as more energy-efficient than HPS because the motor only needs to assist when steering input is made. It also avoids hydraulic-fluid leakage and disposal.

The video says electrical assistance can remain available if the engine stalls, unlike assistance from an engine-driven hydraulic pump.

Steer-by-wire

Steer-by-wire replaces the mechanical connection between the steering wheel and the wheels with sensors, electronic signals, an ECU, and steering actuators.

Sensors measure steering-wheel angle and speed. The ECU interprets the input and commands the actuators to turn the wheels. Unlike EPS, which retains a mechanical connection, steer-by-wire has no mechanical fallback unless one is specifically designed into the vehicle.

Safety relies on redundancy, such as multiple sensors, backup communication and power systems, and redundant actuators. These features are intended to make the system fail-operational if a component fails.

If some steering actuators fail, systems may use methods such as torque vectoring or brake-based yaw control to provide limited emergency control, though not full steering capability.

The video cites steer-by-wire concept and racing vehicles, including a Porsche Cayman GT4 that finished second in its class at the 2020 24 Hours of Nürburgring, and a Mercedes-AMG GT3 that competed the following year.

Overall takeaway

Automotive steering has progressed from mechanical gears and linkages to hydraulic and electric assistance, and now to electronically controlled steer-by-wire systems. Each approach aims to make vehicle control easier and more responsive, while newer designs introduce additional electronic safety and redundancy requirements.

Speakers and sources featured

• One unnamed narrator/voice-over presents the explanations and examples.
• No other speakers or explicitly cited sources appear in the subtitles.