Four-Wheel Steering (4WS)

Four-Wheel Steering (4WS) is an advanced chassis technology that introduces active steering capability to the rear axle. By turning the rear wheels in either the same or opposite direction to the front wheels, the system delivers enhanced low-speed agility and superior high-speed stability.

💡 Operating Principle: Counter-Phase at Low Speeds, In-Phase at High Speeds

The core function of four-wheel steering is to dynamically alter the rear-wheel angle according to vehicle speed, delivering two distinct dynamic benefits:

• At low speeds, counter-phase steering (Agility Mode): At lower speeds (typically below 40–60 km/h), the rear wheels turn at a slight angle in the opposite direction to the front wheels. This virtually shortens the vehicle's wheelbase and reduces the turning circle by up to 20%, allowing large vehicles to execute tight U-turns and park with the effortless agility of a compact hatchback.

• At high speeds, in-phase steering (Stability Mode): At higher cruising speeds, the rear wheels turn in the same direction as the front wheels. This in-phase steering significantly reduces the risk of tail-out behaviour and body yaw during rapid lane changes or cornering, enhancing high-speed stability and driving confidence.

🛠️ From Mechanical to Intelligent: Technological Evolution

With continuous engineering advancements, four-wheel steering has evolved from mechanical setups to sophisticated electronic architectures, offering ever-increasing precision and intelligence:

• Mechanical and Hydraulic Systems: Early mechanical setups relied on complex linkages and rocker arms, while hydraulic systems introduced fluid pumps and control valves for power assistance. However, these setups were bulky and constrained by relatively basic control logic.

• Electric Power Steering (EPS): Modern mainstream 4WS systems predominantly utilise Electronic Control Units (ECU). By processing real-time sensor data—including vehicle speed and steering wheel angle—the ECU accurately regulates the rear-wheel steering angle and direction with rapid response times and flexible calibration.

• Steer-by-Wire (SBW) and Four-Wheel Independent Steering: Representing the next frontier, Steer-by-Wire removes the physical mechanical column entirely in favour of digital signal control. This paves the way for ultra-precise four-wheel steering and complex vehicle dynamics, such as crab-walking (diagonal movement) and tank turns (in-place rotation).

🏎️ Technical Positioning: Rear-Wheel Steering as a Form of 4WS

In today's mass-production passenger car market, what is commonly referred to as "rear-wheel steering" is essentially the standard implementation of four-wheel steering in road-going cars. Both share the exact same engineering principle and goal—actively steering the rear wheels to elevate handling performance. The main distinction lies in application scope and maximum steering angles: commercial and specialised vehicles may demand extreme rear steering angles, whereas rear-wheel steering in luxury saloons and sports cars is finely tuned to integrate seamlessly with the entire chassis management system.

Today, falling production costs mean 4WS is no longer exclusive to RM1,000,000-class luxury flagships like Porsche and the Mercedes-Benz S-Class. The technology is rapidly trickling down to more premium models, establishing itself as a benchmark feature for improving the agility and manoeuvrability of larger vehicles.