Four-wheel steering improves vehicle mobility at slow speeds and on off-road tracks, enhancing low-speed agility and reducing the turning circle. It also increases stability when towing a trailer. Some cars use this technology to enhance steering reaction, boost stability at high speeds, and reduce the turning radius at low speeds.
Modern four-wheel steering systems use computers and actuators to control the back wheels, allowing them to turn in the opposite direction from the front wheels at moderate speeds in some systems.
In this reading, we’ll explore what a four-wheel steering is, its diagram, genesis, cars with it, its types, and how it works. We’ll also learn its advantages and disadvantages.
Let’s get started!
What Is A Four-Wheel Steering?
Car manufacturers use four-wheel steering (4WS), also referred to as all-wheel steering, in a range of high-end and performance vehicles. It allows the driver to actively control the back wheels while making turns, enabling simultaneous steering of the front and rear wheels. This system reduces the space required to turn the vehicle, with a 21% reduction in the turning radius compared to a two-wheel steering system. As a result, a vehicle can make a U-turn in roughly 20 feet instead of 25 feet thanks to the Quadra Steering technology.
How Four-Wheel Steering Works
Rear-wheel steering is a device that adjusts the angles of the rear wheels, either turning them in tandem with the front wheels or in the opposite way, to improve a vehicle’s low- or high-speed agility. The toe refers to the angle at which a wheel is oriented toward or away from the car, affecting high-speed stability (toe-in) or low-speed agility (toe-out).
Both four-wheel steering systems result in the same movement from the rear tires, with the front and rear wheels turning in the same direction for greater high-speed stability.This improves the performance of larger, heavier vehicles compared to when only the front wheels turn. Watch the video below to learn more about four-wheel steering:
Diagram Of Four Wheel Steering
Cars With Four-Wheel Steering
Despite the impression that four-wheel steering is uncommon in cars, it is actually an option for many different car types. The table below shows the car’s with four-wheel steering:
| Acura | BMW(series) | Mitsubishi | Porsche | Ferrari |
| Acura RLX | BMW 5 | Mitsubishi Galant VR-4 | Porsche 911
|
Ferrari GTC4Lusso
|
| Acura TLX | BMW 7 | Mitsubishi 3000GT | Porsche 991 | Ferrari 812 Superfast
|
| Audi A6 | BMW 8 | Porsche Cayenne
Porsche Panamera |
Ferrari F12 | |
| Audi A7 | BMW X5 | |||
| Audi A8 | ||||
| Audi Q7 |
Related: What is a Car Chassis? its Diagram And Parts
Types of Four-Wheel Steering
Rear-wheel steering systems vary from manufacturer to manufacturer, yet they all accomplish the same goals. The majority use electro-mechanical versions, like Audi’s Dynamic All-Wheel Steering, Porsche’s Rear-Axle Steering, and the Active Kinematics Control (AKC) systems that ZF supplies to automakers like Ferrari and Cadillac.
Some, like Nissan’s former HICAS (High-Capacity Actively Controlled Steering) system, rely solely on mechanical systems. These two systems, once more, alter the rear wheels’ toe in or out in essentially the same way, but they differ in what activates them.
In a mechanical system akin to Nissan’s HICAS, which has not been utilized in Nissan automobiles since the R34-generation GT-R or in Infinitis since the G37, the wheels were moved by hydraulics driven by the power-steering pump. Speed sensors would then determine the direction and amount of rear-wheel rotation.
A comparable technology was seen in Honda’s Prelude Si 4WS. These days, electromechanical four-wheel steering systems are much more prevalent and efficient than their predecessors. Compared to their predecessors, modern four-wheel steering systems offer much more precise wheel positioning, angles, and functions.
The ECU of the car and several sensors spread across the drivetrain control these systems. Manufacturers vary in how much steering angle the back wheels permit, ranging from 1 to 15 degrees, even though the fundamental outcome is the same.
Four-Wheel Steering Phases
The following are the phases in a car’s four-wheel steering system:
The Negative Phase
During the negative phase, the front and rear wheels travel in different directions. The curving radius decreases as the two axles rotate in opposing directions. Because of this, the vehicle requires less parking space, which is advantageous in areas where parking and traffic are significant issues.
The Neutral Phase
Only the front wheels rotate to the right or left during this phase, while the rear wheel stays neutral or straight. Traditional vehicles use this drive at an average speed.
The Positive Phase
During the positive phase, the front and rear wheels go in the same direction. When driving on a highway, this motion of the front and rear axles makes changing lanes easier for a 4WD vehicle. This phase is typically used at greater vehicle speeds for improved handling and agility.
Advantages of Four Wheel Steering
This technology can provide several advantages in terms of handling, maneuverability, and stability, especially in larger or performance-oriented vehicles. Here are some key benefits of four-wheel steering:
Enhanced Stability
Stability is essential for feeling safe when driving. Thankfully, the four-wheel steering system was created in part for that purpose. You have better control over the car when all four wheels are steering. You will appreciate the improved stability if you are driving quickly and switching lanes frequently.
Greater Safety
Every driver desires a vehicle with excellent handling and turning. But not everyone can operate a sports car. However, four-wheel steering enables you to turn without producing a significant degree of body roll. This is safer as well as more enjoyable because the car maintains more control.
Tighter Rurning Radius
You can turn your car in a tighter turn with a smaller radius if it has 4-wheel steering. The rear wheels turn in opposition to the front wheels because counter-phase steering is initiated at lower speeds. This technique can undoubtedly benefit you if you want to drive with more assurance. Parallel parking, U-turns, and other tricky maneuvers won’t be a problem for you.
Faster Steering Response
You want your automobile to react quickly when you make a turn, but some vehicles just don’t. The four-wheel steering system, however, offers a far faster reaction. You’ll notice that the car replies to your request almost instantly at any speed. Overall, the steering should be more accurate, whether turning or changing lanes.
Disadvantages of Four-Wheel Steering
While there are advantages, there are also several disadvantages associated with this technology:
High Cost
The cost of a vehicle with this cutting-edge technology will increase. The cost of the system development and automobile production is more for the automaker, and you pay more as a result. Additionally, you should anticipate these prices to increase if the system needs to be fixed. This is because a lot of the systems are constructed with cutting-edge components.
Higher Cost of Defect
There is a greater possibility of malfunction for each steering wheel. There are unique electronic bits and components in every steering wheel. The entire system will go down if even one of these fails. Four-wheel steering systems hence require extra upkeep. It might, however, also entail more frequent maintenance.