Four wheel steering

Understanding how four wheel steering works

When parking at slow speeds and on constrained off-road tracks, the four-wheel steering is intended to provide better vehicle mobility. The technology improves low-speed agility and enables a smaller turn circle for the driver. The purpose of a 4-wheel Steer is also to increase trailer-towing vehicle stability.

Some cars use a technology known as four-wheel steering (sometimes known as all-wheel steering) to enhance steering reaction, boost vehicle stability when navigating at high speeds, or reduce turning radius at low speeds.

Most active four-wheel steering systems use a computer and actuators to control the back wheels. Typically, the front wheels can turn farther than the back wheels. Some systems, such as Honda’s Prelude line’s system and Delphi’s Quadra steer, allow the rear wheels to be directed in the opposite direction from the front wheels at moderate speeds.

Thus, in this article, we’ll be discussing how four-wheel steering works as the meaning, working, diagram, types, genesis, benefits and drawbacks will be discussed.

Four wheel steering

So, let’s dive in!

Contents

What is a four-wheel steering

The Quadra Steering System, Rear Wheel Steering, Wheel Steering, or Quadrasteer are further names for the four-wheel steering system. It was created by Delphi for use in automobiles and is owned by General Motors. With the help of this device, a driver can actively control the back wheels while making turns.

Most steering systems are designed to react to the driver while they are driving. However, with a quadra steering system, we may steer both the front and rear wheels of a car simultaneously. It enables the driver to steer the vehicle on the road to turn it right or left as desired.  The front and rear wheels of this system are parallel to one another and steer in the same direction.

Compared to a two-wheel steering system, this steering method requires less space to turn the vehicle. The turning radius can be reduced by 21% using the Quadra steer steering system. Therefore, if a vehicle can make a U-turn in a 25-foot space, the driver can do so in roughly 20 feet thanks to the Quadra steer technology.

diagram of four wheel steering

How does four-wheel steering work

In order to improve a vehicle’s low- or high-speed agility, rear-wheel steering is a device that, when the steering wheel is turned, activates the angles of the rear wheels and either turns them in tandem with the front wheels or in the opposite way.

Toe refers to the angle at which a wheel is oriented toward or away from the car; thus, “toe-in” and “toe-out.” Both negative and positive descriptions of the toe are possible. Toe often refers to the front wheels of an automobile, and it can alter the vehicle’s high-speed stability (toe-in) or low-speed agility (toe-out) depending on whether both wheels are pointed in or out.

In tandem rear-wheel steering, the mechanism of the vehicle adjusts both rear wheels’ toes simultaneously, causing the rear wheels to move right or left simultaneously and point in the same direction. The way the toe operates on a car’s front wheels is quite different from this.

Even though each method is distinct, all four-wheel steering systems result in the exact same movement from the rear tires. The front wheels turn in the direction of travel while the rear wheels revolve in the opposite way when the steering wheel is turned at low speeds, effectively minimizing the turning circle of the vehicle. Low-speed moves are now quicker and simpler as a result.

For greater high-speed stability, steering at higher speeds causes the front and rear wheels to turn in the same direction. In terms of performance, this implies that a Porsche Panamera, which is long and rather heavy, can keep up with a Porsche 911, a sports car with a shorter wheelbase.

Additionally, these systems improve the performance of larger, heavier vehicles compared to how they would operate if only the front wheels turned. Examples of this include the Mercedes-Benz S-class, Bentley Flying Spur, and Lamborghini Urus.

Watch the video below to learn more about four-wheel steering:

Different types of Four-wheel steering

Although they all accomplish the same goals, the rear-wheel steering systems offered by different manufacturers vary. The majority of systems use electro-mechanical counterparts, such as Audi’s Dynamic All-Wheel Steering system, Porsche’s Rear-Axle Steering, and the Active Kinematics Control (AKC) systems supplied by ZF to manufacturers such as Ferrari and Cadillac. Some systems are mechanical-only, such as Nissan’s old HICAS (High-Capacity Actively Controlled Steering) system.

Again, both of these systems alter the toe-in or -out of the rear wheels, but their means of activation are different. Hydraulics supplied by the power-steering pump were utilized to actuate the wheels in a mechanical system like Nissan’s HICAS, which hasn’t been employed in Nissan since the R34-generation GT-R or in Infinitis since the G37. The direction and magnitude of the rotation of the rear wheels would then be calculated using speed sensors. A comparable technology was used in the Honda Prelude Si 4WS.

In comparison to those previous models, electromechanical four-wheel steering systems are now much more prevalent and sophisticated. The modern four-wheel steering systems give far more precise wheel placement, angles, and capabilities than their predecessors. They are controlled by the car’s ECU and a number of sensors along the drivetrain.

The basic outcome is the same, but manufacturers also vary in the amount of steering angle the rear wheels can accommodate, which can be anywhere between 1 and 15 degrees.

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 turning 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.

four wheel steering diagram

Drawbacks of four-wheel steering

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.

The genesis of the four-wheel cars and how they work

The genesis of Four Wheel Steering Cars are;

  • Nissan GT-R HICAS.
  • Honda Prelude Si 4WS.
  • Mitsubishi 3000GT VR-4/GTO.

Nissan GT-R HICAS

Although the Skyline GT-R platform from Nissan is famous for using the HICAS technology, it wasn’t the first to do so. The 1986 Skyline GTS was the vehicle on which the technology was initially used in practice after being first demonstrated in 1985.

Shin’ichiro Sakurai, the creator of the Skyline, created HICAS while working at Nissan. The chief engineer was substantially involved in the dangerous R380 while working for Prince before Nissan acquired it. He was renowned for his mastery of language as well. That also applies to his explanation of how HICAS should look.

How it work

Sakurai’s eventual successor, Naganori Ito, once stated what his mentor desired from the HICAS system:

“The Skyline’s fundamental tenet is to provide dependability and exceptional driving performance. A vehicle that perfectly reflects the driver’s intentions is the ideal. When the rider is mounted on the horse and the animal is moving, it is analogous to a horse and rider uniting.

A horse propels itself forward by exerting torque and pushing off with its rear legs. It makes perfect sense. This is a good illustration of a rear-wheel-drive automobile. But if you pay closer attention to how a horse moves, you’ll notice that it also propels itself off the ground with its front legs and steers its movement with its hind legs. Cars require four-wheel-drive and four-wheel-steering systems to replicate this. The ATTESA and HICAS systems perform these tasks.

Nissan explains how HICAS functions as follows:

“Rear wheel steering on earlier HICAS models was accomplished by hydraulics. The hydraulic system employed speed sensors to determine how much and which way to steer the rear wheels. It was driven by the power steering pump. Later models, known as Super HICAS, switched to an electronic actuator for the rear steering rack, greatly lightening the system. The Super HICAS calculates how rapidly you’re entering a turn using information from a speed sensor and a steering-wheel angle sensor, then modifies the angle of the rear wheels to suit the driving situation. Rear-wheel steering on HICAS and Super HICAS vehicles is restricted to around one degree in either direction.

Honda Prelude Si 4WS

Honda didn’t quite release the Prelude Si 4WS when you would have expected it to in the late 1980s. On second consideration, a sporty four-door with all-wheel steer built on a budget automobile makes perfect sense when you consider that much neon from that era was made by Escobar.

How it work

The primary motivation behind Honda’s four-wheel steering system for the Prelude Si 4WS was to “propel the handling and maneuverability of the automobile into a new dimension.” Honda started working on the 4WS system, which created a steer-angle-dependent four-wheel steering system, in 1977. The four-wheel steering system on the Prelude was entirely mechanical and consisted of two steering gears, one at the front and one at the back, connected by a middle shaft.

Honda provided the original news release for the Prelude Si 4WS, which included a thorough explanation of the system’s operation.

According to the press release, the front steering gearbox’s rack-and-pinion system “causes the rack to move laterally when the driver turns the steering wheel.” “The front wheels are guided by this rack stroke. A second rack and pinion located inside the gearbox are utilized to rotate an output pinion shaft at the same time.

The rear steering gearbox receives rotation from the steering wheel through the center shaft of its output pinion shaft. To steer the rear wheels through the tie rods, a stroke rod inside the rear steering gearbox moves axially. Even stranger is how that related to the car’s speed.

According to the press release, “the output stroke advances in one direction for steering-wheel inputs that are less than about 140 degrees from the straight-ahead position. The stroke and the relative motion at the rear progressively and smoothly decrease and eventually change direction for angles greater than that. As a result, the rear-steering gearbox has a system that gradually changes the output direction in response to the size of the steering input.”

Mitsubishi 3000GT VR-4/GTO

Although the formidable Mitsubishi 3000GT VR-4 is solely known in the United States, the Mitsubishi Galant VR-4 and the debut of the Dynamic Four system can be linked to the GTO’s Japan-only ancestry. Mitsubishi’s Dynamic Four, hence the name, wasn’t just a single system like the others below; it also had four-wheel drive, four-wheel steer, four-wheel independent suspension, and four-wheel ABS.

The 1987-released Galant VR-4 served as the prototype for both the powerful Lancer Evolution and the 3000GT. Additionally, this prototype rally car gave rise to the first active suspension system on the market, Active ECS, as well as Dynamic Four for two-wheel-drive cars. Mitsubishi named the umbrella its Active Footwork System, which is a fantastic term for a collection of systems, seeing the two as the opposing sides of the same coin.

How it works

“The Active Footwork System adopted for the Galant this time is a generic name for the Active Four (four-wheel-drive models) and Active ECS (two-wheel drive), which primarily consist of the following suspension systems to create more room for driving from low to high speeds and to make driving itself easier in the age of high performance,” according to the Galant’s initial news release. By enhancing the traction between each tire and the road surface, this innovative new system enhances the vehicle’s dynamic performance in terms of acceleration, cornering, and braking.

According to the press release, the four-wheel steering system is a fully hydraulic system that responds to steering force and vehicle speed to further enhance steering response in the medium to high-speed range. Although it depends on the steering effort and a vehicle speed of more than 31 mph, that is accomplished by hydraulic pressure being transferred to the rear suspension’s trailing-arm joints and causing them to flex up to 1.5 degrees.

Three years later, Mitsubishi unveiled the 3000GT (known as the GTO in Japan), with the slogan “The GTO. Its high levels of performance are made to be enjoyed by drivers of all skill levels safely, happily, and whenever their fancy strikes them.

The four-wheel steering system of the GTO operated as follows, according to the original Japanese press release: “A hydraulic actuator is attached to an intermediate joint on the end of the trailing arm. In order to make the rear-wheel steering angle proportional to the front-wheel steering effort, the actuator is controlled by a rear-wheel steering pump connected to the front-wheel power-assist hydraulic circuit. Because the rear-wheel steering pump distributes oil in quantities corresponding to the rotational speed of the rear wheels, the rear-wheel steering angle is related to vehicle speed.

Related Article

Which cars have 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 following are cars that have four-wheel steering:

AcuraBMW(series)MitsubishiPorscheFerrari
Acura RLXBMW 5Mitsubishi Galant VR-4Porsche 911

 

Ferrari GTC4Lusso

 

Acura TLXBMW 7Mitsubishi 3000GTPorsche 991Ferrari 812 Superfast

 

Audi A6BMW 8Porsche Cayenne

Porsche Panamera

Ferrari F12
Audi A7BMW X5
Audi A8
Audi Q7

 

That is all for this article, where how four-wheel steering works as the meaning, working, diagram, types, genesis, benefits, and drawbacks are been discussed. I hope it was helpful, if so, kindly share it with others. Thanks for reading, see you around!


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