Suspension: Even better off-road, more dynamic than ever on the road

May 5, 2018
Affalterbach

The Schöckl: this is where all G-Class generations have found their feet, and where the test drivers know every little obstacle. The Schöckl is the 1445‑metre high mountain near Graz, Austria which Mercedes-Benz uses as a test site for practical trials of the G-Class. The 5.6 km route includes gradients of up to 60 percent and lateral inclinations of up to 40 percent. During the development stage, a "G" has to endure a good 2000 strenuous kilometres on this very demanding course. Plus there are a further 4000 kilometres of rough tracks. The new G-Class masters the route with noticeably more control and comfort.

"There are many reasons for this extraordinary performance," says Dr Gunnar Güthenke, Head of the Off-Road Product Unit at Mercedes-Benz. "First we have our new suspension technology with independent front suspension, the adaptively adjustable dampers and the electro-mechanical steering."

The G-Class: far more than a cross-country vehicle

The new G-Class benefits from almost 40 years of experience and expertise in the off-road segment. The primary goal of development was to redefine the quality of the handling both on an off the road. This goal has been achieved: the new G-Class performs even better off-road, while on the road it is significantly more agile, dynamic and comfortable than its predecessor. In 2014, joint development work on the suspension was started by Mercedes-Benz G GmbH and Mercedes-AMG GmbH. The result is an independent suspension with double-wishbone front axle in combination with a rigid rear axle. As part of their work, the engineers had the task of fighting for every millimetre, because off-road capability not least also means maximum ground clearance. The raising of the axles makes a decisive contribution in this respect, while requiring a strut tower brace in the engine compartment to achieve the ruggedness objectives.

The components of the double-wishbone front suspension are directly mounted to the ladder-type frame without a subframe. The lower wishbone's attachment points on the frame in Z-direction are positioned as high up as possible. This arrangement ensures good driveability beyond the asphalt. Specifically for the G-Class, the new front axle is designed in such a robust way that the off-road performance and off-road capabilities of its predecessor are maintained and partly even surpassed.

Equipped in this way and with a ground clearance of 270 mm to the front axle gear, the G-Class provides plenty of potential for maximum assertiveness and driving pleasure in off-road terrain. This is further enhanced by a maximum front spring travel of 85/100 millimetres and a ramp breakover angle of 25.7 degrees.

However, the specifications for the G-Class not only included off-road solidity and superiority, but also better driving dynamics and comfort on asphalted roads. Thanks to the new front axle design, the on-road performance of the G-Class has therefore been enhanced at the same time. On the road, the "G" is as agile as it is comfortable and provides the driver with a better steering feel. The off-roader stays on track more solidly, and is agile and effortless when driving off-road.

With the "G", the fun really starts where others have to give up

The exceptional handling characteristics and driving safety on account of the driver's high level of control need to be experienced at first hand. However, the following figures clearly show that every little detail to improve the off-road characteristics has been checked and optimised where possible.

As before, high ground clearance and long suspension travel form the basis for the further improved off-road characteristics of the G-Class. The figures speak for themselves:

  • Slope climbing ability of up to 100% on suitable surfaces
  • Ground clearance between axles, plus 6 mm, now 24.1 cm
  • Maximum fording depth now 70 cm when driving through water and mud, no less than an additional 10 cm
  • Stable at tilt angles of 35°, plus 7°
  • Angle of departure: 30°, angle of approach: 31°, plus 1°
  • Break-over angle: 26°, plus 1°

Thanks to the independent suspension, it was possible to improve the rigidity of the body front end. A strut tower brace, known as a suspension bridge, now connects the front strut towers, which increases the torsional rigidity of the ladder-type frame.

At the rear, in contrast to the predecessor, the new rigid axle is controlled by four trailing arms on each side and a Panhard rod. This makes normal driving on the road even more comfortable. In off-road terrain, the rear spring jounce of 82 mm and rebound of 142 mm plus the ground clearance of 241 mm to the rear axle gear help to ensure a safe ride even in extreme situations.

Bodyshell as robust as never before

How stable the G-Class is in practice already became apparent at an early development stage, after the first endurance runs. To this end the engineers needed to build driveable prototypes from the so-called structural verification vehicles that are produced to ensure passive safety. Worldwide endurance runs under all manner of climatic conditions commenced very early on. All in all, the vehicles covered 2.4 million kilometres during the development phase. Endurance runs on the Schöckl mountain were also a fixed part of the test programme. "The engineers reported back that the bodyshell is better than ever before," says Dr Gunnar Güthenke.

DYNAMIC SELECT: make your choice

DYNAMIC SELECT is now available with several driving modes for the G-Class. This allows adjusting the vehicle characteristics in seconds at the touch of a button, as the system modifies the characteristics of the engine, transmission, suspension, steering and assistance systems at the driver's behest. The driving modes "Comfort", "Sport", "Eco" and "Individual" can be set conveniently via the DYNAMIC SELECT rocker switch. "ECO" mode, for example, makes a particularly fuel-efficient and quiet driving style possible, as the exhaust flap is automatically closed. In "Sport" mode, on the other hand, the shift points of the automatic transmission, the throttle response of the engine and the parameters of the electric steering system and exhaust flap are changed. "Individual" allows drivers to configure their own preferred vehicle settings.

DYNAMIC SELECT provides a host of options in combination with the new suspension with optional Adaptive Damping System. The driver is then also able to modify the vehicle's damping characteristics in Sport and Comfort modes using the DYNAMIC SELECT switch.

Put simply, the G-Class detects the particular condition of the road and sets the appropriate damping characteristics, so that the damping in off-road terrain is stiffer, for example. In contrast, in Sport mode the G-Class boasts a more agile response when driving on the road.

To adapt the damper response, the kinetic and potential energy currently stored in each wheel is ascertained and calculated in real time from the spring travel and its derivatives. Together with the body acceleration, the control unit computes individual signal values for the solenoid valves of each damper. The suspension therefore regulates each wheel individually, improving both on-road ride comfort and off-road performance.

In its standard specification the new G-Class is equipped with a conventional steel suspension and a frequency-selective passive damping system. Frequency-selective means that the damping characteristics vary according to the number of bumps crossed in a certain time.

The new "G-Mode" paves the way where there is none

One of the prerequisites for the improved off-road handling characteristics is the new "G-Mode". The G-Class changes to "G-Mode" independently of the chosen driving mode as soon as one of the three differential locks has been activated or the LOW RANGE off-road reduction gear has been engaged. This off-road mode adapts the adjustable damping of the suspension and the steering as well as the accelerator characteristics, avoids unnecessary gear shifts and thus ensures optimum control and maximum off-road capability. A small "G" icon discreetly lights up in the instrument cluster. The "G" swallows rough ground so easily that the driver is able to enjoy inch-perfect manoeuvring even in the steepest terrain, and receive excellent steering feedback on the traction provided by the surface.

As direct as possible, as indirect as necessary

As standard the G-Class is now fitted with electromechanical rack-and-pinion steering, which now allows driving assistance systems such as Parking Assist to be implemented. In addition, the electromechanical steering uses less energy than a hydraulically assisted steering system. Depending on the driving mode, one of three sets of steering characteristic lines, namely Comfort, Sport and Off-road, comes into effect. This ensures a comfortable or sporty steering feel on the road, but also straightforward and precise feedback in unpaved and demanding terrain - always paired with sufficient steering power assistance. In a nutshell: as direct as possible, as indirect as necessary.

Internally ventilated brake discs are used at the front and rear axles, with a diameter of 354 and 345 millimetres and a thickness of 32 and 22 millimetres. This helps to reduce the weight of the G-Class, reducing fuel consumption while improving ride comfort. An electric parking brake is provided as standard.

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