by Adrian-Liviu Dorofte

The new GL- and GLK-Class: Effortless superiority on- and off-road

The new GL-Class which has been available since November 2012 is the pinnacle of perfection in the ATV and SUV world. It offers a luxurious interior with seven full-size seats and superlative ride comfort accompanied by highly dynamic performance on dry, wet or wintry roads. The premium SUV also boasts outstanding off-road capabilities, thanks to new suspension developments and innovative dynamic handling control systems which enhance both driving pleasure and safety on the road. In a nutshell, the GL-Class is a seven-seater, all-terrain S-Class.

The optional ON&OFFROAD package for the new GL-Class uses six different driving modes to optimise driving dynamics and handling safety by providing the optimum drive control needed to cope with the wide spectrum of operating conditions encountered both on and off the road. Drivers have the choice of an automatic mode, two specially programmed off-road modes as well as three on-road modes – “Winter”, “Sport” and “Towing”.

The specific driving modes for all-wheel drive resolve a conflict of objectives that has previously hampered further development of 4MATIC and the 4ETS electronic traction system as well as ESP® and acceleration skid control (ASR). To take an example: on off-road tracks or snow-covered roads, it is important that the control systems respond very gently due to the low friction coefficients, but this makes a sporty set-up virtually impossible. Conversely, a sporty basic setup impairs performance abilities in off-road terrain and snow. In the past, excellent compromises were always found which worked brilliantly under all conditions. The new ON&OFFROAD package with its specific driving modes, however, enables driving dynamics and handling safety to be optimised almost as far as is physically possible under all operating conditions by maximising networking between the individual control systems.

In terms of “hardware”, the ON&OFFROAD package comprises an underguard, a two-stage transfer case with low-range ratio, an inter-axle differential lock and enhanced AIRMATIC functionality that allows a maximum ground clearance of 285 millimetres and a fording depth of 600 millimetres.

Winter driving mode: more fun, more safety

The driving mode is chosen using a rotary control on the centre console. To ensure the selected driving mode – in this case “Winter” – is clearly indicated, a special snowflake graphic appears in the instrument cluster, while the COMAND screen shows the GL-Class in a wintry, snow-covered landscape.

The ON&OFFROAD package’s winter driving mode optimises handling on roads affected by snow, ice or freezing rain and when using snow chains, and offers drivers added safety with its well-defined, predictable reactions. The extensive fine-tuning work carried out focused on further increasing longitudinal traction, at the same time as improving lateral dynamics and handling safety. The development team was able to implement these specifications to impressive effect using targeted control mechanisms in the drivetrain.

When pulling away with or without the steering turned, the inter-axle lock in the centre differential is triggered earlier in order to increase traction and reduce understeer when accelerating briskly. In parallel to this, the 7G-TRONIC PLUS switches to the “gentler” ECO mode and automatically engages 2nd gear when pulling away to avoid high wheel slip. Finally, a flatter response curve gives the driver more sensitive control over the accelerator pedal.

- Maintaining a locking torque that has been set in the centre differential for longer improves handling stability and helps the driver by making the self-steering characteristics more definite.

- Higher ASR slip thresholds when driving in a straight line result in high traction levels as well as safe operation with snow chains with outstanding tractive power.

- ASR slip thresholds lowered when cornering in order to ensure stable handling characteristics at all times as far as is physically possible.

ACTIVE CURVE SYSTEM for safe fun in the snow at its very best

When the ON&OFFROAD package is combined with the ACTIVE CURVE SYSTEM (ACS), a specially programmed winter set-up guarantees dynamic driving pleasure while giving the driver excellent control over the vehicle for a high degree of handling safety. ACS uses active anti-roll bars at the front and rear axles to compensate for the roll angle of the body through bends, increasing agility and driving pleasure in the process. At the same time, the system is capable of giving the vehicle greater traction, especially in wintry road conditions with low grip levels.

The ACTIVE CURVE SYSTEM “Snow mode” features two control strategies. Firstly, many of the parameters needed for driving on wintry roads are already incorporated into the basic functions, i.e. when the ON&OFFROAD package’s Automatic driving mode is activated. This means that the system’s reactions to the driver’s steering inputs will be less dynamic on slippery surfaces. External influencing factors, such as fluctuating friction coefficients on roads that are partially covered in ice or snow, are balanced out faster though. Thanks to this control strategy, the GL becomes far more docile, even if the vehicle switches between moderate oversteer and understeer.

Secondly, the system control for the winter driving mode includes a special control algorithm. In just the same way as the shaped skis thrill alpine skiers by closely following the desired line even through turns with a tight radius, the car handles in tight bends in this mode. This control strategy produces increased traction on snow-covered road surfaces by dynamic displacement of the wheel loads. If the driver turns into a tighter bend while travelling at a constant speed or accelerating, the wheel load and, as a result, the traction will be increased at the front wheel on the outside of the bend. Doing so minimises the understeer that is otherwise typical in this driving situation. If the driver then reduces the steering angle when exiting from the bend while travelling at a constant speed or accelerating, the load at the rear wheel on the outside of the bend will be raised instead. This has the effect of increasing lateral support at the rear axle, so that the vehicle’s handling is stabilised in the same way as when entering the bend. This time though, it is the tendency to oversteer that is countered.

GLK: Rock-solid character in a fresh guise

Following the world premiere in April 2012, the new Mercedes-Benz GLK is displaying its fresh guise. Its claim to leadership of the compact SUV segment is underscored by trailblazing assistance systems, engines matching efficiency with agility and an extended range of equipment and appointments.

The newly designed exterior lends the GLK added dynamism. The body combines classic elements of all-terrain vehicles with the design idiom of the current Mercedes-Benz models. Stringent lines, expansive surfaces and the smooth-surfaced, volume-emphasizing front and rear areas harmonise with the hallmark GLK body features which are typical of classic, functional all-terrain vehicles. Apart from the attendant benefits in off-road terrain, this design also offers concrete advantages in day-to-day use. The high seat position provides a commanding view of the traffic situation, with the body lines also designed for excellent visibility.

More possibilities with Offroad Engineering package

The 4MATIC on the GLK is based on the version featuring on the C-, E-, CLS- and S-Class, whereby its outstanding off-road capability sets it apart from the saloons and coupés, however. For keen off-road enthusiasts, an Offroad Engineering package is additionally available to further broaden the scope for off-road adventures. At the touch of a button a special drive programme is started which varies the shift points of the 7G-TRONIC, "softens" the accelerator characteristics and activates the ESP®off-road functions with off-road ABS and a special off-road 4ETS system. An additional switch activates Downhill Speed Regulation (DSR), which automatically maintains a preset speed between 4 and 18 km/h on steep downhill stretches. The driver is able to vary the speed at any time by means of the cruise control lever.

Assistance systems familiar from the S- and E-Class feature as standard to enable a further improvement in active safety and driver-fitness safety and take the compact SUV to the top of its market segment. Electric steering with STEER CONTROL, which supports the driver in unstable driving conditions by triggering an impulse which can be felt on the steering wheel, prompting countersteering by the driver in the correct direction, Brake Assist (BAS), which provides additional brake power when emergency braking is detected, and ADAPTIVE BRAKE featuring Hill-Start Assist, HOLD function, brake drying in the wet and priming of the brake system all support the driver. The high standard of active safety is ensured by the AGILITY CONTROL suspension with selective damping system, the ESP® Electronic Stability Program with integrated trailer stabilisation and tyre pressure loss warning and, on the 4MATIC models, by permanent all-wheel drive and the 4ETS electronic traction system (except 4x2 models).

Optional equipment: 360°-camera and Active Parking Assist

Optional equipment includes the ATTENTION ASSIST drowsiness detection system and the PRE-SAFE® anticipatory safety system. Additional assistance systems, including active variants, are optionally available. One example here is Active Parking Assist, enabling automatic manoeuvring into and out of parking spaces. To facilitate manoeuvring when visibility is poor there is a backup camera with guide lines or – for the first time from Mercedes-Benz – a 360° camera.
Additional systems are optionally available as individual items or in special packages. The Driving Assistance package Plus comprises DISTRONIC PLUS including BAS PLUS, PRE-SAFE® Brake, Active Lane Keeping Assist and Active Blind Spot Assist. The Parking package combines the described 360° camera including Active Parking Assist and PARKTRONIC. The Lane Tracking package includes Lane Keeping Assist and Blind Spot Assist. Another new development is the Offroad Engineering package in combination with the Intelligent Light System. Offroad Light is available here for trips in difficult terrain. Specific headlamp settings provide for better off-road orientation by more widespread illumination of the field of vision.

Credits: Daimler AG

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