The sturdy, robust body of the GLK-Class is more than just the prerequisite for exceptional standards of active and passive safety. It also forms the foundation
for the well-balanced vibrational and acoustic comfort, while its lightweight construction helps to reduce the vehicle's fuel consumption At the same time, the body with its unitised structure must be able to twist its way through off-road terrain and handle sand, mud or scree tracks, yet still guarantee lasting durability. Just like all other Mercedes-Benz passenger cars, the GLK has all the right credentials to become a vintage car.
Intelligent bodyshell reinforcements for when the going gets tough
The body of the GLK has been carefully adapted to make allowance for the compact SUV's broad spectrum of capabilities. It is composed primarily of high-strength, state-of-the-art high-strength and ultra-high-strength sheet steel, and accounts for 47 percent of the overall weight. The force application points in particular – as the connection points between the body and chassis are known – are strengthened with solid reinforcements to preserve the excellent driving dynamics and active safety under all handling conditions. These structural measures have the added benefit of enhancing the vehicle's acoustic and vibrational comfort, which both set new benchmark standards in the compact-SUV segment. Additional reinforcements are to be found in the floor assembly, the propshaft tunnel and the links to the body pillars. The firewall is made up of four sheet sections whose material thickness varies in accordance with the individual peaks in load, thereby maximising stability whilst minimising weight. The lower sections of the firewall are 1.25 mm thick, whilst those at the top have a thickness of 0.8 mm. The dashboard is supported by a square aluminium section, which is in turn bolted to the two A‑pillars at both ends, substantially strengthening this part of the body. A supplementary strut braces the steering's jacket tube against the firewall, preventing any steering tremble when the engine is idling.
The entire front end of the body is bolted to the structural components behind, enabling cost-effective repairs to be carried out following collisions without the need for welding work. The front-end assembly comprises an extruded aluminium section, a single-piece crash box made from aluminium which connects to the front longitudinal members, as well as a multipiece sheet steel framework which holds the headlamp assemblies, the bumper, the washer fluid reservoir and the bonnet catches. A frame-type integral support made of high-strength steel acts as the axle and engine carrier. It is here that parts of the wheel location componentry, the steering gear and the engine mounting are secured. The rear-end assembly consists of an ultra-high-strength flexible steel bumper bracket with welded crash boxes made from reinforced sheet metal.
Effective corrosion protection for a long vehicle life
Effective corrosion protection is particularly crucial in the case of SUV models and off-roaders. This is exactly why all GLK models feature a series of precisely harmonised protective mechanisms, which are underpinned by full galvanisation of the body. Instead of refining the entire bodyshell with an even coating of zinc applied by electrolysis, the selective use of components with different coatings brings about a substantial improvement in the overall level of protection.
In addition to fully galvanising the body, its resistance to corrosive attack is further enhanced by applying a protective coating to the cavities, sealing the body flanges and employing a specially designed paintwork system. Following the phosphating and cathodic dip priming stages, the Paint Shop at the Mercedes-Benz plant in Bremen applies a series of coats, including the primer coat, the coloured base coat and finally the top coat featuring nano technology for a more scratch-resistant finish. In view of its environmental impact, the development engineers dispensed with a PVC underbody seal, opting instead for full underbody panelling. The panelling system furthermore offers superior aerodynamics, can be easily replaced if it becomes damaged, and effectively protects the underbody against stone chipping.
Systematic torture – introducing the dynamic MEKO programme
During its development, the GLK had to withstand the rigours of the Mercedes-Benz dynamic corrosion endurance test programme known as MEKO. This takes as its yardstick the most extreme climatic conditions in the world, such as constant exposure to cold and salt spray in Canada, the tropical humidity of Thailand, or the extreme temperature fluctuations in Dubai with the resulting formation of condensation. Then there's the heat of the searing South African sun coupled with longer journeys along dust roads and gravel tracks. The automotive torture specialists also incorporated a whole series of dynamic load tests, including driving on rough roads, along mud, dirt and stone chipping tracks, through torsion sections, at high speed and through water. For it is only by subjecting the body and its detachable parts to constant levels of mechanical stress that the effectiveness of the extensive corrosion protection can be truly put to the test. Over a period of 16 weeks, the test subjects have to endure a daily torture programme, with alternating phases of salt spray, humid heat and dry heat in climate chambers followed by the dynamic load cycles. The test drivers are given the weekend off, but the punishment continues relentless for the cars, as they face up to Arctic cold, tropical heat or continuous rainfall in the climate chambers. Once the Mercedes-Benz corrosion endurance test programme has concluded, the body is dismantled right down to the smallest detail in order to inspect the results. It is only by disassembling it in such meticulous fashion that the effectiveness of the corrosion protection in the body flanges and cavities can be subsequently examined and optimised where necessary.
Airflow characteristics a tremendous achievement by SUV standards
Achieving good aerodynamics and soothing aeroacoustics posed two of the major challenges during development of the GLK. Normally, a basic body structure with an angular design and steeply inclined front windscreen would preclude a smooth airflow pattern around the vehicle. Yet, by systematically eliminating the sound conduction paths into the passenger compartment, the aerodynamics engineers succeeded in keeping wind noise levels low, especially at higher speeds. The principal measures:
Strengthening of the bodyshell structure and implementation of effective sealing measures
Door sealing concept featuring two continuous sealing levels and three in key areas
Strengthening of critical areas of the outer skin in order to reduce low-frequency wind noise
High-quality anti-drumming coatings on sound-emitting sheet-metal surfaces
The panoramic glass sliding sunroof that can be specified as an option now comes with a novel new air-deflecting mesh to suppress the booming sound when driving with the sunroof fully open and keep the interior virtually draught-free, despite the generous size of the opening. And although it features large exterior mirrors and enlarged air intakes, the GLK boasts a low drag coefficient of cd = 0.34, placing it in the lead group of competitors in this segment. This outstanding reading can be attributed to the painstakingly detailed work carried out by the aerodynamics experts. The enhancements made to the bodywork focused on the streamlined styling of the front and rear aprons and tail light assemblies, and on optimisation of both the sealing in the area around the radiator and of the way in which the airstream is channelled through the engine compartment in order to make efficient use of the available cooling air. The detailed work carried out on the A-pillar, the water deflector and the large exterior mirrors likewise had an important role to play. Drag in the vicinity of the vehicle's underbody and wheel arches is reduced by the continuous underbody panelling, including an aerodynamic-enhancing diffuser at the rear and specially shaped wheel spoilers.
The formidable handling stability – especially when travelling at higher speeds and in crosswinds – is assisted by the way in which uplift is distributed favourably between the front and rear axles. Safety is boosted by effectively minimising the build-up of dirt on the exterior mirrors, as well as on the side windows and rear windscreen. The water-catching channel on the A-pillar has been specially designed to prevent water from overflowing onto the side window, even in heavy, steady rain. The exterior mirror housing collects any water that strikes it in a groove running around its circumference before directing it outwards to a defined drip point. The rear windscreen is kept clean thanks to a windscreen wiper which is automatically activated whenever the front windscreen wipers are switched on and reverse gear is engaged.
High-intensity headlamp system as standard, Intelligent Light System (ILS) as an option
The GLK-Class comes equipped with a powerful H7 headlamp system, including
an H7 main beam that features the proven free-form reflector technology. The standard front fog lamps are integrated into the front bumper trim, while indicator repeaters in the exterior mirror housings, each comprising four LEDs, ensure that the driver's turn signals are even more clearly visible from the front and the side.
As an alternative, customers are able to opt for the Intelligent Light System (ILS) with bi-xenon headlamps. Here, unlike conventional light systems, the light from the headlamps is adapted dynamically to suit the driving situation and weather conditions. The range of functions includes the active light function, country mode, motorway mode, along with enhanced fog lamps and dynamic headlamp range control. The cornering light function is integrated into the headlamp with the ILS system. Below is a summary of the individual functions:
With the Intelligent Light System, the conventional dipped-beam headlamps with their proven asymmetric light distribution are replaced by the new country mode, which illuminates the road verge on the driver's side more broadly and brightly than before. This enables drivers to orientate themselves more easily in the dark, and respond more rapidly when other road users cross the road.
The new motorway mode, which comes on automatically at speeds above 90 km/h, increases the driver's range of vision by up to 60 per cent. This lighting function is activated in two stages. The Intelligent Light System first increases the output of the bi-xenon bulbs from 35 to 38 watts, thereby increasing the light's intensity and providing noticeably better illumination of the carriageway and the side verges. The second stage of the motorway mode is triggered at 110 km/h, when the bi-xenon modules are elevated slightly. The new motorway mode has a range of around 120 metres, and the driver is able to see about 50 metres further at the centre of the cone of light than with conventional dipped-beam headlamps.
Enhanced fog lamps:
The enhanced fog lamps are designed to improve driver orientation when visibility is poor. This new lighting function is activated at speeds below 70 km/h, as soon as the rear fog lamp is switched on. The variable headlamp technology makes it possible to pivot the bi-xenon headlamp on the driver's side outwards by eight degrees, while lowering its beam of light at the same time. This illuminates the inner half of the road more brightly and reduces the degree of backglare caused by light reflected back by the fog. The enhanced fog lamps remain switched on up to
a speed of 100 km/h.
Active and cornering light functions:
Depending on the steering angle, yaw rate and vehicle speed, the active light function pivots the headlamps sideways by up to 15 degrees in fractions of a second to greatly improve illumination of the road ahead. On a long sweeping bend with a radius of 190 metres, the driver is able to see 25 metres further than with conventional dipped-beam headlamps as a result of the active light function, which, incidentally, operates with both dipped and main beam.
LED tail lights are also included as part of the Intelligent Light System (ILS) package.