The second chapter in the story of one of the most exciting and successful sports cars began in March 2004 when Mercedes‑Benz presented the new SLK-Class. The design reflected the sporty, powerful nature of the new vehicle at first glance. The long bonnet, raked windscreen, wide doors and short rear were all typical roadster hallmarks, and on the 4.08 metre-long SLK, they were even more pronounced than on its predecessor. This was the result of a 30 millimetre longer wheelbase and 72 millimetre longer body, distinctive, arrow-shaped tapering at the front and rear and a wedge-shaped silhouette. With details such as the striking nose section, special aerofoil blades in the radiator grille and the twin exhaust system reminiscent of a racing car, the design of the new SLK underlined the fact that this two-seater was part of a long Mercedes-Benz tradition of sports car production. The extremely short overhangs at the front and rear concentrated attention on the wheels. Viewed from the side, the 16‑inch wheels and the flared wings emphasised the powerful, dynamic character of the new SLK-Class. Two oval, chromed tailpipes, distinctive tail lights and an organically integrated, powerfully accentuated rear apron were significant style features at the rear.
The headlamps were not only an elegant and eye-catching feature, they also met the highest technical standards. Mercedes-Benz replaced the previous reflector technology for the low-beam headlamps with a newly developed projection system. This offered broader and more even illumination of the road ahead and also gave the low-beam headlamps a greater range. Fog lamps with halogen bulbs were also part of the standard equipment. These were housed in the bumper trim and, in conjunction with the optional bi-xenon headlamps, offered a new cornering light function. The tail lights also featured cutting-edge technology: in total 32 light diodes were responsible for the brake lights and tail lights. Their range extended across the full width of the tail light; when braking, this red area was illuminated significantly more brightly than in the tail light function.
The interior design uncompromisingly followed the roadster philosophy: the dashboard had a sporty, technical feel. The colour contrast alone, with silver-coloured control elements set in black-finished areas of the steering wheel, the centre console and the tunnel trim, announced the SLK-Class's independent design concept. The two large, clearly visible circular instruments were set in silver-painted cylindrical surrounds.
The SLK-Class was available for the first time with the cutting-edge COMAND APS control and display system: the large colour display (6.5-inch) with cutting-edge TFT (Thin Film Transistor) technology was characterised by high brilliance and colour rendering and its 16:9 aspect ratio made it suitable for films. The DVD player played DVDs, audio CDs and MP3 CDs. Text messages could be read on the COMAND screen and answered using the multimedia unit.
The range of colours for the SLK‑� � � Class had also been revised: while in 1996, when the first version of the roadster was launched, powerful, intense colours were the order of the day, the trend now was for more subtle shades. The sports roadster offered its most diverse range of colours in conjunction with leather appointments. Here SLK customers could choose from six interior colours: black, universe blue, orient beige, dusky red, alpaca grey and tobacco brown for the exclusive nappa leather appointments. In conjunction with the twelve exterior colours, this resulted in a wealth of options when it came to giving the sports car an individual colour scheme.
The attractive body was equally dazzling in technical terms, with a Cd value of 0.32, for example, impressive body rigidity and a tank capacity of 70 litres. The innovative vario-roof with which the SLK set trends in 1996, had been further developed and technically perfected by the engineers in Sindelfingen. It opened and closed even faster, in 22 seconds, and thanks to the pivoting rear window took up even less space in the boot than before: with the vario-roof open, the boot's load capacity according to the VDA measuring method was 208 litres – 63 litres more than the previous model. This major improvement was made possible by a new, complex roof design. Its highlight was the pivoting rear window. The rotation ensured that, after opening, the window fitted snugly into the curved area of the roof shell. For the first time the vario-roof could be operated using the remote control in the vehicle key as an option.
Detailed aerodynamic modifications to the underbody panelling, the wheel spoiler and the breakaway edge on the boot lid achieved two essential aims, reducing drag and improving driving stability at high speed and when braking. This made a key contribution to handling safety.
The new AIRSCARF neck-level heating was an innovative heating system which made its world debut in the roadster as an optional extra. It was fitted between the seat backrests. At the touch of a button temperature-controlled air flowed out of the special ventilation outlets in the head restraints, warming the passengers' neck and head during the journey – like an invisible scarf. This optional new development, which no other car in the world offered, constantly adjusted the blower speed, ensuring the best possible distribution of warm air in every situation. This adaptive control was active at up to 120 km/h, following which the system switched to a constant setting. The output could also be manually adjusted in three stages.
Notwithstanding, with the vario-roof open it was not completely possible to prevent draughts behind the occupants. The remedy here came in the form of the standard draught-stop, which could be expanded across the two roll-over bars in a few simple steps and was held in place by press-studs.
An innovation designed to ensure optimum climate comfort on board was THERMATIC air conditioning, which was part of the standard equipment for the SLK 350 and the SLK 55 AMG. For even more demanding drivers, Mercedes‑� � Benz had developed the luxury THERMOTRONIC automatic climate control, equipped with sunlight and pollutant sensors and regulated separately for the driver and passenger.
In addition, the new SLK‑Class offered comfort advantages when it came to aeroacoustics: with the vario-roof closed the noise levels inside were equivalent to those of a coupé. The roadster was also the quietest-running vehicle in its class – as confirmed by tests in an aeroacoustic wind tunnel at the University of Stuttgart using a new concave-mirror measuring method. Because the vario-roof absorbed wind noise better than a soft top, the noise levels inside the SLK‑Class at 140 km/h were up to 6 decibels lower than those of other roadsters. This was half the figure of its rivals.
The sports seats offered impressive fore-and-aft adjustment and levels of comfort that were perfect for long-distance journeys. Another new feature: the backrests of the driver and passenger seat folded forward and the back of each featured a coat hanger.
On top of this, the larger dimensions of the body created more space and comfort for the passengers. The vehicle had grown in length (plus 72 millimetres), in width (plus 65 millimetres), in height (plus 20 millimetres) and in wheelbase (plus 30 millimetres).
The second-generation SLK not only had driver and passenger airbags but also newly developed head/thorax side airbags. These were housed in the backrests of the front seats and protected the head and chest. The vehicle was also fitted with a roll-over sensor which recognised this type of accident and supplied the data to the central control unit for the retention systems. Following this, the microcomputer activated the belt tensioners and the head/thorax bags in the SLK seats – whether the vario-roof was open or closed.
The engine line-up offered a choice of three petrol engine variants with an output range from 120 kW (163 hp) to 265 kW (360 hp). For the first time in this vehicle class these included an eight-cylinder engine from Mercedes-Benz AMG.
The V6 engine in the SLK 350 was a completely new development. From a displacement of 3498 cubic centimetres it developed 200 kW (272 hp). Its torque of 350 newton metres was available from as low as 2400 rpm and remained constant up to 5000 rpm. Its NEDC combined consumption of 10.6 litres per 100 kilometres underlined its advanced technology. In conjunction with the 7G‑TRONIC seven-speed automatic transmission, fuel consumption was just 10.1 litres per 100 kilometres. This made the new SLK 350 around 3 percent more economical than the previous SLK six-cylinder model with automatic transmission, despite its 25 percent higher output.
The SLK 200 KOMPRESSOR's 120 kW (163 hp) engine also made its debut in this Mercedes‑Benz model series. It was part of the new four-cylinder generation with the unique TWINPULSE system which offered further advancements in terms of output, torque, smoothness and fuel consumption. The TWINPULSE system combined different technologies such as supercharger, balancer shaft, charge-air cooling, variably adjustable camshafts and four valves per cylinder. Its NEDC combined consumption was 8.7 litres per 100 kilometres.
Alongside a six-speed manual transmission and a five-speed automatic transmission, the SLK‑Class offered a further new addition: the world's first seven-speed automatic transmission, 7G‑TRONIC, was available as an option for the SLK 350 – offering more powerful acceleration, faster bursts of speed, improved fuel consumption and enhanced shift comfort. In the SLK 55 AMG it was fitted as standard. Both automatic transmissions could also be operated manually using buttons on the steering wheel. In addition to manual mode, there was a choice of "C" (Comfort) and "S" (Sport) mode.
The sporty chassis and suspension set-up differed from the previous model as a result of a newly developed three-link front axle, rack-and-pinion steering and even more powerful brakes. Details of the multi-link independent rear suspension were modified and adapted to the increased track width. Depending on the model variant, the standard equipment for the new SLK-Class included 16-inch, 17-inch or 18‑inch light-alloy wheels. Sports suspension with a lower-slung body was available on request.
The V8 powerplant in the SLK 55 AMG offered a displacement of 5439 cubic centimetres, had an output of 265 kW (360 hp) at 5750 rpm, achieved a peak torque of 510 newton metres at 4000 rpm and accelerated the two-seater from stationary to 100 km/h in 4.9 seconds. The electronically limited top speed was 250 km/h. With its high pulling power and typical AMG V8 sound, the SLK 55 AMG assured its occupants an unmistakably dynamic experience. The 7G‑TRONIC with AMG SPEEDSHIFT adapted to both a dynamic and a comfort-oriented driving style. The driver could choose automatic or manual gearshifts, using either the Touchshift selector lever or the two shift buttons on the AMG sports steering wheel. In manual "M" mode the driver was truly able to harness the immense pulling power generated by the V8 engine as there was no automatic downshift under full throttle or during kickdown; the transmission remained in the selected gear. Furthermore, AMG SPEEDSHIFT did not automatically shift up a gear when it reached the engine speed limit in manual mode. The SLK 55 AMG was also fitted with AMG sports suspension and composite brakes.
The design of the SLK 55 AMG reflected its exceptional class: the central stylistic elements at the front of the vehicle were the arrow-shaped nose and the distinctive projection-beam headlamps with their clear-lens covers. In addition there were AMG multi-spoke light-alloy wheels (18-inch) with mixed-size tyres, longitudinal gills on the bonnet, the AMG sports exhaust system with two twin tailpipes and dark-tinted lenses for the tail lights and third brake light. The warm air escaped via air outlets at the sides and side skirts made the roadster's centre of gravity appear even lower. The SLK 55 AMG also differed from other variants of the new SLK‑Class in its clear-lens, chrome-ringed fog lamps in the front apron, the black-painted cross fin in the radiator grille and the air flow break-away edge on the boot lid which reduced lift by up to 36 percent.
The interior was characterised by fine nappa leather trim on the seats, the central door panels and the armrest. The AMG sports seats, with their independent upholstery format, featured pronounced side bolsters to optimise lateral support; Alcantara panels in the shoulder area improved side support when cornering at speed. Dynamic accents were also added by the AMG sports steering wheel which was adjustable for height and reach and featured shift buttons, and the attractive instrument cluster with its 320 km/h scale.
In June 2005 the SLK 280, with a V6 engine, an output of 170 kW (231 hp) and a displacement of 2996 cubic centimetres, was added to the range. Shifted manually, it accelerated from 0 to 100 km/h in 6.3 seconds and its NEDC consumption was 9.7 litres.
From August 2006 Mercedes-Benz offered drivers who wanted to emphasise the dynamic nature of the SLK‑Class even further a Sports package for the four and six-cylinder models. The package included sports suspension with 18‑� � � inch light-alloy wheels and size 225/40 R 18 (front) and 245/35 R 18 (rear) tyres plus a large 17-inch brake system with perforated brake discs at the front axle. The body had been lowered by 10 millimetres. Externally, the SLK with Sports package could be recognised by its dark headlamp surrounds and an AMG spoiler lip on the boot lid. Inside, red seat belts and red topstitching in the door trim and seats, on the leather steering wheel and on the leather-trimmed shift/selector lever gaiter added a sporty touch. The floor mats also featured red edging and the needles in the instrument cluster were red. The black roof liner and the carbon fibre-look trim strip above the glove compartment provided an effective contrast.
The "Edition 10" show car, which Mercedes‑Benz presented at the Paris Motor Show to celebrate the tenth anniversary of the SLK‑C lass, was available from January 2007. It was characterised by a unique colour scheme and material selection in the interior. The new matt grey metallic paint finish "allanite grey magno" also heralded a trend for the future. The special model was available in a limited edition of 350. It was offered as standard in black. Highlights of the "Edition 10" included light-alloy rims with a dark grey, high-sheen "chrome shadow" finish, embellished with black/silver badges featuring the Mercedes star logo. The ten-spoke rims were fitted with size 225/45 R 17 (front) and 245/40 R 17 (rear) wide-base tyres. The sports car was also characterised by dark-tinted tail lights and badges on the wings engraved with "EditI0n". The interior primarily featured black leather. The special "Edition 10" model was available in the form of the SLK 200 KOMPRESSOR, the SLK 280 and the SLK 350.
In December 2007 Mercedes‑Benz presented an extensively modified SLK. The engineers had redeveloped around 650 components to take model series R171 into its second life cycle.