| In January 1996 Mercedes-Benz unveiled at the North American International Auto Show in Detroit their concept study of a leisure-time vehicle featuring permanent all-wheel drive. This prototype of a sport/utility vehicle captured the visiting public's attention with the future design elements of the Mercedes-Benz ,All-Activity Vehicle" (AAV) which was then in an intensive stage of development.
The European premiere of the AAVision design study took place two months later at the Geneva Automobile Salon. It was also there that the designation of ,M=class" as future name for the new member in the Mercedes-Benz passenger car family was communicated for the first time.
One year after the AAVision's world premiere the public could take a first glance of the technique of the M=class. The presentation included the chassis, the drive-train with intelligent four-wheel drive as well as the newly developed 3,2=litres V6_engine.
A new torsion-resistant ,box concept" forms the backbone of the safety-enhanced separate frame of the M=class. The two dropped frame side rails are welded to three cross members to assure a maximum of stability and torsional rigidity. There are deformational elements integrated in the front and rear cross members, absorbing the impact energy in an accident occurred at low speed to reduce damage at the frame side rails. Supporting frames for front and rear wheel suspension and ten rubber mounts dampen the transmission of the road's unevenness and noise to the bodywork.
The chassis of the M=class is unique. It is the only line of models of its family equipped with all-independent suspension on front and rear axle. This concept does not only guarantee driving stability and security at a much higher level, but also it makes more chassis clearance under the engine possible.
The wheels are guided at the front axle by two A-frame arms each, with the upper arm as well as the damper fixed directly to the frame; the front auxiliary frame supports the lower arm and the steering gear. The wheel suspension/springing is done via torsion bars, upheld by the middle arm, and via an anti-roll bar at the lower A-frame arms. The structure of the rear wheel suspension is similar except for the springing which is done by a combination of coil springs and dampers with progressive spring action instead of the torsion bars. At the rear axle the upper arm as well as the spring- and damper-elements are fixed directly to the frame whereas the lower A-frame arm and the anti-roll bar are supported themselves by an auxiliary frame.
The drive-train of the M=class has been designed for the permanent all-wheel drive; the driving torque is distributed on the front and rear axle in a ratio of 48_:_52 via a one- and two-piece propeller shaft, respectively, by the transfer case with integrated interaxle differential. In contrast to the traditional four-wheel drive vehicles the drive system of the M=class abandoned the differential locks of the conventional construction method. It has been made possible through a new version of the electronic traction control system ETS modified for the four-wheel drive. In case of a wheel spinning on icy surface the ETS is activated automatically and increases the brake-pressure on the wheel as long as it takes to reach a certain given speed difference. The driving torque on the wheels with good grip on the road is increased and a maximum of traction is achieved. The ETS replaces three conventional differentials to give the car the best grip and manoeuvrability on any ground. Even with difficult manoeuvres the steering ability and cornering stability are no longer limited.
The steering and braking system correspond just as well to the highest standards of security. Like the saloons and the T-saloons of the E=class, the M=class is provided with rack-and-pinion power steering and the dual-circuit braking system comprises disc brakes at front and rear wheels with the front discs being internally ventilated. With the anti-lock system ABS, modified for off-road usage and part of the standard equipment, cadence braking is automatically employed to prevent wheels from locking up from a speed of 8_km/h on, unconstrained by the road's condition. With the off-road reduction engaged and a speed of up to a maximum of 30_km/h a special off-road algorithm is activated reducing the braking distance on loose gravel, for instance.
On May_21st,_1997, four months after the innovative chassis- and drive-concept had been presented in Detroit, the new sport/utility vehicle finally had its premiere in Tuscaloosa in the U.S._State of Alabama where the board of directors of Daimler-Benz inaugurated the same day the new plant for the production of the M=class in presence of the governor of Alabama and more than 5.000_guests.
An extensive process of selection resulted on September_30th_1993 in the decision for Tuscaloosa, where the construction of the plant began on May_4th_1994. Three months later the Mercedes-Benz U.S. International, Inc. (MBUSI), founded especially for development, planning and production of the M=class, lanced a broad campaign to levy qualified workers for the new plant. In spring 1995 the first employees were engaged and intensively trained on their job in Germany, e.g. at the forerunner plant in Sindelfingen. The production of the first M=class cars then began in February_1997.
The MBUSI is in constant collaboration with 65_system suppliers providing the complete pre-assembled modules "just in time" and ,just in sequence" to the conveyor lines. The vertical integration of the new plant could be reduced like this to approx._20%.
The M=class, with the internal designation W_163, is not only an important documentation of the enterprise's globalization strategy, but as third new model line presented in 1997 after he CLK and the A=class it represents as well another milestone in the Passenger Car Division's productive offensive. Their reception in print and broadcast media was particularly positive and the production capacity could hardly satisfy the client's demands. Apart from the competitive price, the high standard in security and the appealing design of the models this success is definitely thanks to the many-sided concept. The M=class unites the unique comfort and driving safety of a Mercedes-Benz passenger car with the true grit and all-terrain ability of a classic off-roader and as if it weren't enough it offers the space and variability of a luxury saloon with room to spare.
The backrests of the rear seat can be folded away in three parts and the rear seat bench folds just as easily in shares of 1/3_:_2/3 to the front and provides plenty of possibilities for the interior's arrangement. A second row of rear seats offering place for two more passengers on individual seats in driving direction can be furnished on demand. When not in use these two seats can easily be dismounted or folded away to the sides.
In addition to this the M=class is equipped with numerous technical innovations improving safety features, comfort and economy. Important components are above all the driving authorisation system ELCODE accomplishing theft protection and comfort operated by an electronic door- and ignition key. It is a constituent of a high-performance data-network that enables a rapid and reliable communication between the control elements in the engine-compartment and the passenger's cabin. Daimler-Benz is the first producer world-wide to link local partial nets via a data-interface and to create like this a comprehensive digital network.
Another novelty, the Active Service System ASSYST, improves the economy of the car particularly by constantly analysed the oil quality in the engine. The on-board computer assesses how the car is actually being used and then establishes when the next service or oil change is needed matching like this exactly the engine's needs. It thus keeps the trips to the service bay to an average of every 20.000_km instead of constantly every 15.000_km.
The details of safety-concerning equipment correspond to the traditionally high Mercedes-Benz standard: height-adjustable automatic seat belts with the seat-belt tighten system and the seat belt load limit-system are fitted on the M=class as standard just like the airbags for driver and front seat passenger and sidebags for the front doors which is the first time in an off-road vehicle.
Concerning the passive security the M=class fulfils already all the requirements of the European Union in force from 1998 on as well as the future demanding US American regulations and above that they comply to the high Daimler-Benz standards.
The chassis frame has been developed and optimised in the construction phase with special attention to front-, rear- and side collisions. The demands were to stay within a programmed maximum deformation of the vehicle while maintaining a stable passenger cabin to guarantee the passengers a minimum of load and sufficient space to survive in case of a collision. In the engineering department a lot of stress has also been put on the increasing realisation of the protection of the partner, a study a lot of research has been done on at Daimler-Benz resulting in a continual improvement in compatibility.
With the particularly low front-end structure with the possibility of controlled deformation and the deep frame the M=class can absorb even some of the impact energy of the opposing car - a detail especially important, or even life-saving, for the passengers of smaller cars otherwise so often put at a disadvantage.
The M=class was put on the market in the USA and in Canada in September 1997. The first versions available were the ML_320 with the 3.2=litres engine known already from the CLK and the E=class, performing here 160_kW (218_hp) and combined with the standard feature of an electronically controlled 5-speed automatic transmission. The entirely newly developed V6_engine, assigned to the construction line M_112, is characterised by a couple of advanced innovations like the three-valve technology, the twin-spark ignition as well as the low-friction light-alloy cylinder liners. It is produced in the high-technology engine plant at Bad_Cannstatt, inaugurated officially as ,Plant of the Future" on April_9th 1997, only six weeks before the works in Tuscaloosa.
The European customers will be able to experience next to the ML_320, available from spring 1998 on, the less expensive model with a 2.3=litres in-line engine of four cylinders. This aggregate performing not less than 110_kW (159_hp) is part of the regular Daimler-Benz engine line and has long been proving its power in the C- and E- class. The ML_230 offer comprises the 5-speed manual transmission as a standard but in contrast to the more powerful brother the air-condition is not part of the basic package.
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