- First autonomous body for the upper mid-range series
- A coupe as exclusive variant appears in 1968
- The Mercedes-Benz 240 D 3.0 is the first production car with a five-cylinder diesel engine
The new Mercedes-Benz models of the mid-size series 115 and 114 made a clean break with the “tailfin” era with its unitary body. The saloon was sporty, elegant, up to date, and above all a saloon in its own right. It was a demonstration of respectable flair and love of technical innovation. On top of that it reflected the awareness of its developers for the newly defined role of an intermediate model series. Experts and public alike greeted the new intermediate class model from Mercedes-Benz enthusiastically when it was first presented to the media in January 1968. Internally designated with the abbreviation /8 because of its year of birth, the family of vehicles was soon dubbed the “Stroke 8.”
With the “Stroke 8″ of 1968 Stuttgart started a design revolution that laid the foundations and set the standards for the subsequent generations of the midsize model series from Mercedes-Benz, today’s E-Class. Initially the model range comprised six saloons: the four-cylinder 200, 220, 200 D and 220 D models formed the 115 series, and the two six-cylinder variants 230 and 250 were designated the 114 series. As the top-of-the-range model the Mercedes-Benz 250 was distinguished from the other models by its double front bumper. From the beginning the demand for all models was high and soon resulted in long waiting times for delivery.
Development work since 1961
Designers and engineers began planning the new model series as early as 1961 – the year in which the small tailfin had just reached the market. Project leader was Dr. Fritz Nallinger, Mercedes-Benz chief engineer, member of the Board of Management and Technical Director of Daimler-Benz AG. The technical structure of the forthcoming vehicle was determined by Karl Wilfert, Head of Body Development. Responsible for the design was Paul Bracq, assisted by Bruno Sacco. This new intermediate class had to be an independent, successful model – that was clear to Development from the start. So the shared body was no longer an option. Stuttgart therefore strove to create a complement to the new luxury class 108/109 series for the year 1968.
As early as 1960 chief engineer Nallinger defined important benchmarks for the new vehicle. In direct comparison with the luxury class model the design was to be appreciably more compact than differences between the four and six-cylinder variants of the shared body allowed. In view of the smaller exterior dimensions, it would be important to ensure good space economy in the passenger compartment. The shape had to be timeless in its simple elegance. In 1964 the designers’ models already showed the outlines of the future saloon. At that point, however, different designs of the front end were still under discussion. In analogy to the former distinction between four and six-cylinder variants, the versions of the new model family with smaller engines were to get a simpler front end with horizontally arranged rectangular headlamps. Finally, in early 1965, a decision was made to refrain from such differentiation, to which the two model series numbers 115 and 114 later still would testify. This was the year in which Professor Dr. Hans Scherenberg took over project management, when Nallinger went into retirement.
Other body variants developed in addition to the saloon were a coupe, a long-wheelbase saloon and a station wagon. Whereas the sportier two-door and the long-wheelbase version of the saloon actually made it into production, the station wagon was ultimately barred from series production. On the other hand, the basic design of the rear end was later harmoniously transferred to the next model series, the 123, with only minor changes. In 1967 the production facilities for the new series were set up in Sindelfingen. Prior to the market launch proper, 1100 preproduction vehicles of the two series were produced there, limited initially to six models.
1968: Double premiere in Sindelfingen and Geneva
Mercedes-Benz presented the “Stroke 8″ in 1968 in a double premiere: the series had its debut in front of trade journalists gathered at Sindelfingen in January; the general public got its first chance to assess the new saloon at the International Motor Show in Geneva that March. The six models initially available met with the broad approval of the experts and the general public. The view expressed by the motor magazine auto motor and sportthat Mercedes-Benz had dared to take a “stylistic swing to the left” can surely be put down mainly to the political situation of 1968. The “Stroke 8″ deserved all the more praise for its clear, classic yet modern lines and its fresh, sporty appearance.
And yet the Mercedes-Benz character that determines automotive identity was fully retained in this model. The designers and engineers handled a task well that called for innovation and sensitivity. On the one hand, a clearer distinction now was made between the luxury and upper mid-size categories in the Mercedes-Benz product line-up. On the other hand, the family resemblance between the now independent models was still visible, as were their origins in the “tailfin” generation.
Complete range: debut of the new series with six saloon models
The new Mercedes-Benz started out with six saloon models. The 200 and 220 were powered by the new four-cylinder M 115 carburettor engine, with 2-litre displacement (70 kW/95 hp) and 2.2-litre displacement (77 kW/105 hp) respectively. The 200 D and 220 D diesel variants also featured a new engine, the OM 615, in a 2-litre version with 40 kW (55 hp) and a 2.2-litre variant with 44 kW (60 hp) output. The 2.3-litre in-line six-cylinder M 180 engine of the 230 model was already familiar from the predecessor model; it developed 88 kW (120 hp), as in the “tailfin.” New in the engine range was the 2.5-litre in-line six-cylinder M 114, which generated 96 kW (130 hp). For the new petrol engines of both series, Mercedes-Benz relied on proven technology: the 200 and 220 models (M 115) and the 250 (M 114) were equipped with in-line carburettor engines with two overhead valves per cylinder and an overhead camshaft. The four-cylinder power plants (petrol and diesel) proved so reliable that the 123 series that followed in 1976 was initially equipped with the M 115 and OM 615 engines.
Good handling owing to the diagonal swing axle
The outstanding constructional detail of the new model series was to be found under the boot: the “Stroke 8″ models were fitted with a so-called diagonal swing axle, making this the first Mercedes-Benz production car to have a rear axle with semi-trailing arm. The diagonal swing axle, equipped among other things with auxiliary rubber springs and a torsion-bar stabiliser as standard, was an advancement of the single-joint swing axle introduced in 1954 in the 220 a, and was used in all Mercedes-Benz cars from 1955 onwards. Compared with the predecessor models, the new axle afforded distinct improvements in handling characteristics without sacrificing ride comfort. The improved handling quality was also acknowledged by international motor journalists, who were invited to the old Targa Florio course in Sicily for a preliminary road test in December 1967. Snow, ice and the narrow mountain roads of the Madonie placed great demands on the suspension, but the Stroke 8 gave an excellent account of itself.
And the “Stroke 8″ was not a lightweight by any means. Wheelbase and weight of the upper mid-range series of Mercedes-Benz had grown consistently bigger from the “Ponton” (2.65 metres/104 inches, and 1.22 metric tons//2690 lbs) through the “tailfin” (2.70 metres/106 inches, and 1.28 metric tons/2822 lbs) to the “Stroke 8″ (2.75 metres/108 inches and 1.36 metric tons/2998 lbs). However, the overall length of the new model, 4.68 metres (184 inches), was less than that of the 110 series. The new proportion of overall body length to wheelbase was also visible in silhouette, with balanced proportions and clear lines. The additional weight was due mainly to measures designed to improve passive safety, which put into practice the ideas of Mercedes-Benz engineer Béla Barényi, a pioneer in this field.