Technical highlights of the Mercedes-Benz 300 SL (W 194)

300 SL racing sports car (1952):

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  Lightweight tubular space frame
  
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  Coupés designed with roof-hinged Gullwing doors
  

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  Six-cylinder in-line M 198 engine with petrol direct injection
  
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  Vehicle body made from magnesium sheets
  

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  Breathtaking sports car with racing sport genes
  
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  The Gullwing coupé fascinates experts and public
  
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  Maximilian E. Hoffman campaigns for a production SL
  

The bodywork with its flat, long bonnet and distinctive splash guards above the wheel arches, featured many elements of the W 194/11 prototype from 1953, for instance the typical powerdomes. And the family likeness extended to the area below the bonnet, too, for the W 198 I adopted the fuel direct injection of the prototype. In the 300 SL the 6-cylinder in-line engine had a nominal output of 215 bhp (158 kW) enabling a top speed of 260 km/h according to the relevant brochure. This value was calculated for an engine speed of 6500 rpm and a rear axle ratio of 1:3.25. In actual fact, though, the vehicle did not quite reach this value: on an official test drive carried out by the factory in August 1954 it reached a maximum speed of 247.5 km/h, averaged between outward and return legs, the best speed in one direction was 252 km/h. However: for a cultivated road-going sports car of the time these were outstanding values.

This exceptional driving performance was matched by an exceptional price, because in 1954 29,000 Marks was a fortune. The 190 SL Roadster, unveiled together with the 300 SL, cost 16,500 Marks, placing it in the upper price segment, too. For comparison: at that time a Mercedes-Benz 200 (W 180) luxury saloon with a six-cylinder in-line engine could be acquired for around 12,500 Marks. In the summer of 1954 production of the 300 SL started up. The production vehicle possessed a series of detail improvements, including a greater level of comfort, over the exhibition car.

It was only natural for the 300 SL to have its world première in New York, for it was Maximilian E. Hoffman – since January 1952 official importer for the Mercedes-Benz brand for the US market – who campaigned intensely for the construction of a production sports car. Apart from the series 180 and 300 Saloons, he was particularly interested in the 300 SL (W 194) racing sports car, whose great successes boosted the popularity of the Mercedes-Benz brand in the United States explosively. Hoffman saw assured sales prospects for a production version of the car. At the same time he broached the idea of a smaller SL roadster based on Type 180 – this was how the 190 SL came to be.

Daimler-Benz was fully taken up with design and development tasks, so that the Stuttgart-based company even cancelled its originally planned participation in sports car races in 1953. Because of this, Hoffman’s demand for a 300 SL Sports Coupé was not exactly opportune, although it did have a certain attractiveness of its own, for a true sports car was still missing in Mercedes-Benz’s portfolio. However, there were only a few months left before the New York Auto Show, which would be an excellent opportunity for the presentation of the new Mercedes-Benz passenger car programme. This lead the Board of Director to decide to turn the 300 SL racing car prototype developed for the 1953 season into a road-going version suitable for everyday use.

After the first tests, the press was beside itself. The German trade journal “auto, motor und sport” wrote: “Among the sports cars of our time, the Mercedes-Benz 300 SL is both the most refined and the most fascinating – a dream of a car.” The British journal “AutoSport” enthused: “The Mercedes-Benz 300 SL is a car with a wonderful external appearance, coupled with virtually unbelievable performance. Its design and production quality border on perfection and the entire concept represents the uncompromising realisation of all the new ideas the car incorporates.”

The hope of success in the United States market also became reality: the US journal Road & Track was equally full of praise: “When a comfortable interior combines with remarkably good handling, with almost terrifying road-holding, a light and at the same time precise steering and a performance that matches or even exceeds that of the best cars to date, then there’s only one more thing to say: The sports car of the future has become reality.”

The racing heritage of the 300 SL seduced renowned racing pilots and private drivers all over the world into entering the car in sports car races and rallies. In the 1955 Mille Miglia, the team of John Cooper Fitch and his co-pilot Kurt Gesell drove a production SL to superior victory in their category. Werner Engel won the European touring car championship in an SL in 1955, Walter Schock in 1956. The Liège–Rome–Liège marathon rally was won by Olivier Gendebien in 1955 and by Willy Mairesse in 1956. In the USA, Paul O’Shea clinched the American Sports Car Champion’s title in Production Class D of the championship series organised by the Sports Car Club of America in 1955 and 1956.

A total of 30 series W 198 I vehicles with aluminium lightweight bodywork were made in 1955 and 1956. They bore their own specific vehicle identification numbers, except the first car of the series, which was given a steel sheet bodywork vehicle identification number. This aluminium version, 130 kilos lighter than the standard version, was not listed in the price lists but could be ordered just like a regular car. Customers with motor sport aspirations were among the main target groups for this lighter gullwing car.

A further rarity was a coupé with a glass-fibre-reinforced bodywork.

This unique specimen, today the property of the company’s own

vehicle collection, can be identified by two details: on the front wings it sports two headlamps with long chrome strips such as those on the 220 a and 220 S. And the doors do not close as tightly as those of its steel sheet or aluminium sheet counterparts.

The road-going racing coupé became the symbol of success for the rich and the beautiful of its day and age, a dream come true for a few other people and for many a dream they were at least able to see and hear every now and then. The engine's vibrant melody fascinated people just as much as the elegance of the ladies who managed to slide into the depths of the seat and emerge again in well-practiced, perfectly lady-like fashion. By 1957, 1400 customers all over the world had taken delivery of 300 SL Coupés. Very soon the W 198 I became a much-sought-after classic; over the following decades, well-maintained cars continued to fetch astronomical prices. The timeless elegance which the Gullwing coupé radiates to this very day was honoured in 1999 when it was voted “Sports Car of the Century” by an international jury.

Technical highlights of the Mercedes-Benz 300 SL (W 198 I)

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  Lightweight tubular spaceframe
  
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  Coupé with roof-hinged gullwing doors
  

* 30 of which with light-metal bodywork, the first vehicle bearing a steel sheet metal bodywork vehicle identification number.

Appealing and comfortable: Mercedes-Benz 190 SL Roadster, W 121 series, (1955-1963)

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  The first open-top production sports car of the SL family
  
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  A sporty-elegant two seater road-going motor car
  
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  The USA, an important market for the vehicle
  
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  Première for a new four-cylinder engine with a displacement of 1.9 litres
  

At the time Daimler-Benz was fully saturated with design and development tasks – both for production vehicles and also with the preparation for the 1954 racing season, for which the new W 196 R series formula racing car was intended. Due to the enormous workload, the Stuttgart-based company even stalled their planned participation in the 1953 sports car races. The new SLs increased the pressure, but were considered important for Mercedes-Benz’s image and market position. For the 1950s were a time of great expansion after the Second World War. With sports cars Mercedes-Benz would be able to round off its model range with attractive, exclusive vehicles in a new segment – ever since 1935 decidedly sporty cars had been missing in their portfolio. Thus already in mid-September of 1953 the Board’s decision was taken: the 190 SL and the 300 SL were to be built as series production cars.

About five months later both cars were to celebrate their premières in America: they were presented at the International Motor Sports Show in New York which took place there from 6 to 14 February 1954, at that time the most important motor show on the other side of the Atlantic. This meant that the engineers had very little time for development. Speed was of the essence, especially in the case of the 190 SL, which had to be technically redesigned based on the 180 series, whereas for the 300 SL production sports car, the further-developed 300 SL racing sports car served as a model. Already a few days after the Board’s decision, the directors of Daimler-Benz were examining the first sketches, and two weeks further on they were able to assess the first 1:10 scale model, which was followed another eight weeks later by a full-scale model.

The pace of development was raised still further. The floor assembly, which came from the Mercedes-Benz 180, had to be adapted to the new ideas and the right engine had to be found. Moreover, the tight schedule stipulated that the contours of the planers on which the body would be created be finalised by 31 October 1953. The race against time was won: Mercedes-Benz registered a tremendously favourable response to both vehicles at the show.

Until then, the bodies of various models had been available in the two-seater A-version as Cabriolet, Roadster, or Coupé, too. According to chief engineer Fritz Nallinger, this body variant would be replaced in future by the SL vehicles – no longer with the existing formal lines and face, but explicitly in the SL design, which included the star placed centrally on the radiator grille. This was a paradigm change in the model structure, making the 190 SL and 300 SL the symbols of a new product philosophy and the forerunners of the later SL-Class.

While series production of the Mercedes-Benz 300 SL began in August 1954 at the Sindelfingen plant, the 190 SL was thoroughly revised once more because the car displayed at the International Motor Sports Show in New York was neither technically tested nor stylistically mature. In March 1955, Daimler-Benz then presented the final model of the sports car at the Geneva Motor Show. The body was designed by Walter Häcker and closely followed the design of the 300 SL Gullwing Coupé. However, unlike the 300 SL, the 190 SL had a retractable soft top.

The production body showed some clear differences from the show car: the stylised intake scoop on the bonnet was dropped; the forward edge of the bonnet had been moved farther back; there were splash guards above the rear wheel arches too; and the bumpers, indicators and tail lights were modified. The Sindelfingen factory started building the pre-production series in January 1955. Main series production commenced in May.

The 190 SL is technically related to the “Ponton” (pontoon) saloons – commonly so called because of their characteristic body shape – of the W 120/121 series. Their internal designation was W 121, and the 190 that appeared in 1956 was also given that designation. From the beginning the 190 SL was designed as a two-seater cabriolet.

In the 1950s, the meaning of the term “roadster” experienced a change. The classic roadster was a rather spartanly equipped sporty two-seater with detachable side windows, for instance, and a removable fabric top with its roof frame. But the customers’ comfort standards were now higher, and the Mercedes-Benz 190 SL sports car responded to this. Though not a roadster in the classic sense, it was designated as such by the company.

In contrast to the 300 SL, bearing the mark of its racing sport origins, it was conceived as a sporty-elegant two-seater touring and utility car. It was available in three versions: as a car with a fabric top (price in February 1955: DM 16,500) and as a coupé with removable hard top, optionally with or without a fabric top (price in September 1955: DM 17,650/DM 17,100). These prices make clear the exclusive placing of these vehicles in the model range. The 300 SL cost DM 29,000 DM in 1954, and thus considerably more than the 190 SL, however, the sports car was clearly placed above the Saloon – thus Mercedes-Benz offered model 180 at a list price of DM 9450 in 1954/1955. As an optional extra, a third, transversal seat could be fitted in the rear of the 190 SL.

The motor press praised the 190 SL among other things for its safe handling properties. These were ensured by the low-pivot single-joint swing axle already familiar from the 220 a, and other features. The front wheel suspension including the sub-frame was adopted from model 180, from which the floor assembly – though shortened – also came.

A new development was the 1.9-litre petrol engine with the designation M 121 B II. The four-cylinder unit had a single overhead camshaft and is regarded as the forerunner of an entire family of engines. In the Mercedes-Benz 190 SL it developed 105 bhp (77 kW) at 5700 rpm and accelerated the fabric-topped variant from 0 to 100 km/h in 14.5 seconds. The top speed was a respectable 170 km/h – which made it one of the fastest cars on the road in the 1950s and 1960s. The petrol consumption was put at a rather moderate 8.6 litres per 100 km; the 65-litre tank provided adequate range.

During its production run the 190 SL underwent many improvements in details. Clearly recognisable are the wide chrome strips on the upper edge of the door (introduced in March 1956) and larger tail lights (June 1956, as also used on models 220 a, 219 and 220 S). In July 1957, the rear licence plate lamp was moved to the bumper horns to enable fitting the wide licence plates which were being introduced at the time. The rear bumper horns were thus a basic equipment item, while at the front they cost extra; the US versions always had them at the front and the rear as standard. From October 1959, a new hardtop with a larger rear window gave the coupés much improved rear visibility. In August 1960, the lock of the boot lid was changed; simultaneously a recessed handle replaced the previous bow-type handle. In 1963, the last Mercedes-Benz 190 SL rolled out of the production bay. In all, 25,881 were built. Most of them went to the USA – Maximilian E. Hoffman’s evaluation proved right.

A sports variant of the Mercedes-Benz 190 SL

The first sales brochures showed a sports variant of the 190 SL: light-alloy doors, small Perspex racing windscreen, no soft top, no bumpers, heat exchanger or insulating material, gave it a weight of 1000 kilograms, around ten per cent less than the normal road version. The number of units built is not documented, and only very few sports versions found their way to the customers; they probably also came in for further fine tuning with modifications to the four-cylinder engine, lowering of the body, sports shock absorbers and modified springs. The sports 190 SL scored its biggest success in 1956 in the Sports Car Grand Prix in Portuguese Mação, entered by the then Daimler-Benz importer in Hong Kong. The right-hand-drive sports car took first place ahead of a Ferrari Mondial and various Jaguar and Austin-Healey cars. In the same year the Mercedes-Benz general importer in Morocco won his class (GT to two litres displacement) in the Grand Prix of Casablanca. On account of the racing regulations the idea of the sports 190 SL was not pursued any further: in many competitions the vehicle, modified as described, would have been classed as a production sports car and thus would not have had a chance. On top of that a decision of the racing authority FIA (Fédération Internationale de l'Automobile) prevented classification as a GT – it said that a Gran Turismo must have a completely enclosable body – a condition which the converted 190 SL could not meet.

Shortly after the presentation of the Mercedes-Benz 190 SL at the International Motor Sports Show in New York, “auto motor und sport”, Germany, No. 3, 1954, wrote: “The Mercedes 190 SL is an elegant and fast touring sports car that can be used as an ordinary, workaday vehicle, but additionally offers the possibility of successfully competing in smaller sporting events. ... For this new model Mercedes dispensed with its hallowed radiator tradition, as it did for the 300 SL. The very harmonious front end nevertheless shows that elegant and distinguished lines are entirely possible without neglecting the attributes of fashion and functionality.”

The Swiss journal “Automobil Revue”, wrote in its November 14. 1956 issue: “Despite its high output the 190 SL is not actually a sports car, but an uncomplicated touring car that stands with all its four wheels firmly planted on the ground. Thanks to its exemplary handling characteristics it is among the select group of vehicles with which it is possible to reach the highest average speeds safely and without haste, and taking full consideration of all other road users.”

In its spring issue 21/1957, the German magazine “Motor-Revue” published a first road test report. The tester wrote: “When using the prescribed tyres it is possible to accelerate the 300 SL Roadster with turned front wheels at curve limit speeds, without it showing the slightest tendency to break out. This meek character of a sports car with top speeds of 235-250 km/h (depending on transmision ratio) with a powerful acceleration capacity, basically due to soft suspension and exceptional adjustment, make the new Roadster the vehicle with the greatest performance and safest handling that I have ever driven. It seems to me most noteworthy that, with the top in place there is a total absence of vibrations, rumble and resonance phenomena in the interior of the car – also a success of the loving attention lavished on the adaptation of the space frame, wheel suspension and wheels, an adaptation that has been optimally solved.”

In 1960 “auto motor und sport”, Germany, No. 15, 1960, published a detailed test report on the Mercedes-Benz 190 SL: “The 190 SL owes its good reputation not just to its elegant appearance, but also to its robustness and reliability and its accurate handling. The good build quality of the body and the roadster soft top deserve special mention.”

Technical highlights of the Mercedes-Benz 190 SL (W 121)

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  Advanced four-cylinder engine with one overhead camshaft
  
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  State-of-the-art suspension for high-level ride comfort and safety
  
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  Retractable roadster top
  

* Roadsters and Coupés.

A new openness: Mercedes-Benz 300 SL Roadster, W 198 II series (1957-1963)

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  Farewell to the Gullwing
  
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  Hard top optional
  
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  Improved suspension and engine
  

A fundamental improvement: the rear-axle suspension. The single-joint low-pivot swing axle – familiar from the 220 W – was installed in the 300 SL Roadster in an adapted form, being equipped for the first time with a compensating spring. This greatly improved the handling characteristics over those of the original swing axle of the Gullwing coupé.

From 1958 onwards, an optional removable coupé roof with a generous wrap-around rear window was available at a price of 1500 Marks; this could be retrofitted. Noteworthy was the rear window, swinging round far into the sides, and the consummate design of the hard top. Two technical modifications that were incorporated into the production in the course of its six year run are particularly worthy of mention: in March 1961, the 300 SL was equipped with Dunlop front and rear disc brakes, and from March 1962 a modified engine with a light-metal block was installed.

At this time there was a special version of the 300 SL Roadster: the 300 SLS, only two units of which were ever built especially for participation in the North American Sports Car Championship. The reason for this special version was the wish for publicity-effective participation in races in the USA in order to promote sales of the Roadster. The use of the regular production version met with the objection of the Sports Car Club of America to permit participation of the new model already in the 1957 season in the “Standard production” vehicle category. In order to have a chance at least in the only alternative vehicle category remaining, D, the production Roadster was pared down ruthlessly to become the SLS.

On the outside the 300 SLS can be distinguished by the absence of bumpers, by its specially-shaped cockpit cover with air intake slot, the low racing winscreen and the roll-over bar behind the driver’s seat. The work carried out in the Daimler-Benz research department was successful and Paul O’Shea won the North American Sports Car Championship in category “D” far ahead of its competitors.

Production of the 300 SL ended concurrently with the end of production of the 190 SL on 8 February 1963 in Sindelfingen, a date that marks the close of an era: after the production of the 300 model ended in March 1962, only the 300 SL had remained as the last passenger car model with a separate frame in Mercedes-Benz’s production programme. Both versions of the 300 SL, Roadster and Gullwing coupé were right from the very beginning enthusiasts’ cars that have lost nothing of their allure to this day, for many years they have been among the most sought-after and valued classics.