The history of the Mercedes-Benz SL-Class
Jan 10, 2012
From racing car to SL-Class with vario-roof – a summary
  • Motor sport as initial fuse
  • Numerous fascinating models from 1952 until today
Mercedes-Benz 300 SL racing car, W 194 series (1952 to 1953)
The roots of the SL-Class lay in motor sports: after World War II Mercedes-Benz developed the W 194 series 300 SL racing car, whose M 194 engine was derived from the 300 model; engineers increased its output to around 170 bhp (125 kW) for use in the racing sports car. The sports engine was installed at an angle of 50 degrees slanted over towards the left. For the W 194, Rudolf Uhlenhaut, at that time Head of Passenger Car Research at Daimler-Benz, developed a frame weighing only 50 kilograms and made from very thin tubing that was subjected to compressive and tensile forces only. This frame became the backbone of the racing car with which the pilots of the racing department reaped numerous victories in 1952.
The body of this first SL already prefigured features of the later production sports car. Among these, the wide, low racing car front end of the pre-war era, with a Mercedes star affixed to the radiator grille. Characteristic for the coupé: the famous swing-wing doors, deeply incut into the roof. To open, they swung upwards, reminding one of outspread wings, for this the Americans dubbed it the “Gull-wing”, while the French called it the “Papillon” (butterfly). Together with the coupés, several roadsters were also made.
With the 300 SL, Mercedes-Benz won second and fourth places at the Mille Miglia race, achieved a three-fold victory at the sports car race in Bern and a double win at the 24 hours of Le Mans, as well as four victories at the Nürburgring sports car race in 1952. The last great adventure of the season was its participation in the 3rd Carrera Panamericana in Mexico, with a gruelling route covering 3100 km in five days and eight stages. Mercedes-Benz entered two coupés and two roadsters in the contest; these were powered by engines with an output that had in the meantime been increased to 180 bhp (132 kW). Karl Kling and Hans Klenk’s car, as well as Hermann Lang and Erwin Grupp’s car, attained a legendary double victory for Mercedes-Benz in November 1952.
Already for the following year a successor model was developed, the W 194/11; however, it did not get to participate in the 1953 racing season because from 1954 Mercedes-Benz began to take part in Formula 1 racing, so that from the 300 SL the W 198 I series sports car was developed
Mercedes-Benz 300 SL Coupé, W 198 I series (1954 to 1957)
It was to be the perfect suprise: on 6 February 1954, Mercedes-Benz presented the 300 SL series sports car at the International Motor Sports Show in New York. The coupé with the characteristic swing-wing doors of the racing car fascinated experts and general public alike. Not only its form was reminiscent of motor sports, technical details, too, such as the tubular space frame, came directly from the competition cars. This made the 300 SL, W 198 I series, unique among the sports cars of its day.
The production SL was powered by an M 198 engine with petrol direct injection, developed by Mercedes-Benz for the W 194/11 racing car prototype of 1953. In the 300 SL, the 6-cylinder in-line engine had a nominal output of 215 bhp (158 kW), which enabled the car to reach a top speed of 247.5 km/h, as stated in 1954 after an official test drive. For a comfortable street sports car of those days an excellent value indeed. That predestined the 300 SL for use in racing competitions and rallies, where factory drivers and private pilots were able to win numerous victories and excellent placings with it.
Maximilian E. Hoffman, the official importer of the Mercedes-Benz brand in the US, campaigned tirelessly for the series production of the sports car. At the same time he urged the production of a smaller SL roadster, which was later to be the SL Roadster, 190 series.
The 300 SL rapidly became an automotive icon of the 1950s, while it was victorious on many racetracks at the same time. And its charisma remains unbroken to this very day: in 1999 the Gullwing coupé was voted “Sports car of the century” in an international election.
Mercedes-Benz 190 SL, W 121 series (1955 to 1963)
Daimler-Benz AG introduced the Mercedes-Benz 190 SL together with the 300 SL in February 1954 at the International Motor Sport Show in New York. It was designed as a sports car “which owing to its high comfort is intended for a class of customers who want to travel large distances themselves at high cruising speeds in this externally very sporty looking car,” as design engineer Josef Müller wrote in retrospect in 1957. Simultaneously the Mercedes-Benz 300 SL “Gullwing” debuted in New York. As an exciting super sports car it too lent the SL series its character.
The body design of the 190 SL closely followed that of the Gullwing,but it was constructed as a two-seater cabriolet and had a retractable soft top. A nice option to be had was the third-passenger transversal seat. There were three versions: a car with a fabric top and a coupé with removable hardtop, optionally with or without a fabric top. The 190 SL was given the internal series designation W 121, like the 190 Saloon that appeared a little later in 1956. The 190 SL is technically related to the “Ponton” (pontoon) saloons – commonly called that because of their characteristic body shape – of the W 120/121 series. The suspension, for example, from model 190 (W 121) onwards featured the familiar low-pivot single-joint swing axle and the front wheel suspension including subframe. The floor assembly – albeit shortened – was also taken from the saloon.
The 1.9-litre petrol engine, on the other hand, was an entirely new development. This four-cylinder unit had an overhead camshaft and is regarded as the forefather of an entire family of engines. In the Mercedes-Benz 190 SL it delivered 105 bhp (77 kW) and accelerated the fabric-topped variant from 0 to 100 km/h in 14.5 seconds on its way to its top speed of 170 km/h. During its production life the 190 SL underwent many improvements in details. The last unit was built in 1963 at the Sindelfingen plant, ending a production run totalling 25,881 vehicles.
Mercedes-Benz 300 SL Roadster, W 198 II series (1957 to 1963)
In 1957, the Gullwing coupé was superseded by the 300 SL Roadster. Like its predecessor, this vehicle, too, was created upon the initiative of Maximilian E. Hoffman. Technically, the roadster was basically the same as the coupé, but through modification of the side sectors of the tubular space frame, it was made possible to reduce the entry height enough to allow the fitting of conventional doors.
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 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. At the wheel of this car, Paul O’Shea won the 1957 North American Sports Car Championship in the D category far ahead of competitors.
Production of the 300 SL ended together with the end of productionof the 190 SL in Sindelfingen on 8 February 1963. Both versions of the 300 SL, the roadster and the Gullwing coupé were enthusiasts’ cars from the very start and are today among the most sought-after and most valuable classic cars.
Mercedes-Benz W 113 series (1963 to 1971)
At the 1963 Geneva Motor Show, Mercedes-Benz presented the new 230 SL – internal series designation W 113. It was designed as a comfortable high-performance two-seater touring car and replaced the 190 SL and 300 SL models. Three versions were available: an open-top car with a folding soft top, an open-top version with hardtop, and finally the hardtop coupé. The hardtop coupé had no soft top and soft-top compartment; this freed up more room for luggage. All three versions could be driven with the top open. As an optional extra a transverse rear seat was available.
The exterior of the 230 SL was characterised by clear, straight lines and the unmistakable SL face including the large, centrally positioned Mercedes three-pointed star. The hardtop with high windows and a roof borne up only by slim pillars conveyed an impression of lightness; with its inwardly directed curvature it reminded one of Far Eastern temples, and straightaway the car had a nickname: “Pagoda”.
Since it was based on the floor unit of the famed “Tailfin”, the world’s first saloon with a safety body, this SL also had a rigid passenger cell and crumple zones in the form of easily-deformable front and rear segments. As in the saloon the interior was designed so as to reduce injury hazards in accidents, meaning that there were no hard corners and edges. As in the previous model, seat belts were available as optional extras. The steering gear was moved from the crash-imperilled front section to the firewall; the steering column yielded to axial compression and additionally featured a joint that prevented the feared lance effect in an accident. In 1967, the telescoping safety steering column and the impact absorber in the steering wheel were added.
The chassis, adopted from the 220 SE Saloon, was tuned to the requirements of the sporty car. The suspension was taut, but for a sports car was almost atypically comfortable. The six-cylinder engine also came from the saloon, but was modified for use in the SL. The engine, its bore enlarged to give it a displacement of 2.3 litres, developed 150 bhp (110 kW) and was designed as a sporty drive unit.
The successor to the 230 SL came in 1967: the Mercedes-Benz 250 SL. The changes mainly concerned the engine and the braking system. The engine, its displacement enlarged by 200 cubic centimetres, had the same output, 150 bhp (110 kW), but ten per cent more torque. The 250 SL was thus appreciably more flexible in its response. In addition to the three body versions known from the 230 SL, the 250 SL was available as an optional extra in a fourth version, a coupé with rear bench seat, shown for the first time in March 1967 at the Geneva Motor Show. Less than a year after the presentation of the 250 SL, it was replaced by the 280 SL with a 2.8-litre engine and an output of 170 bhp (125 kW). From 1963 to 1971 a total of 48,912 “Pagodas” were built – remarkable for a sports car with such high standards.
Mercedes-Benz R 107 series (1971 to 1989)
The R 107-series SL rolled out on the highway in spring 1971, first as 350 SL (147 kW/200 bhp), from autumn 1971 onwards and at first only for the US, as series 350 SL 4.5, and then with the Geneva Motor Show from 1973 onwards for all markets as series 450 SL (165 kW/225 bhp). For the first time in the history of the SL series an eight-cylinder power plant did duty under the bonnet. Parallel to it the corresponding coupé models of the SLC series (C 107 series) were built until autumn 1981.
Besides elegance and quality the vehicles radiated safety: the crash response of the open two-seater was far ahead of its time. Technically, this expressed itself in a carefully-defined crumple behaviour of coachwork and vehicle skeleton structure, a high-strength A-pillar, and interior appointments uncompromisingly designed according to safety criteria.
In the course of its production “lifetime” of unplanned length (18 years) and immense success, this SL was equipped with diverse six- and eight-cylinder engines. Its model designations were accordingly just as varied. In July 1974 came the 280 SL (136 kW/185 bhp), with the result that there were now three SL engines available to choose from – nowadays nothing unusual, but in those days something a real novelty in the history of this model category. In the course of time all engines underwent modifications (and slightly modified performance figures) to enable better compliance with the emission standards, which had meanwhile started to become more stringent in most European countries.
Production of the R 107 series ended in August 1989, more than 18 years after the production start-up of the 350 SL. With that this SL series set an internal record that will probably never be broken: with the exception of the G-Class off-road vehicles, no other passenger car series has ever been produced over such a long period in the entire history of the company. All told, in Sindelfingen 237,287 open-top cars were built, a number which impressively demonstrates the great popularity of the 107 series. Of the coupé a total of 62,888 were built from 1971 to 1981.
Mercedes-Benz R 129 series (1989 to 2001)
At the 1989 Geneva Motor Show, Mercedes-Benz presented the SL, R 129 series. The first models were the 300 SL (140 kW/190 bhp), 300 SL-24 (170 kW/231 bhp) and 500 SL (240 kW/326 bhp). The stylistically assured, no-frills lines of the slightly wedge-shaped body, the flared wheel arches, the half-spoilers forward of the front wheels, a steeply raked windscreen, the skilfully modelled rear end and the standard light-alloy wheels produced an exceedingly harmonious overall effect. The brand scored a hit with the vehicle. Production capacity was soon stretched to the limit and delivery periods of several years had to be accepted.
This car set new standards in the area of safety. The results of Mercedes-Benz’s rigorous frontal and rear-impact crash tests for the open-top vehicle were sensational. Integral parts of the safety concept were also the automatic roll-over bar, which popped up, sensor-controlled, within 0.3 seconds when a roll-over threatened, and the integral seats, whose resistance in a crash was many times higher than the magnitude of the forces that could be expected. The suspension was adapted to the requirements of a touring sports car and enabled precise handling and fast driving combined with high comfort. In autumn 1992, a further model appeared, the 600 SL with a twelve-cylinder engine and an output of 290 kW (394 bhp).
A first facelift in autumn 1995 brought a slightly modified body design, more extensive standard equipment, and more refined engineering. A second facelift in 1998 employed discreet stylistic touch-ups to give the sports car an even more dynamic look, but mainly meant a change in the engine range, with new six-cylinder V-engines in place of the previous in-line engines, and a new V8 power plant
In summer 2001, production of the R 129 series came to an end after twelve years and a total of 204,940 units. In terms of overall volume it was not quite as successful as its predecessor from the R 107 series (237,287 units); but if average annual production is compared, the R 129 series with some 16,500 units takes a very clear lead.
Mercedes-Benz R 230 series (2001 to 2012)
The most conspicuous innovation in the subsequent SL generation with the internal designation R 230 was the vario-roof: for the first time in the history of the SL it was made possible to have an open-top car and a coupé in one – the transformation took place within 16 seconds. The first model presented to the public in summer 2001 was the SL 500 (225 kW/306 bhp); in the autumn it was joined by the SL 55 AMG (350 kW/476 bhp). In 2002 the SL 350 (180 kW/245 bhp) followed, in 2003 the SL 600 (386 kW/500 bhp) and in 2004 the SL 65 AMG (450 kW/612 bhp).
The design of the R 230 series blended tradition and future through distinctive details. For instance, the air intakes in the front wings adopted a typical feature of the 300 SL from the 1950s. The thin, wing-like segments on these side air intakes – called fins by experts – were a reminiscence, too.
Ever since the “Pagoda” at the latest, the abbreviation SL has been synonymous with pioneering achievements in the areas of active and passive safety in open-top sports cars. With an entirely new, comprehensive concept the R 230-series SL clearly outstripped all previous safety standards. The concept included electronic handling dynamics systems such as SBC™ Sensotronic Brake Control, ABC Active Body Control, BAS Brake Assist, ASR acceleration skid control, and ESP® and extended to the structural integrity of the body in every conceivable type of accident. A number of other features contributing to occupant protection were two-stage airbags for driver and passenger, head/thorax bags in the doors, integral seats, high-performance belt tensioners, belt force limiters, and the sensor-controlled roll-over bar, which goes into action even when the vario-roof is closed.
The first facelift came in 2006. It brought the SL 500 a 285 kW (387 bhp) V8 engine and the SL 350 a 200 kW (272 bhp) V6 engine – both new developments featuring four valves and reduced fuel consumption coupled with a higher output; in the SL 600 it was now 380 kW (517 bhp). The 7G-TRONIC seven-speed automatic transmission was standard equipment. The most conspicuous element of a further model refinement package in 2008 was the new front design, which adapted the SL to the brand’s current passenger car design. In addition, the SL 280 (170 kW/231 bhp) was added to the model range. In 2008, the exclusive SL 65 AMG Black Series expanded the R 230 series in the top performance range. This high-performance coupé was developed in the AMG Performance Studio, and was powered by an engine delivering 493 kW (670 bhp).
In 2008 and 2009, the SL 63 AMG Roadster went into action as Official F1™ Safety Car in Formula 1 racing. The SL, modified for operation on the racetrack, brought to mind the roots of the SL family in motor racing.
In the spring of 2012, Mercedes-Benz is to unveil the R 231 series, the new SL.
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