Mercedes-Benz 300 SLR (W 196 S), 1955
Parallel to the fundamentally redesigned W 196 R Formula 1 racing car, Mercedes-Benz developed a racing sports car from autumn 1953 to participate in the Sports Car World Championship, which had been held since 1953. Technically, both vehicles were largely identical, which was also reflected in the internal model series designation W 196, which was given the suffix S (for Sport) to distinguish it from the Grand Prix racing car.
Apart from the bodywork, which was two-seater in the racing sports car due to the regulations and had a lighting system for the operating conditions, the main difference was the engine: The W 196 S, which was not bound by the displacement limit of Formula 1, was powered by a three-litre version of the in-line eight-cylinder engine and had cylinder blocks made of light metal rather than steel. Furthermore, it was not fuelled with special methanol-based racing fuel, but with regular premium petrol – an important aspect because the regulations stipulated standard commercial fuel and special fuel would have posed additional logistical challenges in endurance road races anyway. Compared to the 2.5-litre version of the Grand Prix car, the increase in displacement was achieved through a larger bore and a longer stroke, resulting in a square bore/stroke dimension. The output of the eight-cylinder engine, which consisted of two separate four-cylinder blocks with a centre output, as in the Formula 1 car, was 306 hp/225 kW at 7500 rpm.
The racing sports car was given a type designation that was chosen for its publicity appeal and which was reminiscent of the successful 300 SL from 1952 and also suggested a proximity to the Mercedes-Benz production vehicles. A press release dated 16 January 1954, which mentioned the new racing sports car for the first time and held out the prospect of participation in the 24 Hours of Le Mans, stated the following: "The new model bears the designation "300 SLR" and represents the design evolution of the familiar "300", "300 S" and "300 SL" model series. (S = super, L = light) The addition of the letter R (racing) indicates that the further development was based on racing cars [...]".
The chassis and running gear were adopted virtually unchanged from the W 196 R Formula 1 racing car, but the racing sports car had a 20 mm longer wheelbase. At around 60 kilograms, an extremely light but at the same time very torsionally rigid tubular frame supported the axles, drivetrain and body. The double wishbone front axle featured the tried-and-tested combination of trapezoidal links of different lengths with a torsion bar suspension that had already been used in the pre-war Silver Arrows, while a single-joint swing axle served as the rear axle. A similar design had already been fitted to the improved 300 SL racing sports car intended for the 1953 season, but was not used for racing. The inboard brake drums, which were also used in the Grand Prix racing car, were a new feature. Their position meant that they could be particularly large and also enabled the unsprung masses to be reduced.
Initially designed as a coupé and already intended for participation in the Mille Miglia and the 24 Hours of Le Mans in 1954, the development of the 300 SLR – practically finished apart from fine-tuning and testing – was put on hold in the spring of 1954 in order to focus all available capacities on the new Formula 1 racing car, which was finally to start in the fourth race of the season at the beginning of July 1954. The 300 SLR only received its finishing touches in the late summer of 1954 after the successful start of the Formula 1 season. In the meantime, the majority of the drivers questioned by racing director Neubauer had spoken out in favour of an open-top racing car instead of the originally planned coupé, mainly because of the expected noise development in the cockpit, and so initially only the open-top version made an appearance in the 1955 World Sports Car Championship. The 300 SLR made its first public appearance at the beginning of September 1954 at the Autodrom in Monza, where it completed test drives under racing conditions during the Italian Grand Prix.
Its high performance potential and unrivalled stability and reliability made the 300 SLR far superior to its rivals, which it proved by winning the Mille Miglia, the Eifel Race, the Swedish Grand Prix, the Tourist Trophy in Ireland and the Targa Florio in Sicily, as well as the Sports Car World Championship. The double victory in the 1955 Mille Miglia was particularly spectacular: Stirling Moss and co-driver Denis Jenkinson won with starting number 722 after 10 hours, 7 minutes and 48 seconds at an average speed of 157.65 km/h, which is still unrivalled today, and Formula 1 world champion Juan Manuel Fangio (starting number 658), who completed the 1000 miles without a co-driver, finished second.
However, the 300 SLR's unique track record was also overshadowed by a serious accident at the 24 Hours of Le Mans, the greatest tragedy in the history of motor racing to date. The French guest driver Pierre Levegh, who had already impressed with his stamina in the legendary 24-hour race in 1952, crashed into the swerving Austin-Healey of Hawthorn's compatriot Lance Macklin on 11 June 1955, just two hours after the start of the race, as a result of an unexpected and completely unpredictable driving manoeuvre by Briton Mike Hawthorn. The unavoidable impact catapulted Levegh's SLR towards the grandstand, where it broke apart and caught fire. This accident, which was not his fault, not only cost Pierre Levegh his life, but also those of 83 spectators. Race control allowed the race to continue despite the accident, but shortly after midnight the Daimler-Benz Board of Management decided to withdraw the two remaining SLRs driven by the Fangio/Moss and Kling/Simon teams, who were in the lead at the time, from the race out of respect for the victims.
In the 24 Hours of Le Mans and the Swedish Grand Prix, a sports car race in August 1955 outside the World Championship classification, the 300 SLR was equipped with an air brake – a flap mounted on the rear section at the height of the rear wheel arch, which could be raised hydraulically by the driver using a hand lever and enabled significantly increased deceleration due to the considerably increased air resistance. A welcome side effect was the increased load on the rear axle, which counteracted the front end diving under braking.
At the height of its success – after winning the Formula 1 World Championship, the Constructors' Championship in the Sports Car World Championship with the 300 SLR, the European Rally Championship and the American Sports Car World Championship in Category D – Daimler-Benz announced the end of its motorsport involvement on 22 October 1955 during a victory celebration at the end of the season. Even if this departure is repeatedly associated in public with the accident at Le Mans, the actual reason for the departure – documented beyond doubt in the archive files – was the intention to use urgently needed resources previously tied up by the racing department for production vehicle development in future.
The decision to withdraw from Formula 1 had already been taken by the Board of Management in spring 1955, and the decision to end the involvement in the Sports Car World Championship was made at the Board of Management meeting on 11 October – just five days before the Targa Florio, the final race of the Sports Car World Championship season, which the Mercedes-Benz team absolutely had to finish with a victory in order to win the title. In addition, the Ferrari team, which was leading the world championship and had driven in two more races than Mercedes-Benz during the season, was not allowed to finish second in Sicily. Against this backdrop, the Board of Management agreed not to disclose its decision so as not to jeopardise the motivation of the racing team already in Sicily. The Targa Florio ended with a one-two victory for Mercedes-Benz and a two-point lead in the world championship.
An improved version of the 300 SLR with a variable-length intake manifold and comprehensively weight-reduced assemblies and components, intended for the 1956 season, was completed as a one-off. The vehicle also had outboard brake drums on the front wheels to save weight. Compared to the cars used in the Targa Florio, the overall weight was reduced by a good 83 kilograms. However, due to the withdrawal from motorsport announced in October 1955, the one-off – like the two coupés completed in the summer of 1955 – were not used in racing.