Readers of the North American “Colliers Magazine” were the first to hear about the new Mercedes-Benz 300 SL Roadster 60 years ago. For the Stuttgart brand gave top photographer David Douglas Duncan the opportunity to showcase a pre-series roadster for the October issue of the magazine in 1956. It was a media coup, and a well considered one. Because in the United States demand for an open-top variant of the 300 SL was very high. The market was an important one for the segment of luxurious sports cars: since 1954 Mercedes-Benz had already exported a large proportion of its coupés to North America, a good 800 of a total of 1400 vehicles built. Duncan, who had himself driven a 300 SL “gull-wing” for years, shot the roadster from the W 198 model series on the Stelvio Pass and also at the main Mercedes-Benz factory in Sindelfingen for the photo spread. The final series version was then unveiled by Mercedes-Benz in March 1957 at the Geneva Motor Show. By 1963 a total of 1858 units of the roadster were built, and from 1958 it was also available with a hardtop.
The publication “Motor Revue” wrote of the new sports car: “Where the engine and driving characteristics are concerned the 300 SL Roadster is a masterstroke.” The magazine characterised the sports car as “a touring vehicle for two people, featuring superior performance and roadholding“. It was not just the specialist press that was impressed by the open-top version of the “gull-wing” coupé. Media such as the weekly newspaper “Die Zeit” reported on the premiere of the “300 SL Roadster from Mercedes-Benz with no end of noteworthy improvements” (issue dated 21 March 1957).
Roadster tradition from motor racing
In 1952, the Stuttgart brand’s first motorsport season since the end of the Second World War, the SL drove home some brilliant successes. This is why the series version, the 300 SL “gull-wing” (W 198) was derived from it, and presented by Mercedes-Benz in February 1954 in New York at the International Motor Sports Show together with the prototype of the 190 SL (W 121).
It soon became clear that the market was also very interested in an open-top version of the high-performance sports car. So on 20 February 1954 the Head of Body Testing in Sindelfingen, Karl Wilfert, demanded the development of a 300 SL Roadster as a sample car. Friedrich Geiger, the first Head of the Design Department in Sindelfingen, back then referred to as Stylistics, presented the first drafts on 5 May 1954. Later Geiger then also developed the matching hardtop, which took on the silhouette of the coupé.
Green light for the roadster
On 2 June 1954 the Board of Management gave the green light for building two test cars and one presentation car. In November 1954 series production of the vehicle was put back for the time being. On 26 July 1955 the Board then made its decision: “The decision has been taken to build the 300 SL Roadster with an attachable coupé roof and where necessary to take on extra staff for this“, is how the Board meeting’s minutes recorded it.
Developing the coupé into the roadster was associated with some technical modifications. In particular the engineers had to change the space frame. Due to its high design on the flanks this had once called for the characteristic gull-wing doors of the coupé. The frame was now lavishly redesigned on both sides in order to make classic doors possible without any change in the high torsional stiffness. Modifications were also made at the rear of the frame. On the one hand this created space to install the single-joint swing axle with compensating springs, on the other hand for a practical boot. Lastly, in the tradition of the luxurious Mercedes-Benz 300 S, the roadster was intended to fulfil the role of a sporty touring car much more effectively than the coupé. The changes led to an increase in the vehicle weight of around 120 kilograms.
The roadster’s handling was impressive. A test report by Mercedes-Benz engineer Erich Waxenberger stated: “The 300 SL Roadster with a single-joint rear axle and compensating springs boasts much better roadholding with sports springs and dampers than the 300 SL Coupé with a twin-joint rear axle. The strong tendency to oversteer has been changed to slight understeering, so this vehicle can safely be driven to its limits within a short space of time. According to Mr [Rudolf] Uhlenhaut and Mr [Karl] Kling the 300 SL Roadster lies somewhere between the Grand Prix racing cars and the 300 SLR where roadholding is concerned.” There could hardly have been a better report for the sports car from the fathers of the Silver Arrows. In March 1961 the chassis was further improved with the introduction of disc brakes on all four wheels.
Initially the engineers adopted the engine from the coupé without changing it. The three-litre six-cylinder M 198 in-line engine featuring petrol injection and an output of 158 kW (215 hp) had a grey-cast-iron block. It was replaced in spring 1962 by a 44 kilogram lighter aluminium cylinder block.
Photos © Daimler AG