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.
Indeeed, it was on 2 June 1954 the Board of Management that 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.
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 215 hp had a grey-cast-iron block. It was replaced in spring 1962 by a 44 kilogram lighter aluminium cylinder block.
The tradition of the sporty Mercedes-Benz SL started in 1952 with the 300 SL racing car (W 194) was systematically continued by the 300 SL Roadster: two vehicles known as the 300 SLS were created for the 1957 season on the basis of the open-top sports car, for entering the North American Sports Car Championship. The specially produced models were 337 kilograms lighter respectively than the series version and had an uprated engine with 235 hp. Paul O’S hea, who had already won the championship in category D with the “gull-wing” in 1955 and 1956, took the title for the third time in succession with the 300 SLS. In the early 1960s Eberhard Mahle and Gunther Philipp entered sports car races in 300 SL Roadsters.