The first with eight cylinders: the 107 series (1971 to 1989)
- A total of 237,287 open-top two-seaters produced in 18 years
- Engines again and again updated to reflect the state of the art
- Coupés of the SLC series available until 1981 parallel to the open-top version
In April 1971 a new SL rolled out onto the highway, the Mercedes-Benz 350 SL. For the first time in the history of the model series an eight-cylinder power plant did duty under the long bonnet. From all sides it made the impression of a strong, self-confident, imposing open-top vehicle. Its fathers also gave it an equally well designed, removable coupé roof for the road. Besides elegance and quality the body radiated safety, since the crash behaviour of the two-seater was far ahead of its time.
The decision to manufacture the R 107 series (“R” as in Roadster instead of “W” as in Wagen = car) was taken by the Board of Management after intensive debates on 18 June 1968. At dispute was whether there should be a Targa-roof version, i.e., one with a removable roof panel, instead of the fabric-topped variant, because owing to higher safety standards alarming news was to be heard from the USA regarding the licensing of open-top cars.
That a decision finally was made in favour of an open-top two-seater with a fabric roof and an additional removable hardtop can be attributed to Hans Scherenberg, the head of Development, who fought tooth and nail for it: ”The SL gave me great pleasure, but also caused me great trouble. This was no easy decision for us,” he summed up the decisive meeting.
The coupé question still was unanswered, however. It was not decided that day. Discussion centred around whether one should additionally, and soon, make a four-seater sports coupé based on the R 107 series, or wait for the coming S-Class (W 116) to build it on that basis. But then a production model would not have arrived until much later, in the mid-1970s.
Karl Wilfert, then the head of Body Design in Sindelfingen, developed – pretty much on his own authority – a coupé based on the R 107 and presented it one day to the Board of Management as a “rough draft”. Rejected at first, Wilfert managed to push through his idea of a sports coupé with the tenacity which was so characteristic of him.
And so six months after its premiere the SL was followed in October 1971 by a comfortable four-seater Sports Coupé, the 350 SLC, whose unconventional lines also found it many friends around the world in the course of the years. Internally the series was designated C 107. Up to the windscreen its appearance matches that of the open-top variant; behind the windscreen the overall height and length grows. A flat roof spans the four-seater passenger compartment in a gentle curve, going over into a large and very steep rear window that arches in two directions. The boot lid is slightly convex in shape, unlike the SL’s.
In the side view the length of the Coupé is documented, firstly, by the 360 millimetre longer wheelbase (2820 mm/111 in, versus 2460 mm/97 in), secondly by the line of the side windows. Without awkward B-pillars they are completely retractable, as is usual in a Mercedes-Benz Coupé. The SLC’s coefficient of drag is better than that of the SL so that the Coupé attains the same performance despite an added weight of some 50 kilograms.
A particularly noteworthy fact is that it fully lived up to its classification as a “Sports Coupé,” gaining wins for Mercedes-Benz in many rallies and long-distance races.
Béla Barényi’s safety concept with front and rear crumple zones and a rigid passenger cell found expression in the 107 series in a further developed form. The backbone of the R 107 series is not simply a shortened and reinforced saloon floor assembly, as in the predecessor, but an independent frame-floor unit with a closed transmission tunnel and box-shaped cross and longitudinal members which featured differing sheet metal thicknesses and a resultant carefully defined crumple pattern.
The SL definitely had to be an open-top car, and that being the case the only protection in a possible roll-over would be provided by the A-pillar plus windscreen. They were thoroughly redesigned and had 50 percent more strength to show than in the previously built version. In addition, to enhance its strength the windscreen was bonded into the frame. This resulted in a remarkable power of resistance in the roof-drop test with the result that the open-top car could be licensed for the USA even without a Targa bar. To complete the logic the rear window of the hardtop also was bonded into its frame.
Even in the interior there were pioneering changes to report. The hard dashboard made way for an ingenious sheet-steel design that yields on impact both in the top section and the knee area and is foam-padded. The switches and levers were recessed. Another new feature: the four-spoke steering wheel based on the latest findings of accident researchers. The proven impact absorber was still in place, but the steering-wheel rim, spokes, padded boss and hub were covered with polyurethane foam. As further safety feature the fuel tank was no longer installed in the rear end but above the rear axle, protected against collision. From March 1980 the anti-lock braking system ABS was offered; from January 1982 also airbag and belt tensioner.