1956 Mercedes-Benz 300 SL

The Mercedes-Benz 300 SL was the fastest production car of its time, and its race-bred three-liter overhead camshaft straight-six engine rewarded the gullwing coupe with a top speed in excess of 160 mph. The designation 'SL' is an abbreviation of the German term super-leicht, meaning 'super-light', a reference to the car's tubular-frame construction and the use of aluminum throughout many body components. A total of 1,400 Gullwing Coupes were produced from 1954 to 1957; twenty-nine examples had all aluminum coachwork.

Mercedes-Benz W194 and 300SLR
The 300 SL Coupe was birthed from Mercedes-Benz's Le Mans W194 competition coupe, conceived in 1952 and intended for World Sportscar Championship competition. Chief Engineer Fritz Nallinger suggested the two-seat sports car utilize the in-line SOHC six-cylinder engine from the company's luxurious 300 series. Although the engine and drivetrain were relatively heavy, the chassis was extremely light. Test Department manager Rudolf Uhlenhaut worked with construction engineer Joseph Müller on creating the rigid lattice-work chassis that could accommodate the big in-line six. Weighing 154 pounds, the structure was lightweight and strong, but there was no way to mount conventional doors without compromising the rigidity of the chassis. An ingenious solution was devised, raising the entry so that the doors cut into the roof, with hinges at the top, resulting in the gullwing design.

The 3-liter inline-6 M186 engine produced 175 horsepower and was shared with the 300 'Adenauer' saloon (W186) and the two-seat 300 S grand tourer (W188). What the W194 lacked in power, it compensated with low weight and low aerodynamic drag. Initially using carburetors, the engine was given fuel injection for the 1953 season, along with 16-inch wheels, and the gearbox was relocated to its rear axle. The Elektron (magnesium alloy) body reduced the overall weight by nearly 190 pounds. (This alloy-bodied car was not raced by Mercedes-Benz; instead, they concentrated on Formula One in 1954.)

The W194 300SL represented the return of Mercedes-Benz to international motorsports and was a combination of series-production technology and innovative lightweight construction. Numerous victories and podium finishes were achieved by the W194 during the 1952 season, including 2nd (Karl Kling) and 4th place (Rudolf Caracciola) at the Mille Miglia, a triple victory in the sports car race in Bern (the fourth example driven by Caracciola crashed in what would prove to be his last race), a double victory at the 24 Hours of LeMans, and a quadruple victory in the sports car race on the Nurburgring. At the La Carrera Panamericana, Mercedes-Benz entered two coupes and two roadsters, powered by engines boosted to 180 horsepower. Karl Kling and Herman Lang finished first and second, and a 1-2-3 finish may have been the final result for the Mercedes-Benz team had American John Fitch not been disqualified for permitting a mechanic to touch his car on the second to last day.

Mercedes-Benz sat out the 1953 and 1954 sports car seasons, concentrating instead on developing its new Grand Prix car. When the '300SL' re-appeared in 1955, it arrived as the airbrake-equipped 300SLR, utilizing numerous advancements that were developed and fine-tuned for the company's Formula One program.

1955 was a combination of triumph and tragedy, with the 300SLRs victorious at Buenos Aires, the Mille Miglia, the Nurburgring, Spa, Zandvoort, Aintree, Kristianstad, Monza, Dundrod, and Sicily's Targa Florio. One of racing's worst accidents occurred at Le Mans, claiming the life of team driver Pierre Levegh and more than 80 spectators, prompting Mercedes-Benz to withdraw from racing for many years.

Max Hoffman
American Mercedes importer Max Hoffman understood what the booming post-war U.S. market was seeking, and he recognized that a road-going version of the Grand Prix car would attract affluent performance enthusiasts. At a 1953 directors' meeting in Stuttgart, Hoffmann presented his idea to Mercedes' management, and the company's new general director, Fritz Konecke, agreed to Hoffman's order for 1,000 cars.

In February of 1954, Mercedes-Benz presented the 300 SL at the New York International Auto Show. This was a break in company tradition as they often debuted models in Frankfurt or Geneva; with the U.S. being the target market, it was only natural that the world was introduced to the model in NY. Following a positive reception, production soon commenced at the Sindelfingen plant.

Construction
Dimensions
The 300SL had a 94.5-inch wheelbase, a length of 178 inches, a width of 70.5 inches, and a height of 51.2 inches. The coupe had an overall weight of approximately 3,300 pounds (1,500 kilograms) and the forthcoming roadster tipped the scales at 3,440 pounds (1,560 kilograms).

Chassis
The tubular frame chassis was formed from chrome-molybdenum steel and was designed by Rudolf Uhlenhaut. The straight tubes were assembled as triangles, ensuring strength, and the structure weighed a mere 181 pounds.

The steering was via a recirculating ball that was relatively precise, and the suspension sourced from the W186 was independent with unequal-length double wishbones, coil springs, hydraulic telescopic shock absorbers, and a torsion anti-roll bar. At the back were a low-pivot swing axle, radius arms, and coil springs. The coupe suffered from extreme changes in camber at high speeds due to being jointed only at the differential rather than at the wheels. The roadster did not suffer from this issue as it used a high-pivot geometry setup.

Braking was courtesy of drums sourced from the 300S, with the addition of a brake booster that decreased pedal force. The brake shoes were 4 inches wide, and the front drums were two-wheel brake cylinders/wheels, while the rear drums were one-wheel brake cylinders/wheels. The handbrake operated a mechanical parking brake acting on the rear wheels.

Initially, the roadster would use the same brakes as the coupe; in March 1961, 11.4-inch disc brakes were added at all four corners.

The standard wheels were steel bowl/aluminum rim rivet compound units. Rudge 5J × 15-inch rims were available as optional equipment. The coupe wore 6.50-15 inch tires, while the roaster had 6.70-15 tires.

Engine
The water-cooled, 3.0 liter (182.8 CID / 2996cc) overhead cam straight six had two-valves-per-cylinder, an aluminum head, sand-cast aluminum intake manifold, an 8.55:1 compression ratio, triple two-barrel Solex carburetors, and a Bosch mechanical fuel-injection system. It had a dry sump lubrication for proper oil distribution during high-speed cornering and a lower engine height by the elimination of the traditional oil pan. The engine produced 240 (SAE gross) horsepower at 6,1000 RPM and 217 lb-ft (SAE gross) of torque at 4,800 RPM. Output increased further with a 9.5:1 compression ratio and a sports camshaft. The coupe could be ordered with the higher specification engine free of charge. The roadster had this engine only in its 1957 debut year.

An auxiliary fuel pump allowed for proper amounts of fuel required for extended high-speed operation.

The final 209 vehicles, beginning in March 1963 onward, had a light alloy crankcase.

Transmission
The four-speed transmission had a single-disc dry clutch and gear ratios of 3.34:1, 1.97:1, 1.39:1, and 1:1. Production began with a stock rear-axle ratio of 1:3.42, switching to 1:3.64 at the 41st vehicle for better acceleration. With the latter configuration, zero to sixty mph took 9.3 seconds, and the top speed was reached at 146 mph (235 km/h). The lowest final-gear ratio of 1:3.25 gave the 300SL a top speed of 163 mph (263 km/h).

Coupe Production
The 300SL Coupe was produced from 1954 to 1957, and a total of 1,400 examples were constructed.

- 1954: 166
- 1955: 856
- 1956: 308
- 1957: 70

Mercedes-Benz introduced the roadster variant of the 300SL in March of 1957 at the Geneva Motor Show, with production commencing two months later and coinciding with the final assembly of the Gullwing coupes.

The roadster was similar to the coupe but with a re-engineered version of the coupe's tubular space frame, conventional front-hinged doors, a revised rear structure, and an improved suspension. Detail differences included larger front fenders, larger 'euro' headlights, a smaller grille, a rounder front windscreen and a chrome accent strip running down the side of the car. The fuel-injected 3.0-liter six-cylinder engine had a cast iron block and an alloy cylinder head. The transmission was a fully synchronized, four-speed unit.

The updates to the tubular space frame resulted in lower sill trusses which accommodated conventional front-hinged doors. The revised rear structure, along with a smaller (26.4 gallon) fuel tank, provided more trunk space and accommodated a low-pivot swing axle suspension. The bodywork continued to be comprised of steel, with aluminum panels for the trunk lid, floors, bulkhead, door skins, sills, and hood.

The roadster weighed approximately 275 pounds (125 kilograms) more than the coupe, with the additional weight offset by a slight increase in horsepower. It was also more expensive; the 300 SL coupe was priced at DM 29,000 in Germany and $6,820 in the United States. The roadster was DM 32,500 in Germany and $10,950 in the US.

A hardtop became optional in September 1958.

Roadster Production
The Roadster was produced from 1957 to 1963, with a total of 1,858 units constructed.

- 1957: 618
- 1958: 267
- 1959: 200
- 1960: 241
- 1961: 256
- 1962: 182
- 1963: 94

More examples of the Roadster were built compared to the coupe (1,858 vs 1,400), but the Roadster's lifespan was seven years compared to the coupe's shorter 4 years of production.

by Daniel Vaughan | Jan 2025