Guide: Mercedes-Benz W198 300 SL Gullwing - a Historical & Technical Appraisal
BACKGROUND
Following a 13-year absence owing to the onset of World War 2 and subsequent need to get the company back on a firm financial footing, Mercedes-Benz finally returned to top flight motor racing for the 1952 season.
Instead of a single seat Grand Prix-type machine like the firm had used to such great effect during the 1930s, 1952 would see Mercedes campaign a purpose-built Sports Prototype at events like the Mille Miglia and Le Mans 24 Hours.
The resultant W194 300 SL proved an enormously impressive machine, taking the fight to the likes of Ferrari, Maserati, Jaguar and Aston Martin – and winning.
During that ‘52 campaign the 300 Sport Leicht most notably secured wins at Le Mans and the Carrera Panamericana as Mercedes re-asserted itself as a serious player in the world of motor sport.
1952 was also significant in that Mercedes appointed a new US distributor: Max Hoffman.
When Hoffman placed an order for 500 road-going versions of the 300 SL in early 1953, the Mercedes board immediately sanctioned an intensive development programme to create a suitably refined production version of their all-conquering race car.
Work started with a pair of existing W194s.
One of the cars damaged on the 1952 Carrera Panamericana was sent to Mercedes’ Sindelfingen works where it served as a styling mule. The factory in Stuttgart addressed themselves with development of the engine and drivetrain.
In little more than a year, the hot, cramped W194 endurance racer had been transformed into the type of superbly crafted machine for which Mercedes had become renowned.
The company launched what remains their most recognisable model, the iconic W198 300 SL ‘Gullwing’, to an awe-struck audience at the New York Motor Show in February 1954.
Based on the fixed head version of the W194 with its roof-hinged doors that opened upwards in a fashion hitherto unseen, the startling W198 caused a sensation on account of its elegant yet radical styling, its array of innovative engineering solutions and a level of performance that promised to be out of this world.
Production started six months later in August 1954 with assembly taking place at Mercedes’ Sindelfingen plant.
CHASSIS
The W198 shared its tubular steel chassis with the W194.
Both spaceframes had a wheelbase of 2400mm and weighed just 70kg.
Engines were canted at an angle of 50° to allow for the lowest possible frontal area.
Large side members to increase torsional rigidity resulted in very high sills and meant conventional doors were not an option; the Gullwing solution was a necessity rather than a styling trick.
Suspension-wise, unequal length wishbones were used at the front and a double swing axle at the back. As the swing axle was joined only at the differential and not the wheels themselves, extreme changes in camber could be encountered at high speeds or on poor surfaces.
Coil sprung telescopic dampers were fitted all round along with servo-assisted Alfin drum brakes.
A torsion bar stabiliser was installed at the front.
The fuel tank was located behind the rear axle. Compared to the W194, it was reduced in size from 45 gallons to 34.5 gallons.
Steel 5 x 15-inch bolt-on wheels came with an attractive three-pointed star hub cap. Dunlop, Englebert and Continental tyres were all available.
Track was fractionally wider than the W194 at both ends to free up additional cockpit space.
ENGINE / GEARBOX
The engine was essentially an improved version of the iron block Straight 6 single overhead cam motor used in the W194.
Most significantly, it came with Bosch direct mechanical fuel-injection, the first time such a system had been used on a series production car.
Bigger valves than the W194 were also fitted and the aluminium alloy cylinder head was redesigned to make changing spark plugs easier (this had been a difficult task on the W194 because of the engine’s mounting angle). The cast aluminium dry-sump lubrication system was specially designed to conform to this unusual positioning.
Early cars had a cast aluminium valve cover, but this was soon switched to magnesium.
Magnesium was also used for the cooling fan.
The crankshaft was forged steel and came with a vibration damper.
Ignition was via a single coil and one spark plug per cylinder.
Like the rest of the 300 range, displacement was 2996cc thanks to a bore and stroke of 85mm and 88mm respectively.
The compression ratio frequently varied from car-to-car, particularly in the early days of production when anything from 8.0:1 to 8.7:1 was used. The compression ratio of each engine was stamped on the block adjacent to the serial number plate below the chain tensioner.
With the standard 8.55:1 compression ratio, Mercedes quoted a peak output of 220bhp at 5800rpm and 207lb-ft at 5000rpm.
Transmission was via a four-speed all-synchromesh gearbox with single dry-plate Fichtel & Sachs clutch and an open differential.
BODYWORK
Unlike the rather functional lines of the W194, the W198 was draped in a sumptuous new body. Designed for utmost aerodynamic efficiency, it was arguably the most handsome production car of its era.
Body panels were mostly welded steel. Aluminium was used for the doors, bonnet, bootlid, sills, bulkhead and floors.
The wide front intake was embellished with a chrome shroud and large three-pointed star complete with decorative whiskers either side.
Full width bumpers were fitted front and rear.
All four wheelarches featured distinctive splash guard eyebrows which helped break up the otherwise slab-sided design.
Elaborate engine cooling vents carved out from the front fenders were accessorised with two anodised aluminium trims to match those on the sills.
Given the W198’s considerable width, the cockpit was well inset from the flanks. Each Gullwing door featured two gas-filled struts and, to make access easier for the driver, the steering wheel tilted backwards on its hub.
INTERIOR
Directly behind the tilting steering wheel was a simple curved binnacle which housed instrumentation for road and engine speed. The body coloured dash fascia housed further gauges for fuel and oil pressure (to the driver’s left) plus oil and water temperature (to the right).
All W198s were left-hand drive and came with a centrally mounted clock.
A variety of toggle switches were mounted on a full width turned aluminium panel underneath the dash fascia.
The knee roll and dash top were upholstered in leather to match the sills, seat bolsters, cabin pillars, rear section of the transmission tunnel, door panels and cockpit sidewalls.
Seats came with a choice of three colour combinations for the plaid cloth centres: grey and green, grey and blue or cream and red.
The headliner was nearly always light grey fabric.
Because of the Gullwing door profile, the main side windows could not be raised or lowered. Instead, they had to be removed when stationary and stowed in special pockets behind the seats. Fortunately, opening quarterlights were fitted to every car.
Another practicality issue was load space. As the boot was taken up with the spare wheel and fuel tank, luggage had to be stowed on a carpeted deck behind the seats.
OPTIONS
Customers could choose to enhance their cars with a number of optional extras.
They included an exterior colour other than Silver Grey, Rudge wheels with knock-off hubs, full leather upholstery, fitted luggage, a Pespex wind deflector, a Becker radio, seat belts and wing mirrors.
There were also a variety of axle ratios on offer: 4.11, 3.89, 3.42 or 3.25 instead of the standard 3.64:1.
Gullwings equipped with the 3.25 or 3.42 ratios received 180mph/300kmh speedometers as opposed to 160mph/270kph items.
For those buyers who desired a little more performance, Mercedes offered a Sonderteile engine with a racing camshaft and 9.5:1 compression ratio. These motors produced 240bhp at 6100rpm.
Competition springs and dampers were another desirable addition. When fitted, ride-height was around an inch lower and handling was much improved (albeit at the expense of comfort).
WEIGHT / PERFORMANCE
The Gullwing had a kerb weight of 1295kg.
With the standard axle ratio, top speed was 155mph and 0-62mph took 7.1 seconds.
W121 190 SL
Launched alongside the W198 at the 1954 New York Motor Show was Mercedes’ new W121 190 SL. This similarly styled two-seat Convertible was based on a unitary steel floorpan and used a 1.9-litre four cylinder engine.
Like the W198, Max Hoffman had ordered an initial batch of 500 W121s.
EARLY PRODUCTION CHANGES
Mercedes’ ongoing development programme meant the W198 Gullwing was subject to a series of improvements during its three-year life.
Gear ratios were changed early on as was the long gear shift lever which had initially eliminated the option for a radio. A short shift lever mounted further back on the transmission tunnel was quickly adopted along with a new clutch lever assembly.
ALUMINIUM BODYWORK OPTION
In February 1955, Mercedes introduced an aluminium bodied variant that weighed 130kg less than the standard model.
These lightweight cars were given type number 198.043 whereas the steel-bodied derivatives used type number 198.040.
In addition to the all-aluminium body, 198.043 variants came with Plexiglas side and rear windows, Rudge wheels and competition springs / dampers. Most examples were built with the optional 240bhp Sonderteile motor.
LATER PRODUCTION CHANGES
1955 also saw the ATE brake servo switched to a Treadle-Vac unit. Additionally, the welting between the wheelarch eyebrows and fenders was eliminated and the front grille’s concave three-pointed star emblem was replaced with a flat two-piece star.
In 1956, an externally mounted oil pressure pump was added to the engine along with dual point ignition.
END OF PRODUCTION
Production ended in May 1957.
By this time 1400 Gullwings had been completed.
29 of these were aluminium-bodied examples.
Around 80% of production was exported to the USA.
The W198 Gullwing was immediately replaced by a W198 Roadster that remained in production until 1963.
COMPETITION HISTORY
Although Mercedes’ main focus was on their W196S 300 SLR for the 1955 sports car season, the factory did contest a couple of events with works W198 Gullwings.
One such outing was for John Fitch and Kurt Gesell who placed fifth overall and first in the Grand Touring class on the Mille Miglia (April 30th to May 1st).
Later in the year, Karl Kling won the over two-litre GT support race for the Swedish Grand Prix at Kristianstad (August 7th).
On both occasions, 300 SLRs were victorious in the outright classification.
A considerable number of privateers also had success in W198s.
Among the most notable victories were those of Olivier Gendebien (1955 Coppa d’Oro dell Dolimiti and 1955 Liege-Rome-Liege Rally), Armando Zampiero (1956 Monza Coppa Inter Europa), Walter Schock (1956 Nurburgring Eifelrennen) and Willy Mairesse (1956 Liege-Rome-Liege Rally and 1957 Spa Grand Prix for GT cars).
Werner Engel won the 1955 European Touring Car Championship driving a W198 SL, a feat repeated by Walter Schock in 1956.
Across the Atlantic, Paul O’Shea clinched the 1955 and 1956 Sports Car Club of America Production Class titles.
Text copyright: Supercar Nostalgia
Photo copyright: Mercedes-Benz - https://www.mercedes-benz.com
Further Reading:
Frequently asked questions
The best hand-picked examples
Individual car stories
