BEST OF BREED
The spectacular 300SL Roadster offered both glorious open-road motoring and sophisticated technical refinement
Article Gary Anderson with Bob Platz
Images Denis Tanney & Nancy More
When Max Hoffman, U.S. distributor for Mercedes-Benz, convinced Daimler-Benz in 1953 to put a customer version of the 300SL racecar into production, the combination of the distinctive gullwing doors and the comfort of a closed cabin led the product planners to decide that the first version to be introduced would be the Gullwing Coupe.
Nevertheless, very soon after design work began on the coupes, designers and engineers began work on a roadster version with the goal of correcting the shortcomings of the coupe that were the result of rushing the car to market. Of particular concern was the difficulty in entering and exiting the vehicle due to the high sills and gullwing doors, the lack of roll-down windows because of frame design, unpredictable rear-end behavior – especially with the radial-ply tires – and lack of luggage space in the trunk.
Hoffman also felt that U.S. demand, especially on the West Coast, would be much stronger for a roadster that offered the pleasures of top-down motoring. Hoffman’s appraisal proved prescient: After good sales of 867 units in 1955, the first full year on the market, Gullwing sales dropped to only 311 in the following year.
With the top down, the Mercedes-Benz 300SL Roadster remains one of the most distinctive and beautiful cars ever made.
This example, ordered in late 1957, is one of the few shipped with the Rudge wheels that were only available that year, retrofitted with the optional hardtop that became available in 1958.
The stressed tube-frame chassis was the obvious starting point in correcting the Gullwing’s deficiencies. Torsional rigidity between the front and rear had to be maintained while lowering the center connections below the doors. Diagonal struts were added to brace the lowered side sections, which permitted lower sills and larger doors that could include roll-up windows. With the loss of the rigidity provided by the coupe body, the roadster also needed many of the mainframe tubes to be increased in both diameter and wall thickness. The rear section was also modified to move the spare tire under the trunk floor and the fuel tank was made smaller, freeing up space for luggage in the trunk.
Oversteer in the Gullwing, that could come on with little warning and become uncontrollable if the rear tires lost their grip, was largely caused by the swing-axle rear suspension adopted from the 300 limousine and stiffened to provide responsive handling. To counter this, the Roadster chassis was modified to install the single-pivot swing-axle rear suspension from the 220a sedans, but with a coil spring mounted above the differential and linked to the axles by vertical struts. If a rear wheel hit a bump while cornering, this additional spring would be compressed, stiffening that rear corner and preventing potential snap oversteer behavior.
A major benefit of the new suspension was that softer springs could be used on the roadster to provide a more comfortable ride than those that had been required on the coupe. A roadster version of the 300SL with the new chassis was first spotted in summer 1956 on the test track in Stuttgart by the German magazine Auto, Motor und Sport, hinting at the possibility of a new 300SL model.
In the new car, engine compression on U.S.-market models was increased from 8.55:1 to 9.5:1 because of the ready availability of 100-octane gasoline. This change provided an additional 25 horsepower, useful to offset the 250 pounds of increased weight with the beefed-up frame tubing, added suspension pieces, folding top apparatus and wind-up window mechanisms.
In addition, the Roadsters had the special sports camshaft that had been optional on the Coupes. Cars shipped to the United States would be supplied with the lower 3.89:1 rear axle as standard. This provided additional acceleration but at the cost of reducing top speed to 137 mph – both changes appropriate to U.S. traffic conditions and speed limits.
The lower top speed was probably a good thing anyhow; with the drum brakes, braking performance hadn’t improved, even with the addition of a bigger servo.
The introduction of the roadster version of the 300SL as the successor to the Gullwing was made official at the Geneva Motor Show in March 1957. On the stand, the car displayed the same distinctive grille, eyebrows over the wheel wells, and complex side vents in the front fenders of the Gullwing. However, from the front, the appearance had been significantly updated with single-unit headlamp clusters that incorporated turn signals and parking lights.
In addition, with a folding top in place of the coupe top, the car displayed an attractive wraparound windscreen and long graceful rear deck accentuated by a neatly designed top mechanism allowing the cloth top to fold completely under a sleek metal tonneau cover behind the driver and passenger. With the folding top and roll-up windows, purists might argue that the car should have been called a cabriolet, but “Roadster” was what it said on the placards.
On the interior, there were a number of design changes. Most obvious was that the handbrake, mounted on the Coupe between the seat and the doorsill, was moved to a more usual position next to the transmission tunnel. Switches were recessed in the dashboard in a nod to safety. The steering wheel no longer had the folding mechanism that had been necessary on the coupe for entry and exit and was more like the sedans, including the presence of a horn ring.
On the dashboard, minor gauges were changed to a ribbon style and moved to a position between the two main dials, a design that would be carried through the remainder of the lineup in the 1960s. The roadster was much more civilized and comfortable than the coupe, though at the sacrifice of the coupe’s competitive feeling.
With the introduction of the Roadster, Mercedes-Benz ended production of the Gullwing as well as the 300Sc coupe, roadster and cabriolet, perhaps because it was felt that the Roadster would be a sufficient showroom draw.
Sales in the first year of production were a satisfactory 554 units, the highest sales year, though still lower than the peak year for the coupe. Sales during the next five years would be at a lower but steady rate of approximately 250 per year, although the roadster still provided the showroom attraction that had been intended with the design.
The major enhancement to product strategy occurred in 1958 when an attractive removable hardtop with a practical wraparound rear window, displayed on this example, was made available as special equipment. Also of note, Dunlop disc brakes at the front and rear replaced the Alfin drum brake system in March 1961, well after our example was produced. From March 1962, a light-alloy engine block replaced the engine block carried over from the Gullwings.
However, by 1962, with Jaguar introducing its new E-Type roadster in the United States, Mercedes-Benz product planners decided that the 300SL had served its purpose. Production of the roadster, along with its sibling, the 190SL, was discontinued in early 1963. In total, 1,858 Roadsters had been produced. To replace both models, Mercedes-Benz introduced the 230SL, splitting the difference on performance and cost.
With the rarity, elegance and performance of the roadster, it has been an iconic collector’s car from the very end of production. Although selling for less than the coupe while costing more to restore because of its added complexity, in recent years the gap has been closing and the million-dollar mark in the market is now routinely exceeded.
Our thanks to Bob Platz, who shared with us for the photography in this article this beautifully restored black-over-tan Roadster with the rare combination of original Rudge wheels and retrofitted removable hardtop.
SPECIFICATIONS
1957 Mercedes-Benz 300SL Roadster
TYPE: Two-door two-seat roadster
with folding soft top and retrofitted optional hardtop
ENGINE: M198 Overhead-cam 2,996cc Inline-6, Bosch fuel injection, dry-sump lubrication
HORSEPOWER: 240 hp (SAE) at 6,200 rpm TORQUE: 228 lb-ft at 4,800 rpm
COMPRESSION RATIO: 9.5:1
TRANSMISSION: 4-speed manual DIFFERENTIAL RATIO: 3.89:1
WHEELS: Rudge centerlock competition
WHEELBASE: 94.5 in LENGTH: 178 in CURB WEIGHT: 3,135 lb
TOP SPEED: 137 mph ZERO to 60: 7.2 sec FUEL CONSUMPTION: 15-20 mpg
Modified tube frame allowed hinged doors to be fitted and the top to fold beneath a sleek upholstered tonneau cover.
Spare was relocated below the trunk, freeing space for luggage.
Increased engine compression added 10 horsepower. 
All ancillary components and labels are exactly as originally produced. This example displays the optional fitted suitcases made by Baisch, standard tool roll and wheel mallet for the Rudge centerlock wheels. 
Roadster remains graceful with soft top in place.
Updated interior set the Roadster apart. Inside, Roadster dash had ribbon-style minor gauges located between the main dials (all with U.S. markings on this example), steering wheel was similar to sedans, and parking brake was moved to transmission tunnel. 
On the road: the Roadster had more horsepower and better handling than the Coupe. 
Body-colored Rudge center-lock wheels were supplied on fewer than 30 Roadsters; this example has correct Dunlop RS5 bias-ply tires. 
Period-correct Talbot Berlin wing mirror. 
The Becker “Mexico” radio ordered with this car has the correct “delete plate” filling the space for an international tuning bar.