Classis test: Mercerdes 300SL

Silver dream machine

Current rumours that Mercedes-Benz may be considering a return to Grand Prix racing in the next few years after the success of the Sauber-Mercedes team in sports-car racing have something of a parallel in the years after the Second World War. German technical prestige had reached a zenith just pre-war, Mercedes-Benz and Auto-Union decisively beating the rest of Europe with their powerful silver cars and superb organisation.

As the disruption of conflict settled and the production of cars resumed, rumours began to circulate that the Stuttgart company wanted to re-establish that prestige on the track, and in 1952 the factory announced its first post-war competition car. Although the long-term intention was to return to Grand Prix racing, the company chose to pit its engineers and team members in international sports-car events first, to ensure that the whole operation had been brought to a pitch capable of winning against the best European competition.

The car which brought the silver livery of pre-war glories back to the tracks was known as the 300SL (for super leicht) and used the independent double-wishbone front suspension and rear swing-axle of the 300 saloon in a smooth and streamlined closed bodyshell attached to a multi-tube space-frame chassis. Heavily tuned, the six-cylinder overhead-cam engine, though vertical in the prototype, was radically canted over for “production” team cars to reduce frontal area and lower the centre of gravity.

But what caught the public’s imagination was the unusual door operation, now invariably known as “gullwing”. In years since, this has become a sort of exotic fad, notably on the De Lorean, and you can if you choose spend a great deal of money on a very tasteless gullwing conversion for a perfectly good modern Mercedes 500SLC. However, Mercedes’ choice was a typically logical one.

As first shown in 1952 the gullwing opening did not even intrude into the side of the car; instead only the roof and the side-window lifted, which was enough to comply with the sports-car regulations while keeping the side structure very strong. By the time the cars appeared for the Mille Miglia in May the doors had extended halfway down into the body sides, but the simple central-hinge solution was retained.

There are in any case only one or two ways of providing the necessary access room; the roof can swing out with a conventional door, as Eric Broadley later chose for the Ford GT40, or the whole unit could pivot forward longitudinally much as Bertone did with the Countach; both involve complex hingeing and seal problems, though the latter was used on the simpler open works 300SL. Putting the hinges on the centre-line of the roof is actually the simplest answer to the problem.

Yet this eye-catching detail was peripheral to the advance warning that the Mercedes-Benz machines gave the racing fraternity; in the 1952 season the silver cars entered for five top-rank events. These were the three most famous and demanding endurance races (Mille Miglia, Le Mans and Carrera PanAmericana) and two major sports-car races supporting Grands Prix at Berne and the Nurburgring. It was a bold selection which showed complete confidence, and which was vindicated for design chief Rudolf Uhlenhaut, himself an extremely fast test-driver. The season began with second and fourth places on the Italian road race, and swept on to victory in the other four.

But when the opposition (Ferrari and Jaguar in the main) was catching its breath for 1953, a communiqué from Stuttgart floored everyone by announcing that the 300SL would not be raced again. It had served its purpose by proving that the cars could beat the world, and that the organisation behind them was ready for the next step — a Grand Prix team for 1954.

If Grand Prix racing is the shop-window there must of course be attractive products, and it was not long before a 300SL went on sale to the public. Though the shape of the steel body had been slightly modified for the better, it was very close in specification to the 1952 works cars, using the multi-tube structure, swing-axle rear suspension and the canted engine, but this time fitted with fuel-injection. In this form it produced 212 bhp at 5800 rpm, enough to make it the fastest car in production: between 150 and 160 mph depending on which of three final-drive ratios was fitted. For customers who could afford it, a version with aluminium doors, bonnet and boot-lid was also made available, as was a competition roadster with all-aluminium body.

At £4300 it was an expensive car: injection was an extravagance justified for improved efficiency, the huge brake-drums were heavily finned, and the bulk of the car, including the complex welded frame, was hand-assembled. In addition the angled engine made it impossible to build a right-hand-drive version. Originally there was no intention of putting the car into production, but when Mercedes-Benz received an order for 1000 cars from its American agent the board quickly revised that decision.

It was demand from across the Atlantic which also led to the production of an open roadster version in 1957, but the high sills and tiny doors first seen on the converted works 300SLs at the Nurburgring in 1952 would simply not do for the sort of market which could afford this superfast machine. The problem was overcome by referring to the later design first seen at Berne and then at Le Mans that same year where, in order to meet the exacting standards of the scrutineers, extended doors were used to reach the spaceframe.

Two years before the 300SL roadster was revealed, Mercedes complicated the situation by introducing two other cars with some visual resemblance, but very different in structure and aim. One was advanced and significant and took the company back into sports-car racing: the 300SLR, which used the Grand Prix car’s eight-cylinder desmodromic engine and running-gear under a sports-racing body, either open or coupe, and which so famously carried off the fastest-ever Mille Miglia win in 1955 (with Stirling Moss and DSJ aboard). The other was a sensible attempt to offer a cheaper sports-car which could be built on a proper assembly line — the four-cylinder 190SL. Purists will suggest that the real 300SL disappeared when the gullwing ceased production in 1957, and that the roadsters are softened “boulevard” cars, particularly in later form with low-pivot rear wiles which made them less tricky to drive on the limit or in the wet. Yet they are substantially the same in performance, and if there had been no coupes, the roadster would certainly occupy an undisputed place as the great sports-car of the Fifties.

The car that Motor Sport was loaned has the astonishingly low mileage of some 52,000, having been stored every winter by its doting Canadian owner, before corning to the UK. It is an early example of the roadster (1057) and retains its drum brakes, although many owners have converted to discs at much expense.

Very often the choice of multi-tube spaceframe construction imposes great restrictions on space use within the frame, but the Mercedes-Benz designers manipulated the tubes cleverly to minimise this, concentrating the strength around the edges of the necessary holes in the structure. The sills are as wide as a gullwing’s, but easier to swing the legs over, being that much shallower, while under that long rounded tail there is a quite respectable boot with the huge 15in high-profile spare tyre lying in a well.

Only under the dash can a couple of tubes be seen, running up from the door pillar to the dash, until you open the bonnet. Then the enormous engine can be seen in a cradle of 25mm diameter tubes, the lorry-sized cam-cover leaning to the left and almost touching the vertical damper and spring, while the block itself is obscured by the massive inlet and exhaust manifold castings which lie almost horizontally on top of the (non-crossflow) unit.

Similar ingenuity went into the hood mechanism. That padded trim behind the seats is false, and merely provides a locating rim for the rear edge of the roof, which, in fact, disappears entirely under a rear-hinged cover. It is erected in a minute or less, being released from under the cover and then tensioned down on top of it and locked into the screen rail with two smooth-acting spiral peg levers. The assemblage operates as smoothly and solidly as everything else on the car, though in fact the hood itself is one of the few items to have been replaced recently.

On the gullwing the high sill meant that a tilting steering wheel was needed to let the legs slide under it; no such complexity on the roadster, although the two-spoke wheel is the same pattern and typical of MB cars of the time. By the time the works racer of 1952 reached its wealthy customers in 1954 it had gained in interior lavishness, and the 1957 roadster reflects its luxury tourer role.

Between the two main dials are four small vertical strip gauges for water and of temperatures, oil pressure and fuel, with small controls in a row beneath, including separate heating and ventilation levers for each side. Finely engineered details abound: the sliding cover over the interior light, the dash-top ashtray and cigar-lighter, the arm-rests which open to reveal an oddments tray.

One of the great pleasures of driving the 300SL today is the superb flexibility of this potent engine. Despite its 212 bhp (225 in later years) the high-compression unit trickles in traffic like a modem car, with no sign of fluffing or oiling. The tall gear-lever moves with reassuring clicks between the four ratios and the engine’s smooth pull is there on all of them; top will speed the car from pedestrian rates to illegal speeds without pausing, gently at first, then building up with a deepening bellow.

Fourth is strong enough for fast motoring much of the time, but the real satisfaction is in coming out of a hard bend in second, watching the tach needle tick off the markers before dropping sharply back and climbing again in third, and then feeling the same sort of surge in fourth as well, and all the while surrounded by the glorious bass roar. Thick fins on the drums (inboard at the rear) let them absorb heavy use, and they work very well at high speeds; from perhaps 20-40 mph they feel strong but pull unevenly, while at walking pace the servo seems to lose its sensitivity and become an on-off switch.

Michelin 185 XV tyres have replaced the cross-plies once fitted, and must cushion further the already gentle ride. Yet this does not mask the outstanding behaviour of this chassis, incorporating much learning gained from the sports-car and Grand Prbc seasons of 1954 and 1955. It settles into bends with some roll and then digs its claws in, adhering to the curve perfectly. Quick gearchanges fail to upset it, and the steering response is lovely. On straights, though, the wheel feels a little dead, and under braking it changes again, becoming vague and responding to any uneven pulling from the brakes.

Contemporary reports said that the low-pivot aide with its compensating spring connecting the two halves across the differential allowed mild and controllable oversteer at will. We did not try that, as the value of a roadster is now climbing towards that of a gullwing, and most roads in the south of England are rather crowded for these antics. But there are some exceptions, and as both car and driver warmed up, the average speed rose too. Hard braking alternated with that exciting growl as the silver-blue Mercedes sprinted over some quiet Surrey roads towards Hampshire, absolutely at home through every sort of bend at speeds which would without drama easily match a well-driven sports-car today. No wonder that for the lucky few it was the Grand Tourer par excellence. GC