Mercedes SL Heritage

The Origins Of The SL

Some of the most popular pages on this site are dedicated to the wonderful Mercedes SL - so lets take a look at its origins, development and heritage. If you go back far enough, then strictly speaking the first of the line was a Mercedes, without the 'Benz'.

The "28/95" model was announced in 1921, prior to the merger with Benz in 1926. It was fitted with a 725Occ six-cylinder engine and, unusually for the period, four-wheel brakes. Early versions were not supercharged, but a 'blower' was later added, and Max Sailer used one of these cars to finish second in the Targa Florio.

The Influence of Dr. Ferdinand Porsche

But it was the 33/180, or "K" model, that would establish Mercedes-Benz as a manufacturer of highly polished sports cars. Designed by a then little known Dr. Ferdinand Porsche, who was Mercedes technical director at the time, it featured a 6.2-litre six-cylinder engine with a single overhead cam valve gear layout, and was equipped with a supercharger.

The interesting thing about the use of the supercharger was that it was not permanently engaged, but rather brought into use by a mechanical linkage when the driver fully depressed the accelerator.

Bentley, Mercedes main rival on the race track, was to quickly learn that this use of the supercharger "only when needed" gave the car a huge reliability advantage - that naturally translated into race success!

This supercharger also differed from most other layouts in that it pumped air into the carburettor while on its way to the engine (rather than extracting the air/fuel mixture from the carburettor) and hence impelling it into the engine.

This worked well enough at high engine speeds, but at low engine rpm it consumed a great deal of power. At the time the "K" model was claimed to be the first-ever standard road car to have a 100mph top speed, and while it was a very impressive car to look at, it suffered from having the most appalling brakes and roadholding.

In 1927 an improved version of the 'K' was introduced, the 36/220 or "S" model. It had a larger, 6.8 litre engine which developed 120bhp at 3000rpm, and that was without engaging the supercharger. When the driver did engage the supercharger the power would shoot up to a whopping 180bhp, giving the "S" a top speed of around 110mph. But even more importantly than the increase in power and speed, the "S" had much improved handling, due greatly to its lower centre of gravity.

Naturally the brakes were also upgraded - and a total of 146 of the "S" were manufactured. To prove the point, Rudolph Caracciola and Otto Merz drove 'works' racing examples, the latter winning the German GP of 1927, with other Mercedes-Benz models in second an third places.

The SS and SSK

The "SS" arrived in 1928, this being a lighter version of the "S" (and thus starts the tie in with "SL"). The engine was further enlarged to 7020cc, however this model was soon followed by arguably the most famous of the early Mercedes sports cars, the "SSK".

While the wheelbase was shortened, a larger engine was installed which was good for 170bhp (unblown) and an enormous 225bhp with supercharger engaged. While there would be only 112 "SS" built, it was surely a tragedy that a paltry 33 "SSK" models were built.

Both were successful competition cars in Works' drivers' hands. Caracciola won the British Tourist Trophy race of 1929, averaging a whopping 78.26mph (remember this was 1929!) in rainy conditions, although many would claim it was because of the wet conditions and the resultant reduction in tyre wear that helped Caracciola to victory. He soon silenced his critics, by taking his SSK to victory in the Irish and German Grands Prix of 1930 and 1931 respectively.

The ultimate development of this family was the "SM" model of 1931, of which only five examples were ever made, and these were for the company's own use! The"SM" used the same engine as the "SSK", but had a larger supercharger fitted.

We cannot confirm or deny the following, but it has been reported that, with supercharger engaged, the "SM" would make a Trumpeting Elephant noise. But whatever it sounded like, it must have sent a tingle down the spine of the driver when he had a whopping 300bhp on tap.

Never ones to rely on engine capacity alone, Mercedes engineers copiously drilled holes through the chassis to reduce weight, and they were successful, as the car weighed in at only 2700lb, way less than the competition.

It was, in every way, a fearsome machine, having a top speed of 147mph (in ideal conditions), and one fitted with a purpose built streamlined body actually clocked 156mph. Caracciola would soon rack up another victory, taking out the 1931 Mille Miglia single handed, and later the German Grand Prix (putting to shame a couple of Type 51 Bugattis).

Mercedes Enters Grand Prix Racing

It was only natural therefore that parent company Daimler Benz would soon want to "officially" enter Grand Prix racing, and would turn their attention away from the "guts and glory" road monsters and develop smaller, lighter and better handling racing cars. For the 1930s, they developed a very different type of road car which upheld the company's sporting image.

The "500K" was a 5 litre supercharged grand tourer, introduced in 1933, beautifully made and finished, but with rather disappointing performance. It was softly sprung, and more suited to the Corniche than the Nurburgring. Its overhead valve straight eight-cylinder engine developed 110bhp (unblown) and 160bhp with the supercharger engaged.

The "500K"s replacement came in 1936 with the 540K, effectively the same chassis, and with a similar appearance and choice of bodies, but a 5.4 litre version of the engine with 115bhp (unblown) or 180bhp with supercharger engaged. Even so, this car had a maximum speed of only 105mph.

Unfortunately the second world war would virtually destroy the Daimler-Benz company, and it would not be until 1952 that they were able to showcase their new sports car. And what a car it was, featuring a sleek body style, with a coupe roof and lift-up gull-wing doors, all built upon a chassis made from a mass of small diameter tubes, dubbed the "space frame".

The engine fitted to the first prototype was good for 175bhp, and was a development of the new 3 litre saloon unit, but canted well over to one side to allow a low bonnet line. In June, Hermann and Lang would drive the car to victory in the Le Mans 24 Hour race, at a record 96.67mph average, and this was just one of many wins during the season.

Enter The Legendary 300SL

However, it was not until the spring of 1954 that the 300SL production car was announced, with modified styling and a more passenger friendly trimmed interior. The engine had been further developed, now enhanced with direct fuel injection and producing 215bhp from its 2996cc capacity, giving the car a top speed of around 150mph.

It was a formidable car, perhaps only let down by the high-pivot swing axle rear suspension, which could produce vicious oversteer in hard cornering conditions. This suspension set up would remain a contentious issue through later model SL's (even though it would undergo numerous revisions) until being phased out with the introduction of the "350SL" in 1971.

The coupe gave way to an open roadster (300SL Roadster) from 1957, with conventional front-hinged doors, and an optional hardtop was available. More important still, this derivative had a much more effective low-pivot swing axle rear suspension set-up. And by the time production ended in 1963 some 3250 cars had been built.

The More Affordable 190SL

But these two cars were extremely expensive, and Mercedes needed to create a more affordable sports car to compete with the likes of the Austin Healey and Jaguar E-Type. The answer came in 1955 with the release of the "190SL".

It may have lacked some of the glamour of the larger car (being based on the floor-pan, engine and suspension of the 180 saloon), but retained Mercedes key values of roadholding, quality and desirability. The 4 cylinder engine may not have kept up with the competition, but not many seemed to mind when, all things considered, the reliability and allure of the three pointed star sat up front.

It was during the reign of the 190SL that Mercedes developed perhaps their most ferocious racing sports car, used in only the 1955 season, the legendary 300SLR. This was based on the general layout of the then-dominant W 196 Formula, however changes were made to the space frame chassis to allow two seats and an all-enveloping body style. Its 3 litre straight-eight engine had desmodromic (positive opening and closing) valve gear, and produced 300bhp, giving the car a top speed of 180mph.

Perhaps its only real weakness was that drum brakes were used, at a time when Jaguar's D-Type was revolutionizing motor racing with disc brakes. To provide extra braking capacity, the Mercedes engineers developed a massive hinge-up air brake across the tail, behind the cockpit, which was not only effective from high-speeds, but when in operation it put considerable down force on the rear tires, in the process increasing the overall cornering power. A total of ten cars were built, of which two (that remained un-raced) were almost 300SL 'Gullwing' look-alikes. In one season, the team cars entered six events, winning five!

Tragedy Strikes At Le Mans

Things could not have looked brighter for Mercedes, but tragedy was just around the corner at Le Mans. Some three hours into the race, a 300 SLR would collide with an Austin Healey, plunging the hapless Austin into the grandstands.

The crash and ensuing fire killed the Austin's driver and over 80 of the spectators. Mercedes-Benz immediately withdrew the remainder of its team, even as Sterling Moss and Juan Manuel Fangio in their SLR were leading the top Jaguar D-Type by more than two laps.

Mike Hawthorn and Ivor Bueb, who were piloting the Jag, went on to a rather hollow victory - while it would take until 1988 for Mercedes to return to competitive racing, when they would join forces with the Swiss Sauber team in the Sports Prototype Championship, then lining up on the grid with its partner AMG in the German Touring Car Championship (DTM).

The Beautiful Pagoda's

But lets get back to the SL's! It would be in 1963 that both the 190SL and 300SL would be replaced by a single car - the 230SL. The layout and philosophy was much similar to that of a small car, and it used a conventional pressed steel body/chassis hull, and suspension and engine components lifted from the latest 220SE saloon model.

The engine, at first, was a 170hp/2306cc overhead-cam six-cylinder unit, with indirect fuel injection (that was almost a work of art), there was power-steering (unusual for this period), and the existing low-pivot rear suspension was carried over. To many people, this model is best remembered by the unusual 'pagoda' style of its optional hardtop, although interestingly there was some sales resistance to this feature when it was first released.

However the car's image was instantly improved when the 'works' rally driver Eugen Bohringer took one on the Liege-Sofia-Liege marathon rally of 1963, and won it outright. Two developments of this car were produced - the 250SL, built in 1967, and the 280SL (with a 2778cc engine) produced from 1968 to the end of production in 1971.

The Incredibly Popular R107 Panzerwagens

Then came arguably the most popular SL of all, the R107 350SL. Much larger and 'softer', brimming with creature comforts and still directed at the same luxury-conscious clientele. The monocoque construction used drive lines and suspension from the current saloon models, notably the still unreleased 1972 S-Class. The 3.5 litre V8 engine was a beautiful device, producing 220bhp at 5800rpm and giving the autobahn cruiser an effortless top speed of 130mph.

But the new SL was far from being 'Super Light', weighing 4000lb and requiring massive 4 wheel disc brakes. A 4.5 litre V8 engine was soon optional (standard in the US), the extra size being required to help maintain the cars performance in light of the additional anti-pollution gear being incorporated during the environmentally conscious 1970's. And, for the first time ever, a long-wheel 2+2-seater fixed-head coupe would be available - the 350SLC and 450SLC.

By the end of the 1970s, the latest light-alloy 3.8 and 5.0 litre versions of the V8 engines were fitted, and production would continue until 1989, a run of 18 years! While the previous model SL was nick-named the 'Pagoda', the R107 would be dubbed 'Der Panzerwagen' due to its reliability, strength and longevity (some examples covering over a million miles without the removal of the heads!)

But Mercedes decided to once again dabble in the 'super car' genre, developing a ultra-high-performance prototype, the Wankel rotary engined C111. This state-of-the-art mid-engined two-seater coupe used fully independent suspension, while the 3 Rotor 3600cc engine was good for 280bhp and a top speed of around 160mph.

The breathtaking performance was not the result of the engine alone, the sleek fibreglass body having a low drag co-efficient and sitting extremely low to the ground. Within a year Mercedes had developed a second evolution, this time using a 4 rotor engine with a 4800cc capacity and good for 350bhp and 190mph.

Ultimately however the cost and ongoing reliability issues would force Mercedes to shelve the project, the C111 joining the BMW M1 as the stuff of legends.

Also see:
Mercedes History
Mercedes SL's By Model
Mercedes Benz 1886-2007 Powerpoint Presentation