Part Two: The matinée idol’s lesser-appreciated sibling.
Like everybody else, Mercedes-Benz’s engineering teams had rather a lot to contend with by the late 1960s. Not simply developing the nascent W116 S-Class, the most ambitious and luxurious mainstream saloon yet to bear the three pointed star, or perfecting the advanced rotary-engined C111 prototype – in addition to ongoing developments for both conventional petrol and diesel powertrains, there was also a seemingly limitless tsunami of emissions and safety mandates emanating from the land of the free.
Facing large investments, and no small level of commercial risk associated with new model programmes, the Mercedes-Benz supervisory board are believed to have vetoed a proposal to directly replace the existing W111/112 coupé and convertible models.
However, longstanding head of Body Development and Research, Karl Wilfert believed he had the solution, developing a proposal for a fixed-head, four-seater coupé version of R107, which was then presented to the supervisory board.[1] Given the level of technical and production-engineering carry-over, a business case was established and the programme officially sanctioned in 1969.
The C107 which emerged employed a longer wheelbase version of the R107 body, lengthened aft of the door strike-plate by a not inconsiderable 360 mm (14.2 inches). Rear compartment aside, the cabin was near-identical to that of the sister-SL model; the driving environment being as up to date in ergonomics, and materials as it was in passive safety features.
While the SLC’s external style closely followed that of its 2-seater sibling, the extra length in the body did not simply provide a more commodious cabin, it also moderated the SL’s somewhat truncated silhouette – a factor of its short 2460 mm (96.6 inch) wheelbase – the extra length enabling a somewhat more balanced shape.[2]
But while one dimension giveth, another taketh away; the addition of the fixed canopy raising a number of packaging and engineering-related questions which the car’s slightly inharmonious mien would have difficulty answering. A certain mismatch between height and length for example, meaning that like its SL sibling (if for differing reasons), the C107 too lacked a wholly convincing set of proportions.
Furthermore, as Mercedes body engineers discovered, despite the additional length aft of the doors, the retracting rear quarter windows as designed could not avoid fouling the rear wheel wells. Since a Mercedes coupé without a fully retractable suite of side glazing was as unthinkable as larger, thicker C-pillars would have been from a visual perspective, an ingenious trompe d’oeil solution was arrived at; a series of metal louvres vacuum-sealed between an additional pair of fixed rear quarter panes, the upward slanting DLO outline closely reflecting that of the SL’s removable hard top.[3]
It was a clever if rather frivolous solution, one which not only seemed a little out of character for the normally somewhat po-faced Sindelfingen carmaker, but one which successfully masked the rather seat-of-the-pants nature of its execution. But not only would it prove as aesthetically divisive as it was influential, it would become the SLC’s defining feature.[4]
Very much in the US Personal Luxury Coupé vein, the SLC, while not entirely in a class of its own, lacked much by way of direct opposition at its Frankfurt motor show debut in October 1971. This would arrive in the fullness of time, but not before the paradigm shift of the 1973 oil embargo.
Two years later saw the advent of the SLC’s closest on-paper rival, Jaguar’s much delayed XJ-S. Browns Lane’s offering was faster, more sporting in responses and arguably, more rakish in appearance, but neither car were what the gentlemen of the press would describe as ravishing beauties. In Autumn 1975 Car Magazine pitched a 450 SLC against Jaguar’s newly launched GT and found the two cars very closely matched indeed.
While Car’s Mel Nichols found the Jaguar’s handling to be beyond reproach, he discovered that the SLC, while initially feeling less nimble, was in fact just as surefooted – a possible consequence of that longer wheelbase. The XJ-S could show the Mercedes a clean pair of heels in the higher speed ranges, where its superior aerodynamics aided matters, but in most conditions Nichols found the SLC to be just as quick. Where the Mercedes really scored was in cabin space, ambience and standard of finish, which was light years ahead of the rather austere looking (and in places, feeling) XJ-S. The Mercedes got the nod, by a hair.
The SLC’s fine chassis was likely the rationale behind the car’s motorsport career, initially fielded by AMG in 1978’s European Touring Car Championship, driven by Hans Heyer and Clemens Schickentanz. The SLC scored a single victory in three years of campaigning, taking the win at the Nürburgring Six Hours in 1980 with Schickentanz and Jörg Denzel sharing driving duties.
In the Autumn of 1977, Mercedes introduced the 450 SLC 5.0, featuring a brand new all-aluminium 4973 cc V8 engine, destined for the upcoming W126 S-Class range. This model, featuring front and rear spoilers was intended to homologate the car for the following year’s World Rally Championship, where the SLC would be fielded in selected events, driven by amongst others, Hannu Mikkola.
From the outset, both 107 models had been intended to receive a wide range of engines; Mercedes’ M130 six cylinder, the 3.5 litre M116, 4.5 M117 litre V8s and ultimately, the M950/3 and M950/4 Wankel units. However, Mercedes, like everyone else lost faith in rotary power, while the advent of a newer 2.8 litre M110 unit saw this selected as the entry level powerplant.
This 182 bhp fuel injected 2746 cc unit made its debut for both SL and SLC models in 1973, the delay arising from supply being prioritised for the saloon models. Despite being no great performer in the heavyweight SL/SLC duo, this economy engine did much to maintain European demand in a more straitened post-1974 environment.
1980 saw the 5.0 litre V8 become standardised, alongside a smaller capacity 3818 cc V8, which would become the mainstay US market engine, owing (it’s believed) to CAFE fuel efficiency strictures. The 1979 advent of the W126 would seal the SLC’s fate – Mercedes-Benz product planners decreeing that Sindelfingen’s large coupé ambitions were henceforth better served under S-Class underpinnings. In 1981, the C126 was introduced – the big coupé rendering the SLC obsolete with close to 63,000 built over a near-ten year lifespan.
Overshadowed by its more glamourous SL counterpart, which not only outlived it by some considerable margin, but outsold it as well, the C107 SLC nevertheless proved surprisingly successful, and given its shared underpinnings, highly profitable. But more than anything, the SLC would prove unique in the Mercedes-Benz pantheon – the first and last of its ilk.
[1] According to some sources, Karl Wilfert developed the C107 in secret, thereby risking censure from his superiors. This however is not borne out in the official telling of the car’s development.
[2] Was the R107 SL’s wheelbase slightly too short? There is reason to suspect that it was, just as there are (purely aesthetic) reasons to suggest the SLC’s was (slightly) too lengthy. Proportions notwithstanding however, the SLC presents a more realised, more convincing visual proposition than its 2-seater sibling.
[3] The incredibly complex three-quarter vent treatment was very much Karl Wilfert’s idea and visual taste, for which he argued forcibly, and successfully.
[4] The C107 SLC was received with a good deal of interest at Allesley, Coventry; with none other than Sir William Lyons singling it out as a benchmark for the nascent XJ-S then in development. Curiously, a similar issue arose with the treatment of the rear three quarter glass – Jaguar stylists also opting for a less than convincing vent arrangement. The influence of the 107 series proved more widespread – seen in the the De Tomaso Longchamp/ Maserati Kyalami duo and arguably, Cadillac’s Allanté.
Another notable SLC aficionado was a certain LJKS.
Source: Mercedes-Benz 280 SL – 500 SLC – Der Schritt zur Modellvielfalt : Günter Englen. I am also indebted to Christopher Butt for his kind assistance.
Driven To Write 
Good morning Eóin. Thank you for solving the mystery of those louvres for me. I always found them a dissonant detail on an otherwise handsome design. The right-hand side of the prototype above, with the single-piece rear side window, looks much cleaner. I’m not sure that a wider C-pillar mightn’t have been a better solution. I might try to Photoshop this later.
The louvres are still a better solution than this mess:
That little quarter-window, presumably to solve the same problem, is horrible.
Ugh, you’re right Daniel! The other day I was looking at one, black as are most of them here in Spain, and boy that little window stuck out like a bad pimple.
By the way, I wonder if a modern interpretation of those louvers would have worked on that modern Benz coupé (Photoshop hint! 🙂 ) . I’m too lazy to check the actual denomination of said coupé as the current MB lineup is so huge! I pitty the sales people that have to memorize all that alphabet soup.
Maybe Mercedes could have tried a mechanism like the BMW E9’s where the window goes halfways down, then is rotated by ninety degrees and disappears in the sidepanel with the Hofmeister kink pointing downwards. This obviously only works with the window either fully up or fully down, something that most probably would have been not acceptable at Mercedes.
Hi Eóin, very interesting post!
Ah the C107 SLC, Stuttgart’s Chevrolet Monte Carlo! Jokes aside, I always thought the SLC looked too long and flat, like it could bend in the middle at any time, compared to its SL sibling. However, recent years have made me change my mind and its design has now grown on me. My favourite detail is actually those cool encapsulated side window louvers!
Here’s some alternative proposals for the SLC. The original first, followed by a mild widening of the C-pillar, then a more radical treatment that includes altering the rear screen so it wraps around further, to stop the C-pillar looking overly wide.
For the mild version to work in practice and allow the window to wind down fully, a small sail panel might be needed in the lower trailing corner of the rear side window.
Nice, Daniel! The third one, with the more curved rear screen is my favourite. May I suggest instead of a sail panel, a widening of the chrome trim on the lower corner of the C-pillar. You could probably add a MB star on it to break the expanse of chrome, although it may be too close to the BMW roundel on the C-pillar of the BMW 3.0 CSL.
I have a suggestion for a completely different roof section. I’ve pondered this question before, perhaps even mentioned it here, but I think it would’ve worked if they had cribbed the roof from Fords Thunderbird. Instead of that very curved wraparound rear screen, they could’ve gone for a more rectilinear theme with a very wide and flat C-pillar and a flat rear screen. Those curves feel very malplacé on a Benz anyway, if you look at the SLC from above you will notice how absurdly curved the rear screen really is.
Hi Cesar. That’s a good idea about a wider chrome trim on the trailing edge of the rear side window. I’m relieved that you like my efforts, especially as you like the louvres on the original!
Hi Ingvar. Is it the 1958 Thunderbird you had in mind?
That would be an interesting melange…not sure it would work, but what do I know? 😁
Yes, that’s the one. Ford used the same roof for a decade afterwards. What I’m after is the width of the C-pillar, the angle, and the parallell lines. That makes for more formal lines, I think it would’ve worked for a 600 coupe as well. The Uhlenhaut coupe is all glass, it works on the six-light sedan but for a coupe I would’ve suggested the Thunderbird treatment.
Mercedes already tried something in this direction and gave us an example of how not to do it
“… I’m relieved that you like my efforts, especially as you like the louvres on the original!”
Haha! Remember I’m also the one who likes horizontal character lines/creases, including the little ribs on the bottom of R107/C107 🙂
I’m struck by how closely the rear of the later Mk2 Ford Granada resembles the rear of this Mercedes-Benz.
How about this, Ingvar? It’s a compromise to combine a more formal roofline with the curves of the SLC:
Tricky, but we’re on to something! If the rear screen had the same angle as the front screen? And if the leading edge and trailing edge of the C-pillar were parallel? Now it looks like the C-pillar is slightly wider at the top?
Hello Daniel,
Second to Ingvar’s Thunderbird suggestion, perhaps you can include this solution in your considerations: the 1967-71 Thunderbird 2-door hardtops had a rear side window that retracted sideways into the C-pillar:
Have fun!
Hi Bruno. That’s very neat, but it would still necessitate a split side rear window in the case of the SLC, otherwise the C-pillar-would need to be inordinately wide, in which case the window could retract downwards anyway!
The black car in your detail photo is a (Lincoln?) hardtop sedan. The retracting rear-quarter window is a lovely, unusual detail on a four-door car.
Hi Daniel,
A small correction to your reply: the top detail photo of the black car is not a Lincoln 4 door but a Thunderbird 2 door hardtop just like the red one shown under it. You are right however that an arrangement such as that needs a wide C pillar, but that is (I thought) wat Ingvar meant by using a T-Bird style roof with a flat rear screen?
Ah, my mistake, thanks for putting me right, Bruno.
I couldn’t visualise a rectilinear ‘turret’ like that of the Thunderbird sitting on the SLC’s lower body, hence my compromise proposal for a more ‘formal’ coupé than the production car.
Here you go:
Well, it works for me! More stringent and formal, it looks more related to the hardtopped SL than the SLC is for real. Though i fear rear headroom would be somewhat compromised, but it’s interesting seeing how the design could be neatly tidied up. Thanks!
You’re welcome, Ingvar. Glad you like it! I don’t think rear-seat headroom would be much less than in the production SLC as the roof is only marginally shorter.
I never liked the SLC. The R107 might be a little too short (I would respectfully disagree, though) but the C107 is way too long. On top of that I don’t like the louvres. Just my two cents.
I’d love to have been a fly on the wall when such decisions are made. Did Wilfert really have to dig in with these louvres with heated arguments, flailing gesticulating arms around to the solution leaving others shaking their heads in despair? Or a case of “my design – tough!” ? Whatever the route, the satisfaction levels must be high on seeing the car sell well.
Daniel, full marks for your attempts but my eyes prefer the baroque clay model – sorry
They were trying the louvres in the W116 prototype, so it seems it was a theme that grew legs within the studio. As I gather it was very close to production ready and I’m very glad they finally turned it down.
Ouch! That’s you off my Christmas card list, Andrew. 😁
https://www.carstyling.ru/en/car/1975_bristol_412_covertibile/images/29870/
Hi Constantinos. Yes, the Bristol 412 Zatago, neither Bristol nor Zagato’s finest work…😲
Ahem, yes, your final iteration is spot on, Mr O’Callaghan…
Here are some pictures of the rear window treatments that they were trying out for the W116, as mentioned by Ingvar.
I think Daniel’s versions are an improvement, but that the SLC’s wheelbase is too long.
https://www.w116.org/library/design/
I’m a little late to this one, but as a current owner of an early R107 (in a very fetching shade of bright yellow), and having never being entirely convinced by the SLC variant, I thought I would address what I see to be the main styling issue. I don’t think the rear window is the problem, but the retention of the shorter car’s doors. I have attempted a professional restyling and my first ever stab at embedding an image into a WordPress comment. Only pressing “POST COMMENT” will confirm if this works; my apologies if it doesn’t!
Good morning Jeff, and well done on mastering the dark art of embedding images into your comments!
Your longer door certainly improves the stance and makes more sense of the long wheelbase. I don’t fancy trying to open that door in a tight parking space, although a hinge mechanism similar to that on the Renault Avantime might solve the problem. Much improved access to the rear seats too.
as a happy C107 owner, I can attest the original doors are already massive as they are. Making them even longer would make leaving the car in tight spots even more impossible than now (or would require Renault Avantime-style doors).
“… I’m relieved that you like my efforts, especially as you like the louvres on the original!”
Haha! Remember I’m also the one who likes horizontal character lines/creases, including the little ribs on the bottom of R107/C107 🙂
Hi Bruno,
Those sliding rear quarter windows on the Thunderbird are so cool and they reminded me of other cool features of some American cars from the 1960s and 70s, such as:
The cool rotating headlights on the 1966 Dodge Charger:
The Buick Riviera headlight covers:
Thunderbird sequential turn signals (which were mechanically activated as well):
The Corvette concealed wipers:
The 1970s GM full size wagon “Clamshell” tailgates:
The 1977-78 Oldsmobile Toronado XS wire-bent rear window:
https://www.google.it/url?sa=i&url=https%3A%2F%2Fbarnfinds.com%2F1978-oldsmobile-toronado-glass-house%2F&psig=AOvVaw1unyRHI1SYexATcqLq9dDC&ust=1620455243069000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNjhybL4tvACFQAAAAAdAAAAABAb
Hi Cesar and thanks for the videos. I love all these clever mechanical innovations that were a feature of American cars back in the day. I suppose the present day equivalent is the proliferation of software driven functionality, but this, for me at least, doesn’t have the ‘surprise and delight’ of mechanical features.
Indeed Daniel, in terms of fascination, a clever mechanism beats software gimmicks any time. Reliability is another matter though, as can be seen in some of the videos, especially the slow, uneven headlight covers. At least they seem like they’re trying their best, lending these mechanisms a kind of human aspect. A LED light would just stop working, with no drama and no reason.
Two small points. One, is that the appearance of the 1971 interior (five decades ago) is breathtaking in its enduring rightness. This alone is an loud and resounding testimony to the magic worked by M-B´s designers. They had to imagine from nothing this level of quality or at least have the wits to see what suppliers could to. The second point is that, for me, like the XJ-S the “wrongness” of the SLC is of equal heft to its rightness. Out of odd compromises emerged something no fully rational process could have devised. The louvred windows and the Saarinen-style trim make this car endlessly fascinating. I am sorry to say it wins in the hypothetical battle of the burly ´bahnstormers, leaving the XJ-S licking the self-inflicted wounds of woeful packaging and five-designs-on-confusion. And the dodgy trim, inside and out. I am glad the XJ exists but I much prefer the Wirtschaftswunder feel of the Mercedes.
In case this series has inspired any readers to get a c107 of their own.
https://bringatrailer.com/listing/1978-mercedes-benz-450slc-12/