Precious mettle

Rich in competition pedigree, even though it never raced, the Mercedes Uhlenhaut coupé has become one of the most fabled cars of all time. We were offered a stint at its helm – a rare but welcome privilege
Writer Andrew Frankel
Photographer James Lipman

Sometimes a racing car can be so special it needs only to exist to ensure its place in history. With an impeccable provenance and pedigree and given sufficient scarcity, it need not even race before taking its seat among the most fabled of all.

The Jaguar XJ13 is one obvious example: the status it enjoys today is out of all proportion to that it would have been accorded had Jaguar not wisely realised it was already obsolete by the time it was in a fit state to be raced. It might not have won any events, but equally it didn’t lose any either. With our disbelief willingly suspended, it has become a hero and not a failure.

Had it raced, the chances of the car on these pages failing would seem to be zero. It’s not as rare as the XJ13 – indeed, with a total production run of two it’s positively common by comparison – but had it raced as intended in both the cancelled 1955 Carrera Panamericana and at Le Mans in 1956, it seems a foregone conclusion that it would have added further to the extraordinary successes of the Mercedes-Benz racing team. At the time Motor Sport called it the 300SLR saloon, but today it is known only after the man who developed it and then used it as his road car. This is the Uhlenhaut coupé, and some credible sources will tell you that were one of the two to be offered for sale, it would prove to be the most valuable car in the world.

I think today many people perceive the coupé as the successor to the 300SLR, whose Mille Miglia-winning ways in the hands of Stirling Moss and Denis Jenkinson are part of motor racing legend. In fact it was anything but. The two cars were built as part of the 10-car SLR production run and received chassis numbers 0007/55 and 0008/55. The former sits as a permanent exhibit in Mercedes-Benz’s extraordinary Stuttgart museum and has not run in decades, but the latter is on the button and now patiently waits for me at the company’s Unterturkheim test track.

You can read more about Rudolf Uhlenhaut, the Anglo-German engineer who transformed Mercedes road and racing cars both before and after the war, in the panel on page 67, but for now let’s look in a little more detail at his creation.

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One reason for its perceived value is its appearance. Unlike the W196 F1 car and even the open 300SLR, the coupé is a car of exquisite beauty, shaped in-house by both man and machine in the form of the full-sized wind tunnel that had been on site since before the war. From a distance you might even mistake its domed roof and gullwing doors for those of a 300SL, but while their names differ by just one letter the cars are related only by their badges.

Its real parent is the W196R Grand Prix car that made its debut the year before and (with a little early-season help from Maserati) carried Juan Manuel Fangio to his second world championship. For while the SLR’s Elektron magnesium alloy bodywork was unique, almost everything it contained was taken directly from or else closely related to the F1 car, including its spaceframe of complex 25mm tubes that provided the same distance between the front and rear wheels as the longest of the three wheelbases used by the W196.

The engine, for instance, is the 2.5-litre GP motor bored slightly and stroked significantly to provide absolutely square (78x78mm) dimensions, a 3-litre capacity and an explanation for why Mercedes chose such a small motor when Ferrari was using capacities up to 4.9 litres. Just to get the engine up to 2982cc required binning the W196’s iron liners and chrome plating the bores of the aluminium block. It also had a different firing order to the F1 motor, not to mention the addition of battery, starter motor and alternator. With a magneto providing the engine sparks and with no need for headlights let alone windscreen wipers, the W196 single-seater was able to dispense with them all.

The engine itself was in unfashionable straight-eight configuration, but with the drive being taken from the centre like that of an Alfa 8C, it’s easier to understand the configuration as two straight fours sharing a common crank. It had twin overhead camshafts and direct mechanical fuel injection, and was mounted at a 33-degree slant to lower the bonnet line as far as possible. Eventually it would give about 310bhp at 7800rpm, though to this day tales rattle around Unterturkheim about Fangio bringing back cars that had been past 10,000rpm with no apparent ill consequences; the tachometer in the coupé is calibrated to 11,000rpm. The engine’s strength has been most commonly attributed to its desmodromic valve gear, which dispensed with conventional springs and instead mechanically picked up each valve and returned it to its seat.

The five-speed transaxle ZF gearbox is carried over unchanged from the F1 car while inboard finned drum brakes at each corner (to minimise unsprung weight) followed W196 thinking too, as does its double wishbone front suspension and rear swing axle, both sprung by torsion bars.

And there you have it. Lessons learned designing the 300SL meant that turning the open SLR into a closed gullwing coupé was relatively straightforward, and with a beautifully tartan-trimmed cabin (blue for 0007, red for 0008) and a complete set of period dials, you need to remind yourself that this apparently civilised coupé is directly derived from the most technically advanced and successful F1 car of its era.

At least until you sit in and fire it up. The sill is wide but dropping down into the car is easy enough with the vast, well worn, wood-rimmed wheel removed. Only then does this car reveal its inner truth. The driving position seems somewhat gynaecological, with the brake and clutch pedals a matter of feet apart. Look down and you see the gear lever plunging into its open gate, the layout engraved in roman numerals on the steel ball your hand now grasps.

Someone leans in and re-attaches Rudi Uhlenhaut’s steering wheel. It’s the real deal: vast in diameter and well worn at the circumference. Uhlenhaut’s wheel – I’d make a special journey to see that alone, yet here I am about to use it in his own car. His 300SLR coupé. It seems as ridiculous to write as it must be to read.

I’m not going to dwell on its value because it is unknown, and as someone as eminent as former president of Bonhams Europe Simon Kidston has recently called it the most valuable car in the world, that’s good enough for me.

As neither coupé is nor will ever be for sale, it is literally priceless.

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The starting process is almost too easy. You push the key to activate the fuel pumps, pull a switch to turn on the mag, press the start button and wait for the churning to stop. With fuel injection it doesn’t take long.

It’s hard to describe what happens next save to say that if sound were matter that could be seen, it would be like a block of flats falling on the car. This direct-injected desmodromic straight eight does not make a nice noise, but its volume is fascinating, terrifying and compelling in equal measure, in much the same way as the shower scene in Psycho. It just draws you in. I’ve heard this engine before when standing next to its open relatives at the Goodwood festival, but sealed inside the echoing chamber of the coupé’s cockpit, it takes flaming, spitting, deafening aggression to a new level. And that’s at a fast 2000rpm idle.

Happily the clutch is a little less heavy than I’d expected and a lot more progressive. The noise still rampages around the cabin, hinting none too subtly that this car is one with which you should not mess, but actually making it move is fairly straightforward.

Keeping it moving is more difficult. Over the years I’ve taken pride in being able to handle cars with syncro-free gearboxes, reversed gear layouts and centre throttles. Even cars with all three, like a pre-war Aston, is not usually a problem. But the SLR’s gears, all of which engage beautifully, are scaring me witless.

The problem is that while first and fifth are exactly where you’d expect them to be in most five-speed gearboxes, second is across the gate and directly below third, while fourth is across again and directly below fifth. So if you execute what you think is a perfectly normal three-four change by just pulling back, it actually gives you second. And if that doesn’t bear thinking about, consider what happens if you do what comes naturally when changing down from fifth and move the lever across the gate and back: that also gives you second. Doing an unintended five-two shift would be one of the easiest and most expensive things I have ever done in a car.

Think. Across the gate and slot back into second – quick check of the map on top of the gear lever – then straight forward into third and let the engine go. The motor is disdainful of low revs, but comes alive at 3000rpm. The unholy alliance of noises in the cockpit now meld into one scything sound as the SLR powers forward, leaving the poor camera crew in the following E-class estate wondering which way it’s gone. It makes you want to shout expletives and even with a passenger on board you could, because he or she would never hear them.

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The track at Unterturkheim is not particularly short, but there are lots of bumps, dips, undulations, ripples and strange, SLR-unfriendly surfaces, all of which need avoiding. I am aware of being very busy, managing the gears, the track, the engine (which I’ve promised myself will not exceed 6000rpm) and the bloody awful brakes. Did I mention them? At low speeds the brake booster doesn’t work so it feels like you must put your foot through the bulkhead just to ease to a halt, and at high speeds there’s just not much retardation – no wonder the open SLRs were fitted with air-brakes for Le Mans: as it stands you feel an Aston DB3S or even a drum-braked Ferrari Monza (let alone a D-type Jaguar) would take yards out of the SLR into each braking zone.

But in every other aspect it feels years ahead of its time. The engine is massively strong and, unlike its six-cylinder British opponents, not based on an already ageing road car motor. True, the rival Ferrari engine was also F1-derived but with the same capacity and half the cylinders, it was never going to produce anything like this amount of power. The delivery is quite linear and builds steadily to its apocalyptic crescendo, by which time the car is simply mauling the track as you throw gear after gear at it. Just once I got into fifth on the short main straight, saw the world flying past my window at some unmentionable three-figure speed and instantly backed off. I don’t know much, but understand when enough is enough in a priceless commodity like this.

And I apologise for repeating the word, but no other will do.

Not that there had been anything save the brakes and gear layout to suggest this is a difficult car to drive. It would have been inappropriate to drive it up to and past the adhesion limit but I still went fast enough to feel the chassis starting to earn its keep beneath me. It felt utterly benign, with accurate steering and the kind of broad, neutral balance that makes you want to drive it for days – which had it taken part in the Carrera is exactly what would have happened.

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Nearly 60 years later it was time to give it back and, to my surprise, I was ready. The pleasure I felt – not to mention the relief – of handing it back unharmed was almost a match for the sublime experience of trying it.

If you are one of a handful of people accorded the honour of driving what might be the most precious automotive property there is, only one thing actually matters. If I’d driven it flat out and missed a shift through cockiness or tiredness, I’d not need Mercedes never to forgive me because I’d take care of that myself. As a window into a world of technological and engineering excellence unsurpassed at the time, the Uhlenhaut coupé is so much more than a car: it is a time machine. And as all those lucky enough to use it to travel back to another world should know, time is the one thing you do not mess with once you’re there.

Without the help, trust and enthusiasm of Michael Bock, Gert Straub and everyone at Mercedes-Benz Classic who gave up a large part of their weekend for this test, none of the above would have been possible. Thank you all.

The man behind the landmark
Uhlenhaut’s coupé is recognised as a paragon of German engineering, but its architect was born within the London suburbs

Rudolf Uhlenhaut was born in Highgate, north London to an English mother and a German father. His life’s work at Mercedes began in 1931 but it wasn’t until 1936 that, still not quite 30 years old, he took over the racing department.

He soon worked out that the reason Mercedes’s W25 Grand Prix car was being eclipsed by Auto Union was that the team had engineers who couldn’t drive and drivers who weren’t engineers and were therefore unable to explain what was wrong. But Uhlenhaut was gifted in both spheres and soon discovered the W25’s structure was too weak and its damping too firm, creating an unstable platform for the needlessly stiff suspension to work upon, unintentionally making the chassis frame the primary springing medium.

He channelled what he knew into the 1937 W125 and from that moment until war intervened three seasons later, Mercedes was the dominant force in Grand Prix racing. At the cessation of hostilities Uhlenhaut took over the testing of road cars, but Mercedes turned to him one more when it elected to go racing again in 1952. The W194 prototype that won the Carrera Panamericana and at Le Mans that year was a triumph for an impoverished company and, when productionised with gullwing doors as the 1954 300SL, it became a landmark of road car design, too.

In tandem with his road car commitments, Uhlenhaut also designed the W196 F1 car, the 300SLR sports car and, of course, the coupé that would come to bear his name. Nor had his driving skills deserted him over time: at one test session with the W196 at the Nürburgring in 1955, Fangio came in complaining about the car’s set-up. So after a lunch Mercedes described as “substantial”, Uhlenhaut – at 49, five years Fangio’s senior - jumped into the F1 car still wearing his jacket and tie, lapped three seconds faster, came back and told the world champion there was nothing wrong with the car a little practice wouldn’t fix.

When it became clear his beloved coupés would be denied the racing career they deserved, he turned them into road cars, driving one from Stuttgart to Sweden so his drivers could try it out in practice for the Swedish Grand Prix. All sorts of stories exist about his exploits in the car, some apocryphal, others possibly not, but it is generally accepted that everyone knew Herr Uhlenhaut was on his way to work long before he actually arrived at the factory.

After Mercedes’ retirement from racing at the end of 1955, Uhlenhaut returned to road car design and was responsible for all Mercedes’ output, including the Pagoda SL and the game-changing S-class before retiring, a little deaf, in 1972.

He died in Munich in 1989, aged 82.