The brilliant, rare Mercedes-Benz 300SL Lightweight

By Charlie Calderwood

| 11 Nov 2025

Classic & Sports Car – Mercedes-Benz 300SL Lightweight: back to the start

Although it was a roadgoing, productionised version of Rudolf Uhlenhaut’s W194 sports-racers, the 300 Super Leicht Gullwing as we know it lost some of its eponymous lightness as it transitioned into what many consider to be the world’s first supercar.

In order to achieve further racing success, however, Mercedes-Benz chief of engineering Fritz Nallinger then had an idea to shave off some pounds: producing a short run of aluminium-bodied road cars.

Only 29 would be built, and the example you see here was the very first.

The aluminium-bodied Mercedes-Benz was listed as ‘300SL Lightweight’ on English-language invoices, making it the ‘Super Light Lightweight’

There was some irony in this. The corporate pivot towards Formula One in 1953 had led to Uhlenhaut’s improved, aluminium-bodied 300SL racer, known as ‘Hobel’, turning into 1954’s steel-bodied road car, the W198 – and now Nallinger was switching it back again.

The standard car already used aluminium door, bonnet and boot panels to bring its weight down to 1225kg.

That made it slightly lighter than a Chevrolet Corvette or Ferrari 250 Europa, but far heavier than the 250GT Berlinetta, Aston Martin DB3S and Maserati A6GCS it would more likely meet on a circuit.

The Mercedes-Benz 300SL Lightweight’s roof vents draw heat from the cabin

From the spring of 1955, buyers could specify aluminium and save 85kg over its steel-bodied counterpart, further helped by Plexiglas for all but the windscreen, for the sum of DM5000.

That premium was the equivalent of about £430, or the price of a new Morris Minor Traveller.

All of the 29 alloy-bodied 300SLs were sold to private individuals as Mercedes-Benz stepped out of circuit racing after the 1955 season.

Most customers were privateer racers who could be expected to achieve some success for the model, including John von Neumann, Rob Walker and Briggs Cunningham, but some were simply sold to those willing to stump up the cash.

The uprated Mercedes-Benz 300SL feels more composed than the standard car

Carl Kiekhaefer was, as you would hope for the first recipient of the ultimate version of such an icon, in the former category.

Kiekhaefer, the industrialist behind the Wisconsin outboard-motor giant Mercury Marine, didn’t limit his motive interests to the water: he was a car nut, too.

He had founded his own NASCAR team for the 1955 season in order to promote his outboards, mopping up two consecutive championships straight away and bringing a new level of professionalism to the sport.

The first to use uniformed overalls and covered trailers, and flush with brand-new equipment, it isn’t hard to imagine why the Yankee interloper proved unpopular with the overwhelmingly southern-state – and at that point quite amateur – NASCAR establishment.

The NASCAR influence is clear on this Mercedes-Benz 300SL Lightweight’s doors

You only have to look at this Merc’s ‘300SL’ side lettering to see the NASCAR connection.

In period it wore these painted-on digits alongside Mercury Outboard livery, just like one of Kiekhaefer’s Chrysler 300s.

Its only confirmed race was the 1955 Raleigh Speedway 100-mile run, an event that accompanied the NASCAR fixture on the long-since-demolished, paperclip-shaped track in North Carolina.

Kiekhaefer’s soon-to-be-championship-winning driver Tim Flock drove to victory in the Mercedes, averaging 78.2mph ahead of Ford Thunderbirds and Chevrolet Corvettes.

There are few visual giveaways to separate the one-of-29 Mercedes-Benz 300SL Lightweight from its steel-bodied sibling

Afterwards, he said he had found it such a serene experience that he’d turned on the radio for part of the race.

He wasn’t up against the Aston Martins, Maseratis or Ferraris the alloy-bodied 300SL had been built to beat, but it would have been satisfying for Flock nonetheless, especially given that his brother and fellow Kiekhaefer driver Fonty beat him to the line in the NASCAR race that weekend.

Any trace of further races, if they did happen, have been lost.

Kiekhaefer appears to have fallen for the car as a personal possession rather than a throwaway racing car, despite the fact that he also owned a steel-bodied 300SL.

The Mercedes-Benz 300SL Lightweight’s rich red leather was optional from new

He was photographed in it with his children, and on his passing he gave it to his son, Fred, who eventually sold it to the Brooks Stevens Automotive Museum in Milwaukee.

Later it was bought by Samuel Robson Walton of the Walmart family, and was subjected to extensive restoration from 1996-2004.

In 2006 it came to its present keeper, Friedhelm Loh, who was then one of the world’s great Mercedes-Benz collectors but has since broadened his tastes to all marques.

Much of his collection, including the 300SL, is now on display at the Nationales Automuseum near Frankfurt, Germany.

Deep bucket seats in the Mercedes-Benz 300SL Lightweight’s cabin

Other alloy Gullwings had more extensive racing careers: Alberico Cacciari competed on the Mille Miglia in 1956 and ’57 in his, for example, but it didn’t take long for the 300SL body-material pendulum to swing in the other direction.

Without the strength of a steel body bracing the tubular chassis, the alloy cars were susceptible to such flexing that the shells are known to pull themselves off their mounting points under hard driving.

Mercedes stopped making them after just one year.

Even by August 1955, three months after Kiekhaefer took delivery of his aluminium-bodied car in Chicago, the company’s four works rally cars, the Sportabteilung 300SLs, would be built with steel bodies.

The Mercedes-Benz 300SL Lightweight’s slant-six engine makes 237bhp

Uhlenhaut and racing manager Alfred Neubauer agreed that the stronger shells were better suited to challenges such as the Tour de France Automobile and Liège Rally.

In short, then, it didn’t really work.

But the exoticism of the alloy-bodied SLs doesn’t end with their thin, easily dented panels: they boast plenty of other special equipment.

Under the bonnet is where the really groundbreaking innovation is to be found on any 300SL, and here the car’s fuel-injected 2996cc straight-six is enlivened even further by a sondertiele (special parts) camshaft and increased compression ratio to provide an extra 15bhp.

‘The lower, firmer and lighter Mercedes-Benz 300SL gets around the flowing bends in the foothills of the Rothaar Mountains with rare composure’

That was, impressively, enough to put the output of the Merc’s sturdy single-camshaft motor level with a Ferrari 250GT Berlinetta’s lively V12 of the same capacity.

Front drums with enlarged cooling fins attempted to correct the tendency of all mid-’50s Silver Arrows to struggle with brake fade, while stiffer dampers and springs promised greater cornering abilities and a reining-in of the snappy characteristics of the swing-axle rear.

Each car was supplied with two sets of rear-axle ratios, one to standard and the second to the purchaser’s spec.

Kiekhaefer also paid the extra $350 (£125) for Rudge wheels – an option on all 300SLs, still built out of steel but featuring centre-lock, knock-off hubs.

The Mercedes-Benz 300SL Lightweight’s knock-off Rudge wheels were a cost option

Approaching the prospect of driving the Kiekhaefer Mercedes-Benz 300SL, I’ve deliberately blinkered myself to the question of how much the car may be worth.

I later learn that an alloy-bodied 300SL in need of restoration sold at the RM Sotheby’s Rudi Klein Collection sale in Los Angeles for $9,355,000 in October 2024.

That fact as yet undiscovered, however, I open the iconic Gullwing door and thread myself in.

It’s hard to get aboard thanks to the wide sills, but I don’t feel the need to tip the steering wheel on its quirky release mechanism.

The Mercedes’ two-spoke steering wheel hinges down to aid ingress

Later in our photoshoot, photographer Max looks at me in horror as if I’ve broken the car when I pull the chromed lever that unlocks the steering wheel and it falls downwards on its hinge.

Not the first time such a prank has been played on an unsuspecting 300SL passenger, I’m sure.

Kiekhaefer’s selections of red leather and bright white paint were, again, choices for which he paid extra – extensive and overpriced options lists on exotic cars are nothing new.

Worth it, though: the contrasting colours are jubilant in the sunlight, and so characteristic of the mid-’50s.

The Mercedes-Benz 300SL Lightweight’s passenger-side bonnet bulge is to dodge the engine’s distinctive inlet manifold, the other is for symmetry

A small, rubber-covered piece of chassis tubing can be seen next to the driver’s left leg, diving from under the dash to the high sill.

It was a useful aid to salesmen, who could point to a visual confirmation of both the car’s spaceframe construction and the reasoning for its inconvenient access.

Once the door is closed, covering the huge door jambs, the interior is perfectly pleasant if pretty similar to that of any other contemporary Mercedes.

There’s a twin-dial binnacle and lots of lovely chrome, but some lingering 1950s austerity in the carpeted transmission tunnel, accordion-style rubber gearlever gaiter and a handbrake lever made of a simple steel tube with a button in the end.

The Mercedes-Benz 300SL Lightweight’s doors open using chromed struts

Other than a slightly tight pedalbox, where the throttle is almost tucked behind the brake, it’s comfortable once you’ve negotiated that awkward entrance.

It’s the view out of the Mercedes 300SL that’s unusual. You can see the lower half of the door bulging out from under the window in your peripheral vision, while the front wings extend much wider than the windscreen.

Contemporaries commented that it looked like a UFO on the road from the outside, and it certainly gives that impression from behind the wheel.

It’s a spaceship, but a 1950s spaceship with red leather and bevelled chrome on the dash.

‘An aluminium body saved 85kg over its steel counterpart, further helped by Plexiglas for all but the windscreen’

Your first few gentle miles in this Mercedes-Benz reveal a remarkably ‘normal’ car to drive.

It rattles and shakes over bumps more than a contemporary 300 Adenauer, but it otherwise feels like a torquey, sensible saloon around town, with a civilised idle and synchromesh on all of its gears.

That low-speed refinement, in the face of the performance you know the car is capable of, really sets the 300SL apart from its contemporaries from Modena.

It’s towards the faster end of the Gullwing’s capabilities where this alloy-bodied 300SL’s special talents lie, however.

The alloy-bodied Mercedes-Benz 300SL enhances the feeling of relentless acceleration

Although surely slightly quicker from 0-60mph than the 8.8 secs of a standard steel car, it’s not the ferocity of the acceleration that impresses particularly, but its persistence.

Mercedes’ ‘six’ just keeps pulling, even at higher speeds, in a brilliantly linear, unfussed way.

It’s so far from the drama of a Colombo V12 – that’s not to say the Merc doesn’t make a nice noise, because it does, but it’s the ease of speed that feels so beyond its 1955 vintage.

Mercedes-Benz ditched the aluminium-bodied 300SL Lightweight after just one year

This car, though, is at its most special in the corners.

Being lower, firmer and lighter, it gets through the flowing bends in the foothills of the Rothaar Mountains with a rare composure.

Only once do I detect a slight tuck from that swing-axle rear, which can make the normal Mercedes 300SL prickly to drive.

A more committed pilot on a track could draw out that behaviour, but this car simply resists it that much further.

The Mercedes-Benz 300SL Lightweight’s badge doesn’t betray its racy spec

The unusually thick-rimmed plastic steering wheel is remarkably free from interference and judder, while the gearshift is uncommonly easy for a car of this age and performance.

The lightweight coachwork of the 29 aluminium Mercedes-Benz 300SLs might have proved to be a blind alley, but perhaps the headline-grabbing bodyshell is something of a red herring when understanding the significance of these rare Gullwings.

The best parts of this privateer package are actually its tuned engine, stiffer suspension and upgraded front brakes.

‘An extra 15bhp levelled the output of the Mercedes-Benz 300SL’s sturdy single-camshaft motor with a Ferrari 250GT Berlinetta’s lively V12’

Mostly these were bits taken from the W194 300SL race cars and the Hobel prototype, but here they were as a package on a road car that customers could actually buy.

The four steel-bodied works Mercedes-Benz 300SL rally cars – with which Stirling Moss won the Tour de France Automobile, among other honours – all followed an almost identical specification, such was the efficacy of these special parts.

So, does this car represent the ultimate version of the W198 Gullwing?

Yes, but the alloy body that identifies it might just be the least important part.

Images: Max Edleston

Thanks to: Nationales Automuseum, The Loh Collection

Factfile

Mercedes-Benz 300SL Lightweight

Sold/number built 1955-’56/29
Construction tubular steel spaceframe chassis, aluminium body
Engine iron-block, alloy-head, sohc 2996cc 45° slant-six, Bosch mechanical fuel injection
Max power 237bhp @ 6100rpm
Max torque 217lb ft @ 4800rpm
Transmission four-speed manual, RWD
Suspension independent, at front by double wishbones, anti-roll bar rear swing axles; coil springs, telescopic dampers f/r
Steering recirculating ball
Brakes Alfin drums, with servo
Length 15ft (4572mm)
Width 5ft 10½in (1791mm)
Height 4ft 3¼in (1302mm)
Wheelbase 7ft 10½in (2400mm)
Weight 2500lb (1134kg)
Mpg 21
0-60mph 8.8 secs (standard 300SL)
Top speed 155mph (depending on axle ratio)
Price new £3075
Price now £5-10m*