Guide: Mercedes-Benz W196S 300 SLR
Background
Mercedes-Benz returned to motor racing in 1952 with the W194 300 SL. This three-litre sports racing car proved an enormous success and won four of the five races it contested to include the Le Mans 24 Hours and Carrera Panamericana. Only the Mille Miglia (where the W194s placed second and fourth) failed to yield victory.
Mercedes had chosen to re-enter sports car racing because Formula 1 was organised to Formula 2 regulations at the time and the two-litre unsupercharged engine limit did not meet the firm’s technical aspirations.
However, it was announced ahead of time that, for 1954, proper Formula 1 regulations were to be reinstated with a 2.5-litre unsupercharged engine limit.
With this in mind, Mercedes-Benz abandoned any notion of a 1953 competition programme with the W194 300 SL and focused their attention on developing a suitable F1 challenger.
The resultant W196 arrived at the 1954 French Grand Prix.
Following his switch from Maserati, Mercedes driver, Juan Manuel Fangio, won four of the remaining six F1 races with a W196.
1955 would see Mercedes expand their motor sport activities to include an attack on the World Sportscar Championship. The six-round contest comprised events in Argentina, the USA, France, Great Britain and a brace of road races in Italy.
Mercedes would participate from round three onwards taking in the Mille Miglia, Le Mans 24 Hours, Dundrod Tourist Trophy and Targa Florio. Outside of the championship, they would also compete in the domestic Nurburgring Eifelrennen and the Swedish Grand Prix.
Competition for the new W196S 300 SLR was expected to be fierce. In addition to Scuderia Ferrari, Mercedes would be up against works teams from Jaguar, Maserati and Aston Martin.
For the task, Mercedes essentially created a Formula 1 car with two-seat fully enveloped bodywork.
Engine / Gearbox
Compared to the Grand Prix racer, the 300 SLR received an enlarged engine as, unlike F1, the World Sportscar Championship did not impose any limit on displacement.
The resultant Type M196S straight six was a long stroke version of the F1 powerplant.
By extending the stroke from 68.8mm to 78mm (which matched the bore dimensions) capacity rose from 2496cc to 2982cc.
As the sports car engine would have to run for considerably longer than the F1 variant, compression was dropped from 12.0:1 to 9.0:1.
To reduce crank flexing, power take-off was from the centre of the engine via a gear rather than the end of the crankshaft.
Otherwise, the two motors were largely similar.
The engine block was formed from Silumin lightweight alloy as was the twin cam head with its desmodromic valve gear.
Ignition was via two spark plugs per cylinder and a pair of high voltage Bosch magnetos. Bosch also supplied the mechanical fuel-injection system.
Other equipment included a ten roller bearing crankshaft and dry-sump lubrication.
The engine was front longitudinally mounted and canted at 53° to the right.
As opposed to special methanol-based racing fuel used by the F1 car, the 300 SLR ran on 65% low lead and 35% benzene.
Whereas the smaller, more highly stressed F1 engine produced 290bhp at 8500rpm, the 300 SLR developed 310bhp at 7400rpm. Its torque rating was 235lb-ft at 5950rpm.
Transmission was via a five-speed gearbox with dry single-plate clutch mounted in unit with the differential behind the rear axle.
Chassis
The chassis was a welded aluminium tubular spaceframe.
Compared to the W196 F1 car, it had modified two abreast seating and a wheelbase extended from 2210mm to 2370mm. Rear track was widened by 22mm.
Front suspension was via double wishbones and torsion bars. At the rear was a single-joint swing axle with longitudinal torsion bars. Telescopic shocks were fitted all round.
The drum brakes had a 350mm diameter at the front and 275mm diameter at the rear. Each axle ran off its own hydraulic system. As the drums were too large to fit within the SLR’s 16-inch diameter wheels, they were mounted inboard at either end.
The wire wheels were 6 and 7-inches wide front to rear.
A 155-litre fuel tank was installed behind the back axle.
Bodywork
With its flowing lines, perfect proportions and elegant details, the 300 SLR was arguably the most handsome sports racing car of its era.
The bodywork was fashioned from ultra-light Elektron magnesium alloy.
The primary intake was flanked by shapely front fenders with covered headlights. A secondary duct was carved from the enormous front hood.
Two large vents were located down each flank. On the passenger side, these were used as exit points for the megaphone exhausts.
As per the regulations, the 300 SLR came with full complement of lighting and also carried a spare wheel.
At the back of the car was an aerodynamically formed head rest, a duplicate of which could be added if a navigator was present. Should a navigator not be required, a rigid body coloured tonneau was usually fixed in place above the passenger seat.
Interior
Bucket seats were trimmed with tartan fabric centres and blue vinyl bolsters to match the sills.
The drilled metal dash was body coloured. It housed a detachable three or four-spoke wood-rimmed steering wheel and gauges for engine speed, oil pressure and water temperature.
All nine 300 SLRs were left-hand drive with a centrally located open-gate gearchange.
Weight / Performance
Weight was a quoted 900kg.
With a power-to-weight-ratio approaching 350bhp per ton, the SLR could top 180mph and sprint from 0-62mph in under five seconds.
Testing
Testing began in secret in late 1954.
The new car was then publicly spotted in early April 1955 as Mercedes conducted a series of tests on Italian soil to prepare for the Mille Miglia.
Stirling Moss and Karl Kling did most of the driving; they dished out severe punishment to the various 220, 300 SL and 300 SLR training cars.
In one famous incident, Moss wrecked a 300 SL Gullwing when he collided with a lorry containing unexploded bombs. Meanwhile, Kling racked up an astonishing 30,000 miles as the entire loop from Brescia to Rome and back was covered on every training run.
1955 Mille Miglia
For the 1955 Mille Miglia (which took place over April 30th and May 1st), new rules permitted drivers without navigators.
Four SLRs were entered. Juan Manuel Fangio drove solo as did Karl Kling. Stirling Moss was joined by Denis Jenkinson and Hans Herrmann was navigated by Hermann Eger.
There was also a works Gullwing for John Fitch and Kurt Gesell in the GT category.
The SLRs carried two spare wheels in the trunk and large enough fuel tanks that they would only have to refuel at Pescara. This would keep the weight down for the vital section over the Abruzzi mountains.
Unusually, the weather was sunny all the way.
Driving the sole 4.4-litre Ferrari, Eugenio Castellotti set an extremely fast pace from the off. He averaged 119mph over the opening 188 mile stage to Ravenna, but his forceful driving proved too much for the 121 LM and his engine expired near Ancona.
The lead then briefly passed to Moss, but at the next control, the Ferrari 118 LM of Piero Taruffi headed the field.
Taruffi had established a 15 second margin after Moss ran off course through a detour near Pescara that had not been used in practice. The Englishman smashed through some straw bales and into a shallow ditch, but reversed out with only superficial damage.
Undeterred, by Rome, Moss had taken command and held a near two-minute lead which was further extended at Viterbo when Taruffi was forced out with engine damage caused by an oil pump failure.
Shortly before the Rome checkpoint, both Herrmann and Kling had retired in separate incidents. Herrmann (who had been lying second at one stage) was forced out with mechanical trouble. Kling hit a tree and broke three ribs after trying to avoid some errant spectators.
By this time, Fangio’s SLR was suffering intermittent fuel-injection trouble. However, even if his car had been running smoothly, it was doubtful he could have matched the speed of Moss and Jenkinson.
Fangio later lost more time changing a fuel line and eventually finished second, some 22 minutes behind Moss who broke almost every available record. Third place went to the works Ferrari 118 LM of Umberto Maglioli and Luciano Monteferrario that finished 13 minutes behind Fangio.
Mercedes also won the GT category with Fitch and Gesell taking fifth.
SLR Coupe
After the Mille Miglia, Mercedes began to develop an SLR Coupe for use in long-distance races.
Expected to be ready some time in August, chief engineer, Rudolf Uhlenhaut, ordered a pair of the new cars and planned to race them at the end-of-season Carrera Panamericana.
1955 Nurburgring Eifelrennen
In late May, Mercedes took a trio of SLRs to the Nurburgring for the annual Eifelrennen which, at the time, was Germany’s biggest sports car race.
The 228km event was round two of the German Sportscar Championship and attracted 28 high quality entries for ten laps of the infamous Nordschleife.
Fangio, Moss and Kling each had an SLR.
Their main opposition was a pair of Ecurie Ecosse Jaguar D-types, a works Ferrari 118 LM and a further four privateer Ferrari sports cars with drivers of varying quality. The junior class was dominated by Porsche 550s with the odd small displacement Maserati and OSCA also in attendance.
Both the D-types crashed in practice: Desmond Titterington was hospitalised with a broken nose while Jimmy Stewart’s car was hurriedly repaired but then retired on the opening lap of the race.
By contrast, the SLRs streaked away at the start and proved unbeatable.
Moss set the fastest lap on his fifth tour (breaking Lang’s 1952 record with a W194 SL).
By half distance, the trio of silver cars led Giuseppe Farina’s works Ferrari by three minutes.
Third place Kling’s SLR developed valve gear trouble on lap eight. He was overtaken by Masten Gregory’s Ferrari 750 Monza which had passed Farina to inherit the final podium spot.
As per team orders, Moss allowed Fangio to take the lead late on and the Argentine won by a tenth of a second.
1955 Le Mans 24 Hours
Two weeks later, Mercedes were present for the Le Mans 24 Hours, a race they had fortuitously won with the W194 in 1952.
For 1955, there were several works teams capable of taking outright victory.
Expecting one of the greatest battles ever, an estimated 400,000 spectators showed up to watch.
Unlike previous years, the organisers only allowed open cockpit cars to participate.
Mercedes created a sensation by adding air brakes designed to reduce wear on the rear brakes and tyres. The air brake consisted of a hinged flap operated by hydraulic rams controlled from a lever on the dash. It automatically lowered again when second gear was subsequently engaged. All three cars were equipped as such.
Fangio and Moss shared one of the cars, Kling was co-driven by Andre Simon and John Fitch was joined by Pierre Levegh.
During practice, Moss had a slight collision with the DB HBR of Claude Storez which caused Maserati’s Jean Behra (who was standing in the pits at the time) to be thrown against the counter and require hospital treatment.
Eugenio Castellotti’s Ferrari 735 LM was routinely a second quicker than next best Moss who had been fastest through the Mulsanne speed trap at 181mph. However, the Jaguars had been lifting off to keep their powder dry for the race.
Fangio initially made a poor start as his trouser leg snagged on the gear lever. At the end of lap one, he was 14th. Meanwhile, Castellotti led, Levegh was seventh and Kling was twelfth.
With one hour gone, Fangio had moved up to third, Kling was sixth and Levegh was seventh.
On lap 16, Hawthorn’s Jaguar took the lead and Fangio moved into second, just one second behind. The pair thereafter exchanged the lead several times setting a pace Castelotti’s Ferrari simply could not match.
After two hours racing, the top six was Hawthorn, Fangio, Castellotti, Maglioli, Kling and Levegh.
Half an hour later, tragedy occurred.
Heading down the pit straight, Hawthorn pulled to the right-hand side of the track and started to brake for his stop in front of Austin-Healey driver, Lance Macklin. Macklin swerved out from behind the slowing Jaguar straight into the path of Levegh’s SLR.
Levegh ploughed into the back of Macklin’s car which acted as a ramp and launched the Mercedes into the air.
The SLR skipped over a protective earth bank at 125mph and barrel rolled into the crowd.
Levegh was thrown from the car and fatally fractured his skull.
83 spectators were killed in what remains motor racing’s most catastrophic crash.
A shocked Hawthorn handed over the lead Jaguar to Ivor Bueb while Fangio and Kling both stopped for Moss and Simon to take over.
The Mercedes crew considered withdrawing, but with the death toll still unknown, they decided to consult the directors at Stuttgart. This proved difficult as, owing to the terrible accident, all telephone lines were down.
The organisers themselves decided that nothing would be gained by stopping the race.
Following the disaster, Moss went into the lead followed closely by Bueb, both of whom were a lap clear of the third place Castellotti / Marzotto Ferrari which retired shortly before 8pm.
After six hours of racing, Fangio / Moss led the works D-types of Hawthorn / Bueb, Rolt / Hamilton and Beumann / Dewis. Kling / Simon were fifth in the other Mercedes.
By midnight, the Fangio / Moss SLR had a two lap lead over the second place Jaguar, but at 1:45am, the order came for Mercedes to withdraw while in first and third positions.
This left the Hawthorn / Bueb Jaguar with a five lap lead which it retained until the end. Peter Collins and Paul Frere finished second in a works Aston Martin DB3S followed by the Ecurie Francorchamps D-type of Jacques Swaters and Johnny Claes.
Post Le Mans
Following the Le Mans disaster, a whole raft of events were cancelled to include the notoriously dangerous Carrera Panamericana.
Mercedes decided they would abandon motor sport at the end of the 1955 season.
1955 Swedish GP, Rabelov
The first of the new SLR Coupes was present as a spare car for the Swedish Grand Prix on August 7th. It had been built on the chassis used by Moss and Fangio at Le Mans.
The event comprised 32 laps of the new four mile Rabelov circuit at Kristianstad which had been constructed under the enthusiastic direction of the Royal Swedish Auto Club in just a few short months.
A crowd of 75,000 showed up to watch Mercedes take on factory teams from Ferrari, Maserati and Aston Martin.
However, the small but high quality grid was further reduced as Paul Frere (Ecurie Francorchamps), Mike Hawthorn (Scuderia Ferrari) and Peter Collins (Aston Martin) failed to make it through practice for one reason or another.
Bumps on the long main straight caused several cars to become airborne, particularly the two SLRs present for Moss and Fangio which were attaining very high speeds.
Moss set the pole time on Saturday, just before the rain started. Fangio was second on the grid followed by Castellotti (Ferrari 121 LM), Salvadori (Aston Martin DB3S) and Behra (Maserati 300 S).
Moss shot away after the Le Mans-type start and led for the first lap followed by Behra and Castellotti.
On lap two, Moss relinquished the lead to Fangio and, by lap four, the two SLRs were nearly 20 seconds clear.
The rest of the race was a demonstration of high speed reliability with Moss invariably a yard or so behind Fangio in his customary role as shadow to the F1 world champion.
Castellotti eventually finished third, some 90 seconds behind the two Mercedes.
1955 Dundrod Tourist Trophy
Two rounds of the 1955 World Sportscar Championship still remained. Mercedes’ next engagement was at the penultimate event: the Dundrod Tourist Trophy in Northern Ireland.
Held on September 18th over 84 laps of a gruelling 12km road course on the outskirts of Belfast, Mercedes took three race cars and a brace of spares including the SLR Coupe that had appeared in Sweden.
Moss would share one car with Fitch, Fangio was in another with Kling and the third was entered for Wolfgang von Trips and Andre Simon.
Opposition came from the Aston Martin, Maserati, Ferrari and Jaguar factory squads. However, the SLRs were in imperious form with Moss and Fangio fastest in practice.
The event began with a Le Mans-type start at 10:30am.
Moss initially slotted into third behind the D-types of Bob Berry and Mike Hawthorn, but hurtled past them both before Jordan’s Cross.
At the end of lap one, Moss led from Hawthorn, Berry, von Trips and the Aston Martin DB3S of Peter Walker. Jean Behra’s works Maserati 300 S and Fangio followed close behind.
Shortly after the second lap began, there was a seven car pile up at Cochranstown that cost the lives of British drivers Jim Mayers and Bill Smith.
Henri de Barry’s 300 SL Gullwing was leading Ken Wharton’s Frazer Nash when, on the approach to Deer’s Leap, Wharton tried to pass the painfully slow Mercedes but decided to abort before the blind hump and fell back.
Jim Mayers’ Cooper T39 had to take evasive action and hit the left-hand side of the road at around 100mph. Mayers’ car struck several concrete pillars on the opposite side of the road and disintegrated.
Debris was strewn everywhere, including the fuel tank which burst into flames. Mayers was still in the front part of the car as it was catapulted through the air and was killed when he was hit by Bill Smith’s Connaught AL/SR which landed among the wreckage and was also set ablaze.
By the time the medics arrived, it was too late for both Mayers and Smith.
Several other drivers caught up in the accident suffered burns to their faces and hands.
As ever, the race carried on.
Moss continued to build his lead as Fangio steadily rose up the leaderboard to third behind Hawthorn’s Jaguar.
On lap eight, Moss clouted the bank at Quarry, but his speed was unaffected.
The lead cars variously pitted between laps 25 and 30.
Moss was the last to stop for Fitch to take over. One of his rear tyres was in ribbons and part of the rear wing had to be removed which involved the use of several mechanics. This allowed Hawthorn’s co-driver, Desmond Titterington, into the lead. Fitch emerged in second followed by Kling, Collins and von Trips.
Fitch came in to hand the SLR back to Moss at 1:30pm, by which time the Jaguar had a lead of over two minutes.
Soon, another tragedy unfolded when Richard Mainwaring was fatally injured when his Elva Mk1 crashed at Tornagrough. The car turned over and caught fire with the unfortunate Mainwaring trapped inside.
With 50 laps gone, Moss was still over two minutes behind the lead Jaguar when Titterington entered the pits to hand back to Hawthorn.
Three laps later, the Jaguar’s lead had been cut to just a couple of seconds and, on lap 56, the SLR went ahead.
Meanwhile, Kling had handed his SLR back to Fangio and the Argentine was third, some 80 seconds behind the Jaguar.
Moss made a surprise stop on lap 61 for fresh rear tyres and some extra fuel which enabled Hawthorn to flash by just as the SLR restarted its engine.
Moss closed the nine second gap within one lap and re-took the lead which he held until the end.
As Moss crossed the finish line, Hawthorn (who was by now nearly three minutes behind) had everything lock solid at Quarry which forced the Jaguar into a spin. Unable to get the car going again, Hawthorn’s misfortune promoted Fangio to second and Kling (who had joined the SLR of von Trips and Simon) to third.
1955 Targa Florio
The final round of the 1955 World Sportscar Championship took place at the Targa Florio on October 16th with everything still to play for.
Ferrari led with 19 points, Mercedes and Jaguar were level on 16 points and Maserati were fourth on 13 points.
Both Maserati and Ferrari would have to drop a couple of points if they did well in Sicily as only a manufacturer’s best four results counted.
Jaguar would certainly not win the title as they didn’t attend.
Mercedes took three SLR race cars and two spares including the previously seen SLR Coupe. Ferrari also ran a three car team that included an 860 Monza and two 750 Monzas. Maserati had no less than six works cars on hand, most though were under two-litres.
The 936km event comprised 13 laps of the 72km Little Madonie circuit. The first car set off at 7am and the rest followed at 30 second intervals thereafter.
Moss was partnered by Peter Collins, Fangio with Kling and Desmond Titterington joined Fitch in the third SLR.
Moss set a record pace on the first lap; he passed 16 cars to establish a one minute 15 second lead over second placed Castellotti’s Ferrari 860 Monza. Fangio was a further 50 seconds down the road followed by Luigi Musso’s Maserati 300 S. Titterington was fifth.
Moss set another record on lap two, but had a lucky escape the next time round when he slid on some mud, hit a wall and then flew over a three foot bank into a field. After a dozen attempts to clear the bank, Moss managed to drive back onto the circuit. Collins then took over the battered car once the mechanics had given it a once over. The entire episode cost twelve minutes.
Meanwhile, Robert Manzon took over from Castellotti in the now lead Ferrari. Fangio handed the second place SLR to Kling on lap four shortly before Titterington swapped with Fitch.
The hard-charging Collins closed in on the leaders despite also clouting a wall and further mangling the Mercedes.
Fitch reshaped the back end of his SLR when he slid into a wall which forced the bootlid open.
With seven laps gone, Collins had miraculously re-taken the lead from Manzon’s Ferrari and handed the SLR back to Moss. Castellotti took over from Manzon with a 90 second gap to Moss, but the points for second would be enough to secure Ferrari the World Championship. The 860 Monza was a comfortable two minutes ahead of third place Fangio with Fitch running fourth.
However, in a dreadful tactical error, Ferrari were forced to bring Castellotti into the pits as he had already covered the maximum six laps permitted to any one driver.
This promoted the Fangio / Kling SLR to second and handed Mercedes the championship by 24 points to Ferrari’s 22.
Moss and Collins eventually won by an incredible four minutes and 41 seconds despite their earlier twelve minute delay for repairs. Titterington and Fitch placed fourth.
As expected, Mercedes withdrew from motor sport at the end of the 1955 season.
Text copyright: Supercar Nostalgia
Photo copyright: Mercedes-Benz - https://www.mercedes-benz.com
