This revolutionary Mercedes changed the racing world in 1932

Much to the disappointment of its star driver, Rudolf Caracciola, Mercedes-Benz announced that it was getting out of motor racing. The year was 1931, and the financial crash of ’29 was still having a worldwide effect on sales.

The timing interrupting Caracciola’s meteoric career couldn’t have been worse. He’d just won the tortuous Mille Miglia in Italy driving one of the factory’s four specially constructed lightweight SSKLs. It had been a momentous victory over the full might of the works Alfa Romeo team–the first such win, in fact, for a non-Italian.

That success had brought international prestige to both Caracciola and Mercedes. Even though he’d been teamed with Wilhelm Sebastian as co-driver, Caracciola had driven the entire 1000 miles solo, setting a record that stood until 1955, when Stirling Moss and Denis Jenkinson finally returned to again win for Mercedes in a 300 SLR.

And then, to top off the ’31 season, Caracciola also claimed victory for Mercedes at the International Avusrennen on the fastest track in Europe, a unique pair of side-by-side, 6-mile straights near Berlin known as the Avus circuit.

Importance of Aero

Originally conceived in 1921 as a high-speed test track for Germany’s burgeoning auto industry, Avus eventually became part of Germany’s first autobahn, connecting the cities of Berlin and Darmstadt. In time, the Avusrennen event gained international attention because it consistently attracted Europe’s fastest cars and drivers seeking record speeds.

Caracciola planned on winning again at Avus in 1932, but without factory support, he realized that Italian rival Alfa Romeo’s latest masterpiece, the 8C 2300 Monza, offered his best chance of collecting the event’s recently announced prize of 7000 reichsmarks. Caracciola was torn by loyalty to Mercedes and Germany, but an almost certain victory driving one of the fast red Monzas was simply too powerful an aphrodisiac to resist.

He conferred quietly with his friend and technical mentor Alfred Neubauer, Mercedes’ towering on-track presence and unquestioned director of the firm’s motorsports activities. Both were acutely aware that Caracciola’s mount for the previous year’s win, even with the extra power of a recently added supercharger, was a design already more than 4 years old and at the end of its impressive reign of superiority.

Rudolf Caracciola–center in the top photo and, above, driving to the 1931 Mille Miglia win–faced a big question for 1932: What to drive next? Photography Courtesy Mercedes-Benz AG

The two agreed that the newer supercharged Alfa, despite lacking some 4.8 liters of engine displacement compared to the SSKL’s 7.1, still had the advantage. Its smaller frontal area was more suited to Avus’ long straights, while its lighter weight and superior brakes could also be expected to perform better on entry to the circuit’s two broad, constant-radius connecting turns.

Winning was a priority for Germany. Caracciola and Neubauer were realists and could sense that a major political change within the country would soon help refinance Mercedes’ return to dominance in international competition. Until then, though, they both agreed that having Caracciola win for Germany in the Alfa was better than his running second in the aging Benz. Caracciola reluctantly signed with Alfa Romeo on one condition: that his Monza be painted white, Germany’s national racing color.

Recognizing the promotional value of his status as one of Europe’s preeminent drivers, Alfa management was more than pleased with Caracciola’s highly publicized selection of the Monza for the Avusrennen; it subtly implied the superiority of the Italian design. In a negotiated compromise at the signing of contracts, Alfa’s director of racing agreed to the driver’s terms regarding the white livery but requested that the nose of the Monza be left in Alfa Red to signify its Italian origin.

A Radical Plan

Even with Mercedes officially out of racing, team boss Neubauer still planned to share his sage strategy and timing expertise with Caracciola. He would also offer some limited technical assistance to those privateers still racing for the German marque.

Among those hoping to join Caracciola with a seat on the factory’s team when conditions returned to normal were Hans Stuck and Manfred von Brauchitsch, names not then well recognized but ultimately destined for Grand Prix stardom under Neubauer’s careful tutelage. Both young Germans would be driving works-prepped SSKLs–at least, that’s what Neubauer assumed.

That all changed when von Brauchitsch quietly approached Neubauer with a plan to radically modify his car for the Avus race. He claimed to have a speed secret that would give his car a distinct advantage on Avus’ long straights, and it involved essentially scrapping its body and replacing much of what Neubauer had developed over the past four seasons.

The imperious Mercedes team manager was incensed: Herr Neubauer wasn’t accustomed to having private entrants tell him what might be changed or improved on “his” carefully developed racing cars.

Even at the risk of severing his tenuous relationship and obvious advantage of Neubauer’s patronage and technical support, von Brauchitsch quietly reiterated what Neubauer already knew: that his SSKL actually belonged to von Brauchitsch’s wealthy friend Baron von Zimmermann, who had been sponsoring his career for the past three seasons.

In hopes that Neubauer wouldn’t take the proposed modifications to the baron’s SSKL as a personal affront, von Brauchitsch explained that it was actually the baron who was backing the plan.

Mercedes-Benz might have officially left the sport, but Manfred von Brauchitsch (top, in the coat) and Reinhard von Koenig-Fachsenfeld (middle) had an idea: Fit an aerodynamic body to the brand’s SSKL chassis (above). Photography Courtesy Mercedes-Benz AG

Neubauer’s silent glare only reemphasized his opposition to whatever senseless idea the two idealistic mutineers might have. Then Neubauer learned there were actually three more revolutionaries on von Brauchitsch’s team: the designer, Reinhard von Koenig-Fachsenfeld; the body builder, Walter Vetter; and team mechanic Willy Zimmer.

Von Brauchitsch, from a prominent German military family, had become well acquainted with the racing career of von Fachsenfeld, a young nobleman who was infamous in German racing circles for winning the nation’s top motorcycle championship in 1924 on a bike of British origin.

What’s more, he had done it entirely on his own using self-developed aero concepts, so he was only too familiar with the resistance encountered by technically challenged privateers with unresolved dreams of succeeding against factory support. He’d faced the same reluctance to try something new from the formally trained engineers at the German motorcycle manufacturers he’d first approached.

Initially they wouldn’t even listen to his seemingly radical ideas for improving top speed by reducing resistance to the invisible properties of air. So later, when he began using those same concepts to increase performance and then beating the works teams on his “foreign” bike, they may have been secretly impressed but not exactly pleased.

Earlier in his career, von Fachsenfeld had been influenced by the work of Hungarian aerodynamicist Paul Jaray, who had vastly improved the performance of the German Zeppelins during World WarI. By the late ’20s, Jaray’s groundbreaking work on aerodynamics had influenced the appearance and performance of much in aviation, but his theories had not yet penetrated deeply into the world of automobiles or motorcycles.

Their speeds had not yet matched those of aircraft, but von Fachsenfeld, in addition to being a serious racer, was also a visionary and could sense the coming value of Jaray’s work in motorsport. He continued to work on the subject, developing new ideas on his own.

Von Fachsenfeld used that self-acquired knowledge to build ever-faster bikes for himself as well as for manufacturer NSU, which was then trying to set the world’s speed record on two wheels. Von Fachsenfeld eventually applied for a patent on his proven research, but he was refused the document because he’d not yet graduated from college. Understanding the value and significance of his work, the government instead offered him a position as an assistant to Dr. Wunibald Kamm, the head of FKFS, the government’s advanced research facility in Stuttgart specializing in aerodynamics.

A Striking Unveiling

Von Fachsenfeld was more than familiar with the Avus circuit’s potential for high average speeds, as he had tested there himself. He was certain that his lines for a special aero-friendly body of his own design mated with an SSKL chassis could significantly increase its top speed.

He also realized that Neubauer would more than likely resist any suggestion of change. Still, he had enough confidence in his concept to meet with von Brauchitsch, the baron, and mechanic Willy Zimmer to convince them to adopt his plan to win the race.

The rebodied Benz, quickly christened “the Gherkin” by those at Avus, brought something new to motor racing: aerodynamics. Could it run with traditional machines like René Dreyfus’ Maserati? Photography Courtesy Mercedes-Benz AG

Once certain of von Fachsenfeld’s concept, the team visited coachbuilder Walter Vetter in Cannstatt to see if he could complete von Fachsenfeld’s new panels in time for the race. Vetter explained that the timing was critical but promised to have the new body finished in time for practice.

Vetter completed the body, but there was no time left for paint. Von Brauchitsch and Zimmer drove their radically shaped new racer, finished with a handsome brushed-aluminum surface, on public roads directly to the Avus circuit.

A Fast Favorite

The reactions to the arrival of von Brauchitsch’s new racer can only be imagined, as it was unlike anything ever seen before. Since the unfamiliar form was based on the SSKL’s rather imposing chassis, it was considerably larger than the sleek new Maseratis, Bugattis and Alfa Romeos that made up most of the race entries.

Upon seeing it, everyone seemed to have a different opinion. One take from the general public was soon picked up by the commentators on the track’s public address system: Von Fachsenfeld’s new body shape looked like a pickled cucumber.

So the “Gherkin” moniker was soon part of common conversation in the garage and paddock area as well as in the grandstands. That amusing aspect of the unusual form seemed to cast a favorable light on von Brauchitsch’s racer. He seemed pleased that his new car was attracting so much positive attention and favorably promoting him and von Fachsenfeld as true innovators. As ungainly as its appearance might have been, von Brauchitsch’s gleaming silver Mercedes had fans and competitors seriously discussing its potential.

Still, Neubauer was less than pleased. The car was, in his estimation, unsightly and a visual affront to all that Mercedes traditionally stood for. When first inspecting the car, he immediately came up with several reasons he expected it to fail. He seemed certain the fully enclosed body would limit cooling of critical components, especially the differential and transmission. Mechanic Zimmer listened carefully and made a note to check transmission and rear end temperatures during the first practice.

Von Brauchitsch’s initial laps delivered an unsuspected revelation. Even though he’d spent hours at speed in the same chassis, his first reactions to this new aerodynamic form were extremely negative. He got out of the car complaining that the handling had been ruined and, worst of all, he couldn’t stop. In von Fachsenfeld’s memoirs, he shared von Brauchitsch’s first impressions: “This thing is darting all over the road and it won’t stick in the corners; it’s simply far more difficult to drive. I’m not comfortable.”

Somehow nothing felt as it should, and he seemed discouraged that his small team’s collective decision to rebody the car had been a serious mistake.

Von Fachsenfeld quietly took him aside and showed him his lap times. Incredible: They were easily seconds faster than Hans Stuck’s in the stock-bodied SSKL.

With renewed confidence, von Brauchitsch again climbed into the cockpit and sped out to see if this body was really the secret advantage they’d all expected. He returned ecstatic with the ability to properly use his newfound speed and actually run at what felt like a much slower speed in the circuit’s two broad, constant-radius turns. “It’s amazing. It feels so much easier to drive; I don’t have to try as hard. I love it!” he remarked, according to von Fachsenfeld.

Relearning to Drive

Neubauer, too, had kept watch on the silver Gherkin. He was impressed–even more so when Zimmer showed him the temperatures recorded at all points, including the engine. Everything was running cooler.

The only concern that von Brauchitsch revealed to Neubauer was the engine’s ability to survive, as it was too easy to exceed the redline of 3600rpm. He admitted that he’d actually eased off on the throttle until he could get back to confer with Zimmer and Neubauer.

Von Fachsenfeld explained that reduced aerodynamic drag had actually attenuated the expected heat on all components. When Zimmer revealed the special air intake that he’d cut into the car’s underbody to duct cool exterior air onto the differential, Neubauer began to grasp the car’s true potential.

He turned to Zimmer and asked him to confirm the rear axle ratio: 2.5:1, same as the year before. Neubauer didn’t bother to explain that it would be faster and easier to change the entire axle than to extract and rebuild the differential to change ratios.

The new body on von Fachsenfeld’s racer had completely changed its handling. “You must understand,” von Fachsenfeld recalled telling von Brauchitsch, “that everything you were used to with the stock body has now changed. Smooth airflow will now completely affect the way you drive the car–especially when braking. There’s no way you can go as deep into the corners as you used to. Speeds at your usual braking points are now much higher, so there’s now very little aerodynamic drag to assist corner entry. Your brakes are now simply less capable of retarding these higher speeds, so you’ll have to adjust your driving to compensate.”

After practice, von Fachsenfeld showed the team his calculations based on lap times: Top speeds could easily be increased by at least 12 mph, but a change would be needed so the engine wouldn’t exceed its redline. Neubauer listened closely.

The big, slow-turning Mercedes engine had that maximum rev limit of just 3600 rpm. The SSKL’s supercharged 7.1-liter engine was a holdover from the early 1900s, when large-displacement, aircraft-derived engines ruled the sport. But much had changed in the five years since it was introduced: The latest Alfas, Bugattis and Maseratis were all smaller-displacement, high-rpm screamers. Neubauer had already made a quiet personal decision to install a taller 2.21:1 rear axle ratio.

Benz: Still in the Game

Mercedes may have been “out of racing,” but the sudden, unexpected potential of von Brauchitsch’s new racer had changed everything. Von Fachsenfeld continued to educate him. “Your directional stability at maximum speed will be less,” he told him, according to his memoirs. “That’s why you may feel the car is less stable. Remember, with your higher top speed, the amount of caster in your front wheels (for directional stability) that was proper with the stock body will now be insufficient.”

He explained that the reason the car didn’t seem to handle as well in the corners was because von Brauchitsch’s entry speeds were too high. Until he had more time in the car, he continued, it might actually be more difficult to determine the car’s actual speed in the fully enclosed cockpit–without the usual engine sounds and turbulent airflow experienced in the old SSKL.

Neubauer, of course, was still providing advice and timing for Caracciola in the white Alfa Romeo, but with practice over and a chance to compare lap times, he’d now taken far more interest in the potential of von Brauchitsch’s Mercedes. He reasoned that it might again be possible for an all-German win.

It had also become patently obvious that von Brauchitsch’s times were significantly faster than Stuck’s in the stock-bodied SSKL. But most importantly, his lap times were now easily competitive with Caracciola’s best in the works Alfa and those of Albert Divo and René Dreyfus in the two fastest Bugattis and Maseratis. The aero advantage was starting to show.

Withstanding the Speed

The real problem for everyone was top speed. Avus was truly unique because of the undue loads it placed on engines, running gear and especially tires.

Each of Avus’ twin parallel straights was slightly more than 6 miles long, so there was simply no time to “breathe” an engine or cool the heat built up in the rubber. This was not the typical road racing circuit where a driver would be on and off the throttle every few seconds.

An even greater problem was the centrifugal force on overheated tire treads. Some teams were already planning to stop and change tires at least once.

Even at Le Mans, with its infamous 3-mile-long Les Hunaudières straight leading to the town of Mulsanne, several teams had consistent reliability problems due to sustained top speeds. And Le Mans was nothing compared to Avus.

In Germany, the sustained full-throttle loads of some 2 minutes, twice each lap, would be four times the length of a single lap at LeMans. Engine and tire technology had simply not developed to match this year’s unexpected speeds at Avus.

Neubauer, ever the practical tactician, realized that durability for tires and engines would be as important at Avus as outright speed. He’d already calculated, from past experience, that at least half the Avusrennen field would probably retire before the checker.

For that reason, he contacted the engineers at Continental Tire for special rubber for the event. The company had come up with a lighter-weight tire with no tread to reduce the centrifugal forces expected. If it didn’t rain, which might cool less affected tires, both Caracciola and von Brauchitsch would have a slight edge in reliability and maybe even top speed.

Rudolf Caracciola’s white Alfa Romeo (No. 33) sprinted into the early lead while von Brauchitsch’s taller gearing mired his rebodied SSKL to a mid-pack start. Photograph Credit: Sueddeutsche Zeitung/Alamy

In the final day’s practice, every entrant seemed to have found more speed, with several of the fastest Bugattis and Maseratis consistently breaking and rebreaking the previous day’s officially posted record.

The fastest practice/qualifying lap was recorded by Frenchman Albert Divo in one of the two works Bugattis, putting him on the pole for race day. Next to him on the front row was Caracciola in the white Alfa, with another Bugatti on his right. Von Brauchitsch was back on the outside of the second row, another of the latest Bugattis alongside.

Neubauer had closely compared the speeds and overall times of “his” two Mercedes as well as Caracciola’s in the Alfa and the fastest times set by the factory entries from Bugatti, Alfa Romeo and Maserati. Neubauer’s advise to von Brauchitsch after final practice: “If you attack these newer cars too early in the race with your extra speed, you will only put more stress on your engine, tires and brakes. With your new axle ratio, you’ll now have the extra speed to win this race, but you must use it wisely; wait until the last lap. Dreyfus and Divo are quick, but I don’t expect them to last. You must let Caracciola set the pace.”

Neubauer had calculated that it would take at least an hour and a half to cover the 15 laps and 124 miles. Most of those would be at full throttle. That was the main reason he’d had Zimmer install a new rear axle with a taller ratio: to ease the load on von Brauchitsch’s engine.

At the start, it was Divo in a Bugatti who took a commanding lead, with Dreyfus a close second in the 16-cylinder Maserati. Under advice from Neubauer, Caracciola carefully sat in fourth, with von Brauchitsch in sixth.

With some 200,000 highly partisan German fans cheering for Caracciola, the general expectation in the stands was high that their national champion would win again. Avus was essentially Caracciola’s home track; he’d already won there twice, and it was a matter of national pride that, even without Mercedes’ official support, he was still racing under German colors. Even though Caracciola’s practice times had not matched those of the two fastest French stars, the probability that Neubauer had some secret plan to ensure a win for Germany seemed common knowledge.

Divo in the Bugatti had clocked the fastest overall top speed in practice of 162.5 mph and was using every bit of the engine’s potential to stay ahead of Dreyfus in the V16 Maserati. But, as Neubauer predicted, they couldn’t hold that pace. Dreyfus headed for the pits on the second lap with a malfunctioning throttle. Guy Bouriat, in the second Bugatti, moved up to take his spot. By the third lap, England’s dark horse threat, Sir Malcolm Campbell in the Sunbeam, had faded, allowing Caracciola and his shadow, von Brauchitsch, to each move up another place.

For lap five and the first half of the sixth, Divo continued to hold the lead, but Caracciola and von Brauchitsch had now closed up to second and third. Seconds later, the overstressed engine in the Bugatti finally blew. Caracciola and von Brauchitsch swept into the lead, with thousands of cheering Germans now certain that their hero would win.

One of the race’s most dramatic moments occurred on lap eight, far down the lead straight and out of sight of most of the fans crowded near the finish line.

Von Brauchitsch, closely drafting the white Alfa, pulled out alongside and, using the advantage of his new gearing–and, until this moment, an unused, carefully hidden extra 600rpm–easily swept by Caracciola to lead him across the start/finish line on the return straight. The silver racer seemed to fade back as if it had lost power, and Caracciola again took the lead. There was near pandemonium in the stands.

To the surprise of all, Dreyfus’ Maserati suddenly pulled out of the pits and returned to the fray. The Frenchman had one goal: to set the race’s fastest lap. German industrialist Fritz von Opel had posted a 1000-reichsmark prize for that speed, and the works Maserati team was certain it could do it.

The race’s full fuel load had been drained to lighten the car for the single fastest lap. Dreyfus and the screaming V16 Maserati turned a brilliant 5:35.2 to win the prize, then pulled into the pit to the admiring cheers of those who had been mesmerized by the technical battle unfolding with the race’s new leaders.

With seven more laps to the checker and Caracciola in what now seemed a commanding lead, the race became a German versus German battle with the unique attributes of each driver’s car on full display. Caracciola’s Alfa would go deeper into the turns and even gain more yardage as the Italian racer’s superior road holding became evident. But then, on the straights, von Brauchitsch’s Benz showed its superior top speed, easily closing the gap.

On the final lap, with Caracciola again in the lead, the organizers were already hoisting the Italian flag on the winner’s podium. This was a race of marques, not drivers. There seemed no possible way that the speeding Alfa Romeo could lose.

But then the impossible seemed about to unfold. The hundreds of fortunate fans lining the “less interesting” long back straight saw it happen: Von Brauchitsch’s Mercedes easily closed on Caracciola’s Alfa, eased up alongside, and sped past to what seemed a commanding 100-yard lead–and then eased off!

In the previous laps, von Brauchitsch had calculated exactly how much space he’d lose to Caracciola in each turn. Now, he used his extra top speed to build that buffer so he’d still lead coming out of the final turn. He took the final 180 very carefully so as not to run wide or lose his critical distance.

Von Brauchitsch led Caracciola across the finish with 6.5 seconds to spare. That victorious moment created such a cacophonous roar from the stands that even the sounds of the winning engines could not be heard, and it lasted for minutes. For the excited fans, it was actually a triple victory for Germany, as Hans Stuck in the conventionally bodied SSKL finished third. Only five of the original 16 starters completed the race.

Equally as important as Mercedes’ victory was the emergence of a new design paradigm: aerodynamics. Von Fachsenfeld’s contribution created an astounding realization that motor racing had somehow changed completely; it had entered a new era of top speed determined by form instead of power.

Mercedes’ strength had always been horsepower, but now superior aerodynamics had taken an equal if not more commanding position–certainly on the fastest of Europe’s circuits, like Le Mans, Monza and Spa.

Like many race wins, von Brauchitsch’s victory at Avus was a team effort. Above, von Brauchitsch stands between mechanic Willy Zimmer (left) and Mercedes-Benz racing manager Alfred Neubauer. Photography Courtesy Mercedes-Benz AG

The winner of the 1932 Avusrennen had set an all-time, international average speed record for a major race. Von Brauchitsch had averaged 120.5mph for 124 miles. His record stood until 1937, when a high-banked turn was added to the Avus circuit and Herman Lang averaged 162 mph in the first of the works-built Silver Arrows.