Porsche 962 CK6

Kremer Racing’s long-lived success

“If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck,” the famous saying goes. That does not necessarily apply to the legendary Porsche 962C endurance racer.

At the 1988 edition of the 24 Hours of Le Mans, there were twelve 962s on the start line but at least four of these had never seen the inside of the Porsche Motorsport facility at Weissach. These were built around fresh, more sophisticated chassis provided by third-party specialists. That they used Porsche-sourced engines and many other major components explains why they could still be fielded as Porsche 962Cs and fooled many untrained and even trained eyes. Among the most famous of these Porsche 962-based derivatives was the CK6 created by Kremer Racing.

This is one of the very last and most advanced 962 CK6s built.

Established in 1962 by brothers Erwin and Manfred Kremer, the Cologne, Germany–based team quickly became one of the leading Porsche privateers. Not only did Kremer Racing field Porsches, the relationship was so close with the factory that the team was allowed to acquire works body shells and built up their own cars. Initially, these followed the same specifications as the factory 911 RSR and Turbo racing cars but during the second half of the 1970s improvements were made on the Porsche designs. This culminated in the 935 K3 that was introduced. It featured revised aerodynamics and improved chassis and engine performance, compared with the complete 911 Turbo–based 935 produced by Porsche. The K3 was hugely successful and won the 24 Hours of Le Mans outright in 1979.

At the 1990 24 Hours of Le Mans, this CK6 was raced in an art-car livery by German artist Peter Klasen.

This success was of course the result of the talent gathered at Kremer Racing but was also helped by the pragmatism at Porsche. Even though the cars were built at the Kremer facility, they still incorporated most major components that were sourced and – crucially – bought from Porsche. These components included the body shell, engine, gearbox, and drivetrain. For Kremer, this was a way to get an edge over the competition, as it allowed the team to incorporate improvements first used on the works cars before they were made available in the customer 935s produced by Porsche. The K3 was so successful that Kremer Racing also sold upgrade packages and complete cars to customers. At the end of the day, if a 935 K3 won a race, it was a Porsche that won the race, so it was a win-win situation for everyone involved.

The main visual change was the separate rear wing on the CK6.

In 1982, the all-new Group C regulations were introduced, which shifted the focus from production-based machinery like the 935 to purpose-built racing cars. To this end, Porsche produced the 956, which was the company’s very first car to use an aluminum monocoque chassis. During the 1982 season, it was raced exclusively by the factory team but customer cars would be made available as well. As the client specification 956 was not due until the 1983 season, Kremer Racing built their own “CK5” sports prototype based around a spaceframe chassis to compete in Group C during the 1982 season. As it turned out, the 956 and subsequent 962C was superior in every aspect to the CK5, so Kremer Racing briefly had to revert to a more conventional Porsche customer role. At the 1983 Le Mans, Kremer ran the very first private 956 available for Michael and Mario Andretti, and Philippe Alliot, alongside the CK5.

From the front it is harder to distinguish a CK6 from Porsche's own 962C.

By the second half of the 1980s, the 962C was starting to show its age and with six consecutive Le Mans wins between the 956 and 962C, Porsche had little interest in continuing to develop the cars any further. Production of customer cars continued unabated, and the last ones were sold as late as 1991. At the same time, the Kremer brothers were once again looking to gain an edge on the competition. Options were limited as the top-level class featured either other 962Cs or works cars from other teams that were not available to privateer teams. This left Kremer Racing the choice of building a completely new Group C car or take the 962C and make further improvements to the design. The two areas of the Porsche design that could use the most attention were the aluminum monocoque chassis and the aerodynamics.

With the nose removed, the honeycomb aluminium chassis is clearly visible.

As mentioned above, the 956 used Porsche’s first monocoque chassis. This was constructed using load-bearing aluminum sheets that were riveted to steel bulkheads. The only major difference between the 956 and 962C was a slight increase in wheelbase to allow the pedal box to be moved behind the front axle. This was a change made to comply with the regulations, which were aimed at giving the driver’s feet at least some protection in case of an impact. Fatal accidents behind the wheel of Kremer-entered 962Cs of Manfred Winkelhock at Mosport in 1985 and of Jo Gartner at Le Mans in 1986 showed that the monocoque chassis was perhaps not as strong as it should be. Building a new monocoque chassis was not an easy task, so help was called in from John Thompson and TC Prototypes company in the United Kingdom.

Later raced in a conventional livery, Klasen repainted the car during the restoration in 2014.

Thompson specialized in chassis fabrication and was even called in by Ferrari to construct the Italian manufacturer’s first Formula 1 monocoques ahead of the 1973 season. It was decided to create a facsimile of the 962C chassis but using aluminum sheets with a honeycomb core. This alone would make the chassis a lot stronger and more rigid. Long time Kremer Racing team manager Achim Stroth recalls that to get the design right “we used reverse engineering.” He hastily adds: “With some undisclosed internal information.” In addition to getting a stronger chassis, Stroth explains that there were further benefits for Kremer Racing: “It was again a cheaper solution, in case of an emergency a new chassis could be sourced faster and using a proprietary design also allowed for the opportunity of further improvements.” The first two chassis built by Thompson used the 962-110 and 962-118 chassis numbers of the cars destroyed in the two fatal accidents.

Between the rear bulkhead and the separate rear wing, the CK6 is all Porsche.

By retaining the layout of the 962C, Kremer’s CK6 could be built up using Porsche-sourced suspension components and also the twin-turbo, flat-six engine and gearbox. Initially, the new Kremer 962s were fitted with standard bodywork but later a proprietary high-downforce design was created. This was made possible in part by the stronger chassis, which could cope with the increased loads much better. For Porsche, downforce had not been quite as important, as Le Mans was always the main objective. Much of the 962C’s downforce was generated by the “ground effect” tunnels that ran on either side of the engine will an integral rear wing served mainly to balance the car. The Kremer-developed downforce package had a separate rear wing, which could be set up much more aggressively to make the car more suitable to run tracks considerably tighter than Le Mans.

Among the most famous liveries used by the Kremer team was that of Japanese company, Leyton House.

For Porsche, Kremer Racing’s independent efforts were again not a problem at all as Stroth explains: “Porsche did not complain, because we would call the car a Kremer 962 CK6, and the sports code required us to name the chassis after the engine supplier.” The German manufacturer had little to lose but much to gain: “Porsche continued to supply many parts and services, as before, even the latest development parts.” If anything, Kremer Racing and other privateers doing similar things helped Porsche to work through the backlog of orders for the 962C and the IMSA GTP specification 962. It must have also been nice for the German manufacturer to see improved 962s on grids around the world at no development cost of their own.

Demonstrating how stiff the chassis is, this CK6 lifts its front left wheel through the "Corkscrew" at Laguna Seca.

The first two Kremer Porsche 962s appeared halfway through 1986 season using the “118” serial. The second chassis, tagged “110,” debuted at the start of the 1987 season. If that was not confusing enough, there were additional chassis built that were again tagged with these existing Porsche numbers before Kremer Racing eventually tagged the Thompson-built chassis with their own CK6 numbering system, which in itself was not straightforward to decipher. As a result, the Kremer Porsche 962 CK6s are a historian’s nightmare even though they were raced at a period when correctly documenting chassis numbers at events was already a well-known practice. This was of course of no concern to Kremer Racing as the only thing that counted was getting their latest 962 CK6s on the grid.

The cockpit of the CK6 with the turbo boost knob well within reach.

Entered for Volker Weidler and Bruno Giacomelli, the first CK6 debuted at the 1986 Spa 1000 km race. Starting twelfth, the German/Italian pairing crossed the line in eleventh place. Later in the year, the two drivers finished fourth overall in the Fuji 1000 km. The final outing that year came at the Kyalami 500 km where Wayne Taylor and James Weaver suffered an engine failure in the second heat. The first time two CK6s lined up together was at the 1987 Jarama 360 km World Championship round. Interestingly, the grid at Jarama also included a Brun Motorsport 962, which used one of the Thompson-built tubs and a Richard Lloyd 962, which featured an altogether different aluminum honeycomb chassis developed by Nigel Stroud.

One of the first CK6s, this example still features the integrated rear wing.

While the CK6 was certainly a considerable improvement, the factory TWR Jaguar and Sauber Mercedes efforts had raised the bar even higher in the World Sports Car Championship. As a result, the Kremer Racing cars were most successful in the Japanese Sports Car Championship and the Interserie championship in Europe. The first win came at the 1987 Interserie Most with Volker Weidler at the wheel of the second of four CK6s to use the “118” serial. The third 118 CK6, liveried in striking Leyton House colors, placed an impressive fourth overall at Le Mans in 1987 with George Fouché, Franz Konrad, and Wayne Taylor. In addition to numerous race wins, the CK6 would also become the 1990 Interserie champion with Bernd Schneider doing the driving duties in a Yokohama-liveried example.

It was a far safer place to be inside the CK6 thanks to the reinforced chassis.

Among the Kremer factory drivers was Italian Giovanni Lavaggi, who had also raced a conventional 962C: “It is not easy to make a comparison between the two cars because they used different tires.” He continues: “Kremer had Yokohama tires (definitely not the best in my opinion) and we always suffered of over-steering in acceleration due to wheel-spin on power. Nevertheless, we succeeded to reach a podium at the Nürburgring in 1989, just behind the two official Sauber-Mercedes.” Lavaggi is a trained engineer and suggested some subtle changes be made to the rear suspension: “The modification was effective and we were faster, but it revealed a part that was too weak and broke quite soon, therefore the team went back to the original setup.” Another thing that stuck with Lavaggi about the CK6: “Kremer had always very strong engines.”

The powerful water-cooled, twin turbo engine supplied by Porsche.

Even though Porsche had effectively ceased 962C development at the end of the 1988 season, Kremer Racing was in a prime position to make further improvements to the design. John Thompson had in the meantime learned some valuable lessons while lending his services to the TWR Jaguar Group C effort. The British team fielded cars that were not built from aluminum or aluminum honeycomb but from carbon-fiber composites, which was both stronger and lighter. Erwin and Manfred Kremer were also interested in this new material and accordingly, the CK6 was re-engineered and the last examples built during the early 1990s featured carbon-fiber composite monocoques. It would take Porsche until 1998 before the German manufacturer produced its first carbon-fiber composite chassis.

Another early 962 CK6, this is one of the cars that used the 962-110 serial.

The Group C category was abandoned at the end of the 1993 season but the Kremer brothers were not quite ready to let their proprietary chassis go. The result was the CK7 Spyder, which was effectively a 962 CK6 with the roof and ground-effect tunnels removed. The CK7 was replaced by the Kremer K8 in 1994, which complied with the World Sports Car or WSC regulations. That opened the door to all the major endurance races for Kremer Racing. The crowning achievement to the career of the CK6, CK7, and K8 came at a rain-soaked 1995 Daytona 24 Hours where Lavaggi together with Jürgen Lässig, Marco Werner, and Christophe Bouchut claimed the outright victory. A Kremer K8 raced at Le Mans as late as 1998 and a final win was scored in the 1997 Monza 1000km race, piloted by John Nielsen and Thomas Bscher.

The Kremer Racing Porsche 962 CK6 was the most successful of all the privately developed 962C derivatives. With the first victory scored in 1987 and the final one for the K8 evolution, the design was not just successful but also long-lived.