Callaway C7R

[carreragt10]

Callaway C7R

From 1994 through the beginning of 1997 Callaway Cars, Inc. and Callaway Competition GmbH pursued a project to design, construct and campaign a super high performance GT automobile. The goal was to broadcast the capability of the Callaway organizations in the areas of complete car construction. This car is not really a Corvette, but has certain aspects of it. Besides that: if you take apart the C5R, you won't find much standard Corvette parts either!

The Callaway C7 was designed to be a competition car with a road car derivative. Two cars were built for competition at Daytona and Le Mans. As of 1997 changes in the international motor racing regulations made the project unfeasible to continue. However, several of the projects objectives were met, and the cars remain as one of the high water marks for Callaway's overall reputation as a car manufacturer.

What follows is the original text written at the time of planning and construction of the prototypes. We have left the original text unmodified so that the reader may get some insight into the original objectives and judge how well the goals were accomplished.

"The Callaway C7 is a 680 hp, front mid-engine, rear transaxle, rear drive, two seat sports GT, constructed in carbon fiber and weighing less than 2500 pounds. The Callaway C7 concept and execution is consistent with GT1 practice of the day resulting in medium complexity and extreme light weight. The use of modern materials and Callaway's tight focus on mechanical integrity has created a most exciting sports-racing car.

This automobile embodies the four traditionally important elements of successful sports cars: power, simplicity, character, and beauty.

Power
Automotive performance is defined by a simple concept: power to weight. The Callaway C7 was designed to be the most powerful, lightest weight sports GT commercially available.

All memorable automobiles have been powerful. From the Stutz Bearcat to the Shelby Cobra, the cars that we admire and remember today are the ones that were powerful in their day. The Callaway C7 has a power/ weight ratio of 3.6 pounds per horsepower. By comparison the McLaren F1 in road trim has over 4 lbs/hp and the Ferrari F40 is more than 6 lbs./hp. The Callaway engine is a naturally aspirated 6.8 liter Callaway aluminum V-8 similar to the SuperNatural powerplant developed for the Callaway Corvette. In racing trim, it produces over 680 hp limited by the air restrictor mandated for LeMans. The engine configuration represents the most straightforward method of achieving high power and reliability.

Simplicity
The Callaway C7's mission, to win GT Endurance races, requires that the car be extremely simple. Simply designed, simple in construction, simple to work on and simple to repair. Every element of the Callaway C7 is prejudiced to minimize weight and volume and to promote efficiency. The target weight for the road version is 1000 kg. To accomplish this ambitious goal, each detail of the vehicle accomplishes multiple functions. For instance, the central carbon fiber monocoque is the chassis structure, the fuel tank and the seating. We have reduced the vehicle to a remarkably pure and functional device.

Character
Desirable cars have shared a common element, they have been one man's concept of the automobile. The Callaway C7 is Reeves Callaway's vision of the ideal vehicle: powerful, simple, beautiful, and lightweight.

Beauty
The Callaway C7's styling at once both evokes the traditional powerful cars of our time and reflects the functional requirements of GT racing. The construction in carbon fiber by Callaway Competition in Germany brings the extraordinary talents of Karl-Heinz Knapp, Ernst Woehr, and Giovanni Ciccone to this automobile. As with all Callaway cars, the look of the Callaway C7 is central to its design. The body styling is by Paul Deutschman who has been responsible for the styling of the Callaway SledgeHammer, the Callaway AeroBody, the Callaway Speedster, and the dramatic and successful Callaway SuperNatural Corvette LM that raced at Le Mans in 1994 and 1995.

Competition
Many successful production cars have either stemmed from competition cars, or used competition as an important part of their development plan.

The organizers of the 24 Hours of Le Mans, the A.C.O. (Automobile Club de l'Ouest), and the FIA, have created a set of regulations for Grand Touring cars that are specifically drawn to make the GT cars competitive for overall victory in the world's most important endurance races. These changes created the opportunity for Callaway Competition to race the Callaway SuperNatural Corvette Le Mans in 1994 and 1995, winning the Le Mans GT2 pole both years and finishing second and third in class, and ninth and eleventh overall, in 1995. The Callaway C7 is a completely new and original construction, not related to the Callaway Corvette, intended to take full advantage of the A.C.O. Le Mans regulations in the most competitive class, GT1.

The sports-racing version of the Callaway C7, the C7R, will debut in international GT endurance events in 1997. The focus of the competition program will be development of the Callaway C7. Callaway will then offer a road going version, the Callaway C7S, to enthusiasts worldwide. It will be directly derived from the Callaway C7R's racing experience.

Timing
Callaway will campaign the C7 during the '97 competition season and devote the year to the development of the racing version. Simultaneously, the road version will be undergoing homologation, compliance testing, and production engineering. Customer cars, in both C7R and C7S versions, will be scheduled for delivery in 1998. Orders for both the Callaway C7R and C7S are now being accepted.

Callaway C7

[carreragt10]

THE AMERICAN DREAM

Callaway Cars has developed the radical C7R with one goal in mind - an American GT victory at Le Mans. Peter Brock on the state of the notion; photos by the author.

When Reeves Callaway entered his two brand-new C7R prototype GT1 racers at the Le Mans pre-qualifying trials last year, he thought the radical front-engined design had an excellent chance of success. And it did, almost....

As it turned out, a frustrating series of minor hitches conspired to prevent the C7Rs from qualifying for the world's most important endurance race. This was a bitter disappointment for Callaway, but he quickly recovered. Knowing that time stands still for no one, he immediately left France and headed back to his European HQ in Liengarten, Germany. It had taken weeks of 18-hour days to prepare and test the cars for Le Mans, so after returning home the exhausted team took a brief rest. Then they rebuilt the cars once more, and within a few days were running their own 24-hour endurance test at Hockenheim to further refine the machines for the 1997 endurance-racing season.

What they learned was that the C7R's potential was even better than expected; the more they tested, the faster it went. Eventually, the Hockenheim tests led to another long-term development program and major changes to the car's original layout.

Because of its radical design, the C7R had alarmed the French officials, who in turn decided to rewrite the GT-class rules for 1997. They informed Callaway of their intentions several weeks after Le Mans '96, and serious development at Liengarten ground to a halt until the final '97 rulebook was printed the following October.

When the new Le Mans rules were received, Callaway again met with the race organizers to reconfirm his entry for '97 and review the changes that would be necessary for acceptance. He was told that as impressed as the organizers had been with the C7R's concept, they were seriously concerned about certain aspects of its design.

While the car had indeed complied with the '96 rules, Callaway's interpretation could, if left unchallenged, soon lead to machines that were considerably more exotic than the ACO's vision of production-based GT cars.

Callaway's innovations proved the danger in reaching too far beyond the organizers' expectations. Often, the result is an all too familiar scenario wherein the visionary constructor is handed his head-with the advanced ideas still intact!-on a silver rulebook, complete with grand admonishments seeking to justify this action as "good for the sport." One need only look at Jim Hall's Chaparrals of the 1960s, many of which were loaded with brilliant ideas that were banned before they could be objectively evaluated, to realize that modern race-car design is a field that neither encourages nor rewards true innovation.

The French tech directors for Le Mans, Alain Bertaut and Daniel Perdrix, specifically objected to the C7R's aerodynamic devices. They decided to change the rules so that Callaway's innovative internally-mounted front wing and boomerang-shaped rear wing would be illegal in '97. In short, Bertaut and Perdrix believed that with its rear wing swept so far forward, the C7R might produce more downforce than the ACO wanted GT cars to have. As a result, the rules were subtly rewritten so that all rear airfoils, when seen from above, had to conform to the body's shape and fit within a strictly defined rectangular area above the rear end. (Thus, all the cars at Le Mans '97 will probably have rectangular, squared-off tail sections to enable them to run the largest possible wings.)

When Callaway was finally informed of the '97 rules, these changes seemed like serious setbacks. Hundreds of hours had already been spent developing the '96 aero package, and these were essentially wasted. Undaunted, the team immediately set out to reshape the C7R's body in composite foam. That task done, soon they were heading off to try out the new shape in Pergusa, Sicily, where the mild Mediterranean winter permitted testing in November and December.

Team Callaway found that the ACO-mandated rectangular rear wing and squared-off tail actually worked better than the original design! That, in turn, dictated a need for more front downforce to keep the car balanced at speed. And, since the internal front wing had also been ruled illegal, it was therefore necessary to completely redesign the nose.

The rear-mounted radiators were moved forward into a conventional bottom-feeder system and a large carbon fiber splitter was mounted below the main intake. The entire rear structure and suspension were also redesigned, with Callaway hoping to take advantage of the extra room now available in the rear bay. Only the C7R's original all-composite tub stayed the same.

With the transformation complete, more testing ensued at tracks around Europe, and each set of trials brought more speed and evidence of still-greater potential. But time was running out; soon the cars would have to be shipped to America for winter testing at Daytona in early January, preparatory to the Rolex 24 Hours in early February. As a result, the C7R's last few changes arrived in Florida untested.

At Daytona, it was soon discovered that the car's rear downforce was now so great on the straights and high banks that the spring rates needed to be increased just to keep the car from bottoming out at 180+ mph. With only two days available for testing at Daytona, it was decided to run a 24-hour test at Sebring before the Rolex 24. Since Callaway's regular test driver, Enrico Bertaggia, was unavailable for this, New Zealander Rob Wilson was recruited from Sebring's Skip Barber School. Wilson had been a test driver with March several years earlier, so he was quickly pressed into service to help improve the chassis. With only a few days left before the Rolex 24, it was decided to concentrate on a single car for the race. Wilson helped the team clip several seconds off the initial Sebring lap time.

When the C7R finally arrived back in Daytona for tech and practice, the spring rates had nearly doubled! By this time, the high-tech coupe was almost an entirely different car from the one that had tried to qualify for Le Mans '96.

In practice for the Rolex 24, former Trans-Am driver Ron Fellows went off the course and stuffed the C7R's left front corner hard against a tire wall. That meant another day lost, and when the team's lone car was reassembled for final practice, regular drivers Enrico Bertaggia and Boris Said noticed it was no longer handling as well as it had been before the mishap. The reduced torsional stiffness in the chassis indicated that the all-composite center section had suffered more structural damage than initially believed, and with no way to inspect and repair the tub, Callaway's engineers decided to play it safe: The spring and shock rates were reduced so that cornering loads wouldn't overstress the weakened chassis. This, in turn, necessitated raising the ride height far above its optimum setting. Callaway estimates these changes cost the car more than two seconds per lap.

[carreragt10]

The crash and resulting delays prevented a full-on qualifying effort, but since previous practice times can be counted as qualifying times under the Rolex 24's rules, the C7R sat safely on the 80-car grid. The team started in 25th position, and within half an hour Boris Said had eaten his way up to ninth overall and third in GT1, right behind the Lister Storm and Viper GTSR. When those two cars were temporarily sidelined with transmission problems, the C7R suddenly found itself running first in class.

Callaway's trying season of buildup seemed to be paying off at last when, in the 11th hour, electrical problems sidelined the car for good. It was a disappointing blow, but seen in the proper perspective, the C7R had proven itself at last. Clearly, the design was capable of beating the world's best- now it would be up to Callaway and his team to turn this potential into results.

Reeves Callaway has been a Corvette tuner and racer since 1977. His small, well-equipped factory in Old Lyme, Connecticut produces lots of innovative high-performance cars and parts based on the Chevrolet smallblock V8, and this is the same basic engine he uses in the C7R racer. The C7Rs, however, are produced in Liengarten, Germany, where Callaway currently makes his home. "Most of the world's endurance racing occurs in Europe," he says, "so it just makes sense for us to be as close to those events as possible." There's also a substantial market for Callaway-prepared C4 Corvettes in Germany and the rest of Europe, where unlimited autobahns and an enlightened view toward high-speed touring make Callaway's road cars particularly attractive.

But Reeves' long-term goal is to build his own series-produced sports car, and the C7 project will be its basis-it's the first clean-sheet car from his company, and is firmly on the cutting edge of front-engined technology. Since the C7R was seen at Le Mans' 1996 test day, Ferrari, Lister, TVR, and Panoz-Reynard have all unveiled high-performance front/mid-engined designs of their own. Asked about this curious coincidence, Callaway replies, "I've always felt that a front-engined layout was best for a high-performance street GT, and with today's suspension and tire technology, there's no reason not to put the engine up front. I just think Ferrari and Reynard weighed the advantages of a front/mid-engined layout and came to the same conclusions that we did."

One of the most remarkable aspects of the C7R is its engine, a 416-cid large-displacement Chevy smallblock V8. "We didn't have space in the chassis for a 427 big-block or even a twincam ZR1 engine, but we did need cubic inches to meet the power requirements for the long straights at Le Mans," explains Callaway. By using an alloy Donovan racing block specially cast with increased deck height, longtime Callaway development engineer David Auerbach was able to utilize a stroker crank to satisfactorily raise the cubic inches. "Since the Le Mans regulations limit our breathing with induction restrictors, he felt it was better to limit the engine's rpm and concentrate on airflow, since flow efficiency through the restrictors improves as rpm is reduced." The C7R's engine produces 665 bhp @ 6700 rpm-pretty darn good for a normally aspirated, 2-valve pushrod engine.

To keep the chassis' static balance and polar moment as favorable as possible, the transmission has been moved to the rear. "Right now we're running a conventional 5-speed Hewland transaxle," says Reeves, "but that might change." The new generation of 6-speed sequential-shift transaxles from X-trac and others are lighter and stronger than the older Hewland, and one of these may prove superior in future testing.

As this is being written, Callaway has decided not to run the C7R at Sebring: A 2-car team must be entered at Le Mans to qualify under the '97 rules, and there's no way Callaway's small crew can prepare worthy machines for both events.

Meanwhile at the Sarthe, the French are making every effort to ensure that all participants are true manufacturers with a serious intent to build more than a couple of one-off rulebeaters for Le Mans. In addition to the 2-car rule, all GT entrants must now bring a fully homologated street version of their racers to Le Mans for inspection. The ACO's homologation requirements further insist that the production version meet "all local laws" in terms of lighting, ground clearance, and noise. But of course this is a pretty big loophole-just what does "local" mean, anyway? In any case, the production example must have a full interior with heating, air-conditioning, and a sound system. "Since the C7R racer was originally envisioned as the C7 street machine, all these factors have already been taken into account," Reeves states confidently.

Still, it's obvious that the ACO (which controls Le Mans) and the FIA (the organizers of the World GT Endurance Championship) aren't happy with the recent trend toward hyper-exotic, very-low-volume racing cars posing as street-derived GTs. Both groups naturally want to see more major-factory participation based on true production-derived hardware, the kind of effort exemplified by Dodge's recent Viper GTSR program.

Chevrolet's new C5 Corvette, the Jaguar XK8, and Aston's DB7 would be other logical entrants in a true GT formula, assuming-and this is the critical point-that their manufacturers suddenly manifest the will to go racing. The ACO and FIA are betting heavily that this will happen, but so far it's only wishful thinking.

No matter what, the organizers are aware that true production-based GT racing will never return as long as super-expensive rulebeaters like the McLaren F1, Lotus Elise V8, Porsche GT1, Lister Storm, Callaway C7R, and the upcoming Reynard-designed Panoz GT1 and TRW-penned Nissan R390 dominate the circuits. "If the large manufacturers have to compete against cars like ours," Callaway agrees, "they know they can't win, so there's heavy political pressure at the organizer level to eliminate designs like the C7R."

But then what of the independents? "For us, if that does happen-and it looks almost certain to occur by '98-then everything we've learned about front-engined GT racers could go into a program around the 1997 C5 Corvette," Reeves says. "But it would really be a shame, because we're right on schedule with the C7R. I knew it would take at least a year to prepare for Le Mans; now, the car may be obsolete a year after that."

And you thought the actual racing was the expensive part of this game.

THE AMERICAN DREAM

[carreragt10]

Callaway C7R #4

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Callaway C7R #5

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Callaway C7R #6

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Callaway C7R #7

[blackcat77]

Thanks for posting these. I was hunting for pictures of this car a while back and could only find two or three very poor ones.

[carsnut]

never heard of this before. does it have relations with the C12?

[2ndclasscitizen]

Does Callaway know that Lee Noble stole their bumpers?

[denisvn93]

Great job Callaway!
A vary interestingn for a Le Mans car.

[jorismo]

Are those Toyota Supra rear lights?

[whiteballz]

yes, yes they are.

["Clevor" Angel]

Thats an extremely beautiful car! I love the C7R and a road version weighing only 1000kg is insane!