The Chevrolet Corvette C7.R was the race-going equivalent of the Chevrolet Corvette C7 Z06. Like its predecessors, the C5-R and C6.R, the seventh generation racer was constructed and prepared by Pratt & Miller for Corvette Racing. The C7.R competed in the GTLM class of the newly formed TUDOR United SportsCar Championship, which was later renamed in 2016 to the IMSA WeatherTech SportsCar Championship. The inaugural 2014 season of the TUDOR United SportsCar Championship would also be the debut season for the new Corvette C7.R.
The renamed Grand Touring Le Mans (GTLM) class carried across the same regulations as the previous GT class of the American Le Mans Series. With five years of data from Corvette Racing running a GT2/GT specification C6.R, they transferred a lot of the technology to the new car. Corvette Racing struggled for their first three years in the GT2/GT class with their C6.R, which broke up eight years of consecutive manufacturers titles. They later developed the car enough to find success in 2012 and 2013, taking back to back drivers and manufactures championships. This previous success resulted in the new C7.R immediately being quick taking four class wins in its inaugural season and accomplishing a total of three drivers and manufacturers championships within five seasons. The C7.R also made history in 2015 achieving the triple crown of endurance racing with class wins at the Rolex 24 at Daytona, the Twelve Hours of Sebring and the 24 Hours of Le Mans. The C7.R competed in its final season for Corvette Racing throughout the 2019 IMSA WeatherTech SportsCar Championship before it was replaced in 2020 by the new mid-engined Corvette C8.R.
2013 was a huge year for General Motors and their legendary sports car. Not only was it the 60th Anniversary of Corvette but it was the same year GM unveiled the new seventh generation model Corvette. The new C7 Corvette Stingray was the industry’s most awarded car of 2013, thanks to technology transfer from the race team and a whole new car that shared only two components from the previous C6 model. Throughout 2013 Pratt & Miller focused most of their attention to developing and testing the new C7.R, therefore the 2012 chassis of C6GT-005 and C6GT-006 were used again in 2013 ALMS season. For the motorsport world 2013 would be the final year of the American Le Mans Series after 15 years. Corvette Racing held the ALMS close to their hearts as the team was formed to compete in the series. Throughout their 15 years racing in the ALMS, Corvette Racing took part in 135 races, winning 82 of them. This resulted in nine drivers championships, seven consecutive and 10 manufacturer/team championships including eight consecutive. Those impressive results made Corvette Racing the most successful GT racing team in ALMS history. The 2013 season would also close the chapter for Corvette Racing on their C6.R model, which had brought the team six championships in its eight year run.
Panoz Motorsports sold the American Le Mans Series to NASCAR Holdings, Inc in 2012. The ALMS operated under the International Motor Sports Association (IMSA) sanctioning body, whilst NASCAR Holdings, Inc ran under the Grand-Am Road Racing sanctioning body of the Rolex Sports Car Series. It was announced on September 5th, 2012 that the new ownership would merge the two series to form the TUDOR United SportsCar Championship (TUSCC) for the 2014 season. This would mean for the first time since 2001, Corvette Racing could compete at one of the crown jewels of motorsports, the Rolex 24 of Daytona. For the inaugural season of the TUSCC the organizers would change the name of the GT class to Grand Touring Le Mans (GTLM) due to carrying over the Grand Touring Daytona (GTD) class from the Grand-Am series. The GTD class used GT3 specification race cars, whilst the GTLM class used the same regulations from the Fédération Internationale de l’Automobile (FIA) designed for Le Mans. These regulations saw a small performance difference between the GTLM and the GTD class, with the GTLM cars producing a slightly higher power output and typically lower overall weight than the GTD field. The result of the regulations saw the GTLM cars running faster lap times than the GTD cars, separating the two GT style classes on the circuit.
The C7.R was built in conjunction with the new C7 Z06. Although unannounced during the development of the race car, the Z06 would be the most track-capable Corvette at the time. This would create the closest link in modern times between a Corvette race car and production car. The Z06 and C7.R would share unprecedented levels of engineering and components, which included chassis architecture, engine technology and aerodynamic strategies. US Vice president of Performance Vehicles and Motorsports – Jim Campbell, stated a lot of the Corvette production teams success came from the symbiotic relationship between Corvette Racing and the production vehicles. The C7 Z06 and C7.R were more competitive on the street and race track due to Corvette Stingray, which was heavily based on the C6.R race car.
The first images of the C7.R were released from the test sessions conducted at Sebring between December 9th – 10th, 2013. The test mule was dressed in a chequered style camouflage making it difficult to fully visualize the design cues of the new race car. Despite the camouflage the flared fenders, front splitter, rear wing and rear diffuser easily stood out. Another test session at Daytona known as ‘The Roar Before the 24’ took place between January 3rd – 5th, 2014. The session allowed all teams competing at the Rolex 24 at Daytona to run their cars to collect data for upcoming race on January 24-26, 2014. Corvette Racing ran the C7.R yet again in the same camouflage wrap, but this time featured the red door numbers, red rear wing end plates and red window banner sections, which was the color selected to identify the GTLM class. The official unveiling of the C7.R was on January 13th, 2014 alongside the new C7 Z06 at the North American International Auto Show in Detroit. This allowed the public and media see for the first time new livery of the C7.R, that carried the tradition of a prominently yellow color scheme.
The new C7.R accomplished its first class win in only its third race at Long Beach. It would follow on by taking three more GTLM class wins at Leguna Seca, Watkins Glen and Bowenville, making it four consecutive class victories. At its first outing at the infamous 24 Hours of Le Mans, the C7.R came second in class, which was the first podium for Corvette Racing at Le Mans since their class victory in 2011. In its debut season the C7.R managed to finish third in the GTLM manufactures standings with Antonio Garcia finishing third in GTLM drivers standings.
The following year the C7.R was even more impressive by securing the triple crown of endurance racing, taking a class wins at the Rolex 24 of Daytona, the Twelve Hours of Sebring and the 24 Hours of Le Mans. Throughout the 2015 TUSCC Corvette Racing accomplished a combined total of six GTLM class podiums, including two wins. Despite the success early in the season Corvette Racing would finish third in GTLM manufacturers standings with Antonio Garcia and Jan Magnussen taking third in GTLM drivers standings.
The 2016 season would be the most successful year for the C7.R, collecting both the GTLM drivers title and manufacturers title. With new rules incorporated into the GTLM class similar to the GT3 specifications, the C7.R featured a much bigger aero package. With a larger front splitter, side skirts, rear diffuser and repositioned rear wing mounted further back, the Corvette really benefited from the changes. The series took on a new sponsor creating a rename to the IMSA WeatherTech SportsCar Championship. Corvette Racing collected a combined total of 12 GTLM class podiums, which included five class wins and two 1 -2 finishes. The victory at Lime Rock sealed a milestone for Corvette Racing as it was their 100th win. The success of the team in 2016 handed Oliver Gavin and Tommy Milner the GTLM drivers championship, whilst securing Corvette Racing the GTLM manufacturers championship. The C7.R collected a total of three consecutive GTLM manufacturer championships between 2016 and 2018, with Antonio Garcia and Jan Magnussen taking the GTLM championship in 2017 and 2018.
The Corvette C7.R was retired by Corvette Racing at the end of the 2019 season as it was replaced by the new mid-engined C8.R for 2020. Within its five years competing for Corvette Racing the C7.R started 65 races winning 16 of them. Despite often being a victim of the Balance of Performance, the C7.R never finished lower than third in the GTLM manufacturers and drivers standings.
When it comes to the backbone of a Pratt & Miller Corvette, the rules have always required the production Corvette chassis to be used. For the C5-R the factory steel chassis was used with modifications made to accomodate the race suspension components. The GT1 C6.R used the steel chassis from the base model C6 Corvette, which incorporated minor modifications due to stricter rules introduced in 2005. The C6.R GT, which was the predecessor to the C7.R, was the first Pratt & Miller Corvette race car that used the stiffer aluminum frame from the production Z06 and ZR1 models. The aluminum frame posed new challenges for the fabrication team including welding a steel roll cage to it, but lessons were learned over the production of six race cars. The aluminum frame immediately impressed the team, with the drivers reporting huge levels of mechanical grip and more predictability at the limit.
The production of the new C7.R became an evolution of the C6.R GT, keeping the tradition of using the production aluminum frame. However, for the first time, the chassis for the race car and production Z06 would be built in-house at the Corvette’s Bowling Green, KY., assembly plant. The seventh generation chassis used on the new Z06 would differ from its predecessor thanks to the advancement in manufacturing materials. The new production fabrication process utilized a GM-patented aluminum spot-welding process, Flowdrill-machined fasteners and laser welding making the production structure significantly stronger. For the Corvette Racing team, the result of the new process was a race chassis that was 40% stronger on the C7.R than the one used on the C6.R.
Just like the previous models of Corvette race cars, minor modifications had to be made to the chassis. With bespoke fully adjustable race suspension equipped to the race car, the chassis required different suspension mountings. These mountings were designed to accommodate the wide race tires and large AP Racing brakes. Safety from day one had been a priority for Corvette Racing and throughout their 15 years racing, the safety equipment had seen many improvements. The steel roll cage welded to the chassis was specifically designed to protect the driver and absorb the energy of high speed impacts. With many hours spent designing the roll cage, calculations had been made for the position of each steel tube to send the energy of an impact through it and away from the driver. Despite adding a lot of weight the roll cage makes up in the handling department due a unique design, which increases the overall stiffness improving the overall mechanical grip.
Throughout initial testing the drivers immediately reported back their appreciation of the stiffer chassis. The stronger frame helped improve mechanical grip, due to lowering any chassis flex during corner transitioning. The lack of flex increased the contact of the all four tires, overall improving the drivers use of the friction circle. The new frame also made the attitude of the handling more predictable over rough track segments and changing surfaces. This was an important feature on the C7.R due to the diversity of race circuits in the Corvette Racing calendar. For example Sebring is notorious for its violent bumpy surface, due to the use of concrete tiles with large seams through turn one and 17. The race calendar also included street circuits like Long Beach and Le Mans that feature large portions of closed public roads. Even on a modern smooth track like the Circuit of the Americas, drivers don’t always stay on the flat pavement. Due to pushing the car to its limits the drivers are constantly hitting steep curbing at corner apexes. After his seat time during the ‘Roar Before the 24’, Jan Magnussen reported that all the drivers had similar feedback; that the C7.R was a little bit easier to drive than the C6.R. This was due to it moving around less and the sensation of the stiffer chassis.
For 10 years Katech had been the engine developer for Corvette Racing. After the economic crash in 2008 that forced General Motors into a government bailout, GM were finding multiple ways to save money. This forced the GM Racing program to take a hit, but fortunately there was no plans to end the Corvette Racing program. Despite keeping the Corvette Racing program going, the team needed to find ways to cut back on expenses. The more expensive GT1 class that Corvette Racing had previously competed in, was killed off in 2010 making the cheaper GT2 class the major GT class of endurance racing. Corvette Racing built a GT2 specification C6.R, that started competing halfway through the 2009 ALMS season. Corvette Racing announced that for 2010 they would move to an in-house engine building operation for the Corvette race car. This move was made to further lower costs as in-house was cheaper than paying a third party company like Katech. The move to an in-house operation also benefited GM due to a higher use of technology transfer between the Corvette race car and production car.
For 2014 the same LS5.5-R engine from the previous C6.R was carried over into the new C7.R. GM decided to carry across the 5.5L power-plant after looking at the regulations. The FIA and the organizing entity of Le Mans, the Automobile Club de l’Ouest (ACO), mandate that GTE Pro cars with naturally aspirated motors can not exceed a displacement of 5.5 liters. The alternative is a forced induction motors such as turbocharging or supercharging that must meet a maximum displacement of 4.4 liters. Seeming the C7.R is based on the C7 Z06, building a race equivalent of the 650 hp LT4 from the production car, would mean attempting to reduce the 6.2 liter supercharged V8 to 4.4 liters. The engineers also looked at if a supercharged motor would be wise in endurance racing. Due to the high temperatures created by supercharged motors, there is a risk of heat soaking, which reduces power. A supercharger also adds more complex architecture, due to the pulleys, intercooler and a higher center of gravity. These reasons led the team to stay with natural aspiration due to its reliability, efficiency and compact packaging. Carrying across the LS5.5-R from the C6.R also brought with it three years of data and research, meaning the team had the added confidence in the motors reliability and characteristics.
The motor underwent changes for the new race car including a name of LT5.5 to match the new small block V8 dubbed the LT1 found in the seventh generation Corvette. Throughout its three years in the C6.R GT, the LS5.5-R motor underwent many improvements. The in-house development of the motor took place at the Wixom Performance Build Center, but the new motor struggled during its 2010 debut season. Both cars suffering from engine failure at the 2010 Le Mans 24 Hours making for the first full team retirement for Corvette Racing at Le Mans. This forced the engineers at Wixom to develop the LS5.5-R, which resulted in the motor never failing again. In 2012 regulation changes allowed the LS5.5-R to capitalize on performance improvements as well as evolutionary adaptations. These improvements included the twin 28.6mm air restrictors under the 2012 GT regulations to increase in size to 29.2mm, creating a bump in power. The biggest change saw the engineers at the Wixom Performance Build Center designing a new intake manifold. The result of the new manifold was an increase in power, improvement in driveability, better throttle response and fuel economy.
Where the LT5.5 motor of the C7.R improved over its previous variant in the C6.R was the ability to take advantage of direct-injection. Corvette Racing had previously used direct-injection in the LS7.R motor found in the GT1 specification C6.R. However, after moving to the GT2/GT class the rules were stricter forcing the team to use the same configuration as the production motor the LS5.5-R was based upon. Seeming no engine across the C6 Corvette range utilized direct-injection, Corvette Racing were forced to use sequential port fuel injection. This was partly what influenced GM to equip the new LT series small block V8s with direct-injection. Both the LT1 of the C7 Corvette Stingray and the supercharged LT4 in the C7 Z06 featured direct-injection allowing Corvette Racing to adapt the new LT5.5 to direct-injection fueling.
The advantage of direct-injection for the C7.R was it improves efficiency, which plays a major role in endurance racing. Corvette Racing Program Manager: Doug Fehan had always maintained the car that wins at Le Mans isn’t the fastest but the one that spends the least time in the pits. Corvette Racing were seeing the results of direct-injection typically improving fuel economy by three percent. Despite sounding very minor, three percent could be enough to bypass one whole fuel stop during a 24 hour race, translating to a significant advantage in track position. Another advantage of direct-injection is that it offers more precise throttle control. The smallest change in the throttle position by the driver, delivers an accurate response from the motor. This type of throttle precision is important in motorsports as a driver in most turns can not simply apply full throttle at the apex at risk of spinning the tires or even losing control. Instead most high level race drivers will gradually apply power upon corner exit. With a more precise throttle, the driver isn’t left guessing or over/under applying power due to the lack of response.
In terms of the power output of the LT5.5, GM never officially released the specifications, but instead estimated a power output of 488 hp. The GTE Pro/GTLM class saw an average of 500 hp across its diverse field of cars such as; Ferrari, Porsche, Aston Martin and BMW. Some of these cars produce over 500 hp or under due to the Balance of Performance (BoP). For example the BMW M6 is equipped with a 4.4 liter twin turbo V8. The boost pressure is regulated by the FIA and ACO, which allows the BMW to produce a power output closer to 525 hp. This was allowed due to the larger size of the M6 and its body style being closer to a family sedan rather than a supercar like its competitors. Due to this disadvantage the BMW was allowed a higher power output, developed by higher boost pressure from the turbos. The increased power allowed the M6 to produce similar laptimes to the rest of the GTE Pro/GTLM field. The C7.R was one of the lower powered cars in the class, due to being penalized for its advantages in other areas such as, chassis architecture and balance. For this reason the FIA/ACO added air intake restrictors that lowered the performance ability of the LT5.5. Without these restrictions the LT5.5 would produce almost 750 hp, but for reliability, fuel economy and to meet the GTE Pro/GTLM class rules, the LT5.5 produced closer to 491 hp @ 6,900 rpm and 485 lb-ft @ 4,800 rpm. These performance figures fluctuate throughout the seasons due to the BoP adjustments made by the FIA/ACO. Depending on how competitive or how far off the pace the C7.R was compared to the rest of the field, the air restrictors could be adjusted to alter the power output.
Since 2004 Pratt & Miller had equipped the Corvette race cars with Xtrac sequential transmissions. The sequential transmission allowed the driver to keep their foot planted on the throttle whilst pulling the gear lever back to engage a higher gear. No clutch was required during the upshifts and a ignition interrupter cut spark during the transition of gears to ensure there was no rev spike. To go down gears the clutch pedal was required to ensure an accurate smooth downshift and simple push forward on the gear lever engaged the lower gears. As much as this style of transmission was much faster and accurate than a H-pattern style, human error still could be made, which translated into transmission wear and loss of time. It was still a physical job for the driver to change gear and required one hand to be removed from the wheel during each gear shift.
The more modern and expensive alternative was paddle operated shifters. These shifters had been equipped to the top class Le Man Prototype (LMP) race cars for over a decade, but due to their complexity were not permitted in the GT classes. After the economic crash in 2008, the FIA were trying to create more ways for race teams to save money. Despite a paddle operated transmission being more expensive than its sequential counterpart, the argument was made that the lower wear and tear of a paddle operated transmission would save teams money in the long run. This led to the decision in 2011 for a rule change to permit GT race teams to equip paddle operated transmissions.
Pratt & Miller wasted no time to equip the C6.R with paddle shifters. After many hours testing to tune the spark and ignition cut including the speed matching downshifts, C6RGT-003 and C6RGT-004 were ready for the 2011 season. The new transmission was a success although C6RGT-003 suffered transmission failure at the 2011 ALMS season finale at the Petit Le Mans. For 2012 Pratt & Miller built the last two C6 race cars in chassis C6RGT-005 and C6RGT-006. Both cars underwent many upgrades to take advantage of new rules essentially making the GT class faster. The Wixom Performance Build Center improved the powertrain, which included a revised calibration of the Xtrac six-speed semi-automatic transmission. The advancements helped the overall functionality whilst allowing for better durability.
Pratt & Miller would carry over the same Xtrac six-speed semi-automatic transmission for the C7.R. With the three years of data collected, more improvements were made to the electronics ensuring the transmission would be more durable and effective. With the C7.R equipped with an Xtrac transmission it would mark the 10th year Corvette Racing had trusted the British based company for their gearboxes and differentials. Ranging across a diverse group of motorsport disciplines such as Formula 1, Le Mans, and the World Rally Championship, Xtrac could be considered the best race gearbox manufacturer in the world. This can be backed by the fact the most successful race cars and teams choose Xtrac for transmissions and differentials.
With a paddle operated transmission being controlled by electronics, Pratt & Miller would design a bespoke, ergonomic steering wheel for the C7.R, with the shifter paddles mounted on the back. The wheel featured six color coded buttons on both the right and left side including two rotary dials in the center to control the fuel map and traction control settings. Other versions of the wheel would later appear on the Pratt & Miller built Chevrolet Camaro GT4.R, with the center Chevrolet bowtie replacing the Corvette emblem.
The production Corvette C7 Z06 the C7.R was based upon has a wheelbase measuring in at 106.7 in. (2,710 mm). That was a one inch increase over the previous C6 model, however, the overall length of the C7 was 1.3 inches longer than the C6 Z06 and ZR1. The height of the C7 had lowered to 48.6 in. (1,234 mm) from the 49.0 in. (1,245 mm) of the C6. Just like the predecessor the Z06 variant of the C7 was wider than the base model Corvette resulting in both the C7 Z06 and C6 Z06 measure in at 75.9 in. (1,928 mm) wide.
The regulations of the FIA and IMSA require GT race cars to use the same wheelbase as their production counterparts due to the use of the production chassis. GM take this rule into consideration when designing their latest generation of Corvette and work in conjunction with Pratt & Miller. When GM introduced the sixth generation Corvette they took advice from Pratt & Miller, which in the chassis department resulted in a longer wheelbase, but a shorter overall length. By decreasing the front and rear overhangs found on the C5 Corvette, the handling of the C6 was vastly improved. The same approach was taken by GM, when it came to the development of the C7 Corvette.
The C7.R race car using the same chassis as the production Z06 shares only two measurements with its production counterpart. Both the race car and production car have the same wheelbase at 106.7 in. (2,720 mm), and an identical overall length of 177 in. (4,496 mm). The rest of the dimensions differ with the width of the C7.R coming in at 81 in. (2,050 mm) a whole 5.1 inches (129.5 mm) wider than the production Z06. The increased width of the C7.R is due to the wider axle track, large racing tires and fully adjustable race suspension. The height of the race car is much lower than the production car by 3.6 in. (91.4 mm). With the C7.R sitting at only 45 in. (1,151 mm) high, the lower height is designed to lower the center of gravity, decreasing body roll, and overall improving handling. The lower ride height of the race car comes with other benefits such as producing less drag and lift. This is very important at circuits like Le Mans, where four long straights make up a large percentage of the lap making straight line speed and stability a necessity. The ride height, however is completely adjustable to cater to any race circuit. Bumpy tracks like Sebring often cause race cars to bottom out, therefore an increased ride height can solve this issue.
The whole C7 range of Corvette was heavier than the previous C6 generation. The previous Corvette C6 Z06 was the lightest in the sixth generation range, weighing in at only 3,131 lbs (1,420 kg). The C7 Z06 was almost 400 lbs heavier than its predecessor weighing in at 3,532 lbs (1,598 kg). Weight plays a major role in motorsports as more mass to move, decreases speed, braking ability and overall handling. Race teams attempt to make their cars as light as possible to be more competitive, however in the past race cars became so light it resulted in higher safety risks. For this reason the FIA mandates that GTE Pro cars must weigh a minimum of 2,745 lbs (1,245 kg) including driver and fluids. This meant the C7.R weighed exactly the same as the previous C6.R GT.
Pratt & Miller found many ways to save weight in the C7.R. The glass of rear and side windows was replaced with polycarbonate and the whole body was constructing from carbon composite, but the major weight saving was created in the cockpit. Compared to the production car no luxury or comfort component was carried over. The interior of the C7.R is purely business featuring only a custom carbon fiber race seat with six-point harness, rear facing camera screen, Bosch digital display, electronics, lightweight A/C unit and a safety equipment such as a fire extinguisher and roll cage. The roll cage adds a lot of weight, but with the absence of luxuries such as sound deadening, insulation, electronic leather seats, carpets, roof lining and the entertainment system makes the C7.R tip the scales at only 2,447 lbs (1,110 kg). When a driver and fluids are added the C7.R meets the FIA minimum weight limit, making it a whole 778 lbs (353 kg) lighter than the production Z06 when race ready.
The base model C7 Corvette Stingray took inspiration from the aerodynamic strategies of the previous C6.R race car. This included the forward-tilted radiator that worked in conjunction with the functional hood vents. Front-quarter panel vents, and rear transmission and differential cooling vents also came as standard. The C7 Z06 equipped with the Z07 performance pack took the aero to another level, including a front splitter inspired by the one found on the C7.R, side skirts and front brake cooling ducts integrated into the front grille. A rear spoiler with a large Gurney flap/wickerbill was included in the Z07 performance package, which altogether resulted in the production Z06 generating the most downforce of any GM vehicle at the time. Corvette Chief engineer – Tadge Juechter, mentioned how they worked concurrently with Pratt & Miller to develop the aerodynamic packages for the Z06 and the C7.R. The same modeling software was used to test both cars, deriving in the wind-tunnel test results and data to be shared.
The aero package found on the C7.R was designed to meet the FIA regulations. For 2011 the FIA relaxed the rules around the rear diffuser of the GT race cars. Pratt & Miller redesigned the new rear diffuser, which included a steeper angle, along with lower rear wheel cutouts. The redesigned diffuser along with new rear wheel cutouts allowed for cleaner air flow under the rear of the car, creating a better use of the Bernoulli effect essentially sucking the rear of the car down. In 2012 the rules evolved further to allow the GT class to utilize a stronger aero package. This included mounted the rear wing 75mm (2.9 inches) higher than the previous wing.
For the C7.R in its inaugural 2014 season, the rules from 2012 hadn’t changed, therefore the aero package of the C7.R was very similar to C6RGT-005 and C6RGT-006. The C7.R added a slightly larger front splitter than the one found on the C6.R, which followed the contours of the C7 front facia. A larger front grille that opened lower down than the production Z06 grille helped feed air to the forward-tilted radiator, that worked coherently with the heat extracting waterfall hood design. A similar hood design had been used across all previous Pratt & Miller Corvette race cars, as it allows the heat from the radiator not to circulate under the hood. The radiator inlet on the C7.R served a second function as it underwent a more intelligent design, which generated smoother airflow over the rear wing. These aerodynamic designs creating more efficiency, which improved the handling and stability at high speed.
Another area the C7 Z06 and C7.R share aerodynamic strategies was with the rear-brake cooling ducts. In the past, all the previous Pratt & Miller Corvette race cars had utilized NACA (U.S. National Advisory Committee for Aeronautics) ducts. This style of air duct has been used in motorsports for decades due to its unique design creating a ram air style intake whilst making a small impact on the overall airflow. The C5-R and C6.R featured NACA ducts on top of the rear bodywork, which provided cooling to the rear brakes, differential and transaxle. Cleaner airflow became a theme for Pratt & Miller with the C7.R, especially to the rear wing. This inspired the engineers of the C7.R to look at taking advantage of sharing the rear-brake cooling ducts found on the production C7 Z06. On the production car these openings are located on each of the rear quarter panels but serve on function of providing cool air to the rear brakes. Although similar in style and location on the C7.R, the openings on the race car are larger and feature a split inside due to the multiple functions they provide. These ducts direct air to the rear brakes like the production car, however, the split also sends cooling to the rear differential and transaxle. For high speed races like Le Mans, the lower section of these ducts, that fed the cooling to the rear brakes, could be covered to lower the drag, improving the overall top speed. With such long straights and the front brakes doing most of the work, the rear brakes cooled down enough between each braking zone, despite the lack of airflow.
2016 Aerodynamic Package Rule Change
In 2016 the FIA and the organizing entity of the 24 Hours of Le Mans, the Automobile Club de l’Ouest (ACO), introduced new rules for the GTE Pro class. The rule change affected the GTLM class in IMSA racing and GTE Pro class in the World Endurance Championship (WEC) including the 24 Hours of Le Mans. With the absence of the GT1 class since 2011, the GTE Pro class had become the highest level of GT racing. Despite being the top-level of GT cars, they shared almost identical performance specifications with the lower tier of GT cars such as the GTD class in the IMSA series and the GT3 cars. This led to the decision of the new rules to enhance the performance of the GTE Pro/GTLM cars, whilst making them safer.
The most notable change in safety for the GTE Pro/GTLM class was the introduction of the FIA-mandated roof hatch. This new hatch allowed better entry for safety workers to the driver in the event of an injury. However, the main purpose of the roof hatch served as access for an extraction device to be inserted into the cockpit to secure the driver’s head, neck and spine. The racing seat also saw adaptations in 2016 for the improved safety of the new regulations The seat was redesigned to meet higher structural performance requirements whilst incorporating larger side restraints. Corvette Racing has been a trendsetter within driver safety and head restraints have been part of the driver cell for years. In 2003 the team introduced the side-impact crash box, designed to help dissipate the force and energy of a driver’s side impact. The primary chassis structure of the C7 Z06 production car also served as a fundamental component within the C7.Rs crash system.
Along with improved safety, the new regulations introduced the possibility of an increased power output in the GTE Pro/GTLM class of roughly 20 horsepower. The increase in power was dependent on the Balance of Performance (BoP) figures between the different manufacturers. The minimum weight limit of 2,745 lbs (1,245 kg) was also reduced by 15 kg (33 lbs). These two changes combined were designed to equate to around a two-second per lap decrease in time at the Circuit de la Sarthe of the Le Mans 24 Hours.
The new round of technical regulation for 2016 allowed manufacturers additional freedom in the aerodynamic design of their GTE Pro cars. The front splitter of the 2016 specification C7.R was overall much larger, extending out further from the front bodywork. The new front splitter worked in conjunction with the flat floor and a new rear diffuser design. These are known as a volume opened areas, therefore the front splitter is not completely flat but features dimension. This is to manage and accelerate the air underneath the car, essentially sucking the car to the ground. Pratt & Miller also added canards/dive planes, to the sides of the front fascia, similar to the ones found on the 2012 – 2013 Corvette C6.R, but much larger. These new aero pieces help force more air over the top of the car, pushing more downforce on to the front wheels, whilst also directing cleaner air flow around the sides. For high speed races such as the 24 Hours of Le Mans, Corvette Racing removed the canards to lower the drag. Added to either side of the front splitter were new stepped turning vanes or carbon fences. These turning vanes were designed to be vortex generators. When multiple vortices in parallel, rotating in the same direction are created, they combined, create one large vortex. On the C7.R the vortexes are manipulated to flow down the sides of the car to create a gate of air, designed to trap more air beneath the car and not allowing it to flow out the sides.
The air that had been directed and accelerated beneath the car by the front splitter, was managed by much larger side skirts that had almost doubled in size than the ones used previously. The new side skirts worked in three ways. First the air that is flowing under the car wants to spill out from the sides, which fouls the aerodynamic principles of the floor design. This would generate lift and a lack of stability therefore extending the side skirts interrupts the natural path of the air, that wants to flow towards the air travelling over the car. Second, the extended side skirts also work in conjunction with the new front splitter featuring the turning vanes. The vortices that have been generated from the front aero package are helped by the large side skirts to restrict any air from being sucked under the car, which would create unwanted lift. The final function of the side skirts is they utilize the side exit exhausts. The side skirts take advantage of the exhaust gases pushing down on them, creating a minor increase in downward pressure.
The final part to the ground air flow of the 2016 C7.R was the new rear diffuser. In previous years the diffuser featured a completely flat design. To capitalize on the rule changes, the rear diffuser became three dimensional, resembling the one found on the C6.R from the GT1 era. The leading edge of the 2016 rear diffuser started at the rear axle centerline and expanded towards the rear of car creating one large venturi tunnel. Side plates were added to help channel the air more effectively along with six longitudinal fences. These fences created seven individual tunnels that increased in width from the outside edges towards the center of the diffuser. These tunnels were carefully designed to improve the efficiency of the air flow and direct it to specific areas of the rear of the car. The new dimensional shape of the rear diffuser helped accelerate the air, resulting in more rear downforce. The rear diffuser completed the aerodynamic floor design of the C7.R and ultimately controlled the desired venturi effect. This effect is created by the larger volume of air in the front that is directed strategically over and under the car by the front splitter. The air is then compressed beneath the car by the flat floor and side skirts. When the air is compressed it accelerates towards the low pressure air of the rear diffuser, where the air is able to expand before exiting. Due to the accelerated air beneath the car it decreases in pressure, which inversely increases the pressure above the car, thus creating downforce.
The final adaptation to the 2016 regulations was the relocation of the rear wing. The shape, size and design of the rear wing remained unchanged from the one used on the C7.R previously. However, the regulations allowed the GTE Pro/GTLM cars to position the rear wing further back, which improved its efficiency and effectiveness. Pratt & Miller redesigned the rear wing mounts that were made to extend past the rear fascia. The previous mounts, extended straight up, therefore the trailing edge of the rear wing was almost flush with the rear bodywork. The new mounts pushed the rear wing 15 cm (5.9 inches) rearwards, therefore the trailing edge of rear wing extended past the rear bodywork. The new location of the rear wing, changed the position of the pressure from the downforce. This effectively created downforce behind the car, applying more pressure on the whole rear end, which improved over the location of the rear wing used previously.
The end result of the 2016 regulation changes to the GTE Pro/GTLM class made the C7.R overall 1.4 seconds faster than the 2015 Corvette C7.R. Despite being quicker overall, at most of the IMSA WeatherTech SportsCar Championship circuits, the lap times between the 2015 and 2016 C7.R were very similar. At Le Mans where the regulations were designed to really come into affect, the 2016 C7.R ran its fastest lap time of 3:53.398. When compared to the 2015 C7.R fastest lap of 3:54.823, the 2016 specification C7.R was 1.425 seconds faster.
The drivers also liked the changes. Jan Magnussen reported back that the new specifications gave the driver more grip and made the car feel a little nicer to drive with the added downforce. Oliver Gavin mentioned how much the whole GTLM class of cars looked amazing. He thought it was great to see how the cars had been developed aero-wise, calling them sexy, aggressive and great for the fans to look at. Gavin also commented on how the regulations had made the GTLM cars a lot more fun to drive, taking them a great step forward, which overall made him very happy.
After GM equipped Brembo carbon-ceramic brakes as standard on the Corvette C6 ZR1, they became an option on some of the high performance GM vehicles. The C7 Z06 came with steel brake rotors, but when equipped with the optional Z07 performance package the brakes were upgraded to carbon-ceramics. Corvette Racing used carbon-ceramic brakes on the Corvette C5-R and the GT1 variant C6.R. In 2009 Corvette Racing moved to the GT2 class were carbon-ceramic brakes were not permitted but steel rotors instead. Corvette Racing did have some previous experience with steel rotors in 1999 due to carbon-ceramics not being allowed in the GT2 class for the Rolex 24 at Daytona. Pratt & Miller 10 years later were required to use steel rotors once again, but fortunately the technology had come a long way. After the initial testing the team were impressed with the performance of the steel rotors. Despite not producing the same absolute stopping power of the carbon-ceramics, the strength, consistency and driver feel met all their desired targets.
For the C7.R, Pratt & Miller continued their 11 year relationship with the British based company AP Racing. AP Racing had been developing the highest standard of race brakes for all disciplines of motorsports, such as Le Mans, Formula 1, NASCAR and the World Rally Championship. Corvette Racing had five years of knowledge with their AP Racing steel brakes on the C6.R GT, therefore the team carried across the same brakes to the C7.R. The brake rotors were made up of 15.35 inch (389.9 mm) vented and grooved iron brake rotors on the front with smaller 14 inch (355.6 mm) rotors on the rear of the same design. The six-piston AP Racing monoblock brake calipers were equipped to both the front and rear, that featured composite pads. The front brake rotors included a quick release function so at 24 hour endurance races like Le Mans and Daytona, worn rotors could be switched to fresh ones at the halfway mark. The Corvette Racing pit crew could accomplish a full front brake rotor change within a 52 second pitstop.
The pedal box equipped to the C7.R featured two master brake cylinders, that allowed the driver to alternate the pressure between the front and rear brakes. This is an important feature within motorsports as the driver can apply in excess of 105 kg (231 lbs) of pressure to the brake pedal. This pressure transfers a lot of load to the tires, which can cause lockup or alter the corner entry characteristics. The driver could adjust on the fly the brake bias via a knob/rotary dial mounted within easy reach. This dial would either move more pressure to the front brakes or rear, which is accomplished via a spherical bearing within the pedal box that adjusts the force distribution between the front and rear master cylinder. The benefit of adjustable brake bias to the driver is that the corner entry can be changed. For example if suffering understeer under braking, adjusting the brake bias to the rear will create better car rotation, resulting in better turn in. In contrast if the car is too loose or unstable under braking, moving the bias to the front can tighten up the cars rotation. Where adjustable brake bias really plays a part in endurance racing is when the fuel load burns away and the weight distribution of the car alters. Also changing weather conditions, which can be common amongst endurance races will require brake bias tuning. Typically races like the Rolex 24 at Daytona features rain during the night hours. Under wet conditions the driver can not apply as much force to the front brakes as they will simply lock up. The driver therefore can alter the brake bias to cater to the changing conditions.
The production Corvette C7 Z06 continued the traditional transverse composite leaf springs matched with magnetic ride controlled dampers. This tried and tested suspension setup helped the production Z06 to produce lap times on par with exotic hypercars at some of the world’s most famous race circuits. For example the C7 Z06 equipped with the Z07 Performance Package accomplished a lap time of 2:41.32 at Virginia International Raceway. Compared to the 2:43.10 of the 875 hp, $945,000 Porsche 918 Spyder, the Z06 was a seriously quick car on the race track. However, the race car would ditch the production suspension setup for a bespoke fully adjustable coil-over race suspension. Pratt & Miller had been using fully adjustable race suspension setups on the factory Corvette race cars since the beginning. This was due to the durability, tunability and ease of quick replacement in case of damage or failure. Due to the coil-over design, the C7.R chassis required modifications for the suspension to have strut assemblies. The coil-overs sit between short/long arm double wishbones, with fabricated steel upper and lower control arms including machined aluminum knuckles.
The dampers used on the C7.R were Moton that featured many tuning options such as, bump stop range, slow bump setting, fast bump setting, slow rebound setting and fast rebound setting. The dampers being fully adjustable allowed the team to control how quick the suspension responded to bumps on the race track. A circuit like Sebring is well known for its bumps, therefore the dampers can be fine tuned to respond slower to the harsh surface, maintaining better contact between the tires and the ground. Race drivers like to maximise the full width of a race circuit. This typically includes hitting the curbing/rumble strips on corner entry and exit at high speed. The adjustability of the dampers allowed the driver to hit the curbs with more aggression without the car going too light or bottoming out, which typically resulted in loss of grip and stability. The race dampers were also extremely durable therefore they could handle the abuse within a 24 hour endurance race without failure.
The springs, that were supplied by Eibach, included adjustable spring rates within the suspension architecture. These springs allowed Corvette Racing to tune the way the suspension responded to the track surface across the diverse type of circuits on the race calender. Softening the spring rates allowed for more weight transfer to the desired wheel, producing more grip. However, too much softness can create excessive weight distribution removing grip from other wheels. This is why race car suspension is stiff to keep the car flat through turns. The springs added with the stiff chassis of the C7.R, created high levels of mechanical grip. These springs were also designed to be very tough to withstand the harshness of motorsports.
The suspension of the C7.R also included fully adjustable toe, caster and camber angle settings allowing the team to tune the positioning of the tires. These tuning options provided the opportunity for the team to capitalize on the tire contact patches, turn in response along with specific positioning to heat or maintain tire temperatures. These options alter the handling characteristics, along with the amount of tire wear produced. At long endurance races like Le Mans and Daytona, Corvette Racing typically attempted to double stint their tires. These tuning options play an integral part in how long the drivers can keep running on the tires before any loss of traction or tire failure.
The suspension of the C7.R also included bespoke, heavy duty, fully adjustable sway bars. The sway bars could be set to be soft or stiff, creating a significant difference to the amount of understeer or oversteer experienced. The sway bars also known as anti-roll bars controlled the amount of transversal body roll encountered throughout cornering. Softening the front sway bar, whilst stiffening the rear will allow more body roll in the front creating better car rotation, thus reducing understeer. In contrast, stiffening the front and softening the rear sway bars would tighten the amount of rotation, reducing oversteer. The C7.R rode on stiff, low suspension that, when combined with its stiff chassis, could affect its handling in some cases. Therefore the sway bars played a major role in enabling body roll for increased grip, without compromising the efforts made to maintain the desired rigidity for the definitive utilization of the friction circle. The sway bars could also be adjusted by the crew during pit stops. Access holes amongst the body work of the C7.R allowed a member of the pit crew to access a speed handle wrench to adjust the softness of the sway bars. The ability to make mid-race adjustments to the sway bars was fundamental to the endurance races due to the ever changing conditions. With the transition of day to night, the air and track temperatures change, which alters the way the tires respond and even the aerodynamics due to air density. Changing the tire pressures for the next round of pit stops will help but the adjustment to the sway bars could completely affect the level of grip produced. In some instances the drivers would simply be dissatisfied with the cars handling, such as the case at the 2016 Rolex 24 at Daytona. The #3 C7.R was suffering with understeer, therefore throughout the pit stops the pit crew made sway bar adjustments that eventually led to the satisfaction of the driver.
The C7.R like its predecessor was popular with the drivers due to the high levels of mechanical grip the chassis and suspension produced. Despite the mechanical grip, the drivers and crew of Corvette Racing had to work with synergy to tune the suspension for each event. Without this team work the C7.R would have struggled to be as competitive as it was.
The 2014 inaugural year of the C7.R marked the 10 year anniversary between Corvette Racing and their tire partner Michelin. Between 1999 and 2003, Goodyear was the tire supplier for Corvette Racing. It was at the 2003 Le Mans 24 Hours that the team were handicapped by the Goodyears compared to their rival of the Prodrive Ferrari running on Michelins. Prodrive were able to double stint their tires equalling to a lot less time in the pits. In contrast, Corvette Racing were needing to change their Goodyears at every pitstop. On top of the lower wear rate, the Michelins produced higher levels of grip, making it impossible for the Corvette to keep with the pace of the Ferrari. The following year Corvette Racing switched to Michelin and have never looked back. The Michelins helped Corvette Racing drop six seconds off their lap time at the 2004 Le Mans 24 Hours compared to the previous years numbers. This decision begun a long partnership between General Motors and Michelin. The two companies collaborating high performance tires for vehicles such as the Corvette C6 ZR1, the Cadillac CTS-V, and the Corvette C8 Stingray.
The C7.R was equipped with Michelin Pilot radials that met the regulations implemented by the FIA and ACO. These regulations restricted the size and compound of the tires, however each tire manufacturer constructs their own tires with a unique blend of particular materials and chemicals. The better construction of the tire compound improves the level of adhesion and wear rate. Michelin are part of a selection of tire manufactures such as Falken Tire, Dunlop and Goodyear to name a few. Despite multiple tire manufacturers, Michelin have proven themselves as the clear pacesetter within endurance racing. They are capable of completing four or more ‘stints’ at Le Mans, equating to around 440 miles (704 km). In comparison to a street tire that may not seem impressive, however a tire at Le Mans are ran at an average speed of 135 mph (216 kph). The Audi R18 TDi was the overall winner of the 2011 Le Mans 24 Hours. It only required nine sets of Michelins that completed a total of 355 laps, a distance of 3,024 miles (4,838 km). One of the three Audi drivers, Benoit Tréluyer, completed 470 miles (752 km) on one set of Michelins. At Le Mans an average tire change costs a team an additional 30 seconds at a standstill on pit road. With the ability to quadruple stint a set of tires it can save in total over 10 minutes throughout a 24 hour race. With Michelins endurance and performance, it is easy to see why a majority of the teams that make up the Le Mans field choose the french tire manufacturer.
The GTE Pro class teams have a choice of three slick tire compound of soft, medium and hard. These different compounds wear at different rates and perform differently but are mainly developed for different track temperatures. A colder track will benefit from the softer compound as it can generate higher levels of adhesion. In contrast a hotter circuit will cause the soft tire to overheat, resulting in lower adhesion levels and aggressive wear. The hard tire would typically be the choice on a hot day due to their higher optimum temperatures and lower wear rate. There is also two choices of grooved/treaded tires for a wet circuit. Michelin worked hard to develop the tread pattern and compound for a rain tire that had enhanced water-clearing capabilities along with good grip. The ‘wet’ tire featured channels to move water out underneath itself, but still had large areas of smooth rubber to increase the contact patch. This tire would typically be used for a wet track with little standing water. For heavy rain the ‘full wet’ tire would be the choice as it featured many deep channels that disperse the standing water. Due to a more complex tread pattern there is less rubber in contact with the track resulting in lower grip, but the trade off is a much lower risk of hydroplaning.
The FIA mandates the GTE tire sizes be 300/33-R18 on the front and 310/41-R18 in the rear. These wide race tires protrude out from the the chassis as far as the rules will allow to increase the axle track for improved stability. The tires on the C7.R are mounted to six spoke, single center locking nut, BBS aluminum wheels. Corvette Racing had consistently used BBS as their wheel choice from 2006. In the GT1 era the wheels were constructed from magnesium, but the GT2 class that evolved into GTE/GTLM require an aluminum construction. This added sprung weight to the Corvette race car, adding an overall increase of 330 lbs in comparison to the previous GT1 C6.R.
The electronics in a race car is very complex due to playing multiple roles. The electronics control the overall operations of the drivetrain and transmission and also monitor the health of the car to the team and driver. There are over 100 individual sensors in a modern GT race car that detect information and data such as tire pressures, oil pressure, tire temperature, gearbox temperature to even the amount of slip from each individual wheel. In the previous GT1 era the telemetry was relayed in real time to pit lane, where the team and technicians could study the status of the car. This information was very useful as it allowed the team to potentially foresee issues that could be solved before becoming fatal, whilst also aiding the team with adjusting the race strategy. When Corvette Racing moved to the GT2 class in 2009, the FIA rules banned the use of real time telemetry in the response to help cut the costs of motorsports. This meant that at each pitstop a member of the crew would need to plug a laptop into an outlet located in the A-pillar of the C6.R in order to upload the data from the previous stint. Later teams made the argument that the removal of real-time telemetry made motorsport more dangerous and expensive due to potentially missing a major component failure that could cause a major accident on track. The FIA and ACO agreed with the points raised and permitted the use of real-time one-way telemetry.
Endurance racing is one of the few remaining disciplines of motorsport that allows for real-time telemetry. Most other forms of motorsports only feature spot-checking of all the vehicles variables, once a lap. The telemetry provides a continuous flow of information to the driver via onboard screens. If issues arise an alarm will be posted on screen for the driver to respond to. The FIA permits the use of one-way telemetry that generates a flow of data from the car to the team on pit road. This provides the team with data such as the motor is running, fuel consumption rate, tire temperatures, aerodynamic load and even displays any mechanical parts thats maybe showing signs of weakening. With the telemetry being studied by the engineers on pit road, they can make calculations to alter the strategy or inform the driver of changes to be made from within the car such as the fuel mixture. The use of two-way telemetry is banned, which allows the crew to calibrate settings to the car from the pits.
The fully digital Bosch DDU 8 dashboard of the C7.R was located centrally and replaced the gauge cluster of the C7 production car. This screen provided important information to driver thanks to the cars monitoring system. At the top of the screen was 10 LED rev lights that changed color sequentially from green, orange, to purple before all 10 lights would transition to red indicating the perfect shift point. When the pit limiter was engaged these LED rev lights illuminated in a steady green. The default screen of the digital display featured in the top right the speed in miles per hour with the fuel predict directly below. The gear indicator sat large and central and in the top left was the temperatures for all four tires. Below the tire temperature display was the fuel remaining in gallons and fuel consumption per lap. To the right and middle was the current lap time, including the time lost or gained per lap. Below the lap time was a battery voltage display and bottom right the alarm indicator, that showed anything from low oil pressure to high temperatures. The rest of the bottom of screen showed the current driver settings such as, traction control setting, yaw setting, engine map and the amount of laps completed within the current stint. To either side of the digital display was a pair of nine LED lights that sequentially lit up from bottom to top in blue indicating the amount of individual wheel slip from either rear tire under acceleration. The more of the LEDs that illuminated, the more the wheels were spinning. The same LEDs would light up in red if either of the two front wheels locked up under braking.
Collision Avoidance System
To the right of the digital dashboard was a Intel monitor that displayed the rear camera view. The C7.R featured a fire wall behind the driver that completely blocked the drivers rear view. This safety feature had been on all the previous Pratt & Miller Corvette race cars, however the rear view monitor first made its appearance on the C6.R in 2005. The C7.R competed in multi-class racing therefore typically four different classes of cars raced at the same time. The C7.R raced in the fastest of the GT classes, however other classes of less restricted cars such as P2 (Prototype 2), DP (Daytona Prototype) and LMP1 (Le Mans Prototype 1) would share the same race track. These faster cars could be upto 30 seconds a lap quicker at circuits like Le Mans, with over 20 mph faster closing speeds. This required the drivers in the GT classes to constantly check their mirrors to ensure they did not block or even collide with a faster car. To help the drivers, Pratt & Miller along with Bosch developed a collision avoidance system on the C7.R. This system registered cars closing in on the rear of the Corvette via arrows on the rear view monitor. If a car was slowly gaining on the C7.R a green chevron would appear above it on the monitor. This chevron would change from green, orange to red depending on the speed a car was gaining, with red being quickly. This was a great visual reference for the driver at identifying if a car gaining was a competitor or a car of a different classification that needed to be let by. Once a car had moved into the blind spots of the C7.R a flashing red arrow would appear on the monitor indicating which side the car was passing on. Integrated into the monitor was the meters the car was behind, displayed on the left and the seconds behind on the right. This system was revolutionary for multi-class racing and eventually became mandatory by the FIA.
Below the rear view camera monitor was a carbon fiber button box in replacement of the C7 production center console. This button box featured a series of switches, buttons and rotary dials for the driver to adjust mid-race.
The top row of buttons, starting from the left:
- Two starter buttons – These buttons engaged the fuel prime and starter motor. They played more of a backup role to the start button located on the steering wheel.
- Neutral button – This button engaged neutral within the transmission, as the paddle shifters could only shift up or down the gears.
- Emergency button – Used incase of an emergency such as injury or control failure of any components within the car.
- Electrical override button – This allowed the driver to override the electrical system of the car within an emergency situation.
- Fuel reserve button – Used for low fuel situations. This button plays more of a backup role due to the C7.R featuring fully automated fuel reserve system.
The second row starting from the left, featuring rotary dials:
- Headlight dial – Turned the headlights on or off as well as the interior light to illuminate the cockpit for night racing.
- A/C dial – Controlled the amount of cold air blowing from the air conditioner. A hose connected to the drivers helmet fed the cool air, however at long races it could get too cold for the driver, so the dial allowed for adjustments.
- Wiper dial- This dial toggled the windshield wiper on or off.
- Steering dial – Controlled the power steering strength, allowing the driver to alter the power for more feedback from the front wheels or in contrast if fatigue has set in at a long race.
- Function – For making adjustments if anything has faulted within the car.
The final row starting from the left:
- Master power switch – Allowing the driver to turn on or off all the power to the car
- Dimmer rotary dial – Controlled the brightness of the screens and lights within the car for night racing.
- Page rotary dial – This allowed the driver to alternate between different information pages displayed on the digital dashboard.
- Fire button – Featuring a protective guard surrounding the button to avoid accidental depression, this button engaged the onboard fire extinguishers in case of fire.
- Brake bias adjustment dial – This dial allowed the driver to make on the fly adjustments to the amount of brake pressure distributed between the front and rear brakes.
Within five years the steering wheel mounted to a Pratt & Miller Corvette race car had advanced from a simple round design featuring three buttons, to a bespoke, complex, 14 button design of the wheel equipped to the C7.R. Pratt & Miller designed the steering wheel for the C7.R, that was constructed from carbon fiber, with aluminum paddle shifters on the back. The wheel was designed for making the task of operating the C7.R easier for the driver. The ergonomic shape of the wheel featured a completely flat bottom, rubberized grips and the top of wheel removed to give a clear view to the digital dashboard. Strategically placed around the center of the wheel were 12 buttons and two rotary dials. These buttons were placed within easy reach of the drivers thumbs in an order of most frequently used.
The buttons from right side, top down:
- Flash headlight – Important for multi-class racing for warning cars of a slower class of your presence.
- Pit limiter – Held the speed of the C7.R to 37 mph or the restricted pit road speed.
- Stop – Shut off the motor, which is a rule for Le Mans that engines must be disabled once the car stops in the pit box.
- Traction control increase – Allowed the driver to increase the strength of the traction control enabled.
- Right turning signal – This is mandatory under the FIA/ACO rules, however is almost never used.
- Alarm clear – Removed any warnings raised on the digital dashboard display.
The two center rotary dials from right to left:
- Fuel map – This toggle switch was frequently used by the driver upon instruction from the engineers on pit road. It allowed the driver to make adjustments to the fuel mixture to adjust throttle settings, engine map or fuel saving.
- Traction control – The traction control toggle switch was used to pick a specific traction control setting between one and 12.
The buttons from left side, top down:
- Radio – This button allowed the driver to communicate with the team, via a microphone located inside the helmet.
- Drink – Race driving is very physical within a high temperature cabin. The drink button shoots water into the drivers mouth via a tube connected to the helmet.
- Start – This button was used to start the car, used typically after a completed pit stop.
- Traction control decrease – Allowed the driver to decrease the traction control strength.
- Left turning signal – Engaged the left turning signal
- Reverse – This button engaged the reverse gear within the transmission. Although rarely used, reverse cannot be selected via the paddle shifters.
The electronics of the C7.R steering was complex Within just the paddle shifters alone (unlike previous lever operated sequential transmission) they sent a signal to the transaxle to change gear, whilst simultaneously sending a signal to the engine. to cut spark and fuel. Under down shifting, the left paddle controlled the downshift of the gearbox, whilst precisely controlling the revolutions of the engine to speed match the lower gear about to be engaged.
Endurance racing requires driver changes during pit stops. This had to be done quickly not to hold up the pit stop, whilst also being safe ensuring the safety belts are all connected, including the drink and radio connectors to the helmet. Despite GTE/GTLM cars featuring fully functional doors, the driver still needs to climb through portions of the roll cage to cramb into the tight bucket seat. For this reason, most race cars feature quick release steering wheels to open up more space for a driver to get in and out of the cockpit. Pratt & Miller incorporated a new design feature to the C7.R to create smoother, less stressful driver changes. The steering column was spring loaded therefore a release handle tilted the steering wheel to high position out of the way of the driver. Once the new driver climbed in, they simply pulled the wheel down back into position meaning the need of the removing the steering wheel was no longer required for the drivers of Corvette Racing.
Within its four years competing in the GT2/GT class, Corvette Racing switched up the previous Corvette C6.R livery each year. The predominantly yellow with black accent color scheme remained, however the style of the graphics was a completely new design for each season.
For the C7.R, Corvette Racing carried over the traditional yellow color scheme that had been associated with Corvette Racing for 14 years. The new livery of the C7.R was a cleaner look compared to the last four liveries used on the C6.R. It was designed to highlight the accents and detail of the C7 Corvette. The main sponsor of Compuware that had been part of Corvette Racing since 2003 was no longer a partner of the team, which its absence simplified the livery of the C7.R. The black accents consisted of the black wheels, stinger hood stripe with the new look Jake Skull, and a black rocker panels that started from the front splitter and gradually raised up the sides towards the rear fascia. A wide slanted silver stripe started behind the fender vents that ran straight down to the side skirts and featured a C7.R logo at the bottom.
The livery of the C7.R appeared to be more focused on maintaining a production Z06 look. For the first time on a Pratt & Miller Corvette race car, a fender emblem that featured the production car name was used. This was created by the fender vents featuring a decal of the new C7 Z06 logo located in the same space the emblem appeared on the production car. On top of the rear quarter panels, detailed stickers gave the illusion of the production C7 quarter panel vents, despite the C7.R not featuring them. The rear fascia even integrated the production C7 slim rear reflectors, that had no use nor requirement on the race track.
Due to the class color coding rules of the Tudor United SportsCar Championship, both the #3 and #4 C7.R featured side mirrors, window banner end sections and rear wing end plates in red. Besides the door numbers, the only way to differentiate between the two Pratt & Miller Corvettes was a white window banner used on the #3 car and the use of a black window banner on the #4 car.
Throughout its five years competing for Corvette Racing, the livery of the C7.R remained unchanged with only minor modifications made to some of the graphics each season.
The American Le Mans Series (ALMS) ended with the 2013 season. NASCAR Holdings, Inc merged IMSA and the Grand-Am series whilst adding a new sponsor to form the TUDOR United SportsCar Championship (TUSSC). The new series followed on with the same format as the ALMS, but introduced the legendary Rolex 24 at Daytona to the calendar as well as Daytona Prototypes. Due to a majority of the teams in the GTLM class (formerly known as the GT class) competing at the Le Mans 24 Hours, it was important for NASCAR Holdings, Inc to conform to the FIA/ACO rules for certain classes. Teams like Corvette Racing would not have the time nor resources to construct cars of different specifications in order to meet mixed regulations.
Typically the start of the season for Corvette Racing was in March for the Mobil 1 Twelve Hours of Sebring, but due to the Rolex 24 at Daytona, the first race for the C7.R would take place on January 25 – 26, 2014. This left Pratt & Miller less time to develop and prepare the new C7.R for competition, therefore public testing in December of 2013. Pratt & Millers new Corvette C7.R was present at the Roar Before the 24 within the first weekend of 2014. This event played almost like a dress rehearsal for the Rolex 24 hour race, allowing all the teams competing to test and tune their cars across three days. The Roar Before the 24 provided Corvette Racing the opportunity to collect fundamental data on their new car, including its pace against the competition.
The official unveiling of the Corvette C7.R was on January 13th, 2014 alongside the new C7 Z06. This gave the media and public a look at the new race car out of the camouflage and in race trim. Race debuts for any car within motorsports is extremely challenging due to the lack of knowledge on the competitiveness and durability of the components. However, for a debut at a grueling 24 hour race, the C7.R would not be eased into its role as the successor for the C6.R. Corvette Racing qualified fourth and 11th with the Oliver Gavin in the #4 car putting in the best lap time. An electrical issue sidelined the #3 car but the team were still optimistic with it being such a long race. During the race the new C7.R impressed with its outright pace, however, unfortunately the gremlins of a brand new car caught up with the team. With less than three hours remaining in the race, the #4 car that was running second in class at the time and chasing down the class leading car, when Tommy Milner noticed the gearbox temperature dramatically rising. Milner immediately took the #4 car to the garages, where the team discovered the transmission bearing had failed. The team switched out the transmission within 30 minutes and the #4 car went back out on track to finish fifth in class. The #3 car managed to take the class lead after starting at the back of the grid within just six hours. Unfortunately engine cooling was an issue and eventually led to the retirement of the #3 C7.R. Despite a disappointing result for the debut of the C7.R, it was obvious the C7.R was a phenomenal race car. The team would take what they learnt from Daytona and improve the C7.R for the rest of the season.
The second race for C7.R was another big challenge as it was the Mobil 1 Twelve Hours of Sebring. This event, despite being half the distance of Daytona ot Le Mans, had built a reputation for being the most punishing to the car and driver, due to its notoriously bumpy track surface. Yet again the #4 car was able to outpace the #3 during qualifying, allowing the two C7.Rs to start 4th and 5th in class. The #4 C7.R was able to lead the GTLM class throughout the race on numerous occasions until tow spins late in the race, followed by issues with the engine with only 30 minutes remaining. These incidents put the #4 C7.R back into sixth in class where it would finish. The luck of the #3 car was no better either, with front bodywork damage caused by a collision with the BMW on the opening lap. Later in the race the fuel pump of the #3 car started to struggle, which led to being replaced, dropping the #3 car down the order to eventually finish eighth in class. Sebring brought with it another disappointing finish for Corvette Racing, but the C7.R again showed its pace that included putting up the fastest lap in the GTLM class.
Round three of the 2014 TUSCC season took the team to Long Beach, California for a 100 minute race on the legendary street circuit. The #3 car would put in the fastest qualifying time, handing the first class pole position for the C7.R, with the #4 starting fourth on the grid. The race for the #3 car was quite uneventful, with the C7.R leading all but one lap. This would eventually lead to the first class victory for the C7.R along with the first win for Corvette Racing in the new TUDOR United SportsCar Championship. The #4 car was able to gain a position early in the race and was gradually closing the gap on the car ahead to eventually run out of time. The #4 car would finish third in class putting both Corvettes on the podium for a historic moment.
Round four took the team north up the state of California to Mazda Raceway Leguna Seca. The #3 car yet again managed to clinch a class pole position, with the #4 car putting in its best time good enough for fourth on the grid. This time around it would not be as easy for the #3 C7.R, with the BMW Z4 GTE stayed within a second behind the Corvette. Jan Magnussen managed to lead all 42 laps of his stint, but was constantly under pressure for the BMW, which forced Magnussen to lock-up his brakes on a few occasions going into the famous Corkscrew. Despite the challenge posed by the BMW and Ferrari, the duo of Magnussen and Garcia held the lead to take the second straight win for the new C7.R. The #4 car of Oliver Gavin and Tommy Milner, struggled with working the rear tires more than the other cars in GTLM and they finished fifth in class.
The next event for Corvette Racing would be the big one for the C7.R, taking its first trip to France for the legendary 24 Hours of Le Mans. The last class win for Corvette Racing at Le Mans was in 2011, so the team was eager to debut their latest generation Corvette race car to the world and hopefully take the class victory. Due to the regulations of Le Mans designating number groups to specific classes, Corvette Racing would use #73 and #74 for the event. The #73 C7.R was able to set the second fastest qualifying time in the GTE Pro class, with the #74 taking fourth on the grid. The C7.R so far in its last two endurance races had suffered with reliability issues, which the team had hoped to eliminate for Le Mans. At the six hour mark of the race Richard Westbrook in the #74 C7.R was leading the GTE Pro class by nearly 30 seconds. The #73 car driven by Jan Magnussen at the time was able to take first from the Ferrari within just 40 minutes of the race start. At the halfway point Tommy Milner in #74 car was hunting down the lead from the Aston Martin, whilst Jordan Taylor in the #73 was in fifth after the C7.R lost nearly two laps in the pits due to the valve stem that allows the car to be raised on its air jacks had failed. With six hours to go the positions of the two Corvettes had changed. Antonio Garcia in the #73 car was in fourth chasing down the fourth placed Porsche. The valve stem issue, including two safety cars had split the Corvette away from the class leader. The #74 C7.R had dropped to fifth in class due to a slipping alternator belt caused by oil from a transmission leak had required time in the pits. Despite the safety cars and valve stem issues, the #73 Corvette was able to fight its way to an impressive second place in class finish at its Le Mans debut. The #74 car lost eight laps repairing the transmission leak and alternator issue, placing them fourth in class at the finish line. Overall the C7.R was very impressive at Le Mans and showed it could be a class winner.
Corvette Racing returned to America for round five of the TUSSC taking place at Watkins Glen International. This would be the first time for the team competing at the historic circuit located in the state of New York. Despite the lack of data, the #3 car was able to qualify second fastest in class, with the #4 car taking seventh. The #3 car of Antonio Garcia and Jan Magnussen led 154 of the 185 laps completed by the GTLM class within the six hour race. The #3 car was able to take the class victory resulting in the third straight win for the duo in the TUDOR United SportsCar Championship. This win moved the duo into first place in the GTLM drivers championship standings, whichalos put Chevrolet at the top of the manufacturers standings. Oliver Gavin and Tommy Milner were running in second behind their teammate for most of the race until a stop and go penalty was handed to the #4 car within the last hour of the race. The race officials penalized the duo for unavoidable contact, dropping them into fourth in class where they finished.
Round six of the TUSSC was a two hour and 45 minute race at the popular Canadian circuit of Mosport. Antonio Garcia was able to qualify the #3 C7.R second in class, whilst the best efforts of the #4 car sealed fourth on the grid. After battling with the Viper of SRT Motorsports, the #3 C7.R took its fourth straight GTLM class victory, extending the lead in the championship standings. Oliver Gavin and Tommy Milner struggled in the #4 Corvette finishing seventh in class.
Round seven would be another first for Corvette Racing at the iconic Indianapolis Motor Speedway. Both Corvettes struggled to adapt to the circuit with the #3 car qualifying sixth in class and the #4 taking tenth. After a two hour and 45 minute race Magnussen and Garcia managed to get the #3 car upto a fourth place finish, whilst Gavin and Milner finished right behind in fifth.
The eighth round of the TUSSC 2014 season took place at Virginia International Raceway. Corvette Racing had a win and a podium in their last two visits to VIR, however they would struggle to keep with the pace of the class winning Risi Competizione Ferrari. The #3 C7.R completed 82 laps to finish seventh in class, whilst the #4 car was the stronger of the two Corvettes was forced off the track mid-race dropping them four laps behind. Gavin and Milner would complete 78 laps taking ninth in class. The seventh place of Magnussen and Garcia was enough to maintain the championship lead for both the drivers and manufacturers standings.
The second to final round of the 2014 season saw Corvette Racing return to the Circuit of The Americas located in Austin, Texas. Magnussen and Garcia held only a six point lead over Jonathan Bomarito and Kuno Wittmer of SRT Motorsports in the GTLM drivers standings. The winner of last year’s race, Jan Magnussen, put in the best lap time for Corvette Racing, placing the #3 C7.R in seventh. Oliver Gavin struggled to keep the pace with the front runners qualifying the #4 C7.R in ninth. This was the least competitive the C7.R had been all season. The race would not be much better for the team with the #3 finishing in ninth and the #4 taking tenth. Magnussen and Garcia dropped to second in the drivers standings by 22 points to Bomarito and Wittmer.
The season finale for 2014 would be at Road Atlanta for the 10 hour Petit Le Mans endurance race. Antonio Garcia qualified the #3 C7.R in sixth place, whilst Tommy Milner put the #4 Corvette in ninth. Throughout the race Oliver Gavin and Tommy Milner displayed their best performances of the year, leading the GTLM class on four different occasions to eventually finish fourth. The #3 Corvette managed to take the GTLM class lead early in the race with a triple stint from Garcia. Unfortunately after handing over to Jan Magnussen the #3 C7.R was involved in a pile up due to pit exit being closed. The left front of the #3 C7.R was badly damaged, which required repairs costing them four laps. This resulted in the #3 car finishing the Petit Le Mans eighth in the GTLM class. Garcia and Magnussen would finish as runners-up to Jonathan Bomarito and Kuno Wittmer of SRT Motorsports whilst Chevrolet would finish third in the GTLM Manufacturers standings.
The debut year of the C7.R was very impressive. The team worked out the issues early in the season and unfortunately a string of bad luck kept Corvette Racing from taking the drivers and manufacturers championship title in only its first year of competition. In total for 2014, Corvette Racing collected six podiums including four wins in the inaugural year of the C7.R. A lot of data and information was collected throughout the season allowing the team to capitalize on the foundations built for next years to come.
The first Corvette C7.R constructed by Pratt & Miller to compete in the renamed Grand Touring Le Mans class of the TUDOR United SportsCar Championship. The C7.R was built to the specifications of the FIA/ACO GTE Pro regulations, that were adopted by IMSA for competition in the USA. Most of the components of the C7.R, such as brakes, suspension, transmission and the basic architecture of the engine was carried over from the previous C6.R. This gave Pratt & Miller an advantage going into the inaugural season, due to the data collected over the last four years.
Where the C7.R was completely new was within its foundations. The C7.R was built in conjunction with the C7 Z06 production car featuring a new aluminum chassis that was 40% stronger than the previous generation Corvette. The new chassis had a wheelbase that was one inch longer than the sixth generation Corvette and an overall length increase of 1.5 inches. With the aero package being strictly limited by the FIA, the improved rigidity of the chassis gave the C7.R an advantage over the competition due to the improved mechanical grip.
The aerodynamics saw a complete overhaul compared to the sixth generation Corvette. Pratt & Miller construction the aero package to the specifications of the FIA, but were able to capitalize on the aerodynamic principles of the C7 bodywork. A new and improved front radiator inlet altered the air traveling over the car producing smoother airflow to the rear wing. The rear bodywork was cleaned up by replacing the previously used NACA ducts for vents relocated to the lower front sections of the quarter panels that resembled the production Z06 rear brake cooling ducts. The bodywork of the C7.R overall improved the effectiveness and efficiency of the rear wing increasing the downforce without exceeding the restrictions of the regulations on the location, height and size of the rear wing.
The engine was the LS5.5-R used in the C6.R for the previous three years. The small block V8 was constructed from the original architecture of the GM LS7, but due to regulations the displacement was limited to 5.5 liters. The introduction of direct injection to the new LT series of V8 used in the seventh generation Corvette, Pratt & Miller were permitted to incorporate direct injection to the race motor. Direct injection improved the throttle response and fuel economy of the LS5.5-R, which was renamed to LT5.5 for its evolution into the C7.R. The fuel economy played a major factor within the C7.R as in the long endurance races, it could add additional laps to the fuel stint, ultimately resulting in a better opportunity for victory.
Chassis C7RGT-001 became the C7.R test mule for Corvette Racing, which ran a few public demo laps at Mazda Raceway Leguna Seca during the Monterey Motorsports Reunion on August 17th, 2013. Corvette Racing later ran C7RGT-001 for a two day test at Sebring International Raceway between December 9th-10th, 2013. C7RGT-001 was wrapped in a black and white checkered camouflage livery until its unveiling on January 13th, 2014 alongside the new C7 Z06 production car at the North American International Auto Show in Detroit.
The TUDOR United SportsCar Championship required teams to attend the ‘Roar Before the 24’ test weekend that took place between January 3rd-5th, 2014. Corvette Racing would need two of their new C7.Rs at the test at Daytona International Speedway in Florida then the same cars would need to be ready for Rolex 24 at Daytona race in two weeks time on January 25th-26th, 2014. The teams typically arrive at Daytona a few days before the race as the free practice sessions start on the Wednesday. This created a dilemma for Corvette Racing in regards to running a C7.R in Florida then display it in Detroit and send it back back to Florida for the race within a 16 day timeframe. To resolve the issue, Pratt & Miller decided to build three chassis in 2014, with C7RGT-002 becoming the #4 car that would be at Daytona along with C7RGT-003 as the #3 car. This left chassis C7RGT-001 available to be used in Detroit for the North American International Auto Show.
Chassis C7RGT-001 spent most of 2014 at the Pratt & Miller factory in Michigan leaving chassis C7RGT-002 and C7RGT-003 for competition. On September 20th, 2014 the 12th round of the TUDOR United SportsCar Championship took place at the Circuit of The Americas in Austin, Texas. On the same day before the TUSCC race, the FIA World Endurance Championship (WEC) were running a six hour race at the same circuit. Corvette Racing made the decision prior to the race weekend that they would run the C7.R in the WEC race. This would mean that chassis C7RGT-001 would make its competitive debut at the WEC race. Tommy Milner along with the two brothers of Jordan and Ricky Taylor would make up the three drivers for the six hour WEC race. #65 was used for chassis C7RGT-001, however the team struggled to find pace in the C7.R at COTA in both the WEC race and TUSCC race with C7RGT-001 finishing seventh in the GTE Pro class and 24th overall.
Tommy Milner ran both C7RGT-001 and C7RGT-002 on the same day in Austin and had some interesting information to report back to the team. He prefered C7RGT-001 over the other chassis as he was made aware that C7RGT-002 was too stiff. For this reason the final race of the season at Road Atlanta for the Petit Le Mans, C7RGT-001 as #4 was used in replacement for C7RGT-002. It would finish fourth in class at the season finale, with Oliver Gavin happy with the the chassis it was used the following year in 2015.
For the 2015 season, little changes were made to chassis C7RGT-001. The same aero package used the year before was carried over as well as the mechanical components. However, the engineers at Pratt & Miller worked hard to optimize the cars setup including the damper and spring rates. With a whole year of racing completed with the C7.R, the engineers during the off season were able to analyze the data improve the C7.R for the 2015 season. This provided a good baseline setup for the C7.R at each race to drive right off the trailer opening up more time for fine tuning on the track. One area that was addressed by Pratt & Miller for 2015 was the brake pedal feel that became the biggest complaint from the drivers about the C7.R, the previous year. The drivers reported a large dead zone in the brake pedal feel that made it difficult to judge accurate braking pressure. With race drivers trying to leave braking to the latest possibility whilst utilizing the trail braking technique, that requires brake pressure to be applied and slowly released all the way to the apex, confidence in the brake feel is essential. To combat this issue, Pratt & Miller went back to Michigan and looked at the problem, which required them to developed their own entirely new braking system. The drivers reported back that the new system was a massive improvement, especially to the consistency that played a major factor at the longer endurance races. Another area addressed in 2015 was better cooling within the rear of the car. By rerouting the cooling ducts to the rear differential, transaxle and the rear brakes, a better cooling balance was created ensuring the brakes were not overheated.
The changes for 2015 made to C7RGT-001 created better lap times than the previous year, resulting in three podiums including the GTE Pro class victory at the prestigious 24 Hours of Le Mans. The win at Le Mans became the eighth all time win for Corvette Racing at the event and still remains today as their last victory there.
At the end of the 2015 season C7RGT-001 was sold to Jun San Chen’s Team AAI of the Asian Le Mans Series. Chassis C7RGT-001 was entered under Team AAI into the GTE Am class for the 2016 Le Mans 24 Hours. Former Corvette Racing driver Johnny O’Connell alongside Oliver Bryant and Mark Patterson finished ninth in class and 39th overall.
The second C7.R chassis built by Pratt & Miller for Corvette Racing to compete in the 2014 TUDOR United SportsCar Championship. C7RGT-002 was a sister car to C7RGT-001 and built to the exact same specifications. C7RGT-002 made its first public appearance at the ‘Roar Before the 24’ test between January 3rd-5th, 2014 in Daytona, Florida.
C7RGT-002 was allocated the #4 for the TUSSC and #74 for the 24 Hours of Le Mans. In 2014, C7RGT-002 was driven by Oliver Gavin and Tommy Milner with Robin Liddell and Richard Westbrook added as a third driver for the endurance events. C7RGT-002 made its competitive race debut on January 25th-26th, 2014 at the Rolex 24 at Daytona. This was not only the first race for the C7.R but the first time returning to Daytona for Corvette Racing since 2001. C7RGT-002 was able to show great pace in its debut race, however whilst chasing down the class leading car, the transmission bearing failed, taking C7RGT-002 out of the race for 30 minutes for a gearbox change to eventually finish fifth in class.
C7RGT-002 collected its first podium at round three of the TUSSC on April 12th, 2014 at Long Beach where it would finish third in class. Unfortunately this would be the only podium for C7RGT-002 in 2014. At round nine of the the 2014 TUSSC at the Circuit Of The Americas, chassis C7RGT-002 was driven by Oliver Gavin and Tommy Milner in a two hour race. Earlier in the same day the FIA World Endurance Championship ran a six hour race on the same circuit. Corvette Racing decided to enter a single C7.R into the WEC race driven by Tommy Milner, Jordan Taylor and Ricky Taylor. Due to C7RGT-001 and C7RGT-002 not being available for the WEC race, chassis C7RGT-001 made its competitive debut in the WEC six hour event. After Milner ran C7RGT-001 and C7RGT-002 back to back he noticed that C7RGT-001 had a softer chassis, which he prefered. This essentially retired C7RGT-002 from competing with Corvette Racing, with C7RGT-001 being used for the final race in 2014 and for the full 2015 season.
After the preference of Tommy Milner, chassis C7RGT-002 was no longer required by Corvette Racing therefore was sold at the end of 2014 to a previous customer of Larbre Competition. Pratt & Miller started selling their used Corvette chassis to the French team in 2010, when Larbre Competition purchased chassis C6 RGT-001 then later chassis C6GT-003 in 2011. In the hands of Larbre Competition, the best result for C7RGT-002 in 2015 was fourth in the GTE Am class at the Fuji Six Hours race in the WEC series. Larbre Competition loaned C7RGT-002 back to Corvette Racing for two rounds of the TUDOR United SportsCar Championship in 2015. C7RGT-003 was involved in huge crash during qualifying at Le Mans, after a mechanical failure in the Porsche Curves caused Jan Magnussen to lose control and damage C7RGT-003 beyond any immediate repair. Whilst chassis C7RGT-003 was being rebuilt by Pratt & Miller at the Michigan factory, C7RGT-002 was used for round six of the TUSSC for a six hour race at the Watkins Glen on June 28th, 2015. It was driven by Antonio Garcia and Jan Magnussen as the #3 car and finished fourth in the GTLM class. C7RGT-002 would need to be used again by Corvette Racing at round seven of the TUSSC at the Canadian Tire Motorsport Park for a two hour and 45 minute race on July 12th, 2015. Garcia and Magnussen would accomplish a podium finish in the GTLM class, before the car was returned to Larbre Competition due to chassis C7RGT-003 being fully restored by Pratt & Miller and ready for use.
C7RGT-002 was raced by Larbre Competition between 2015 and 2017 and accomplishing back to back podiums in the GTE Am class at the Six Hours of Silverstone on April 17th, 2016 and the WEC Six Hours of Spa-Francorchamps on May 7th, 2016. The podiums would continue after Le Mans at the Six Hours of Nürburgring on July 24th, 2016 and the Lone Star Le Mans race on September 17th, 2016.
The last race to date for chassis C7RGT-002, was the 24 Hours of Le Mans on June 18th, 2017. Larbre competition revealed a radical ‘Art car’ livery ahead of the Sunday test day at the Circuit de la Sarthe on June 6th, 2017. The paint scheme was named the ‘Human’ livery and was designed by street artist Ramzi Adek, a mutual friend of one of the Larbre Competition drivers, Romain Brandela. The livery featured Day-Glo paint that lit up in the dark against black backgrounds, with a pop art style graphics. The main idea of Adek was to create a flow of strength and power to carry the drivers through the Le Mans week. Despite finishing 15th in the GTE Am class, C7RGT-002 certainly drew a lot of attention in its final outing.
The third C7.R built in 2014 by Pratt & Miller for Corvette Racing to compete in the TUDOR United SportsCar Championship and the Le Mans 24 Hours. C7RGT-003 was built to the exact same specifications as C7RGT-001 and C7RGT-002. Building a third chassis in the first year of competition was unusual for Pratt & Miller as in the past, typically two new chassis were built each year. Chassis C7RGT-003 was constructed due to chassis C7RGT-001 being the unveil car at the North American International Auto Show in Detroit on January 13th, 2014. Chassis C7RGT-003 became a necessity due to the requirement of two cars to run at the ‘Roar Before the 24’ test session between January 3rd-5th, 2014. With chassis C7RGT-001 being in Detroit on January 13th and the Rolex 24 at Daytona race taking place the following week on January 25th-26th, the best solution was to build a third chassis.
Chassis C7RGT-003 became the #3 car driven by Jan Magnussen and Antonio Garcia with Ryan Briscoe and Richard Westbrook added for the third driver roles at the endurance events. C7RGT-003 made its debut at the ‘Roar Before the 24’ in Daytona, Florida between January 3rd-5th, 2014. It would later then make its first competitive debut between January 25th-26th, 2014 at the Rolex 24 at Daytona. In its debut race C7RGT-003 showed its impressive pace, leading the GTLM from the back of grid within just six hours. Unfortunately at the halfway mark of the 24 hour race, C7RGT-003 started suffering from cooling issues that could not be resolved, eventually leading to its retirement from the race.
Despite the disappointing debut, C7RGT-003 was able to have a very successful inaugural season. In only its third race C7RGT-003 was able to bring home the first class victory for the new C7.R at the Long Beach street circuit. This victory would lead to four straight TUDOR United SportsCar Championship class wins with a second place finish in the GTE Pro class at the 24 Hours of Le Mans inbetween. After the five back to back podiums, C7RGT-003 was able to lead both the TUSSC GTLM Drivers and GTLM Manufacturers standings for 2014. Due to the success of the C7.R, the Balance of Performance (BoP) would intervene making the competition quicker resulting in Corvette Racing held off the podium for the rest of the 2014 season. This would eventually place Jan Magnussen and Antonio Garcia second in the drivers standings and Chevrolet/Corvette Racing finishing third in the manufacturers standings.
C7RGT-003 would also be used by Corvette Racing for the 2015 season. The livery for 2015 was almost identical to the one used previously, however the silver flashes behind the front fender vents got a chrome finish. During the off-season the Pratt & Miller engineers would make the same upgrades to C7RGT-003 as they did to C7RGT-001, which included the improved brake feel and increased cooling, especially in the rear for the differential, transaxle and rear brakes. The upgrades along with a year of date collected on the C7.R would translate into further success for 2015. C7RGT-003 would impress at the season opener, taking the GTLM class win at the prestigious Rolex 24 at Daytona. The momentum would be carried into the second round of the season, where C7RGT-003 took another class victory at the historic Twelve Hours of Sebring. For round three of the 2015 TUSSC season at Long Beach, C7RGT-003 would take third in class, collecting another podium. The triple crown of endurance racing was in sight for Corvette Racing that included a win at Daytona, Sebring and Le Mans. Unfortunately during qualifying at Le Mans, C7RGT-003 suffered a mechanical failure in the Porsche curves that ended with Jan Magnussen crashing hard into the wall. The damage was beyond repairable at the track, that led to withdrawal of C7RGT-003 at the 2015 Le Mans 24 Hours. Fortunately C7RGT-001 would manage to win the GTE Pro class at Le Mans, handing Corvette Racing the endurance racing triple crown. After Le Mans, C7RGT-003 was so badly damaged that whilst it was being rebuilt at the Pratt & Miller factory in Michigan it would miss two rounds of the 2015 TUSSC season. This required Corvette Racing to loan chassis C7RGT-002 for those two races that had previously been sold at the end of 2014 to Larbre Competition. After the rebuild C7RGT-003 was unable to get back onto the podium in 2015 resulting in Antonio Garcia and Jan Magnussen finishing third in the GTLM drivers standings and Corvette Racing taking third in the manufacturers standings.
C7RGT-003 would finish sixth in class at the Petit Le Mans on October 3rd, 2015, which would be its final competitive race. To date C7RGT-003 is currently up for sale at $950,000. With its impressive résumé of historic class wins along with being only one of seven C7.Rs ever built, it is quite the investment.
C7RGT-004 became the fourth chassis built by Pratt & Miller for Corvette Racing to compete in the new IMSA WeatherTech SportsCar Championship, formerly known as the TUDOR United SportsCar Championship. C7RGT-004 was also built to meet the specifications of the FIA and ACO to compete in the 24 Hours of Le Mans and any World Endurance Championship events. Chassis C7RGT-004 was constructed in 2015 and started testing later the same year, which included the Daytona November Test.
For the upcoming 2016 season the FIA/ACO announced that the regulations in the GTE Pro class would adapt to make the highest class of GT racing faster and safer. Since the demise of the GTS/GT1 class in 2011, the GTE Pro class had become the highest level of GT racing. Despite being the elite GT class, GTE Pro shared a lot of performance specification with GT3/GTD cars creating a minor gap in performance within the multi-class racing format. The FIA/ACO decided to address the issue by freeing up some of the restriction placed on the GTE Pro class, especially around the aero package. A slight bump in power and decrease in weight (if required by the Balance of Performance) along with improved safety would better seperate the GTE Pro cars from other GT classes. Due to IMSA adopting the FIA/ACO GTE Pro regulations for their Grand Touring Le Mans (GTLM) class, any team competing in the GTLM class would be eligible for FIA WEC events such as Le Mans.
The safety changes included a new mandatory roof hatch that gave track safety workers better access to the driver incase of an injury, for an extraction device that protected the drivers head, neck and spine. The safety improvements mandated the seat to meet higher structural performance requirements, which included larger side restraints. The 2016 regulation changes created opportunity for teams to increase the power output by roughly 20 horsepower. The minimum weight requirement of 2,745 lbs (1,245 kg) could also be reduced by 15 kg (33 lbs) to 2,712 lbs (1,230 kg). These performance changes were dependant on the Balance of Performance, that altered between the different manufacturers.
The most notable change came to the aerodynamic package, with the FIA allowing additional freedom to the design. The 2016 regulations saw the C7.R get more aggressive aero, that started from the front. The new front splitter increased in length, protruding further from the front fascia, increasing its effectiveness. Added to either side of the splitter were stepped turning vanes or carbon fences that generated vortices to travel down the side of the car that acted as a large air gates, restricting any air under the car from escaping. Added to the front bodywork was removable canards/dive planes, that helped add additional front downforce by directing the cleaner air over the car. For low drag races such as Le Mans, these canards could be removed to help increase the top speed. The final new feature equipped to the front of C7RGT-004 was a pair of pitot tubes located just above the Corvette emblem. These tubes measured the air speed that created more accurate and useful data for the team and drivers.
The side skirts of C7RGT-004 maintained the same production C7 Z06 shape but had been greatly increased in width. The new side skirts worked in conjunction with the flat floor design that utilized the front splitter and rear diffuser to create a Bernoulli effect. For the best results, the air beneath the car needs to be directed towards the rear diffuser. Any compromise to the underflow of the air would decrease the overall downforce. Air under the car can escape out from the sides as well as the air travelling over the car can spill underneath. To avoid fouling the aerodynamic floor design, the new extended side skirts on C7RGT-004 worked in three different ways. With the increased width and help from vortices generated by the front stepped turning vanes, the air travelling below the car was trapped under the car increasing the effectiveness of the diffuser. The air travelling over the car was restricted from spilling below the car, which would generate undesired lift. Finally the side exit exhausts, integrated into the top of the side skirts, took advantage of the increased width by utilizing the exhaust gases that pushed down on them, which added a small increase in downward pressure.
The last upgrade in the floor design featured on C7RGT-004 was the new three dimensional rear diffuser. The diffuser featured on the C7.R in 2014 and 2015 started from the back of the rear wheel opening and was completely flat in design with no side-plates or fences. The 2016 regulations gave Pratt & Miller the opportunity to equip C7RGT-004 with a completely redesigned rear diffuser that resembled the one from the GT1 C6.R. The new diffuser started further back at the rear axle centerline and expanded upwards to the rear of the car with side-plates that created one large venturi tunnel. The addition of six fences/strakes created seven tunnels that increased in width from the outside edges. These seven tunnels were uniquely engineered to help extract the airflow from under the car. This feature allowed the floor design to generate downforce by compressing the air beneath the car, which resulted in the air accelerating towards the low pressure created by the rear diffuser. This effect decreases pressure under the car, that creates an increase in pressure over the car resulting in higher levels of downforce.
The final aerodynamic component affected by the 2016 regulations was the rear wing location. The 2014 and 2015 specification C7.R featured rear wing mounts that were vertical, positioning the trailing edge of the wing in line with the rear fascia. The new regulations permitted teams to mount the rear wing 15 cm (5.9 inches) further back, which altered the area of pressure applied by the wing. Pratt & Miller therefore would design new rear wing mounts that extended the position of the wing behind the rear fascia. This improved the downforce levels produced as the wing applied pressure to the whole rear of the car opposed to the previous location that just applied pressure to the rear axle. These regulation changes resulted in a 1.4 second faster average lap time compared to the previous C7.Rs used by Corvette Racing.
The livery of C7RGT-004 was very similar to the previous liveries used on the C7.R, however the Velocity Yellow changed slightly in tone due to the GM paint introduction for 2016 of Corvette Racing Yellow. The chrome finished flashes behind the fender vents had new graphics of a stars and stripes on silver design, with an added ‘Made In America’ caption below. The black stinger hood stripe, featuring a Jake Skull, extended across the whole top of the car to the rear. The changes were subtle but along with the aero package, they created a more aggressive look.
C7RGT-004 became the #4 car driven by Oliver Gavin and Tommy Milner with Marcel Fässler and Jordan Taylor added as third drivers for endurance events. It was part of historic battle with C7RGT-005 in their debut at the Rolex 24 at Daytona when Oliver Gavin in the #4 car crossed the finish line 0.34 seconds ahead of Antonio Garcia in the #3 car to take the GTLM class win. At round two of the IMSA WeatherTech SportsCar Championship, C7RGT-004 was able to take the GTLM class win at the Twelve Hours of Sebring. At the third round of the season at Long Beach, C7RGT-004 was able to maintain its impressive pace with a second in class finish. Unfortunately at Le Mans, whilst running fifth in class, C7RGT-004 was involved in a crash during the 17th hour of the race that resulted in its retirement. Upon returning to the USA, C7RGT-004 was able to get back to podium finishing second in class at Canadian Tire Motorsport Park, Mosport. The following race at Lime Rock Park, Oliver Gavin and Tommy Milner brought C7RGT-004 across the finish line for another GTLM victory, which would be extra special as it equated to the 100th win for Corvette Racing. C7RGT-004 would collect another class win at the next round at Road America, which would be its final victory for 2016, however, C7RGT-004 would collect another podium at the Petit Le Mans season finale. In total for 2016, C7RGT-004 racked up seven podiums including four wins, that gave Oliver Gavin and Tommy Milner the 2016 GTLM Drivers Championship and Corvette Racing the 2016 Teams’ Championship. This became the first title for the C7.R and the 11th championship in for Corvette Racing.
For the 2017 season, C7RGT-004 was used for just one race. The livery would remain almost identical to the one used the previous year, however the silver flashes behind the fender vents now featured a fading stars and stripes design. At the ‘Roar Before the 24’ test that took place between January 6th-8th, 2017, a red flag was caused by C7RGT-004 during the Sunday session. A fuel injector failure was the root cause behind sprayed gasoline within the engine bay. After the fuel made contact with a hot surface, a fire broke out. Marcel Fässler was behind the wheel at the time and was able to escape without injury. The fire was limited to only the engine bay, however, C7RGT-004 was sent back to the Pratt & Miller factory in Michigan for repairs in preparation for the Rolex 24 at Daytona set between January 28th-29th, 2017. C7RGT-004 was repaired in time for the race and finished ninth in class due to losing laps in the garage after an accident required the power controller and a lower control arm to be replaced. The 2017 Rolex 24 at Daytona would be the final race for C7RGT-004. It would later become a display car for Chevrolet and Corvette promotional purposes.
More info coming soon…