The Riley & Scott Mark III (Mk III) was a sports prototype auto racing car developed by Bob Riley, Bill Riley and Mark Scott of Riley & Scott Cars Inc. Initially designed in 1993, the car was created for the World Sports Car (WSC) category which was to debut in the North American IMSA GT Championship during their 1994 season. It was not until 1995 that the first Mk III was completed, but the construction of further cars allowed a variety of teams to campaign in several North American and European racing series, including competing at the 24 Hours of Le Mans.
In 1999, Riley & Scott evolved the Mk III's designs in order to adapt to the newer Le Mans Prototype (LMP) regulations which were now used in several series. An all-new third design officially known as the Mark III Series C debuted in 2001 as the final variant developed by the company before they moved on to other programs. Several private teams also made their own modifications to their Mk IIIs in attempts to improve the car's performance to suit their own needs.
The original Mk IIIs were used in competition until the end of 2002, in the process accumulating 47 overall race victories in both North American and Europe, as well as championship titles in the IMSA GT Championship, United States Road Racing Championship, Rolex Sports Car Series and American Le Mans Series. Mk III Cs continued to compete until 2005, although they were never able to achieve victories like their earlier predecessor.
Development history In 1993, Bill Riley began initial work on a design for a sports prototype to meet the International Motor Sports Association's (IMSA) World Sports Car regulations. The new regulations, announced during the 1993 season and were intended to be debut in the 1994 season, sought low-cost open-cockpit prototypes to replace the expensive closed-cockpit GTP models used in the IMSA GT Championship. Riley & Scott, already experienced constructors in the Trans-Am Series, were looking to enter the sports prototype category of motorsports.
The new car, known as the Mk III, featured a radical design with tapered rear sidepods that flowed into the rear wing mounts. This opened a large amount of empty space around the rear wheels and exposed much of the floor of the chassis. Radiators for cooling were all placed at the front of the car, under a simple sloping nose. Interest in this design was, however, low and Riley & Scott did not construct a car for the 1994 season. During that same year, Dyson Racing contracted Riley & Scott to aid in improving the team's current WSC car, a Spice DR3 chassis with a Ferrari engine. After completing the improvements for Dyson, Bob and Bill Riley returned to their Mk III design with new knowledge from their Dyson experience. After the Mk III was redesigned, Riley & Scott were able to convince Dyson Racing to replace their Spice-Ferrari with two new Mk IIIs for the 1995 season.
Bill Riley's redesigned Mk III was simpler in its design, allowing more variety for customers, as well as a low cost. Although the extreme aerodynamics of the original design were gone, the car was conceived to be fast enough to compete for overall wins. The redesign and eventual construction of the first car took only four months. The chassis featured a steel tube frame with panels made of carbon fiber. Behind the cockpit the engine bay was designed to be large enough to allow for a variety of naturally aspirated engines, mostly the V8s of Ford, Chevrolet and Oldsmobile that were common amongst IMSA GT privateers. All cars used a 5-speed transmission. The suspension consisted of double wishbones with coil springs attached by a pushrod. A power steering system was also part of the standard Mk III.
The redesigned carbon fiber and kevlar bodywork of the Mk III was developed by aircraft designer John Roncz, who assisted Bob Riley in using early computational fluid dynamics programs to refine the aerodynamics of the new car. Final aerodynamic testing was performed at a Lockheed windtunnel. The nose of the final Mk III was very similar to the original design model from 1993, featuring a nose which sloped downward towards a splitter extended from the front of the car. In the center, a wide intake allowed air into the radiator mounted flat under the nose. The air exited the radiator from two openings on top of the nose and in front of the cockpit. Between these exit vents, teams had the option of installing extra headlights for night races. A circular duct was placed on either side of the radiator intake to allow air to the front brakes for cooling. Behind the front wheels the bodywork was relatively square and flat, with full sidepods running the full width of the car. A rules-mandated full width roll hoop was positioned behind the cockpit. Positioned under the roll hoop was an arched intake for the engine airbox.
On the sidepods several square holes were created in order to allow teams to adjust their cooling and aerodynamics dependent upon engines used, circuits and conditions. The squares could be filled with bodywork of various shapes and sizes, effectively closing or opening the holes as much as the team wished. At the back of the car, the bodywork ended immediately behind the rear wheels, with only the rear wing placed beyond the end of the bodywork. Overall, the aerodynamics of the Mk III were designed to be low in drag but still offer large amounts of downforce.
In total, 17 Mk IIIs were built by Riley & Scott from 1995 until 1998, with a price of approximately $285,000 for a chassis without an engine. In 1999, Riley & Scott continued their development of the Mk III by creating a second series of Mk IIIs. These cars had minor alterations and a further four chassis were built to this specification. Several teams, hoping to remain competitive with the Mk III, also upgraded their cars to match the Series 2 specifications.
Mk III C
Riley & Scott had ended their progressing development of the Mk III during the 1999 season, in part due to the company being contracted by General Motors (GM) to construct a Le Mans Prototype for their Cadillac brand. The resulting Northstar LMP borrowed elements of the Mk III's design and layout. Modern features were included on the Cadillac, including a carbon fiber monocoque replacing the composite monocoque of the Mk III, a roll hoop over only the driver's seat instead of the full width of the cockpit and a relocation of the radiators to lower the nose. An evolved Riley & Scott-built Northstar LMP design appeared in 2001 but the company was not contracted to build the 2002 version of the car.
Once the Northstar LMPs for the 2001 season were completed, Riley & Scott turned their attention back to their Mk III which were still earning victories even without major upgrades in nearly two seasons. Rather than evolving a design which was now six years old, Riley & Scott chose to start from scratch and develop an all-new car which continued the Mk III's simple design, but received some of the advancements that Riley & Scott had used on the Northstar LMP.
At its most basic, the Mk III Series C is nearly identical to the Mk III in terms of its layout. At the front, a slanted nose housed a radiator fed air from a vent above the front splitter and exiting over the top of the bodywork just in front of the cockpit. The sidepods were straight and flat and featured a variety of exchangeable panels for cooling and aerodynamics. An engine intake was mounted behind and above the cockpit, and shrouded an engine bay which could accept multiple naturally aspirated engine designs. Also shared with the Mk III was the use of a steel tube frame and carbon fiber chassis, rather than the all-carbon monocoque used by the Northstar LMP.
Some notable changes to the design of the Mk III for the Mk III C were concentrated on the cockpit and nose areas. While the Mk III had a roll hoop which ran the full width of the cockpit, the Mk III C was designed to share the roll hoop design of the Northstar LMP. This standard hoop was positioned immediately behind the driver's seat and integrated the intakes for the engine, although an optional roll hoop extension was offered, as it was required for the Rolex Sports Car Series. The front of the cockpit was also redesigned, as an aerodynamic windshield was added immediately in front of the driver.
The nose of the Mk III C was notably more rounded than the Mk III. The front fenders were no longer square and tapered as they extended to the front splitter. The headlights were also redesigned, including four lights instead of the previous two. The exits for the radiator were also designed to run the full width of the nose, although the openings were now slimmer than they had been on the Mk III. A new addition was further ducting located on either side of the cockpit designed to allow air from the front diffuser to exit upwards and over the top of the bodywork. The bodywork in general was also lower on the Mk III C, with the exception of the vehicle's fenders.
Mechanically, the Mk III C's transmission was a major improvement from the older car. A new 6-speed gearbox built by X-Trac was part of the package, replacing the previous 5-speed. This gearbox was further enhanced by the option of a pneumatically actuated gear change system developed by Megaline, which was activated by paddles behind the steering wheel, rather than by a traditional gear stick.
In total, five Mk III Cs were constructed by Riley & Scott, although only four were used for competition purposes. Autocon Motorsports' Mk III C, chassis #01-002, was the last car still in use by time it was retired at the end of 2005.
Racing history
1995 – 1997 In early January 1995, Dyson Racing's first Mk III took its first laps of the Daytona International Speedway in testing for the 24 Hours of Daytona later that month. The team's drivers set the fourth fastest time, behind a trio of Ferrari 333 SPs but ahead of the brand two new Porsche WSC-95 prototypes. For the race itself Rob Dyson, James Weaver, Scott Sharp and Butch Leitzinger were assigned to the car and successfully qualified sixth. Their race would be short-lived as the Ford engine failed after only eleven laps. n March, the team entered the 12 Hours of Sebring and improved their qualifying record with a fifth place starting position. The Mk III was able to survive this endurance race and finish for the first time, earning 37th position.
Dyson's second Mk III-Ford was completed by the Grand Prix of Atlanta in April, but it was in the first chassis that James Weaver achieved victory, giving Riley & Scott their first victory as a constructor in only their third IMSA GT event. The season further improved as the team's second chassis won three consecutive races at Watkins Glen, Sears Point and Mosport, as well as earning the Mk III's first pole position at the Mosport event. Dyson Racing ended the debut season with the Mk III by finishing first and second at New Orleans. James Weaver finished second in the Drivers Championship, two points behind Ferrari driver Fermín Vélez.
After a successful debut season, several teams purchased Mk IIIs for 1996. General Motors instigated the use of Oldsmobile Aurora V8s by the Riley & Scott-backed Doyle Racing and Dyson returned with their two entries. Doyle Racing immediately showed the potential of the Mk III-Oldsmobile combination by winning both the 24 Hours of Daytona and the 12 Hours of Sebring. Fighting throughout the season with the various Ferrari and Riley & Scott teams, Doyle won two further events, before Dyson Racing ended the season with three consecutive victories. Doyle Racing's Wayne Taylor won the WSC Drivers Championship, while Oldsmobile was able to win the Manufacturers Championship. Doyle's Mk III-Oldsmobile was also flown to Europe that season to participate in the 24 Hours of Le Mans. The team qualified ninth but a transmission problem forced the car to retire after fourteen hours.