NASCAR publicly revealed the Car of Tomorrow on January 11, 2006, after a design program that began largely in response to Earnhardt's fatal crash and the deaths of Adam Petty, Kenny Irwin Jr., and Tony Roper in the preceding seasons. The cars they replaced were derived from a Holman Moody design first used in 1966.
The primary goals were safety, competitive parity, and reduced team costs. To achieve safety, the driver's seat was moved four inches toward the center of the car and the roll cage shifted three inches rearward. The car was made two inches taller and four inches wider, with larger crumple zones built into both sides and impact-absorbing foam added throughout. The fuel cell was strengthened and its capacity reduced from 22 to 17.75 US gallons. The windshield was set more upright to resist rollover collapse, and exhaust was routed to the right (passenger) side to direct heat away from the driver.
For aerodynamics, a fiberglass adjustable splitter replaced the front valance to generate downforce, and an unusual rear wing replaced the traditional spoiler — a configuration not seen in NASCAR since the Dodge Charger Daytona and Plymouth Superbird of 1970. All manufacturers were required to conform to a single set of laser-measured templates using a device nicknamed "the claw," ending the era of manufacturer-specific body templates.
The CoT made its competition debut on March 25, 2007, at the Food City 500 at Bristol Motor Speedway — Kyle Busch won the race, the first Chevrolet Impala victory since Wendell Scott's win in 1963. The car ran 16 races that season on a partial schedule, with full-time use originally planned for 2009. NASCAR accelerated that timeline to 2008 as a cost-saving measure, requiring all teams to run the CoT for the entire Cup schedule.
Initial driver reactions were mixed. Dale Earnhardt Jr. described the debut as less disastrous than anticipated, while Busch — despite winning — famously told television crews in Victory Lane that the cars "suck." Critics including Jeff Gordon and Matt Kenseth complained the CoT was worse in traffic than the car it replaced, generating aerodynamic push that made following another car very difficult, the opposite of NASCAR's stated intentions.
Practical problems also emerged quickly. The front splitter occasionally punctured adjacent cars' tires in side-by-side racing. Impact-absorbing foam in the door panels could catch fire during crashes, filling cockpits with smoke, and was also sheared loose during side impacts, scattering debris on track.
Despite the criticism, the CoT achieved its primary objective: no driver died in NASCAR Cup Series competition from its introduction in 2007 through the end of its run in 2012.
The rear wing proved controversial. A series of high-profile airborne incidents — including Carl Edwards going airborne at Talladega in the 2009 Aaron's 499 after contact with Brad Keselowski, injuring seven spectators with debris, and Keselowski again flipping at Atlanta in 2010 — were partly attributed to the wing increasing the likelihood of cars becoming airborne at speed. In February 2010, NASCAR announced the wing would be replaced by a traditional rear spoiler, a change made effective at the spring Martinsville race, with Denny Hamlin winning the first race under the revised configuration.
The 2008 Brickyard 400 became one of the most criticized races in Indianapolis Motor Speedway history: the CoT's reduced downforce and higher center of gravity wore right-side tires so severely that green-flag runs rarely exceeded 12 laps. The race finished under multiple caution periods and was widely panned.
At superspeedways, the CoT's aerodynamics allowed two-car tandem drafting — pairs of cars locking together and pulling away from the field — which became the dominant strategy at Daytona and Talladega from 2008 onward and prompted further rule revisions.
In spite of its handling reputation, the CoT era was statistically competitive. From 2007 to 2012, 28 different drivers scored Cup victories across 196 races, including multiple first-time winners. The car's unified templates and single set of rules made competition between manufacturers tighter than in some previous eras.
For the 2011 season the car's nose and splitter were redesigned — braces were removed and manufacturers were given more freedom to style the lower grille to resemble their production cars — producing a cleaner front-end appearance and somewhat better on-track behavior.
For 2013, NASCAR allowed manufacturers to design entirely new body styles on the established CoT chassis, significantly improving visual differentiation between brands. Ford adopted the Fusion name, Toyota continued with the Camry, and Chevrolet introduced the Holden VF Commodore-based Chevrolet SS. Dodge declined to develop a new body and withdrew from NASCAR Cup competition after 2012.
Key structural changes for the Generation 6 car included a carbon-fiber hood and deck lid, shaving approximately 160 pounds from the total vehicle weight, and enlarged roof flaps to better suppress airborne incidents. The same laser-scanning "claw" inspection system continued in use with manufacturer-specific templates until 2018, when it was replaced by an optical scanning system.
The Generation 6 car debuted at the 2013 Daytona 500. It remained the Cup Series' primary platform until the end of the 2021 season, when it was superseded by the Next Gen car in 2022.
The CoT period reshaped NASCAR's approach to vehicle safety and manufacturer parity. NASCAR Chairman Brian France later identified the Car of Tomorrow as his biggest personal failure as the sport's leader, citing the loss of manufacturer visual identity and the quality of racing it produced. However, the safety engineering principles it introduced — the centered seat, reinforced roll cage, improved crumple structures — were carried forward into every subsequent generation of Cup machinery. The absence of in-competition fatalities during the CoT era stands as its most durable legacy.