Cup Series cars (often called "Cup cars") adhere to a
front engine rear-wheel-drive design. A
roll cage serves as a
space frame chassis and is covered by a composite
carbon fiber body. They have a closed cockpit, fenders, a rear spoiler, and an aerodynamic splitter. Fielding a car for one season usually costs
$10–20 million. Each team may build its own cars and engines (per NASCAR's specifications) or purchase cars and engines from other teams. The cars are powered by
EFI V8 engines since 2012 after 62 years using carburetion as engine fuel feed with compacted graphite iron
blocks and pushrod
valvetrains actuating two-valves per cylinder, and are limited to 358 cubic inches' (about 5.8 liters)
displacement. However, modern technology has allowed power outputs near or over in unrestricted form; while retaining the same basic engine design. In fact, before NASCAR instituted the gear rule, Cup engines were capable of operating more than 10,000 rpm. A NASCAR Cup Series engine with the maximum
bore of and
stroke of at 9,000 rpm has a
mean piston speed of 80.44 fps (24.75 m/s). Contemporary Cup engines run 9,800 rpm, 87.59 fps (26.95 m/s), at the road course events, on
Pocono Raceway's long front stretch, and at
Martinsville Speedway (a .526-mile short-track). At the backbone 1.5- to 2.0-mile tri-oval tracks of NASCAR, the engines produce well over 850 hp running 9,200–9,400 rpm for 500 miles, 600 mi for the Coca-Cola 600 Charlotte race. The current NASCAR Cup engines curb weight is roughly at . The front
suspension is a
double wishbone design, while the rear suspension was previously a
two-link live axle design utilizing
trailing arms until the 2022 debut of the
NASCAR Next Gen Car at the
Busch Lite Clash at the Coliseum, which featured the debut of the cars in their first competition and feature fully independent front and rear suspensions with double wishbones and adjustable inboard shocks.
Brake rotors must be made of magnetic cast iron or steel and may not exceed 12.72 inches (32.3 centimeters) in diameter. The only aerodynamic components on the vehicles are the
front splitter,
spoiler,
NACA ducts in the windows only, and side skirts. While the use of
rear diffusers,
vortex generators,
canards, wheel well vents, hood vents, and
undertrays was strictly prohibited into the Gen 6 era, the now-current Next Gen car features a rear diffuser similar to the diffusers used in NASCAR sister organization
IMSA's GT Daytona class. While the cars may reach speeds of about on certain tracks, Russ Wicks drove a modified
Dodge Charger stock car, built to NASCAR's specifications, during a speed record attempt at the
Bonneville Salt Flats in October 2007. NASCAR Cup Series engines carry a Freescale-provided
electronic control unit, but
traction control and
anti-lock brakes are prohibited. Live
telemetry is used only for television broadcasts, but the data can be recorded from the ECU to the computer if the car is in the garage and not on the track. Cup cars are required to have at least one working windshield wiper installed on the car for the road courses (
Sonoma,
Watkins Glen,
Circuit of the Americas, and the
road course layout at the
Charlotte Motor Speedway and
Indianapolis Motor Speedway, as well at Daytona in 2021) as part of the road racing rules package.
Evolution of Cup cars Generation 1 (1948–1964) driven by
Dick Linder in the 1951
Daytona Beach Road Course race. When the series was formed under the name
strictly stock, the cars were just that: production vehicles with no modifications allowed. The term
stock car implied that the vehicles racing were unmodified street cars. Drivers would race with factory installed
bench seats and
AM radios still in the cars. To prevent broken glass from getting on the race track, windows would be rolled down,
external lights would be removed or taped over, and
side-view mirrors would be removed. The 1957 fuel injected 150 model Chevrolet (known as "the black widow") was the first car to be outlawed by NASCAR. The 1957 Chevrolet won the most races, with 59 wins, more than any car to ever race in the cup series. Before the mid-1960s, cars were typically based on full sized cars such as the
Chevrolet Bel Air and
Ford Galaxie.
Generation 2 (1965–1980) 's
Chevrolet Chevelle Laguna In 1965, modified chassis came to the sport.
Mid-size cars including the
Ford Fairlane and
Plymouth Belvedere were adopted and soon became the norm. NASCAR once enforced a
homologation rule that at various times stated that at least 500 cars had to be produced, or as many as one car for every make's dealership in the nation had to be sold to the general public to allow it to be raced. Eventually, cars were made expressly for NASCAR competition, including the
Ford Torino Talladega, which had a rounded nose, and the
Dodge Charger Daytona and
Plymouth Superbird which had a rear wing raised above roof level and a shark shaped nose-cap which enabled race speeds of exactly 200 mph. The Ford-based Mercury Spoiler powered by a Ford Boss 429 engine was timed at 199.6 mph. Beginning in 1971, NASCAR rewrote the rules to effectively force the Ford and Chrysler specialty cars (nicknamed the
Aero Warriors) out of competition by limiting them to 305ci (5.0L). The cars affected by this rule include the Ford Talladega, Mercury Spoiler II, Dodge Charger 500, Dodge Charger Daytona and the Plymouth Superbird. This rule was so effective in limiting performance that only one car that season ever attempted to run in this configuration. Beginning in August 1970, NASCAR handicapped engines over with a
restrictor plate. NASCAR phased in a rule to lower the maximum
engine displacement from to . In 1974, maximum
engine displacement was increased from 430 cubic inches to 433 cubic inches. In 1975, NASCAR reduced the maximum small block
engine displacement from to its present . The transition was not complete until 1977 and coincided with American manufacturers ending
factory support of racing and the
1973 oil crisis.
Generation 3 (1981–1991) in 1984 's #27
Pontiac Grand Prix at Pocono in 1986 The
downsizing of American cars in the late 1970s presented a challenge for NASCAR. Rules mandated a minimum wheelbase of , but after 1979, none of the models approved for competition met the standard, as mid-sized cars now typically had wheelbases between 105 and 112 inches. After retaining the older models (1977 for the GM makes, and 1979 for Ford and Dodge) through 1980, for the 1981 season the wheelbase requirement was reduced to , which the newer model cars could be stretched to meet without affecting their appearance. The
Buick Regal with its swept-back "shovel" nose initially dominated competition, followed by the rounded, aerodynamic 1983
Ford Thunderbird. The
Chevrolet Monte Carlo and
Pontiac Grand Prix adopted bubble back windows to stay competitive. Amid its financial woes, and after dropping its poor performing (both on the race track and for consumer sales)
Dodge Mirada and
Chrysler Cordoba in 1983,
Chrysler Corporation left NASCAR entirely at the end of the 1985 season. 's 1989 Chevrolet Lumina at
Phoenix Raceway 1987 marked a milestone for NASCAR Cup Series cars. During
Winston 500 qualifying,
Bill Elliott established a world stock-car record when he posted a speed of . Then the unfortunate happened; during the 22nd lap of the race, driver
Bobby Allison suffered a flat tire in the middle of Talladega Superspeedway's
tri-oval. Allison's car hit the
catch fence and tore a hole in the fence approximately long. Several spectators were injured in the accident, including one woman who lost an eye. In the aftermath of the crash, NASCAR mandated the use of a restrictor plate at Talladega Superspeedway and
Daytona International Speedway to reduce speeds. By 1989, GM had switched its mid-sized models to V6 engines and front-wheel-drive, but the NASCAR racers only kept the body shape, with the old V8 rear-wheel-drive running gear, rendering obsolete the "stock" nature of the cars.
Generation 4 (1992–2007) 's 1994 Ford Thunderbird at
Michigan International Speedway. Early Generation 4 cars retained boxier appearance from the previous generation. 1992 marked the beginning of the generation that stripped all semblance of "stock" from "stock car racing", the Generation 4 car. Stock body panels were removed from the sport, and steel bumpers were replaced by fiberglass to reduce weight. In 1994, roof flaps were added to all cars after Rusty Wallace's two infamous airborne crashes in 1993. In 1995, the newly designed Chevrolet Monte Carlo returned to the sport, which started the trend of rounder body shapes. When the
Ford Thunderbird was retired after 1997, without Ford having any two-door intermediate bodies, the four-door
Ford Taurus body was used (although NASCAR racers actually have no opening doors). ) in 2005 While the manufacturers and models of automobiles used in racing were named for production cars (
Dodge Charger R/T,
Chevrolet Impala SS,
Toyota Camry, and the
Ford Fusion), the similarities between NASCAR Cup Series cars and actual production cars were limited to a small amount of shaping and painting of the nose, headlight and tail light
decals, and grill areas. Until 1998, the hood, roof, and decklid were still required to be identical to their stock counterparts. This was eliminated when NASCAR allowed significant modifications of the Ford Taurus decklid so the car would fit the required templates. ' 2007
Ford Fusion at
Texas Motor Speedway. By the final year of Generation 4, offset cars (also known as "Twisted Sisters") had become commonplace. It was in this time that NASCAR engaged in the practice of mandating rule changes during the season if one particular car model became overly dominant. This often led to claims that some teams would attempt
sandbagging to receive more favorable handicaps. Because of the notorious manner of the
Ford Taurus race car and how the manufacturer turned the car into an "offset" car (the car was notoriously
asymmetrical in race trim because of its oval shape), NASCAR ended this practice to put more emphasis on parity and based new body rules in 2003, similar to short track racing, where offset cars had become a burden for race officials, resulting in the "Approved Body Configuration" (also known as "common template") design.
Car of Tomorrow (2007–2012) 's 2009 COT in the garage at Las Vegas Motor Speedway, featuring the wing used until the
2010 Goody's Fast Pain Relief 500. In 2007, NASCAR introduced a radically new vehicle specification known as the "Car of Tomorrow" (CoT). The CoT made its debut at
Bristol Motor Speedway in March 2007. Initially, it was only used at 16 selected events. While NASCAR had originally planned to wait until the start of the 2009 season to use the CoT in every race, the date was changed to the start of the 2008 season. Many drivers still had complaints about the CoT, but this new timeline was intended to help teams save money by giving them only one car specification to work on. The design of the CoT has focused on cost control, parity, and driver safety. In 2011, NASCAR altered the nose of the car once more, with the splitter being reduced in size and the braces being replaced by a solid front valence. A major engine change occurred in 2012 with NASCAR's introduction of
fuel injection technology. Initially NASCAR indicated that it would transition to fuel injection midway through the 2011 season but decided before that season to put off the change until 2012.
Generation 6 car (2013–2021) leads a pack of Generation 6 cars three-wide multiple rows back in the
2015 Daytona 500. In 2013, manufacturers were given increased leeway for branding their NASCAR Cup Series cars, creating the Generation 6 race car. These changes were made so the cars would resemble their street counterparts more closely, as was done in the
Xfinity Series in 2011. All NASCAR Cup Series cars began utilizing a digital dash sold by
McLaren in 2016. This dash includes sixteen customizable preset screens, allowing the driver to monitor all the previous info with several additional elements such as lap time and engine diagnostics, for a total of twenty-four data elements. Information can be displayed as a gauge, numeral, bar graph or LED. Having mostly competed with cars based on sedan models during the generation's life, the sales decline of sedans in American car market resulted in return of
pony cars (and thus, coupe-based models) to the Cup Series as Chevrolet switched to the
Chevrolet Camaro in 2018, followed by Ford switching to the
Ford Mustang the following year.
Next Gen (2022–present) . In 2022, NASCAR introduced an all new, seventh-generation car named the Next Gen. A further evolution of the Generation 6 car, the Next Gen features improved
aero and
downforce packages while introducing new technologies (such as center lock wheels and rear diffusers, technologies used in road racing cars) on the track. In addition, the Next Gen car is meant to lower costs and attract new original equipment manufacturers (OEMs) to compete with Chevrolet, Ford, and Toyota. In 2023, a heavily modified Next Gen Camaro fielded by
Hendrick Motorsports entered the
2023 24 Hours of Le Mans, where it finished 39th out of the 62 cars entered in the event.
Setup The automobiles' suspension, brakes, and aerodynamic components are also selected to tailor the cars to different racetracks. A car that
understeers is said to be "tight", or "pushing", causing the car to keep going up the track with the wheel turned all the way left, while one that
oversteers is said to be "loose" or "free", causing the back end of the car to slide around, which can result in the car spinning out if the driver is not careful. The adjustment of front and rear aerodynamic
downforce,
spring rates,
track bar geometry, brake proportioning, the wedge (also known as cross-weight), changing the
camber angle, and changing the air pressure in the tires can all change the distribution of forces among the tires during cornering to correct for handling problems. Recently,
coil bind setups have become popular among teams. These characteristics are also affected by tire stagger (tires of different circumference at different positions on the car, the right rear having the most influence in left turns) and rubber compounds used in tire construction. These settings are determined by NASCAR and
Goodyear engineers and may not be adjusted by individual teams. Changing weather conditions may also affect a car's handling. In a long race, it is sometimes advantageous to prepare a car to handle well at the end of an event while surrendering the advantage of speed at the start. On oval races, rain forces a race to be halted immediately. NASCAR had developed rain tires for Cup Series road racing as early as late 1990s, but initially abandoned them because there at the time were not enough
road courses on the schedule to justify the cost of making more tires to replace them as they aged. The first in-race use of rain tires in the Cup Series were at the
2020 Bank of America Roval 400 and the
2021 Texas Grand Prix. Prior to these,
a 1956 race at
Road America was held in rain;
Tim Flock won the race. ==Cup tracks==