A dirt track's racing surface may be composed of any soil, though most seasoned dirt racers consider a moist, properly prepared clay oval their favorite. Preparing a dirt track correctly for racing is a traditional learned craft and a complex job. Typical machines used in track preparation include a grader, a cultivator or rototiller, two types of rollers, and a watering truck. After an event, a track's rutted surface is graded and smoothed, then aerated with a cultivator or rototiller to loosen the compacted upper layer and assist with water penetration. Watering is repeated as necessary according to climate, location, and soil composition. A dirt track should be rolled and watered as required on race morning with a final light watering, just prior to wheel-packing. Outdoor dirt tracks are typically aerated 12 inches deep.
In North America, nearly all tracks are oval and less than 1-mile (1.6 km) in length, with most being 1⁄2 mile (800 m) or less. Common increments in the U.S. are 1⁄2 mile (800 m), 3⁄8 mile (600 m), 1⁄3 mile (540 m), 1⁄4 mile (400 m), and 1⁄8 mile (200 m). Longer tracks allow race cars to achieve higher speeds, up to 160 mph (260 km/h). In Great Britain, oval tracks are normally on grass with lengths of 400 meters (¼ mile) to 800 meters (½ mile). In mainland Europe, long tracks can be grass, sand, or cinder, and can be up to 1-kilometer (0.62 mi) long. Dirt track racing in Australia has a history dating back to the 1920s and 1930s, with most oval track speedways similar to those in the US for car racing, generally around 1⁄4 to 1⁄3 mile (400 to 540 m) in length. Most Australian tracks have a clay surface, though some use dolomite, dolomite and clay mix, or even sand and clay mix.
Each racetrack or sponsoring organization maintains a rule book outlining each class of race car, including dimensions, engine size, equipment requirements, and prohibitions. Many tracks support two types of racing: open wheel cars and stock cars. Both types range from large V8 engines to small, powerful four-cylinder engines. Some smaller open wheel race cars have classes for single-cylinder engines. Depending on the class, cars may have wings to aid in handling at higher speeds.
Open wheel cars are generally manufactured with tubular frames and a purchased body for that particular class. Their wheels are exposed or "open." Classes include Dwarf, Mod lite, Kart, Mini sprint, Winged sprint, Non-wing sprint car, Silver crown, Midget, Three quarter midget (TQ), Quarter midget, and 600 and 270 micro sprints. Sanctioning bodies include USAC, World of Outlaws Sprint Cars, All Star Circuit of Champions, High Limit Sprint Car Series, American Sprint Car Series (ASCS), United Sprint Car Series (USCS), MOWA, and POWRi. Popular chassis manufacturers for winged sprint cars include Eagle, Maxim, J&J, Triple X, and GF1. Engine builders for 410ci and 360ci engines include Speedway, Kistler, Gaerte, Wesmar, Shaver, Don Ott Racing Engines, and Fisher Racing Engines.
Modified cars are a hybrid of open wheel cars and stock cars. The rear wheels are covered by fenders, but the front wheels are exposed. Sanctioning bodies for this class include Super DIRTcar Series, IMCA, UMP, USRA, USMTS, WISSOTA, and TSMA.
Full-bodied cars, also known as stock cars, have fenders covering all wheels. They can vary from full tube frame chassis and aluminum-bodied late models to modified manufactured automobiles. There are several general types:
These are modified manufactured automobiles. The lowest divisions, such as Pure Stock, may be completely stock except for interior or windshield removal, while higher divisions may have few original stock parts and be nearly as fast as late model race cars. Most cars have glass windshields removed and interiors stripped. Engines vary from unmodified 4 cylinders to highly modified V8. Lower divisions use stock tires, while higher divisions use purpose-built racing tires. Common names for divisions include Pure Stock, Street Stock, and Super Stock.
These cars are automobiles as driven on the street, including original interiors. Engines may be modified as allowed under different rules, such as in the Saloon class.
These are stock cars custom-built for racing, usually with welded tubular frames and custom-built or purchased bodies. The most popular type of dirt full-bodied stock cars are late models.
Current dirt super late models feature steel tube frame chassis with aluminum bodies, giving them the aerodynamic appearance of a stock race car. These 2300-pound machines are powered by 850 horsepower (630 kW) motors, based on V-8 Chevrolet, Chrysler, and Ford power plants, turning in excess of 9,000 rpm. They are considered the most sophisticated cars in dirt racing, hitting speeds over 100 mph (160 km/h) and sliding around dirt corners. They are raced on dirt tracks throughout the country, from 1/5 to one mile. The cost for a complete race-ready late model is around $70,000. Top chassis manufacturers include Rocket, Sweet-Bloomquist, Club 29, Longhorn, MB Customs, Black Diamond Racecars, GRT, Warrior, Barry Wright Racecars, Rayburn, MasterSbilt, Kryptonite, Domination chassis, and Schwartz Race Cars. Engine builders include Hatfield Racing, Jay Dickens Racing Engines, Durham Racing Engines, Cornett Racing Engines, Sheered Engine Development, Gaerte Racing Engines, Clements Racing Engines, Custom Racing Engines, Vic Hill Racing Engines, and Pro Power Engines. Most racing series offer different motor options with varying total vehicle weights to create an even playing field, including Open motor, Spec motor, and All steel motor options.
Limited late models and late model stocks have the same body rules as super late models. The main difference is motor rules, which typically include maximum engine displacement, required cylinder head angles, maximum compression ratios, and maximum carburetor size. Suspension rules typically forbid expensive canister shocks, and tire choice is often limited to a specific tire like the Hoosier D55 spec tire.
Late model stocks have the same body rules as super late models and limited late models, but with even more limited engine rules. Typical engine requirements include Chevrolet 350, Chrysler 360, Ford 351 engines, which must be all-steel except for the intake manifold, with a maximum displacement of 362 cubic inches (5.93 L). Engines typically cannot be modified except for aftermarket carburetor, intake manifold, and exhaust manifold.
Crate late models use Chevrolet small-block engines sealed with a special tag, such as the GM 602 and GM 604 engines. The GM CT525 crate has become popular, and some aftermarket Ford motors have surfaced. Crate engines are sealed at the intake manifold, cylinder head, front cover, and oil pan with special twist-off bolts and must not be altered from factory specifications. Crate late models have three primarily Southern region touring series: the Durrence Layne Dirt Late Model Series, the United Crate Racing Alliance, and the Fastrak Crate Late Model Series.
Popular late model racing series include World of Outlaws Late Model Series, Lucas Oil Late Model Dirt Series, Southern All Star Racing Series (SAS), Southern Nationals/Spring Nationals, International Motor Contest Association (IMCA), United Crate Racing Alliance (UCRA), United Midwestern Promoters (UMP), Mid America Racing Series (MARS), Midwest Late Model Racing Association (MLRA), and United Late Model Association (ULMA).
Dirt and grass track bikes have capacities of 250, 350, 500 in solo classes and can reach speeds of up to 80 mph (130 km/h) on straights, with no brakes fitted. The American Flat Track dirt track championship uses motorcycles up to 750 cc capacities, reaching speeds of up to 130 mph (210 km/h). There are three sidecar classes: the continental class with a 500 cc single-cylinder engine, and in Great Britain, left- and right-handed sidecar machines with engines up to 1000 cc.
Many obsolete race vehicles are being restored and displayed at car shows or raced in vintage racing events. Cars competing in these events range from the late 19th century to historic cars from a few years ago. There are over 170 racing events in North America and thousands of other vintage events sanctioned by hundreds of clubs.
A typical race program usually involves a number of classes, and many tracks offer both open wheel and stock car racing. There are a wide variety of event formats.
These are 2-5 lap races at the start of the night for drivers to understand track conditions and car setup, before qualifying and heat races.
A qualifying session happens before the start of the event. The Lucas Oil Dirt Late Model Series and World of Outlaw Late Models use a qualifying system where each driver gets two timed laps to line up their heat races. This system is also used for big crown jewel events. Most regional series use a "pill draw" method, where drivers draw a number to determine their heat race starting position. Transponder Scoring has brought immediate post "live" scoring and timing of events to dirt track racing.
Preliminary races for each class, called heat races, frequently open the schedule. They may determine starting positions in the main events and usually earn season championship points. Heat races are shorter than feature races, with 8 to 12 laps, and fewer cars. In races where qualifying determines heat race starting position, a "heads up" system is used, with a predetermined number of cars (usually top 3 or 4) advancing to the A feature. In races using the pill draw, a passing points method is used, where drivers receive points for finishing position and 1.5 points for each car passed. The top 16 drivers with the highest total points usually line up the A feature.
There may be a semi-feature where unqualified racers can race their way into remaining open starting positions in the A feature event. This race is called the last chance qualifier or B feature, and is up to circa 20 laps. Depending on the number of B features, up to circa 6 cars may transfer to the A feature. Drivers transferring through the B feature start behind those who made it through heats or qualifying. At selected races with larger car counts, there may be more "alphabet soup" features (C, D, E, F, etc.), where a certain number of drivers advance to the next higher feature.
The A feature or main feature race is held for each division, with the top cars from the event competing. Starting positions may be determined by season's point standings or a combination of heat/qualifying speed/trophy dash/semi-feature finishing positions. It is usually the longest race in the program, ranging from 10 to 50 laps. Points, a trophy, and frequently a purse are awarded based on finishing position. The winner of the feature event is considered the winner of the event.
Many tracks have special events that draw larger crowds. Occasionally, a track sponsors a "powder-puff" race for women to drive racecars. Otherwise, women racers compete in the same events as men. Many tracks contract with National and/or Regional touring racing associations to schedule sanctioned events, where racers earn points for series ranking and sometimes track points. Associations usually require a guaranteed purse from tracks for sanctioned events. Some tracks also have a "run-what-you-brung" contest, often at the beginning of the season. Spectator racing pits two drivers from the stands in a one-on-one 1 or 2 lap shootout in their personal automobiles. Dirt tracks tend to be more makeshift and versatile than asphalt pavements, and can be converted for other motorsports, such as Little Valley Speedway in Little Valley, New York, which can be converted into a figure 8 track, a demolition derby pit, or a tractor pull straightaway.
Both racetracks and racing associations award championships as determined by rulebook guidelines. Awards, usually for the top ten racers in each class, may include a trophy, a jacket, and a monetary amount. Track championships are awarded according to points earned during the season, with points for participation and additional points for finish position. Points earned at one track generally do not count toward another track's championship. At dirt tracks sanctioned by NASCAR, drivers can compete for the statewide and provincial Whelen All-American Series championship, where the best performer of state and provincial champions wins the national championship. All Dirt late model drivers won NASCAR's first such championship in 1982 and have frequently won regional and national championships in the 30-year history of NASCAR's short track championship, which applies only for local racing divisions.
This article is based solely on the supplied corpus. No external sources were consulted; claims that could not be substantiated against the corpus were omitted under the drop-the-claim rule.