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A monster truck is a pickup truck modified with a larger suspension and larger tires, usually for recreational uses. Today pickup trucks are still used, however SUV bodies as well as themed trucks are driven and most of the bodies are now made of fiberglass rather than metal. Themed trucks vary from car bodies, SUV bodies, and even animal themed bodies. A competition monster truck should meet guidelines by being 12 feet tall, 12 feet wide, and as of 2015, should be equipped with specifically made 462lb BKT 66-inch off-road tires. Monster trucks used to be side acts at popular motocross events and mud bogs but today they are usually the main attraction with motocross and mud bogging being the complementary shows.
Monster truck shows typically have two main events, a race and a freestyle competition. Races are conducted as a single elimination tournament on two short, symmetrical dirt tracks that usually include a hairpin turn and a jump over a row of cars. Each round, two trucks race to the finish line on the separate tracks, with the winner advancing to the next bracket. In freestyle events, each driver puts on a performance consisting of stunts such as jumping over obstacles, backflips, wheelies, and doughnuts. A panel of judges assign points to each performance and the driver with the most points is declared the winner. Freestyle performances have a set time limit and only one truck is allowed on the track at a time as a safety measure. Additionally, monster trucks competing in shows are equipped with a remote engine kill switch. At any time, the switch can be triggered by track officials to shut down a truck's engine to prevent it from endangering spectators or the driver.
As of 2017 the freestyle event has become the last event of competition. Drivers are free to select their own course around the track and its obstacles. Drivers will often perform doughnuts, wheel stands, large aerial jumps and even backflips during this segment. Historically, additional items for the drivers to crush such as motor homes and school buses were frequently placed on the track specifically for the freestyle event. However, incidences of debris flying into the stands and causing serious injuries have influenced most event promoters to turn away from such frail obstacles. Most freestyle courses now consist of overly large jumps and ramps formed to allow the trucks to get excessive air and explosive wheelies upon landing.
In addition to its recreational use, the height above ground of the monster truck body has led to it being used for rescuing people stranded by floods.
In the late 1970s, heavily modified pickup trucks were becoming popular and the sports of mud bogging and truck pulling were gaining in popularity. Several truck owners had created lifted trucks to compete in such events, and soon competition to hold the title of "biggest truck" developed. The trucks which garnered the most national attention were Bob Chandler's Bigfoot, Everett Jasmer's USA-1, Fred Shafer and Jack Willman Sr.'s Bear Foot, and Jeff Dane's King Kong. At the time, the largest tires the trucks were running were 48 inches (1.2 m) in diameter.
In April 1981, Bob Chandler drove over cars in Bigfoot in what is often believed to be the first monster truck to crush cars. Chandler drove Bigfoot over a pair of cars in a field as a test of the truck's ability, and filmed it to use as a promotional tool in his four-wheel drive performance shop. An event promoter saw the video of the car crush and asked Chandler to do it in front of a crowd. Initially hesitant because of the "destructive" image that could be associated with Bigfoot, Chandler eventually caved in. After some smaller shows, Chandler performed the feat in the Pontiac Silverdome in 1982. At this show, Chandler also debuted a new version of Bigfoot with 66in. tires. At a prior event in the early 1980s when Bigfoot was still running 48 in.terra tires, Bob George, one of the owners of a motorsport promotion company named Truck-a-rama (now the USHRA), is said to have coined the phrase "monster truck" when referring to Bigfoot. The term "monster truck" became the generic name for all trucks with oversized terra tires.
Exactly who crushed the first car is often debated. There are claims that in the late 1970s, Jeff Dane's King Kong (who referred to his truck as the "Bigger Foot") had crushed cars at Great Lakes Dragway in Union Grove, Wisconsin. Another truck, known as High Roller (currently known as "Thunder Beast"), also claimed to have documented car crushes in Washington State before Bigfoot, though said documentation has never surfaced. Cyclops, then owned by the Dykman Brothers, also claims to have crushed burning cars before Bigfoot. However, the earliest, widely available and verified video footage showing a monster truck crushing cars that exists shows Bob Chandler driving Bigfoot while crushing two mid-1970s automobiles in April 1981. This video was what the promoter viewed that motivated him to ask Chandler to perform the car crush in front of a crowd.
King Kong and Bear Foot each followed Bigfoot to 66-inch-diameter (1.7 m) tires, and soon other monster trucks, such as King Krunch, Maddog, and Virginia Giant were being constructed. These early trucks were built off of stock chassis which were heavily reinforced, used leaf spring suspension, a stock body, and heavy military axles to support the tires.
For most of the early 1980s, monster trucks performed primarily exhibitions as a side show to truck pulling or mud bogging events. In 1985, major promoters, such as the USHRA and TNT Motorsports, began racing monster trucks on a regular basis. The races, as they are today, were in the form of single elimination drag races, held over a course littered with obstacles. The change to racing eventually led truck owners to begin building lighter trucks, with more power. The establishment of TNT's first-ever monster truck points championship in 1988 expedited the process and found teams beginning to use straight-rail frames, fiberglass bodies, and lighter axle components to shave weight and gain speed.
In 1988, to standardize rules for truck construction and safety, Bob Chandler, Braden, and George Carpenter formed the Monster Truck Racing Association (MTRA). The MTRA created standard safety rules to govern monster trucks. The organization still plays a major role in the sport's development in the USA and EU.
With racing taking precedence, several teams began to think in new ways as to how the trucks could be built. Towards the end of 1988, Gary Cook and David Morris debuted Equalizer, a truck with a combination of coil springs and shock absorbers as the main source of suspension rather than the standard of leaf springs and shock absorbers. In 1989, Jack Willman Sr., now with his own truck, Taurus, debuted a new truck which used a solid axle suspension system made of parallel four-link suspensions and coilovers that together weighed in at close to 9,000 pounds (4,100 kg). However, the ultimate coup de grâce came from Chandler, also in 1989, whose Bigfoot VIII featured a full tubular chassis and a long-travel suspension system made of triangulated four-link suspensions, bump stops, limit straps, cantilevers, and shock absorbers charged with nitrogen gas. The truck revolutionized how monster trucks were built, and within a few years most top level teams built similar vehicles.
In 1991, TNT was purchased by USHRA and their points series were merged. The Special Events championship began to grow in popularity with teams as it had open qualifying spots which the invite-only USHRA championship did not have. The Special Events series lost its Pendaliner sponsorship in 1997. The short-lived ProMT series started in 2000.
Even though racing was dominant as a competition, USHRA events began having freestyle exhibitions as early as 1993. These exhibitions were developed as drivers, notably Dennis Anderson of the extremely popular Grave Digger, began asking for time to come out and perform if they lost in early rounds of racing. Promoters began to notice the popularity of freestyle among fans, and in 2000 USHRA began holding freestyle as a judged competition at events, and now even awards a freestyle championship.
Monster Jam is currently the largest and premier monster truck event, touring through the United States, Canada and select regions of Europe. Promoters of monster truck events include:
The first monster truck ever built was a pickup truck that was modified with a larger suspension and larger tires. Today, trucks now have custom built tubular chassis, with four-link suspension to provide up to four feet of clearance, and they also now have fiberglass bodies that go onto the chassis separately and are designed to be easily removed and easily replaced when damaged. Mounted just behind the driver on most trucks are the engines, which are typically supercharged, run on a methanol alcohol and corn-based oil fuel, and have displacement of up to 575 cubic inches (9.42 L). Axles are mostly taken from either heavy-duty military trucks or road vehicles such as school buses, and are modified to have a planetary gear reduction at the hub to help turn the tires. All trucks have hydraulic steering in both the front and the rear (four wheel steering), with the front wheels controlled by the steering wheel and the rear wheels by a toggle switch. The tires are typically "Terra" tires used on fertilizer spreaders, and are of size 66"×43"-25", nominally 66" diameter, 43" width, to fit 25" rims (168×109-63 cm). Most trucks utilize a modified and/or custom designed automatic transmission, such as a Turbo 400, Powerglide, Ford C6 transmission, or a Torque-flite 727. A limited number of trucks utilize a Lenco transmission, which traces its roots to drag racing. Most of the automatic transmissions are heavily modified with transbrakes, manual valve bodies, and heavy duty gear sets. Trucks running a Lenco use a centrifugal clutch as opposed to a torque converter, which are used in automatic transmissions. Lenco transmissions are usually found in two-speed or three speed configurations, and are commonly shifted using compressed CO2.
The trucks have many safety features, several of which are required just to run in the small arenas that the trucks frequent. Trucks are equipped with three shut-off switches: the RII (Remote Ignition Interrupt), one within the driver's reach in the cab, and another at the rear of the truck so that all electrical power may be shut off in the event of a rollover. Many trucks are constructed with the driver sitting in the center of the cab for visibility. Most cabs are shielded with Lexan (or comparable polycarbonate), which not only protects the driver from track debris, but also allows for increased visibility. Drivers are required to wear firesuits, safety harnesses, helmets, and head and neck restraints. Most moving parts on the truck are also shielded, and high pressure components have restraining straps, both in case of an explosion.
While usually exclusively recreational, monster trucks were used for rescuing people stranded by flooding following August 2017 Hurricane Harvey in Texas, US. The large ground clearance holds the body and engine well above the water level, where an ordinary vehicle would be flooded and immobilized.
There are several reports on accidents with a monster truck, resulting in more than twenty deaths and several hundreds of wounded people.
On January 25, 2009, the monster truck Samson was involved in an accident in Madison, Wisconsin that caused the death of announcer George Eisenhart after he accidentally stepped in front of Samson while it was moving.
On March 28, 2009, at the Monster Jam World Finals, the truck Captain's Curse lost its brakes during the run. Alex Blackwell, driver at the time, realized he had no brakes, and steered it. This was an attempt to roll the truck over rather than crashing into the seats head-on. The truck eventually landed several rows in the stands of Sam Boyd Stadium, although no one was injured. 
On October 6, 2013, the monster truck Big Show plowed into a crowd of spectators in Chihuahua, Mexico, killing eight people, and injuring 79 of them. Some speculated the driver was under the influence after the incident.
On September 29, 2014, a monster truck plowed into a crowd of spectators in Haaksbergen, Netherlands, killing three people.
The vehicle's gears contain the same equipment as the others, although they are characterized more by the larger size of its tires, whose diameter can in some cases exceed four meters. The vehicle's length can exceed seven meters.
The world's biggest monster truck is Bigfoot 5, built in 1986, with tires that measure 3.048 m (10 ft).
The world's longest monster truck is the Sin City Hustler which measures 9.8 m (32 ft) long and was created by Brad and Jen Campbell in 2014.
The fastest speed record for a monster truck was achieved in 2014 by Mark Hall in Raminator at a speed of 159.49 km/h (99.1 mph).
The longest ramp jump done by a monster truck was achieved in 2013 by Joey Sylvester in Bad Habit at a distance of 72.42 m (237.7 ft.).
The first monster truck backflip in a scored competition was achieved in 2010 by Cam McQueen in Nitro Circus.