A low hum rises as 18 men and women straddle their machines. Engines snarl as tense hands grip the throttles. For a moment everything is still—the crowd, the racers, and the dust.

Then the green flag waves and the bikes erupt in a fury. The collective engine thunderclap rattles my ribcage. Riders lean forward in defiance of inertia. In a heartbeat, they are gone, off like a pack of wild hyenas in a deluge of din and dust.

Riders jockey for position with reckless abandon as they enter the first turn inches away from one another. The 300-pound bikes hurtle sideways into a slide along the dirt to control their speed, handlebars nearly touching. One slip-up spells catastrophe. But if the riders execute the maneuver, it's a beautiful balance between human, machine, and physics.

The riders rip through the first turn and open up in the flat, pushing speeds of 140 mph as they lap the Red Mile in Lexington, Kentucky.

The Dawn of Dirt

Flat track racing is the only type of motorcycle racing that originated here in the United States, and to this day, two American brands dominate the sport: Indian and Harley-Davidson. It's a rivalry as old as the sport itself, one reborn with flat track racing's revival.

Flat track was born of the delirious, dangerous board track races of the early 20th century. Organizers would build ovals out of oiled wood planks and put on weekend races. The spectacle would regularly draw crowds of 80,000 to 100,000 people.

Board track racing at Speedway Park, Maywood, Chicago, Illinois, circa 1915. National Motor Museum/Heritage Images Getty Images

But racing on oiled wooden planks was ill-advised, treacherous, and resulted in some horrific crashes. After WWII, race organizers decided to move to the dirt to make the sport safer. The two biggest American motorcycle manufacturers, then as well as now, embraced the thrilling sport.

"At the time there were two factories and a whole boatload of privateers, and guess what, those two factories were Indian and Harley," Michael Lock, CEO of American Flat Track, told Popular Mechanics. "Here we go full circle. You come forward 60 years and we're back at it."

The Indian racing team dominated in the 1950s, so unstoppable they became known as the Wrecking Crew. Racers like Ernie Beckman, Bill Tullman, and Bobby Hill were stars who drew fans from all over the country. By the 1960s, British manufacturers like BSA, Triumph, and Norton began entering flat track races and competing with the Americans. The 1970s brought the Japanese brands like Honda, Kawasaki, and Yamaha to the sport. Yamaha famously sponsored Kenny Roberts, who won the Grand National Championship in 1974 and eventually went on to be the first American to win the championship in MotoGP, the most elite racing series in motorcycling today.

Racers enter a corner at the 2017 Red Mile race in Lexington, Kentucky. American Flat Track

In fact, Roberts was a pioneer in the world of MotoGP. His flat track experience changed the way road racers race. Roberts was the first to bring the technique of sliding the bike's rear wheel in a corner from the dirt to the pavement, as well as the technique of hanging a knee off of the bike, which defines MotoGP racing to this day.

The 1980s rolled around, and Honda began applying a level of technical sophistication to flat track that had never been seen before. "Honda decided to treat flat track in the U.S. the same as they would an international race event," Lock says. "They developed specific machinery for racing flat track and won many championships in the mid-1980s."

In the 1990s, flat track and road racing became two separate entities in the U.S., and motorcycle racers gravitated toward the pavement tracks. The dirt racing series began to fade.

Back to the Flat Track

The resurgence of custom motorcycles and DIY pride has led people to once again discover the chaos and joy of balls-to-the-wall flat track racing. "There is a general trend across the motorcycle market away from absolute performance and more toward a kind of nostalgia for you and your machine being one," says Lock.

A racer cornering at the 2017 Red Mile flat track racer in Lexington, Kentucky. American Flat Track

Like the sketchy races across board tracks in the 1930s, flat track racing today is setup for maximum spectator enjoyment. There are a number of qualifying races in each class that lead up to the main event. Each race is a adrenaline-laced shootout that lasts about 15 to 20 minutes. Riders plunge into the torrent of sliding rear wheels, kicking up clouds of dust the whole way. Without any front brakes, the bikes reach top speeds of 140 mph and race within inches of each other.

There are two classes, or divisions, in flat track. The singles division refers to the smaller 450cc bikes that are basically modified dirt bikes. This is basically the farm league for the bigger twins division.

The twins are almost always highly modified factory 700-750cc twin-cylinder machines that produce nearly 100 horsepower. The major development of late in this division is the Indian Scout FTR750, which the company developed from the ground up specifically to win flat track races. "When a company as big as Indian goes 'Ok, we're going to build a custom-built motor just for that sport,' it really turns some heads," says five-time Grand National Champion Jared Mees.

These new bikes have made the defining thrill of flat track even more exciting: the rear-wheel slideouts. "It's almost like a wakeboard on water where you're skimming over the top of the dirt," says Bryan Smith, current Grand National Champion. "We basically have two drag strips that we're going down at 130 mph, and you got to go as fast as you can through the corner to get to the other straightaway. You don't have brakes to slow down. The corner is too big to stop and turn. So you're literally trying the pivot the motorcycle back around the other direction. I think about it likes an NHRA [National Hot Rod Association] drag strip with a corner in it."

Flat track racers pull into the straightaway at the 2017 Red Mile race in Lexington, Kentucky. American Flat Track

Unlike motocross or road races where the riders are spread out over a large area, a spectator in the stands at a flat track race can see all of the action all of the time. The tight proximity and short sprints mean almost every race ends with a photo finish. "The time from the first place guy to the last place guy at the end of the race can be within one second," says Smith. "I won three races this spring and the combined victory [time] out of all three of them was less than 1/100th of second."

The entire atmosphere around a race feels more loose and casual than most other forms of racing as well. At a race on a horse track in Lexington called the Red Mile, the riders seemed baby-faced kids with bright smiles—nothing like daredevils who getting ready to race at speeds of nearly 140 mph. A few sat on camping chairs next to large transporter trucks plastered with sponsor logos, but most hung around the back of the vans and pick-ups that helped get them there, tinkering on their bikes under pop-up awnings and fold out tables. Sandriana Shipman hitched a ride from upstate New York down to Lexington to race that weekend. Cameron Smith travels the country with his parents to enter races. It really is the DIY dirt-slinging fest it seems like, and it's beautiful.

Family and Rivalry at the Track

"Off the track, everyone's always hanging out and going to dinner, but on the track we all want to beat each other," says rider Shayna Texter, a rider the singles division. She has won more singles races than anyone in history, and she has her sights set on becoming the first female champion in any motorcycle race series.

The competition is heated and it can be dangerous. Every racer has had their fair share of close calls and witnessed bad wrecks—if they haven't gone down hard themselves. The cornering is especially hairy, but the raw racing of flat track is what has drawn people to the sport, riders and fans alike.

Flat track racing at Red Mile 2017. American Flat Track

There is a fine line between friendship and rivalry, though. Bryan Smith and Jared Mees, hometown pals and the two favorites to win the Grand National Championship this year, were pitted against each other on different teams last year. The championship came down to the last lap of the final race. Smith finished just ahead of Mees and grabbed his first title in 2016. This year, Mees came out on top to snatch his fifth.

This year, they are both riding for Indian on the new FTR750. They race all year long and then they both go back home to Michigan, where they live 20 minutes apart from each other. But the competition never stops. "In the winter we go riding on the ice with studded tires," says Smith. "If you could see us riding in the woods or on the lake, you'd swear there was a million dollars on the line."

With a ground swell of interest from new fans, an accessible format, a fierce rivalry between two great champions, and a newly minted television deal on NBCSN, flat track seems primed for the spotlight. You can watch it at home, but we highly recommend you pack up the whole family and spend a day at the track watching in person—just bring plenty of sunscreen and some earplugs.

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