Have you ever seen 18 motorcycle racers slide around a dirt track at 140 mph?

American Flat Track Racing - Indian FTR750
American Flat Track

Can you picture yourself drifting a motorcycle around an oval dirt racetrack at 140 mph, bar-to-bar with 17 other riders? Oh, and you have no front brake? That is what American Flat Track (AFT) racing professionals do in an exciting and dangerous motorsport with roots nearly 100 years old. Interest is growing quickly as of late, fueled this year in no small part by the rekindled competition between factory teams from Harley-Davidson and Indian Motorcycle.

Flat track racing, America’s first extreme sport, kicks off the 2017 X-Games that runs from July 13 to July 16 in Minneapolis. Sponsored by Harley-Davidson, the race will be in front of the Mall of America, ESPN MediaZone reports. Harley is sponsoring the flat track event for the second year in a row. AFT is the professional version of Hooligan Racing.

“Harley-Davidson’s official racing department, which started in 1903, has been continuously involved in flat track racing since the 1920s,” Harley-Davidson Product Communications Manager Matt King told Digital Trends.

Prior to World War II Harley-Davidson and Indian were flat track rivals. The sport paused when the U.S. entered the war and didn’t ramp back up until the mid-1950s, by which time Indian had closed its doors.

Polaris bought Indian Motorcycle in 2011. “Indian wanted to come back to racing as part of the plan. America loves two big brands because it re-creates rivalry, gets more people talking about it, and can reinvigorate the sport of motorcycle racing,” Reid Wilson, Indian director of marketing told Digital Trends.

This is Indian’s first full season of professional AFT racing. Indian is sponsoring additional six races in the pro-AFT series, which now has a full 18-race schedule. So far this season, Indian’s team has dominated, winning all but one race and only giving up five of 27 podium spots (for first, second, and third place) in the first nine races.

The rivalry between the two factory teams is helping the sport gain viewers. Since Monday, NBC Sports Network (NBCSN) is broadcasting weekly race recaps.

Professional flat track racing is held on half-mile dirt automobile race tracks and one-mile horse tracks. The Singles and Twins AFT classes have strict equipment rules. The “AFT Twins Technical Standards” allow only four-stroke, twin cylinder engines, with production engines in the Twin class from 649 to 999.9cc and racing-only engines not exceeding 750cc. AFT Singles engines are restricted to 251 to 450cc.

For 45 years Harley-Davidson’s flat track team dominated the sport with the same air-cooled XR750 750cc engine.

American Flat Track Racing - Harley Davidson XG750R
Harley-Davidson XG750R

Indian Motorcycle’s factory team ride the FTR750 racing-only motorcycle, which, like Harley’s XG750R, is liquid-cooled. Gary Gray, Vice President of Product Development for Indian Motorcycle, told Digital Trends there is “a lot better engine temperature control with a radiator and thermostat as a trade off for more weight.”

American Flat Track Racing - Indian FTR750
Indian Motorcycle FTR750

Flat track racing is dangerous. In the 2016 Flat Track Finale, two riders died from injuries sustained in separate accidents, according to Road Racing World. In April, an AFT Singles racer died in a multi-bike accident during the first lap, Road Racing World reported.