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Tooele • The Ultra4 American Rock Sports Challenge returns to Miller Motorsports Park Friday and Saturday, bringing one of the most unique off-road events in Utah back for a second consecutive year.

Few other forms of racing has seen the growth and grassroots commitment as Ultra4 racing, perhaps because the rulebook is very thin.

Vehicles must be capable of running four-wheel-drive, and everything else is unlimited. They must be capable of extreme rock-crawling, yet able to reach speeds over 100 mph. The result is a variety of Jeeps, trucks and buggies ranging from 2,800-5,000 pounds with horsepower ranging from 150 to over 600.

The American Rock Sports Challenge will encompass both Miller Motorsports Park's off-road short course and rock crawling course in one timed race.

Following practice and qualifying on Friday, Saturday's schedule begins with two preliminary races that will feature over 40 teams.

The top half of each of the prelim race finishers will move on to the main event. The bottom half will be entered into a last chance qualifier race, where the top four drivers will also advance to the main event.

Admission for the Ultra4 American Rock Sports Challenge is $10 per day or $15 for both days. Children 12-and-under are admitted free. Military personnel are eligible for a discount on tickets.