ARAPAHOE BASIN • Near the end of a steep, rocky drive to the top of the mountain, Metallica hums through the truck radio.

“We need this song cranked,” Joey Klein said. “Now we’re ready!”

Ready to take on his latest, greatest downhill mountain bike trail in a long career of creating some of Earth’s finest.

Uncle Joey, as the grateful sporting world knows him, is ready to drop down the trail that recently opened for a debut summer

The historic, deep and steep Arapahoe Basin Ski Area is known as The Legend. Now it has a bike trail to match the moniker.

What makes Beavers Loop unique? From three decades of trail-building experience in Colorado and beyond, Klein might know:

“The highest berms in North America, for one.”

Starting near 12,500 feet by the chairlift of the same name, the Beavers Loop is 3-plus miles of fast, flowing fun, with occasional rocks to negotiate and jump and enough ridgeline exposure to raise the hair.

The views are endless for much of the 1,600-foot drop: the jagged Tenmile Range and lake-spotted valleys between, 14,000-foot peaks from Mount of the Holy Cross to Grays and Torreys peaks and the imposing, craggy face of A-Basin’s poster child, Black Mountain.

Riders are getting their first taste of the trail this summer — some finding it to be an instant, high-alpine classic.

This day, Klein stopped to fist-bump one along the track, one among a high-caliber group well-acquainted with the long-beloved line plunging the opposite side of the mountain.

“Someone even said, ‘I’ll never ride Lenawee again,’” the man reports.

Uncle Joey grinned as the guys rode away. “I would never say that about Lenawee,” he said.

But the point is taken.

Lenawee Trail is suspected to have been blazed in the old mining days, and it’s largely been left in its steep, gnarly state — the kind of true, authentic singletrack that Klein appreciates, reminding him of his 1980s beginnings on a mountain bike.

Beavers is different for its official blue rating — “Lenawee’s little brother,” Klein calls it — and for its machine-cut width that can’t be called singletrack. The hope is that the elements tighten the trail over time.

Beavers is also logistically different. Where two-car caravanning is the common approach for Lenawee, which ends out of A-Basin limits, Beavers riders will end back where they started, at the ski area base.

“That’s the thing,” said local rider Zach Ryan. “You get this amazing backcountry ride, and then you can stop at 6th Alley (Bar and Grill) for a burger and a beer.”

Still, the ride must be earned.

Like Lenawee, there is no shuttle or lift to the top of Beavers. (This day in the Metallica-blasting truck, Uncle Joey got a VIP ride courtesy the ski area.) While crews continue to cut a more forgiving trail to pedal up, a harsh and chunky access road is the way for now.

Which matches the “earn-your-turn” vibe at A-Basin, Ryan said. It’s one of Colorado’s last ski areas rebelling against frilly, resort culture, preferring instead to market the most epic terrain that Beavers Loop happens to cross.

“It’s why people come here instead of some mega resort,” Ryan said. “To get that rugged experience.”

Lenawee Trail might boast more rugged qualities than Beavers.

“I don’t want to say apples to oranges,” said another local rider, Maria Leech, “but you can tell people knew what they were doing when they built this trail.”

They were people under the watch of Uncle Joey. For close to 25 years, Klein has traveled the world leading crews under the International Mountain Bicycling Association.

Beavers is a shining moment for A-Basin’s years-in-the-making trail system that may still lack in mileage — fewer than 10 — but not in vertical. It’s a shining, full-circle moment for Klein, who as a kid in the ‘80s was skiing the so-called Beavers area before anyone else really was.

A-Basin formally incorporated the area for the 2017-18 season. Included in the trail map was a run called Janitor’s Only.

That was a nod to the ragtag bunch Klein knew: the Atomic Janitors, who cleaned at night, slept in an attic and woke to hit powder in the morning.

“He used to live in this building,” A-Basin Director of Mountain Operations Louis Skowyra said in the lodge. “He came up here as a total dirtbag and knows every nook and cranny. So he can lay out trails that are good trails, but also that find their way to cool spots on the mountain.”

A-Basin became teenaged Klein’s home away from home in Golden.

“Back in the ‘80s, it was the ski bum capital of the world,” he said.

Thanks to its high, snowy perch along Loveland Pass, the skiing here lasted longer than anywhere else in North America. The longer the better for Klein.

“I used to get really bummed out when the summer came around,” he said.

Then he discovered mountain biking, which has an often-cited birthplace in Crested Butte in the mid-’70s. Racing there took off on Pearl Pass. Racing became Klein’s obsession.

“I never thought I would stop,” he said. “But this trail thing took over.”

Down the pass from A-Basin, Keystone Resort was one springboard to his work with the International Mountain Bicycling Association (IMBA).

Klein recalls washing dishes at Snake River Saloon when an operations boss asked about bike trails that had sprouted elsewhere across ski country. That was in the mid-’90s, Klein recalls.

“Next thing you know, I’m spending two or three weeks out there coming up with a master plan,” he said.

Next thing he knew, he and a partner were assigned to jobs abroad with IMBA.

“Our resume we hand-wrote while living in our school bus,” Klein said. “There was a quote: ‘My favorite thing about building trail was sitting back and watching people get to ride it afterwards.’”

Uncle Joey waited a long time to see them at his old home. While bike parks have become synonymous with ski areas around Colorado, developments have been slower at A-Basin.

That’s been partly due to topography, Klein said. The high-elevation layout that made A-Basin his skiing haven over bigger, more sprawling mountains has made it more complicated for trail construction.

“We’re really confined to this tight, narrow, steep, rugged space,” Klein said.

And there’s the complicated notion of building trail on sensitive terrain and habitat above treeline. It speaks to why Beavers Loop — informed by a U.S. Forest Service-approved plan — is a relatively rare trail, Klein said.

He sees ski areas as the final frontier for such alpine rides — venues that long ago added chairlifts and trails.

“It’s already established as a recreation area. It’s not wilderness, and it’s got the infrastructure,” Klein said. “Yes, we are adding, we are extending our footprint, I understand that. But to me, it’s manageable.”

Manageable for a different kind of ski area experience, said A-Basin’s mountain operations director.

“We’re not trying to build a bike park,” Skowyra said. “We’re trying to build spectacular, cross-country trails that have elements of flow and tech, but are gonna be accessible to everybody.”

As he looked out at some of Beavers’ first riders, Klein was reminded of something he once wrote on a hand-written resume.

After years of designing and hard building, “it’s so weird to see people I don’t know on the trail,” he said. “I’m like a proud father.”