DOWNIEVILLE, Calif. — Rocks. Roots. Butterflies. Face plant. It happens in slow motion as I fly over my handlebars for the third time while riding over 17 miles of fire roads and rocky, single-track trails that drop more than 5,000 feet in the northern Sierra Nevada mountain range.

Riding a full-suspension bike, I was squeezing hard on the disc brakes to maneuver through a patch of gravel near a rocky rivulet when my front tire slid to the right, sending me plummeting to the ground, where I landed hard on my left knee and hip. I threw up a cloud of dust and a shower of expletives.

How did this happen? Were my eyes drawn off the path by a waterfall, a green meadow or an alpine lake? It's easy to be distracted on these trails, but as you skirt past 300-foot sheer drop-offs, that's a sure road to ruin.

I'm in Downieville, about 100 miles northeast of Sacramento, to test the downhill runs that gear heads and biking daredevils rate as some of the state's fastest and most challenging.

As a weekend mountain biker and lifelong Californian, I heard about Moab, Utah, being the ultimate off-road biking destination. I wanted to find a new biking hub that has the respect of veteran riders without Moab's crowds and hype.

After that third wipeout, I dust myself off, pick bits of gravel from my bloody knee and roll cautiously toward the base of the mountain. As I coast into town, I know I'm not done yet.

UNEASY RIDERS

All is quiet on Main Street on a late-summer afternoon, except for the rushing water from the Yuba and Downie rivers, which unite under a bridge a block away.

I'm chatting with the chef of the Grubstake Saloon when a high-pitched zipping sound breaks the stillness. It's the unmistakable din of knobby tires rolling on blacktop.

Bug-eyed and mud-caked, the speeding bikers zigzag down Main Street, in packs of threes, fours and fives, crowing over their conquest of a high-speed dirt-trail plunge from the 7,100-foot summit of Sierra Buttes.

It's a noisy daily ritual, but few locals complain. After all, mountain biking brought Downieville back to life after the gold and timber trades died decades ago. Each year, thousands of thrill seekers take state Route 49 to this tiny community at the foot of Sierra Buttes to explore hundreds of miles of converted gold-mining trails.

Downieville is a true mountain-biking town. All three hotels offer bike lockers, and the town's economic plan includes a chapter on mountain biking.

Each July, the Downieville Classic Mountain Bike Festival inflates the town's population of 300 to 3,000. The town has only one grocery store but two full-service bike shops, Downieville Outfitters and Yuba Expeditions. They're the economic engines of this community.

Several times each day during the dry months, shuttle vans loaded with riders and mountain bikes roar out of each shop to the trail head at Packer Saddle, near the summit of Sierra Buttes. An hour or two later, those same riders come screaming down the mountain, crowding the quiet streets with knobby tires and sweaty Lycra.

RIDE FAST OR ELSE

Looking for something to eat, I wander into Gallows Cafe & Pizzeria — named for the 1880-era gallows near the local sheriff's station — and vacillate when the cashier asks for my order.

"Take your time," the pizza worker says. "You're on Downieville time now."

A teenager in full body pads sits on his bike at the Packer Saddle trail head.

"I just can't wait to start riding," he tells his buddy.

I shared a shuttle van to Packer Saddle with the teens and about eight other guys, our bikes strapped to the roof rack. On the way up, everyone agrees to give me and a photographer a five-minute head start so we can find a good vantage point to shoot photos. But once the riders get on their bikes, they blow us off, leaving us in the dust. The relaxed atmosphere that permeates Main Street doesn't extend to the trails. Up here, it's ride fast or get out of the way.

I strap on my helmet and let gravity take control.

Aqua-blue alpine lakes flash in the corner of my eyes. The blur overhead is a canopy of white and red fir, tamarack and Jeffrey pine. A wooden footbridge launches me over a deep pool at the base of towering waterfalls. Weren't those broad-leafed mule's ear filling that meadow with yellow flowers? It's all moving so fast. At a tiny stream crossing, hordes of painted lady butterflies scatter as I splash through, filling the sky with fluttering wings.

But the trails also flirt with deadly cliffs, slick shale and granite boulders that rise up in sharp angles. Knotted tree roots spring from the route like speed bumps. Rocks the size of a human fist litter the shoulder-width path.

My inner voice becomes shrill: Slow down! Look out! Look at that cliff!

Despite my caution, I wipe out three times, landing twice on hard gravel and once sliding down an embankment of poison oak and broken tree branches. Each time the culprit is something seemingly innocuous: a dirt-filled gully, a slick rock or a jutting root.

At another footbridge, I'm overtaken by six female riders, including twins from Colorado.

"Nothing compares to Boulder, but this place is not bad," says Elise Jones as her twin, Suzanne, pulls up.

'BABY HEADS'

A couple of hours later, I'm part of Downieville's second-most popular pastime: the post-ride bull session.

About 20 of us — including executive headhunters, lawyers, security experts and winemakers — sit on lawn chairs behind the Carriage House Inn, overlooking the Downie River, drinking wine, beer and tequila shots. We talk about our rides, our falls, our families and our work back home. I stagger back to my hotel room, feeling no pain from my earlier spills.

My bike is rattling like a maraca as I speed down a mountain trail known to locals as "baby heads," because the path is sprinkled with rocks the size of, well, you can guess.

It's my second day riding the Downieville trails, and this time I'm joined by Greg Long, a longtime biker and owner of Downieville Outfitters.

"If you can ride Downieville, you can ride anywhere," he says.

The bike, he warns me, tends to veer to the focus of your eyes. Concentrate on the trail and not the hellish cliff near the edge and you'll be fine, he says.

Now I'm rolling over the baby heads and gaining speed. That shrill voice in my head tells me to clamp on the brake until I remember another tip from Long: When in doubt, find a line in the trail, speed up and shoot through. It proves to be good advice, as I fly over the baby heads without a spill. In fact, the advice keeps me accident-free for the rest of the ride. It's a strange lesson to learn.

When I got to Downieville, I assumed that fear and caution would keep me safe. It turns out I should have been relying on speed and confidence.

A couple of hours later, I roll into Main Street again, bug-eyed, mud-caked and crowing, just like the rest of the dirt-smeared bike mob.