IMBA admits it reversed course on the Boxer wilderness negotiations. But the real problem, Dice believes, is that IMBA’s offers of other designations — like national scenic or recreation areas, which offer strict protections against industrial uses but still allow bikes — aren’t taken seriously, especially in California. Wilderness groups, she says, "see it as capital ‘W’ wilderness and everything else is over. So it’s really hard to talk with them about other designations."

Sprung, who was a longtime professional wilderness advocate before joining IMBA, sees bikers as a green group that just hasn’t been invited to join the party. "I think we would be a regular part of the conservation movement, but we don’t have the luxury because our political energy must be spent on defending our right to trails from hikers and environmentalists," he says.

Big bikes, big problems

But a lot has changed since the days when Gary Sprung and his buddies pedaled their early mountain bikes through the West Elk Wilderness. If Marin is the birthplace of mountain biking, then the North Shore of Vancouver Island in British Columbia is where the sport enjoyed its teenage years in the 1990s. From its steep root- and rock-studded trails came a new breed of bikers that changed the sport dramatically.

On private land like Grouse Mountain, and in British Columbia parks, bikers built log trellises and balance beams over boggy and otherwise un-ridable areas. Soon they were building elaborate "stunts" — wooden jumps, teeter-totters, even banked walls of lumber. They blended moves from skateboarding and BMX with traditional mountain biking, and called the new sport "freeriding."

Freeriders pushed the development of stronger bikes that could handle 8-foot drops and insanely steep hills. Many of these bikes now sport 8 to 12 inches of bump-absorbing swing-arms, coil springs and damping cartridges on both front and rear wheels. Equipped with super-stout wheels, big tires and hydraulic-disc brakes, some weigh more than 50 pounds — so much, in fact, that riding them uphill is next to impossible.

Ski areas now sell summer lift tickets to freeriding and "downhill" bikers. British Columbia’s Whistler Mountain Bike Park, freeriding’s top destination, has soared from 10,000 riders in 1999 to a projected 120,000 this year. California’s Northstar resort near Tahoe and Mammoth in Southern California both have freeriding courses, and at least six resorts in Colorado offer "lift-assistance riding." Skills parks, not unlike skateboard parks, are popping up in urban areas as well.

Freeriding is still a small part of the mountain bike scene, largely relegated to specialized playgrounds, but its burlier technology has trickled down. Nearly all high-quality mountain bikes now sport front suspension and disc brakes; most, lighter "cross-country" bikes, are "full-suspension," meaning they have both front and rear shocks. Today, even average riders can charge over obstacles at speeds unthinkable a decade ago.

Because of the speed — and the stealth — of the new bikes, Robert Eichstaedt, a member of the Marin Horse Council, no longer takes novice equestrians out on Marin’s roads. "In the early days, you could hear bikes coming. Now, what you hear is something rushing. For a horse, if they can’t see it, their instinct is to run." Just last year, a biker-equestrian encounter on a narrow trail in California’s Los Padres National Forest ended in a horse falling to its death.

Recently, the faster bikes have spurred some ski areas to clamp down. In 2004, after the death of one downhill racer and the severe injury of another, California’s Snow Summit resort area put the brakes on downhill bikes. Chairlift operators now check bikes to make sure that the suspension doesn’t top 6 inches, the tires are 2.5 inches in diameter or smaller, and the bikes don’t weigh more than 35 pounds.

But it was more than liability concerns that prompted the resort’s ban. Bikers had blazed a mess of illegal trails that careened into the national forest from the top of the lifts. "Guys were just riding everywhere in the woods," Snow Summit President Dick Kun told the cycling magazine VeloNews. "The Forest Service was really pissed off with what was going on, and it probably wasn’t long before they shut it down anyway."

In fact, as freeriding’s popularity has grown, guerilla trails and rickety ramps have sprouted on private and public land around the region, and the new speed and braking has rutted out favorite trails. This summer, tempers flared when Forest Service officials tore out log-rides and other biker-made stunts on trails near Missoula, Mont., and threatened to issue $175 tickets to riders caught on a popular but technically off-limits trail.

Dangerous bedfellows

Sprung and IMBA have long fought to dispel the perception that bikes are "motorcycles without engines," saying that mountain bikers are more like "backpackers with wheels." In 2000, when the Bureau of Land Management released a draft of a new National Off-Highway Vehicle Management Strategy that lumped cyclists with motorized users, IMBA mobilized its troops. Over 10,000 letters flooded BLM offices from mountain bikers concerned that they might lose trail access. Ultimately, the BLM removed bikes from the plan.

But freeriding, with its requisite body armor and full-face helmets, makes mountain biking look a lot like motorcycling. And some of the sport’s most stalwart supporters wonder if the industry is putting bikers’ hard-won trail access at risk by flaunting freeriding and downhilling in videos and magazines.

"We sold freeriding in its most extreme form, then developed bicycles that enabled less-than-talented riders to ride over their heads," wrote Richard Cunningham, editor of Mountain Bike Action, in 2003. "Freeriding puts mountain bike access groups in an indefensible position," he wrote. "All this comes at a time when we are poised to gain the most — and suddenly we could lose everything."