The Pedal Wars : In Marin County, Where Mountain Biking Began, There are Speed Traps, Booby-Traps, Guerrilla Trails and a Decade's Worth of Bad Blood Between Hikers and Bikers.

We round a bend in sweaty silence, doing a mere 5, maybe 6 m.p.h., when we spot two hikers heading toward us on the road ahead--an older couple with canteens and walking sticks in hand. Breeze, the consummate bicycling gentleman, pilots his machine to the edge of the road, giving the walkers a wide berth. Then, as we draw near, he chirps a sunny hello.

The hikers flinch as if stung, and their expressions slump into scowls. As we roll slowly past, they set their jaws and stare straight ahead, marching forward with no word of reply.

Breeze is dejected, but, unlike me, not surprised. "Oh well," he murmurs. With a glance over his shoulder, he pedals onward up the grade, his good time torpedoed, at least for now.

Joe Breeze is 40 years old, and the hair that sneaks out from beneath his bicycling helmet is more gray than brown. Almost 17 years ago, he built the world's first successful mountain bike in his Marin County garage. He is shy, charming and as amiable as his name suggests--both on and off his bike. His friends in the all-terrain cycling world agree: There could be no better ambassador for their sport.

But to the hikers who just rebuffed his cheery greeting, Breeze is someone quite different, a person defined exclusively by the two-wheeled machine he chooses to ride. To them, Breeze is simply one more member of a loathsome breed--those reckless, Lycra-clad, adrenaline-addicted mountain bikers whose mass invasion of Mt. Tam has forever spoiled the serenity they once knew.

Martin Friedman, a Mill Valley potter, remembers how good it was before it got bad. Friedman, a sturdy 80, has been hiking the mountain that shadows his home for 50 years. "In the old days, one could walk along in a reverie, enjoying nature and the peace around you," he says. "It was beautiful, completely tranquil. But now, with the bikes and the aggressive lot who ride them, one must be constantly on alert. You never know when one of these people will whiz past your ear and make you jump out of your skin."

Conflicts over mountain biking are smoldering in almost every region where the explosively popular sport has taken root, from the red rock deserts of Utah to the Adirondacks in New York. Disagreement over where--and even whether--use of the bikes is appropriate in the nation's parks and wildlands has carved a deep chasm among outdoorsy types. Deriding cyclists as thrill-seekers who disrupt the peace and leave environmental scars, the anti-bike forces would like bicycles banned, or at least tightly controlled. The bikers, calling hikers exclusionary elitists, claim their sport can be socially and ecologically responsible and want equal access to the backcountry.

Here in Marin--cradle of the mountain bike phenomenon and a county legendary for its "mellow" attitude--the quarreling is unparalleled, ripening over the years into an all-out turf war. The wins and losses in the battle for Mt. Tam's trails echo in the debate wherever the two sides clash.

Bikers in Marin are on the defensive on many fronts. On the mountain, there are ugly confrontations, occasional acts of sabotage and rangers who use radar guns to ticket speeding cyclists. Down on the flatlands, the struggle is political. Permitted on fire roads but banned from narrower, more scenic trails, bikers have begun dueling for power on the assorted boards that set access rules for Marin's exquisite--and increasingly crowded--open spaces.

On the fringe, meanwhile, lurks a group of ride-free-or-die bikers who have gone guerrilla. Vexed by their exclusion from the mountain's footpaths, they simply built their own--snipping trees and molding earth to carve a clandestine 2.1-mile trail through a remote glen on public land.

They called it the New Paradigm Trail and posted a sign that summed up the frustration and hope of mountain bikers in Marin: "This trail was built by bicyclists knowing that someday it would be discovered. . . . If you can use it safely without damage, that fact will be much stronger than the theories and predictions used to justify the present rules. On the other hand, if we fail here, can you see what this means?

"Keep it secret. The fewer people that know about it, the longer we can enjoy it."