The gap jump had to go. That hurt.

Bill Hawk, a teacher from Sudden Valley, and his friends built it as part of his new trail, called Evolution, which overlapped the route of an older trail, called the Scorpion, on a popular mountain biking area called Galbraith Mountain by locals and Lookout Mountain by officialdom.

Hawk's trail went downhill on a narrow track on a 150-foot log, then jumped 10 feet across empty air to a down ramp. They called it the Stinger. Hawk was proud of it. Other advanced mountain bikers praised it. But the design didn't give riders a way out - if they couldn't clear the gap, they'd likely have a nasty fall. The landowner, Trillium Corp., didn't like it. Neither did the Whatcom Independent Mountain Pedalers (or WHIMPs), who act as stewards for the area.

Hawk built a bridge across the gap. He kept the jump intact, but removed most of the risk - and with it, much of the excitement - from the ride.

The resulting cedar, rock and packed dirt structure is an example of a new style of compromise on the mountain - a compromise the WHIMPs hope signals an end to three years of friction.

It wasn't easy to do.

"I was kind of torn," says Hawk. "I saw the logic in closing it. I was willing to do it just to promote the good relationship."

Before Trillium acquired the mountain in 2002, mountain bikers built trails on the mountain where they chose and as they chose.

Most built trails in the older cross-country style, with wheels staying on the ground. But a few were experimenting with a new style called free-riding, which originated in Vancouver's North Shore in British Columbia. Free-riders ride heavy bikes with big shocks and crave big drops and high narrow structures that test their balance and nerve.

Dan Waters, Tim Carlson and other trail builders were starting to build trail structures in this style: high wooden catwalks, teeter-totters and other obstacles. But Trillium was wary of lawsuits and wanted them gone, so the WHIMPs removed them.

The action angered many free-riders, Waters says.

"It's not like they try to work with the kids. They just tear it out," Waters says. "The WHIMPs have made a lot of enemies."

Three years later, free-riders still build unauthorized trails, and the WHIMPs still tear them out.

Mark Peterson, the WHIMPs president, finds it ironic anyone would consider him an enemy of free-riding. In his day job as the Kona Bicycle Co.'s national advocacy director, he promotes free-riding areas nationwide.

But he also sees unauthorized trail building as a threat.

"There is absolutely no doubt that the number one threat to our sport right now is unauthorized trail construction," Peterson says, adding he has seen mountain bike areas closed because of illegal trails.

As a condition of the agreement allowing mountain bikers to use the mountain, all trail builders must get written permission from the WHIMPs and Trillium before they start work on a trail.

Peterson hopes to stop the cycle of building and tearing up trails by building more structures like the Stinger - sturdily built trail features that exercise free-riding skills while maintaining safety.

The International Mountain Bicycling Association (IMBA) promotes building techniques for safer free-riding areas. They use strong materials, such as rock, cedar and treated lumber and they build structures so they would please a building inspector. Free-riding trails open with difficult stunts, called filters, to warn novices to stay away. And for every jump, there's a way to roll over it, or detour around it.

"Rides are often surprised to learn that land managers will allow very challenging features as long as they have the confidence that they'll be done right," says Mark Eller, communications specialist for the IMBA.

This weekend, a pair of trail-building instructors from the association will visit Bellingham to talk to land managers and teach trail builders. Attending the seminar will be a condition of building on the mountain. Hawk and Waters plan to attend.

Jon Syre, Trillium's vice president of forestry and natural resources and a mountain biker, says Trillium wants all trails to be at IMBA standards.

Syre says the relationship with mountain bikers has gone well.

"We help them with a place to recreate," Syre says. In return, he says, the WHIMPs watch out for fires, help enforce the rules, watch out for damage to the land and pick up trash.

The IMBA standards mean that while free-riders can hone the same skills, they won't have the same thrills. Riding a balance beam one foot off the ground is not the same as riding one elevated six feet.

Tim Carlson, who teaches physical education at Lowell and Larrabee elementary schools, built some of the first free-riding trails in the Galbraith area before Trillium acquired the land. The features allowed now aren't ideal for free-riders, he says, but they work.

"It's maybe not quite as hairball as it used to be, but it's still fun," he says. "It just forced builders to be more creative with stuff that's low to the ground and that's more natural ."