Fifty-plus miles per hour on mountain trails-in a wheelchair. Cutting-edge mountain bike technology helps create unique vehicles that carry mobility-impaired racers into rugged competition.

At the top of a gravel road in the foothills of the Rocky Mountains west of Denver, Colorado, two young men wearing motocross helmets and padded jerseys ease themselves off the tailgate of a pickup and settle onto the saddles of a couple of low-slung vehicles as if they were rodeo bullriders getting set to spring out of the chutes.

Within seconds,they are hurtling down the hill so fast that they must use their brakes to keep from hitting the moving truck in front of them. Careening around curves, bouncing over bumps and zooming down the few straight stretches, they cover the mile or so back to the main highway in little more than 2minutes.

“That was great!” exclaims one of the two as they finish their practice run in a cloud of dust.

The riders, both college students in their early 20s, also have a couple of other things in common. They are both paraplegics and members of an all-terrain wheelchair racing team assembled by a former bike builder who is now devoting his life to freeing the disabled from the tyranny of paved roads and sidewalks.

“I once had a nightmare in which I had lost the useof my legs,” says Michael Whiting, the 36-year-old coach, manager and mechanical genius behind the Wildernet wheelchair factory team. “What bothered me most was not that I couldn’t walk up steps or go to thebathroom without a hassle, but that I couldn’t get into the back-countryanymore and do the things I like to do now. When I woke up, I thought:What if I really were in those circumstances? And that’s when I decided to start designing an off-road wheelchair.”

Whiting’s first effort, the Phoenix 1, named after the mythical bird that rose from its own ashes, was made of heavy-gauge steel tubing and other parts that seem almost primitive today. The prototype weighed close to 60 pounds, almost twice as much as the latest incarnation–a titanium and aluminum cart outfitted with such state-of-the-art components as hydraulic disc brakes, speed-sensitive steering and an independent-suspension design borrowed from the Viking Mars lander.

“The frame on the original chair weighed more than our entire production chair today,” he says.

Whiting’s high-tech chairs, which he still builds by hand in the basement of his unassuming brick bungalow in Denver, aren’t yet well-known in the disabled community. But in the fast-paced world of mountain bike racing, where members of his loose-knit team have been entering slalom and downhill events regularly for the past two years, they are becoming the riders to beat.

The reason: Although the Wildernet machines have no drivetrain, and thus can’t be pedaled, their four wheels and low center of gravity give them extra stability in the turns. On the rough, rutted fire roads and 4-wheel-drive trails where such off-road races are typically staged, Whiting’s racers often reach speeds exceeding 50 miles per hour.

What? Fifty miles per hour in a wheelchair? Yes, that’s the kind of thrill this former English major holds out to the tens of thousands of mobility-impaired Americans whose image of wheelchairs may be as limited as the clunky, hospital-style machines that many still use to get around.

In essence, the innovative designer has come up with a way to adapt today’s most advanced mountain bike technology to the specialized needs of riders whose legs no longer function as shock absorbers.

“My job is to design an interface between existing high-end mountain bike components and our wheelchair frame and saddle,” says Whiting. “This becomes the interface between the person and the terrain.”

Whiting has made only about 30 of the all-terrain chairs in the four years since the first prototype rolled out of his workshop, but he hopes to double that number in the next year as word of his unique design spreads and the market expands. The basic model weighs 34 to 44 pounds, depending on size and construction, and sells race-ready for $4200. That can be up to four times the cost of an average high-performance mountain bike and twice as much as the kind of lightweight chair used in sprint racing and marathons. But as wheelchair athlete/dealer Steve Ackerman notes, “All equipment for people with disabilities is specialized, and as such is more expensive. It’s not something you’re going to see on the shelves at Wal-Mart.”

When Whiting first started thinking about wheelchair design, the prevailing approach–as exemplified by Enduro and Cobra, two earlier manufacturers–was to take an existing chair and adapt it for off-road use.

“I decided to go the opposite way and start with a list of performance parameters for a person in a wheelchair,” he says.

The first challenge was to come up with a suspension system that would enable a 150- to 200-pound rider to go down a rough stretch of road without being bounced to pieces.

Whiting accomplished this on the front end by modifying a fully independent, double-wishbone system manufactured by AMP Research, and on the rear end with a custom-made design featuring independent trailing arms.

The next task was to find a braking system that would bring a chair to a stop quickly, safely and reliably. As Whiting points out, “It’s not like you can

just bail, like on a mountain bike.” By arranging a marriage between hydraulic brake levers manufactured by Magura, of Germany, and high-end disc brakes made by Mountain Cycles, of San Luis Obispo, California, he came up with a system offering four times the braking power of an ordinary bicycle.

The chair can be steered with either the self-centering handlebars or the rear wheels, which are 36 in. apart and canted inward 2 in. at the top for easier arm movement while pushing on level ground. The hubs, heavy-duty 26-in. rims and knobby-tread tires are all standard off-the-shelf mountain bike parts.

Whiting designs the frames and assembles the components himself in what he jokingly refers to as his company’s “world headquarters,” but he farms out the welding and machine-shop work to local craftsmen.

In designing the footrest and the saddle–a canvas sling with 5 in. of play and a backrest that can be adjusted on the fly–Whiting tapped the ergonomics expertise of Jay Medical, a manufacturer of seating and positional products in Boulder. The firm is now the prime sponsor of the 10-member Wildernet factory team called JAY Xtreme/Team Phoenix.

“The idea of an off-road wheelchair racing team,” Whiting says, “appeals to the daredevil in us all and highlights the resiliency of the human spirit.”

Besides competing on the mountain bike racing circuit, the racers–six men and four women, including a couple of world-class monoskiers–will be taking part this summer in a series of clinics designed to introduce the all-terrain chairs to users of standard wheelchairs. ITT-Hartford, the well-known insurance company, has agreed to underwrite the venture. The first course is scheduled for early May at the Big Bear ski resort in California.

“It’ll be a lot of fun,” says Whiting, who will be traveling to the clinics in a truck with as many as 16 of his lightweight racing chairs packed into a 30-ft. trailer. “We’ll take people up on the mountain, go hiking, so to speak, and maybe on the second day we’ll set up a race course and teach them how to negotiate curves and gates. The chair is easier to learn to ride than a regular bicycle or monoski, and it really gets your adrenaline pumping. The best part is that the racers will be there to provide advice, support and