The Mountainbike

Image Gallery Most mountainbike users will likely employ their machines as transportation across the sortof roads (and nonroads) that would thwart skinnier-tired and more delicately framed ""traditional"" multi- speed bikes.

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In the last ten years, the racing-style bicycle has become tremendously popular . . . and for good reasons. The thin-tire, spindly machines are marvels of efficiency on the high way, turning travel into a healthful and entertaining experience. However, if you've ever tried to maneuver one of these specialized machines down a dirt road (or even across the often volcanic landscape of a large city), you know that smooth pavement is just about a prerequisite for riding them.
In fact, once you trespass onto the byways, the narrow, high-pressure tires and quick-handling characteristics of a street bike can turn it into a bone-jarring torture tool that's roughly the equivalent of a mechanical rodeo bull. Worse yet, that sort of abuse takes its toll on the machine as well as on the rider. Stories of wheels collapsed against the far edge of a New York pothole are part of that city's bicycle folk legend. Yes, after one brief sojourn, street pedalers learn to steer clear of dirt roads and rough pavement.
If you graduated from training wheels a few decades ago, though, you probably started out riding a heavy, unresponsive, wide-tired single-speed machine that was difficult to develop any speed on. And if you've since experienced a modern cycle, you're not about to switch back. In nearly every respect, the old "ballooners" were inferior to the racing-style machines that have become so common today. We say nearly. . . because, as you may recall, those stable and forgiving beasts were as much at home on dirt roads (or in a pockmarked alley) as they were on pavement.

ENTER THE KLUNKER

A little less than ten years ago, a group of cyclists (many of them pavement racers) in Marin County, California got the idea of marrying racing technology with sturdy (and cheap!) old balloon-tired bikes. Riding these strange hybrids, the group took to fire roads—steep, crudely prepared paths that allow fire-fighting vehicles to get into undeveloped areas—and created a subculture of off-road bicyclists. Even more important, they started the evolution of a new sort of bicycle, one that could revolutionize the business (and may already have done so).
The modern mountainbike (also called klunker or fat-tire bike) borrows from racing, street, and bicycle motocross technology. The result is a full-sized cycle that takes on rough terrain with ease but also performs quite well on pavement.

As the accompanying chart shows, nearly all such machines have a minimum of ten different gears to choose from (the Fisher Tandem actually has 21). With two or three front sprockets and from five to seven rear ones, there's a ratio to suit just about every imaginable situation . . . from climbing steep hills at a snail's pace to plummeting down long stretches of asphalt. As compared with street cycles, mountainbikes have gears that allow slower speeds while maintaining upper ratios that exceed most bicyclist's desires or capabilities.
Most "big foot" bikes—and all of the models that we've ridden—are equipped with 27"-diameter, 2-1/8" tires that have a knobby (or dual-purpose) tread pattern for traction in dirt and are inflated to about 40 pounds per square inch (PSI). Top-notch street machines, on the other hand, use 27" X 1" or 1-1/4" rubber, with a smooth central ridge for low friction, and get at least an 80 PSI charge. The fat tires on the mountainbikes provide a much smoother ride on rough pavement, produce a small (but noticeable) increase in rolling resistance, and—not surprisingly—are much more surefooted.
Mountainbike frames are, in many cases, derived from the traditional diamond-shaped street chassis. The designs differ in several important ways, though: Generally, the mountainbike's front forks are angled forward farther from vertical for stability, its tubes are lengthened from the crank center line to the rear axle to enhance climbing ability, and its wheelbase is several inches longer overall. As a basis from which to compare the geometry listed for the machines in the chart, an average street machine has a head angle of about 74°, chain stays approximately 16" long, and a wheelbase of about 39". The major effects—in terms of steering—of the off-road cycles' deviations from these norms is that such machines are less responsive on the highway but make that sacrifice in exchange for predictable off-road handling.
To further improve control when taking on rough terrain, all mountainbikes allow a more upright riding position than the crouch used on drop-bar speedsters. The handlebars are similar to those found on motorcycles, and in many cases manufacturers have used controls from the engine-powered machines, as well. For most people, the mountainbike position will prove to be more comfortable on or off the highway. Because the rider isn't bent so far forward, there's less pressure on the wrists, and the angle and position of the seat become less critical for comfort (mountainbike seats also often have quick-release mechanisms that allow rapid movement up and down, and sometimes even fore and aft). Of course, the price one pays for the relaxed mountainbike riding position is increased wind resistance, the single greatest retarding force at highway cruising speeds. Around town, this usually isn't too noticeable . . . but on long highway tours it's a serious handicap.
Another difference between on-and off-road bikes shows up in their brakes. The familiar center-and side-pull binders of street machines can't reach around the fat tires on a mountainbike, so a different approach is used . . . cantilever brakes. These consist of separate mechanisms attached to each side of the frame. One wing of a cable with a "Y" extends to each arm to permit the shoes to push against the rim with equal pressure. Because the cantilever brakes are solidly mounted and have short arms, they flex very little. The result is stronger, more sensitive braking than can be found on most quality street machines. When you add this attribute to the mountainbike's wider tires and more stable frame geometry, you get a cycle that can significantly outbrake its highway competitors . . . even in their own element.
There are also a number of ways in which mountainbikes have been made stronger that conventional street cycles, to withstand the punishment of energetic off-road riding. The frames usually have oversized, chrome-molybdenum steel tubes with thicker walls . . wheel spokes are larger in diameter and laces in stronger patterns . . . axles are solid rather than hollow . . . and headset bearings are often larger. Some of the more expensive machines even have sealed hubs and bottom brackets to protect those precision parts from grit and water. When you're shopping, bi sure to ask whether the bearings themselves, are sealed or if the mechanisms are just fitter with protective cups. Sealed bearings are more effective, but either approach is better than no protection at all.
These reinforcements make mountainbike very durable under any imaginable conditions. Unfortunately, the same measures also add weight. Compared with street machines; a mountainbike costing about the same amount of money will be roughly five pound; heavier. Still, a 30-pound bicycle is a real delight if you grew up on a 45-pound paper boy special. And if you've never had the pleasure of riding a top-notch bike—street or dirt—you'll be amazed how easily you're able to cover ground.

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