Fit for the Trails

Fit for the Trails

BY THE EDITORS OF BICYCLING MAGAZINE

It's important to have a comfortable, efficient position on your mountain bike. By following these adjustment procedures and cycling techniques, you'll handle the varied terrain and conditions that make mountain biking so thrilling, and you'll reduce your chance of sustaining aches and injuries to muscles or joints.

1. Upper body. Strive for a loose, relaxed upper body.

2. Arms. For shock absorption and steering control, your elbows should be comfortably bent, even when you slide well back on the saddle. If you can reach the handlebar only with your elbows locked, get a shorter stem, look for a frame with a shorter top tube, or learn to lean forward more. If your upper arms and shoulders fatigue quickly because you are too cramped, you may need a longer stem or a frame with a longer top tube.

3. Top-tube and stem length. These combine to govern handlebar reach, an aspect of fit to which women should pay particular attention. With a mountain bike's extra-long seatpost, it's often top-tube length, not seat-tube length, that dictates whether to buy a smaller or larger frame size (or even a different make of bicycle). The result should be slightly bent arms and a straight back.

4. Stem height and rise angle. These should place the handlebar 1 to 3 inches below the top of the saddle if you intend to ride trails. This shifts enough weight to the front wheel for climbing control. If you need a high-rise stem, get one. Don't raise a too-low stem past its maximum-extension line--it could snap off or pull out. If your bike has a threadless headset, minimal or no stem-height adjustment can be made; alterations depend on the rise angle.

5. Handlebar. Bar width should feel comfortable and natural with your hands on the grips--21 to 24 inches is common on mountain bikes. Since women's shoulders are normally narrower than men's, many women are likely to find narrower handlebars comfortable yet wide enough for good slow-speed control. (In general, the narrower the bar, the quicker the steering.) If necessary, you can shorten the ends with a hacksaw or pipe cutter. First, though, move your controls and grips inward and take a ride to make sure you'll like the new width. If it's too narrow, you won't be able to control the steering sufficiently. Leave a bit extra at each end if you use (or want to add) bar-ends.

Bars come with varying degrees of rearward sweep, from 0 to about 12 degrees. (A few have as much as 22 degrees.) Try them to see which gives the most natural wrist position. Note that changing the rearward sweep also alters the reach to the grips and could require a different stem extension.

6. Hands and wrists. Try to ride as relaxed as possible without sacrificing a firm grip. Usually, holding the handlebar with pinkie and ring fingers is sufficient, leaving the index and middle fingers to operate the brakes. Keep your thumbs wrapped under the grips, not on top where a jolt could cause your hands to slip off. On rough terrain, grasp the bar firmly to transfer shock to your arms (keeping your elbows bent). A light grip lets the bar vibrate against your hands, causing stinging or numbness. Although squishy foam grips feel good on the showroom floor, firmer, less compressible ones fatigue your hands less and give you a better sense of the terrain under the wheels.

7. Back. A forward lean of at least 45 degrees is most efficient because the strong gluteus muscles of the butt aren't able to contribute as much pedaling power when you're sitting more upright. This forward lean also shifts weight to your arms, so your butt doesn't get as sore. New riders, don't be impatient with yourselves if you can't lean that far forward at first; you'll develop flexibility over time.

8. Butt. When riding, don't always sit squarely in the middle of the saddle. Slide to the rear for added power or to keep the back wheel planted on descents (on steep or bumpier descents, you'll even learn to push your butt off the back of the saddle). On steep climbs, crouching over the handlebar while sitting on the saddle nose maintains traction and keeps the front wheel down.

9. Saddle height. The distance from the center of the crankset axle to the top of the saddle should be 0.883 of your inseam length (measured in stocking feet from floor to crotch). Your knees should be slightly bent at the bottom of the pedal stroke, and, when viewed from behind, your hips should not rock as you pedal. For descents, on a bike so-equipped, a beginner can use the seatpost quick-release to lower the saddle an inch or so to lower the center of gravity; raise the saddle once you're on the level again.

10. Saddle tilt. Most female riders prefer level saddles, but some like a slight nose-down tilt to avoid irritation. A nose-up position can put painful pressure on the genitals when you're leaning forward.

11. Seatpost. On a properly fitted mountain bike, you'll see more seatpost showing than you would on a road bike. That's why off-road posts are commonly 300 to 350 mm long. Don't raise the post above the maximum-extension line that's engraved on it.

12. Knee-over-pedal. Don't use fore/aft saddle position to compensate for improper handlebar reach--that's why stems come in different lengths. When you're seated comfortably, a plumb line dropped from the front of the forward kneecap should touch the end of the crankarm when it's horizontal. Slide the saddle forward or back to achieve this.

13. Frame. You need a lot of crotch clearance so you don't hurt yourself if you need to hop off. This isn't as critical for pavement and smooth dirt riding. There's no advantage, however, to riding a frame any larger than the smallest size that provides enough seat height. Smaller frames are lighter, shorter, and more maneuverable.

Beware--the numbers can be confusing: Some manufacturers measure frame size from the center of the bottom bracket to the center of the top tube, others to the top of the top tube, and others to the top of an extended seat lug. Plus, mountain bikes have sloping top tubes that result in relatively short seat tubes. In this situation, a 13- or 14-inch mountain bike could be the ideal size for someone who rides a 19-inch road bike. The safest way to determine if a frame fits is to road-test it before buying.

14. Feet. If you use toeclips, there should be at least 5 mm (almost ¼ inch) of clearance between the tip of your shoe and the front of the clip when the ball of your foot is over the pedal axle. Because mountain bike shoes are bulky, toeclips for off-road use run larger than road bike clips.

15. Pedaling technique. Smoothness is desirable. However, a mountain bike's longer crankarms, combined with riding steeper climbs and rough terrain, contribute to a slower cadence. On rough trails, pushing a higher gear at a lower cadence lets your legs bear most of your weight, lessening shock to your arms and butt. Ride really bumpy terrain out of the saddle in the "ready position," crouched over the bike so it's free to chatter and bounce under you.

16. Crankarm length. This usually varies with frame size. For added climbing leverage, the same size rider usually uses 5-mm larger crankarms on a mountain bike than on a road bike. In general, most mountain bikes come with 175-mm crankarms, and in most cases these work fine. Upgrading to an unusual length (such as 177.5 or 180) can be expensive, so only do this if you're sure the stock length is causing problems. If so, use inseam measurement to select crankarm length. If your inseam is less than 29 inches, use 170-mm crankarms; 29 to 32 inches, 175-mm; 33 to 34 inches, 177.5-mm; and more than 34 inches, 180-mm. (Crankarms are measured from the center of the crankarm axle bolt to the center of the pedal mounting hole; the size is usually marked on the back.)