Learn to ride skinnies: eyes to the end, roll calmly, train balance. Step by step from a line on the ground to a low bridge, with milestones.
The honest answer first: you ride a skinny by directing your eyes to the end of the bridge, rolling calmly and evenly and making small corrections from hips and bars instead of flailing. The technique is the same as for balance at a standstill and slow riding, only without any room to evade [1] [2]. BASPO names balance as the basis and advises looking forward when riding slowly, not directly in front of the front wheel [2].
Why must you be particularly careful with skinnies? Because they are fun exactly where a mistake hurts. In mountain biking the head and upper extremity are the most common injury sites [3], and in a clinic series of recreational downhill riders, upper-extremity injuries combined with soft-tissue damage dominated [4]. If you fall from a bridge you fall onto your arms.
The effort pays off anyway: in a study of 29 mountain bikers, bike-specific balance correlated clearly with time on a downhill run (r up to -0.78), whereas single-leg stance with open eyes hardly did [5]. Skinnies train exactly this balance.
How hard is it? The first metres on a flat board work in an afternoon. You become reliable on a 30-centimetre-high bridge after weeks (experience-based).
A skinny is not a dare, it is a balance exercise with consequences.
Draw a line about ten metres long on the ground and ride it at walking pace. Your eyes go to the end of the line, not to the front wheel [2]. The bike goes where your eyes look [7].
Milestone: you ride the line five times in a row without a tyre leaving it.
Lay a plank or narrow board flat on the ground and ride over it. Now there is a real track, but no height risk. Roll instead of creeping: a rolling wheel holds balance more easily than a stationary one [7].
Milestone: five crossings in a row without putting a foot down, at even speed.
When you wobble, correct with hips and bars, not with frantic pedalling. The interplay of pedal pressure and brake helps hold balance [1]. One finger stays on the brake.
Milestone: you stop briefly on the plank and roll off again.
Only now comes height: a low, short, dry bridge that you can leave with one step if needed (practice). Eyes to the end, roll calmly.
Milestone: five clean crossings, then one in each direction.
Increase only one of the two, either length or height. In a pilot study of 17 experienced riders, the product of perceived probability of falling and of injury decided whether they rode a wooden ramp; on average they declined at about 13 percent [8].
Milestone: before every increase you can say why you are riding it now.
Skinnies are safety-critical. A fall from a bridge means fall height, and the upper extremity and head are the most common injury sites [3]. In a meta-analysis across cyclists, a helmet cut serious head injuries by about 60 percent [9], a figure for cycling in general.
The DIMB trail rules say: "Control your bicycle." [10] Keep to bridges below your ability, never practise over drop-offs, never alone on high bridges and never in the wet (practice). Get off if you feel unsure. This guide explains and motivates, it does not replace supervised training.
Make the fall height small, not the courage big. The pilot study shows that experienced riders judge ramps by the product of fall probability and injury probability [8]. You can lower the injury side: lower bridge, softer ground underneath, no obstacle next to it (practice). That does not make practice less effective, just less risky.
Eyes to the end, roll calmly and evenly, make small corrections with hips and bars, balance through pedal pressure and brake. Practise on the ground and on flat boards first [2] [1].
To the end of the bridge, far ahead, not directly in front of the front wheel [2]. The bike goes where your eyes look [7].
Low, so low that getting off takes only a step (practice). The literature gives no fixed height. Start on the ground and increase only length or height, never both at once.
It helps only to a limited extent: single-leg stance with open eyes hardly predicted riding performance, bike-specific balance did so clearly [5]. The trackstand is the better-fitting exercise.
Riding a Rock Garden: Line, Speed and Active Suspension on the Trail