Even as you progress, fast descents can be as intimidating as epic climbs. But here’s a secret: speed adds stability to your ride. Slow may feel safer, but often it is not in situations requiring upright stability — the acceleration due to gravity from your head to the ground is going to create a similar impact at 3 mph as at 9 mph. That’s why, whenever you make any moves which may affect balance — starting out from 0 mph, drinking from your water bottle, clipping in, making a turn, going over obstacles or slick surfaces, or cornering — you want to be sure you have enough momentum to get you through the transition.
…bikes lack lateral stability when stationary, and under most circumstances can only remain upright when moving forward. (Wikipedia.)
That means if you’re mucking around seeking out your clip or teetering and tottering over a metal grated bridge, but not moving fast enough to maintain lateral stability, you’re going to become unstable. The physics is so complicated that it requires “three-dimensional, multibody dynamic analysis with at least two generalized coordinates to analyze” mathematically. (Citation.) But its the kind of thing we humans can feel intuitively through our sense of balance.
When we’re learning something new, it is natural to take it slow, but when it comes to lateral stability on a bicycle, speed matters. And it is impossible to balance a bicycle without any momentum, but a very skilled rider can generate very small bits of momentum steering to counteract the other forces on the bike and remain upright:
While performing a track stand, the rider can keep the line between the two contact patches under the combined center of mass by steering the front wheel to one side or the other and then moving forward and backward slightly to move the front contact patch from side to side as necessary. Forward motion can be generated simply by pedaling. Backwards motion can be generated the same way on a fixed-gear bicycle. Otherwise, the rider can take advantage of an opportune slope of the pavement or lurch the upper body backwards while the brakes are momentarily engaged. (Citation.)
When you find yourself moving too slowly, your body will use its sense of balance to try to right the bike by using techniques similar to these. For instance, you may feel the front of the bike veer one way or the other and try to counter it by steering in the opposite direction — all too quickly and grossly out of proportion, but often effective at keeping you upright until your body automatically unclips and you save yourself from a fall:
The rider applies torque to the handlebars in order to turn the front wheel and so to control lean and maintain balance. At high speeds, small steering angles quickly move the ground contact points laterally; at low speeds, larger steering angles are required to achieve the same results in the same amount of time. Because of this, it is usually easier to maintain balance at high speeds. Also, self-stability usually only occurs at speeds above some minimum, and so going faster increases the chances that a bike is contributing to its own stability.(Citation, emphasis added.)
This all takes practice, and it certainly is not necessary to know the math or physics. But next time you wobble only to save yourself at the last minute (or don’t quite clip out in time and tumble), know that you can blame physics!
The take-away message here is: practice transitional moves before long rides when you’re tired. If you’re having trouble with your clips, go to the bike shop and ask them to use their trainer. Practice. Ask them to critique your clipping in and out. Them move to a parking lot where you don’t have to worry about traffic, or a flat, low grassy field where you can fall in relative safety. Practice other techniques this way, too, so that you become proficient and don’t hurt yourself out on the road.
Over the next couple months, I’m going to write a few articles with the lead-in title “Absolute Beginners,” explaining some of the basic principles of cycling. Most of the information is stuff I’ve learned from other cyclists, bike shop mechanics, classes I’ve taken, and Google searches. Please help me out and comment with corrections, additions, or supplements which will help my readers learn about how to operate their bikes!