Using your C of G…


You may, or may not, be aware that as you ride, you are constantly weaving your front wheel from side to side. Just look at your tyre tracks, in fresh snow for example; one relatively steady (rear wheel) and the other weaving back and forth across it (front wheel). This is a visual demonstration of an almost unconscious action you perform to stay upright, maintain balance, control your bicycle’s instability and resist the pull of gravity.

Breezing along a smooth road, these adjustments to the steering are really quite small, barely noticeable. In tricky terrain, at about walking pace, they’re considerably more pronounced.

What you are doing is shifting your centre-of-gravity (or centre of mass). Gravity is constantly pulling you and your bike towards the earth and, because you and your bike are unstable, it’s making you fall over.

In simple terms, you are using steering to keep that centre-point of your mass vertically above your wheels. Every time you begin to topple, you steer into or towards the side you are falling. This action counteracts the effect of gravity by bringing your centre-of-gravity back to the centreline of you and your bike. You will then begin to topple to the other side, and you do the same thing again to maintain balance, and so on.

By deliberately allowing yourself to begin to fall to one side, you can use the same reaction, but slightly delayed, in order to initiate a change in direction of travel; in other words, to steer. You have shifted your centre-of-gravity to that side, then, as a reaction, you turn your handlebar towards, or into, that fall.

If you resist the reaction to steer into the fall and try to cycle straight ahead, your centre-of-gravity remains on that side and continues to pull you down. But, because you are instead steering in the direction of your fall, you don’t fall over; you are effectively counteracting the pull of gravity by controlling your centre-of-gravity’s position just enough to complete the turn.

You can see then that balancing and steering are essentially the same action.

Posted by Doog

…the cloud lifted for me when I pictured how riders (myself included) always relax by taking their hands off the bars. Amazingly, without falling off and steering even!

Provided your riding posture allows enough flexibility, it’s possible to alter your line of travel by shifting bodyweight alone, without moving the handlebar at all. Such moves are not pronounced and very useful for wiggling around small hazards. Also, with a very tight slow turn you remain almost vertical and can rapidly shift your centre-of-gravity to both sides, just enough to keep balanced. This is ‘active’ steering and doesn’t rely on that ‘fall and counteraction’ technique described above – you could topple either side.

Think about what is happening in this regard when track-racing cyclists are cornering on a banked curve; have they had to consciously steer at all?

Conversely, watch a motorcycle speedway racer steering through a bend at around 30-40mph, with their front wheel turned away from the direction of fall and, as action photographs sometimes show, not necessarily in contact with the ground.


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About gmacleland

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One Response to Using your C of G…

  1. Pingback: Stability… | Cleland > L A N D S E E R

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