The point of having numerous gears on a bike is to make riding easier or more efficient. Whether it’s maintaining the ideal cadence, or just getting up a hill, using the gears properly makes the whole riding experience more enjoyable.
Various systems are used to express gear ratios numerically, but it’s rarely necessary to worry about these when you’re actually cycling. The important factors are when to shift and how to shift.
When to shift? In very simple terms, shift down when pedalling begins to feel laboured; shift up when your legs are spinning too fast for comfort. The other two rules are: shift often and shift early.
For any individual, the range of optimal pedalling speeds is quite narrow and keeping within it often requires frequent shifting. On a completely flat road it may be possible to go a long way at constant speed without changing gear but more usually it's necessary to respond to varying gradients or shifting winds. With experience it’s easy to feel when the cadence is right and to shift before it drifts too far from the ideal.
Shifting down to a lower gear may need to be done quickly, especially when a hill starts to rear up ahead. Shifting up is less urgent, unless you are racing or are very concerned to build speed. Otherwise, if the road tips downhill, you can just coast if you want; shift to a higher gear as and when you want to keep pedalling at an optimum cadence.
How to shift? Hub gears may require you to stop pedalling to make a shift, but with derailleurs it’s important to keep the pedals turning. However, if the chain is under heavy tension it may refuse to derail, so it is necessary to ease pressure on the pedals before shifting. With practice this becomes second nature; it only takes a moment, probably just a single revolution of the pedals.
On the flat and downhill there usually isn’t too much pressure on the pedals and shifting is easy. The pressure is greater when climbing hills and this is usually where shifting becomes difficult. The need to lighten pressure on the pedals makes it important to anticipate the need to down-shift. If the hill is forcing you out of the saddle it is a good idea to sit down momentarily so you can take the pressure off the pedals and make the shift.
It is common to see people pushing bikes uphill when the chain is obviously not in the lowest gear position. This usually happens because they have not anticipated the need and have reached a point where they can’t relieve pressure on the pedals in order to change down. Again this underlines the rule: shift early.
Changing up to a higher gear is generally easier. If you’re picking up speed because of a tailwind or downhill then pedal pressure will be light anyway; it’s only if you’re really trying to boost your speed, as in a race, that you need to think about that momentary relief of pedal pressure that allows smooth shifting.
