Although single gear bikes and three-speed hubs have their place, most bikes sold today have multiple gears. Here's how and when to use them.

The purpose of multiple gears is to allow you to ride efficiently, without having to resort to walking up any hills or wasting your energy when riding descents or tailwind sections.

• Road bikes usually have two chainwheels and anything from seven to ten sprockets on the rear wheel giving from 14 (2x7) to 20 (2x10) gears.
• Mountain bikes usually have more gears than their road counterparts. By using three chainwheels and seven, eight or nine sprockets on the rear wheel, they provide 21 (3x7), 24 (3x8) or even 27 (3x9) gears. The mountain bike's range of gears is also wider, to provide some very low gears suitable for steep off-road climbs.
• Touring bikes often have gears similar to mountain-bikes, to cope with long, luggage-laden days with relative ease. 

Preparation

Check that your gears are working properly. If the chain falls off the chainwheel, if the rear mechanism touches the spokes, or if the chain does not engage the sprockets properly when you change gear you (or a bike mechanic) must make suitable adjustments and replace any worn parts. If the chain 'slips' - especially when you pedal harder - you will probably need to replace the sprockets on the back wheel and fit a new chain. (See also Maintenance).

Make sure that you are familiar with operating the gear shifters. The right-hand lever operates the rear gear (moving the chain across the sprockets). The left-hand lever operates the front mechanism, which shifts the chain from one chainwheel to another. When the chain is on the big chainwheel you will be in a bigger gear - usually used for riding along the flat or downhill. The smaller (inner) chainwheels are used for uphill work, riding with luggage, or into a strong headwind, or perhaps around town when you need a low gear to cope with lots of stopping and starting at traffic lights or junctions. Whether you ride on the roads or on trails your gear changing has to be instinctive to avoid any problems with traffic or technical terrain. You may find it beneficial to practice gear changing on a quiet road or simple trail before tackling more difficult conditions.

The derailleur mechanism requires you to keep pedalling to get the chain to shift from one sprocket (or chainwheel) to the next. Depending on the size (number of teeth) of the chainwheels and the sprockets there will be some overlap of gear sizes between the different chainwheels. Whichever chainwheel you use you should spend most of your riding time using the middle three or four sprockets except for more extreme circumstances (steep climbs, flat roads with a tailwind etc). Look ahead (not down at your gears).


Technique

Racing road cyclists tend to pedal at about 90-100 revolutions per minute, as this is most efficient in terms of aerobic capacity and power. Off-road or leisure cyclists usually pedal at a lower cadence, perhaps closer to 70-80 rpm; riding off-road or uphill will inevitably lower your cadence but aim to keep it above 60 rpm at all times. Using your gears enables you to maintain that cadence to use your energy most efficiently, allowing you to ride faster for longer. As you get fitter and more proficient you will find it much easier to achieve and maintain this seemingly high cadence for longer. Select your gears to suit your cadence, not the other way round.
Even with advances in modern gear design, gears do not like changing under very large pedalling pressures at low cadences. So when changing gear, especially uphill, ease off the pedalling pressure just a little to help the chain move across the sprockets or from one chainwheel to the next. This does require some anticipation on steep hills. Front gear changers can be particularly reluctant to move the chain to the smaller chainwheel so select your chainwheel before your cadence drops too low (below about 60 rpm).

When approaching junctions or coming to a stop, drop down a couple of gears (onto a larger sprocket) so that you can move off comfortably with a lower gear when you need to.

Avoid using the extreme gears (big chainwheel and biggest sprocket, smallest chainwheel and smallest sprocket) as the chain may be either too taut or too slack to work efficiently or may even foul the mechanisms. Listen to your gears too. If you can hear the chain 'tinkling' or 'crunching' against other parts, you may need to tweak the shifters to help centre the mechanism, or perhaps some closer inspection and technical adjustment may be required. 

When descending, especially if you are freewheeling, shift the chain onto the big chainwheel and a medium cog, to keep the chain tight and prevent it from bouncing off. This will also be a more appropriate gear for when you need to start pedalling again.

Advanced

With so many gears to use, you can fine-tune your cadence to within about +/-5 rpm of your optimum at all times. This is particularly useful when you are climbing or trying hard (such as when racing).