HISTORY OF DERAILLEURS
Bikes with derailleurs
The derailleur was invented around 1905 and is the standard method of shifting for sport, racing, touring, and mountain bikes. The main benefit is that it offers an extremely wide range of gears and is a lightweight, simple mechanism.
Rear derailleurs come in 5, 6, 7, 8, 9, and 10 speeds, based on the number of cogs on the hub. Front derailleurs come in two or three speeds, which can give a bike as many as 30 possible gear combinations to choose from.
Derailleur maintenance involves cleaning, lubrication, cable management, and basic adjustments. Even though the parts are exposed to the elements, derailleurs are very tough, and replacement parts such as pulleys and cables are available at bike shops.
The shifter is located on the handlebar near the brake, or on the down tube. Shifters pull and relax the shifter cable to select different gears. Some types of shifters are like small paddles, others twist the handle grip. On modern road bikes, the shifters are usually built into the brake levers.
Regardless of the type of shifter, there will be 5, 6, 7, 8, 9, or 10 clicks on the right side, which controls the rear derailleur, and 2 or 3 clicks on the left side, which controls the front derailleur.
USING ALL THE GEARS
Why does my bike have so many gears?
Terrain, your wight and weather conditions (head or tailwinds) will play a definite role in how easily your bicycle moves along the road. You have the option of many gears to assist you in maintaining the desired 75 to 95 cadence through all conditions. The most challenging for most cyclists is climbing hills.
Always shift to a lower gear before you start to climb. If you delay shifting until the going is hard, you may find it difficult or impossible to shift to a more favorable gear. With practice and experience you will be able to shift while climbing. For example, shift to your next lower gear as you initiate the climb. When that gear begins to become difficult or you cadence begins to drop, shift to your lowest. Most hills have slight level areas where you can ease the pressure on the pedals and shift quickly.
If you find you waited too long to shift, try standing up for a couple of pedal strokes to gain momentum, then quickly sit down, ease the pressure on the pedals and shift. If you can't do this, stop, dismount, hold up your rear wheel, crank your pedals by hand and downshift; then remount and continue. Hill climbing technique comes with practise.
The more you climb the more refined your shifting techniques become and the more pleasurable climbing is. Shifting to a lower gear is also desirable to maintain cadence with a strong headwind. Pushing a high gear and low cadence will sap your energy and may injure your knees. Spinning at 75-95 rpm may seem strange at first but you will find that you can comfortably handle any terrain.
Friction vs. Index Shifting
There are tow different styles of shifting that are common on derailleur-equipped bicycles. They are known as friction and index. Friction is the older (and not used as often anymore) style, while index is newer and thus found on most new bikes. What is the difference?
Friction shifting works much like the analogue system, like you find on record players or turn-dial radios. There is a continuous wave with an infinite number of points. When you shift, you must find the point where the chain (guided by the derailleurs) is most "in tune". When the chain is properly aligned on each gear, there should be no "static" sound. You might hear someone say, "trim your derailleur" if you are not properly in gear. This means you must move your shifter slightly in one direction or the other until everything is in tune.
To make these shifting styles work each has their own style of cable housing. The best way to tell index derailleur housing from brake and friction housing is by looking at the end. Both types gain their strength from steel under the plastic, but in index derailleur cables, the metal strands run the length of the housing. In brake and friction housing, the metal is wrapped in a spiral or coiled pattern. The housing is not interchangeable with different shifting types in any way.
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