A Brief History of Derailleurs

Presumably it wasn't long after someone had invented the Penny Farthing bike that someone else said that 'Well, it's very nice...but you know, gears would be useful'.

We won't dwell on the challenges of going up a steep hill on one of these bikes, or the terrors of coming down the other side, but not surprisingly it wasn't long before various versions of gears were being applied to bikes, and they were already in occasional use by enthusiasts before the end of the 19th century.

As a tribute to the clever people who have saved us all so much effort cycling up hills I thought a quick look at how the modern derailleur gears system came into being might be interesting. Some of the stages are rather more recent than you might think...

Note: there are more technical challenges to changing gears than you might think, as you casually flick your SRAM carbon fibre lever to the side to change gears, including the requirements for a mechanism to take up slack in the chain; a method to maintain a roughly constant distance from the control (jockey) wheel to the sprockets; along with a need to cope with dirt and water, and a great deal of ingenuity was needed to arrive at the modern system.

History of the derailleurs

Prior to 1937 changing gears was, to say the least, a laborious process: before then riders needed to remove the rear wheel and turn it around to change gears, since there were different gears on each side of the wheel. Worthwhile if you are about to cycle up Alpe d'Huez but a bit impractical if you are gently travelling across the rolling Devon countryside. In 1938, in a move that must have made a lot of cyclists very happy, the first cable operated gear change was introduced by a company called Simplex.

Improvements in the derailleur system were slow but steady, and in 1949 Campagnola introduced what is generally considered to be the first 'modern' version of what is called the 'parallelogram' derailleur system.

Fifteen years later in 1964 a company called Suntour improved the design with the 'slant-parallelogram' version - the slant allowing the jockey wheel to stay a roughly equal distance from the sprockets regardless of their size and much improving gear changing.

This system continued for about 20 years, and worked very well but had one drawback - changing gears depended on moving a lever that changed the tension in the cable and thus pulled ('derailed') the chain to the appropriate socket. Although this becomes quite accurate with experience it had a couple of problems:

• It is often necessary to change gears 'approximately' and then make a small adjustment to correct, which slowed down the whole gear changing process
• It tends to limit the number of gears it is possible to have, since the adjustment between the gears is quite 'broad brush'

Experience makes this gear change reasonably easy and effective but it was still a significant breakthrough when Shimano invented 'indexed shifting' - that is, the cable moves exactly the right amount to change gears each time you push the gear lever (or turn a handle etc, depending on your type of bike). This also allowed the possibility of having 9, 10 even 11 rear gears and much more flexibility in gearing for riders.

Combined with the use of a front derailleur to choose between two or three front gear wheels, there is now a very large range of gearing available.

The latest development is the use of electronic gear changes, with the significant advantage of very exact gear changes and a reduction in the amount of cables required. These are still quite expensive at the moment so it is unclear to what extent these represent the future of the derailleur system, but there is one thing you should remember in the face of all this sophisticated technology...

...there are a significant number of cyclists who prefer to use a single fixed gear on their bike, with no option to change gears regardless of terrain, because of the training benefits and better cycling experience that it provides, and at a stroke rejecting the 100 years of progress that we have seen in the history of derailleurs. Few of them opt to ride a Penny Farthing bicycle however.