Today the derailleur is more than a simple component that guides the chain on the sprockets. It is one of the most important components when we find out the specs of a bike and it gives you the gears that you need on your bike to be able to ride anywhere. The principle upon it functions is simple, but how did it all start? When and how did the derailleur appear?
The derailleur was impossible to imagine for the first bikes with a modern form (that is at the end of the 19th century). Back then all bikes were single speed and in the best of cases they had a sprocket on each side of the back wheel (a bigger and a smaller one to be used alternately on climbs and flat terrain). In order to use them the cyclist had to stop and reverse the wheel. Then he could go on until he would need to use the other sprocket again. This is, in a sense, a manual gear system.
Next there were mechanisms such as those you can see on the photo displayed below. However they were unsafe improvisations and they were not accepted in competitions because of this.
Before the 2nd World War using a gear system was a sign of weakness and the most ambitious of sportsman did not conceive of using such a fragile invention (which was to prove its potential later). Only in 1936 was it allowed to use a derailleur. In 1937 already the first winner of the Tour of France was using several speeds.
As a chronology of gearing systems that appeared we can start with the free sprocket with a ratchet catch which started being commercialized in 1897. This was the basis for the necessary sprocket blocks that make gearing systems possible.
Next in 1923 Luciene Juy introduces the Simplex, the first rear derailleur with a parallel movement and the front derailleur which allowed using one of the two available chainrings.
Campagnolo developed the Cambio Corsa system which consisted of two rods which helped direct the chain. This happened in 1946.
In 1949 the Italians change their tactics and produce a derailleur similar to the Simplex, which goes sideways and is moved with the help of cables. A year later they put out on the market what we could consider the first modern derailleur, with a rectangular cage and pulleys. From here on its construction was refined using different materials and providing better finishing but the basic principle remained the same.
Even though they were not the first to produce derailleurs the Japanese company Shimano perfected them and their levers. In 1989 they launch the Rapidfire system for mountain bikes and in 1990 the STI (Shimano Total Integration) dual-control for road bikes which meant using the brake lever for gear changing as well. In parallel they launched the HG (Hyper Glide) sprockets which made changing gears easier.
In 1990 Campagnolo offer a reply by launching their Ergopower levers.
The gear system began being seen not as a singular piece but as part of a more complex system that ensured the well-functioning of a bike. It was created to work in harmony with the levers, transmission and wheels. Thus the first completely functional electronic systems appeared. We say completely functional because there were other earlier attempts that failed. In 2009 Shimano launched the first such system. Campagnolo followed and raised the stake by adding the first 11 speed sprocket system to the set. The Japanese replied in turn in 2013 by releasing an 11 speed system as well.