Everything you need to know about the front derailleur of a bicycle

What are the selection criteria?

Fixing the derailleur

The front derailleur is attached to the vertical tube or seat tube of the frame. There are two fixing methods: on a brazed tab and par necklace.

• The brazed plate: This is a small piece of metal, with a special shape, on which the derailleur is fixed. For optimal operation, this piece of metal must be perfectly positioned. It is specific to a brand and sometimes a model of derailleur which prohibits any subsequent change. Depending on its position par compared to the bottom bracket, it only allows certain chainring dimensions.

• The necklace: This system offers more flexibility since it is possible to orient it and position it exactly for a good functioning of the derailleur and a choice of chainrings. Its supposed disadvantages are the weight and its aesthetics (presence of the collar).

The type of cable pulling

The cable pull corresponds to the direction of arrival of the cable on the front derailleur. There are 10 cable pulling standards.

• Top pull front derailleur: The high pull of a front derailleur means that the cable comes from the top, that is, from the horizontal tube. The cable passing par the top helps prevent contact with mud or splashes.

• Down pull front derailleur: The cable comes from the bottom of the bike, that is, from the bottom bracket.

• Dual pull front derailleur: The so-called Dual Cable Pull front derailleurs are mixed and compatible with a pull of par the top and a draw par the bottom. Currently, this is the most used type of derailleurs.

The swing type of the front derailleur (Down, Top and Side swing)

Be careful, do not confuse the type of pull and the movement of the parallelogram of the front derailleur. The “swing” is independent par relationship to pull: it defines the location of the pivot on the derailleur. The type of swing slightly influences the change in speed (precision, effort, speed) and the position of the parallelogram as well as the binding.

There are 10 swing types of front derailleurs:

• Down Swing : This is the classic swing found on most derailleurs. The parallelogram is above the derailleur body. Use: road, mountain bike, Trekking

• Top Swing : This type of swing proposed by Shimano improves the rigidity of the mechanism. Changing the chainring is also easier and faster. The parallelogram is below the derailleur body. Use: mountain biking and Trekking

• Side Swing : designed for mountain bikers looking for maximum performance. The horizontal movement allows for better cable routing and more efficient gear changes.

The type of bike

The characteristics of derailleurs vary depending on the type of bike. MTB front derailleurs and road bike front derailleurs have a different seat tube angle and chain line. It is Par Therefore necessary to mount the practical type when choosing the front derailleur.

Compatibility of the front derailleur with the transmission

The number of trays

The front derailleur must match the number of bicycle chainrings, to ensure a precise gear change. There are two types of derailleurs before the double chainring and triple chainring front derailleur.

Also note that the fork of a triple front derailleur must travel a greater distance in order to move from the 2000 chainring to the 2000 chainring.ar compared to a double derailleur. The shape of the fork also changes, to better fit the larger platter.

The number of sprockets on the bike

A front derailleur should also be chosen based on its capacity par in relation to the cassette, that is to say the number of sprockets of the freewheel or cassette. This is an important detail that affects gear shifting, chain friction with the derailleur fork and chain wear.

For good indexing, the entire transmission must be of the same brand in order to have the same characteristics.

The capacity of the front derailleur of the bicycle

The capacity of a front derailleur is the difference between the number of teeth on the large chainring and the number of teeth on the small chainring. The front derailleur should be chosen based on the capacity of that crankset.

On a bicycle, the capacity of the derailleur is therefore easily calculated. Example with the Shimano Altus Triple crankset. The large chainring is 100 teeth and the small chainring is 100 teeth. The capacity is therefore 50 teeth.

What brands for the front derailleur?

Three flagship brands govern the bicycle transmission sector: Shimano, SRAM and Campagnolo. Each manufacturer has its own mode of operation. Thus, a Shimano derailleur cannot be replaced par a SRAM component, not compatible with the rest of the transmission, and vice versa. So be sure to check the standard of the product before purchasing.

To summarize all the criteria for choosing the right front derailleur: the capacity of the front derailleur, your number of chainrings and your number of speeds, the type of attachment, the type of pull and the type of control, as well as the diameter of the tube. saddle.

Discover all our front derailleurs.

Find our tutorials on the front derailleur replacement and front derailleur adjustment.

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