How to choose your road bike rear derailleur?

Much more difficult than it seems, the choice of derailleur is quite framed. Here's how to avoid making a mistake.

Standard derailleurs

SHIMANO, SRAM or CAMPAGNOLO type
Today's number of gears: 9, 10, 11 or 12
Clevis length: short or medium

Choosing your clevis length

Remember : for rear derailleurSince SHIMANO, SRAM and CAMPAGNOLO don't all operate under the same cable-pulling standard, you won't be able to combine these 3 brands.

As all drivetrain components are designed to operate under a specific gear standard, it is not possible to combine a 10-speed derailleur with an 11V drivetrain, for example.

For SHIMANO and CAMPAGNOLO, the length is determined by the capacity*.calculated as follows: (Maximum cassette tooth - Minimum cassette tooth) + (Maximum chainring tooth - Minimum chainring tooth). For example, with a cassette 11/28 cassette and a crankset 34/50, we calculate (28-11)+(50-34) = 33. You'll need a derailleur with a capacity of 33.

Please note that the large sprocket must not exceed the derailleur's maximum permissible toothing (e.g. 30 teeth).

The greater the tooth differential between the small and large cogs, the more advisable it is to choose a derailleur with a medium clevis.

For SRAM, please consult the brand's compatibility chart.

So just make sure you choose a derailleur that's compatible with your shifting system and has a clevis with your transmission.

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