How to choose your mountain bike rear derailleur?

How to choose your mountain bike rear derailleur?

Choosing a rear derailleur is much more difficult than it sounds. MTB rear derailleur rear derailleur. Here's how to make the right choice.

The standards

  • SHIMANO or SRAM type
  • Number of gears: 9, 10, 11 or 12
  • Clevis length: short, medium or long

Rear derailleur types

Remember: SHIMANO and SRAM do not operate under the same standard. It is therefore not possible to combine components from these brands. (e.g. SRAM controls with a SHIMANO derailleur).

In fact, SHIMANO's pull ratio is 2:1 (2 mm of cable pulled displaces the derailleur by 1 mm), whereas SRAM's is 1:1.

SHIMANO : 1 pressure a = 2 mm of cable b = 1 speed c

SRAM 1 press a = 1 mm of cable b = 1 speed c

All components of a transmission are designed to operate under a single gear standard, so you can't combine a 9-speed derailleur with a 10V transmission, for example.

Which clevis length to choose?

There are three lengths of clevis (Part of a derailleur supporting the two rollers, this can be of different sizes depending on the transmission). short, medium and long.
The shorter the clevis, the more responsive and resistant it is. As a general rule, a long clevis is recommended for triple drivetrains, or for double drivetrains with a longer clevis. mountain bike cassette cassette.

Once you've checked compatibility, it's time to find the right clevis length. This is determined by the number of gears and the gear teeth of your transmission (cassette and cog). MTB chainrings).

For SHIMANO, refer to the capacity (Calculation of clevis length required)calculated as follows :
(Maximum cassette toothing - Minimum cassette toothing) + (Maximum chainring toothing - Minimum chainring toothing). For example, with an 11/36 cassette and a 26/36 crankset, we calculate (36-11)+(36-26) = 35. You'll need a derailleur with a capacity of 35.

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

So make sure you choose a derailleur compatible with your shifting system, and with a clevis* to match your transmission.

a Clevis length

You can choose between the two brands for "zero" assembly. Riders generally report a smoother, more forgiving ride with SHIMANO, and a more responsive, responsive ride with SRAM.

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