**Condensed Answer: **

**Shimano’s 11-speed derailleurs have a different rear shift ratio than 10-speed derailleurs and are therefore not compatible with 10-speed indexed shifters.****SRAM’s exact actuation 11-speed derailleurs are compatible with SRAM’s 10-speed shifters and cassettes.****Campagnolo’s 11-speed derailleurs are compatible with Campagnolo’s 10-speed shifters.**

**Derailleur Rear Shift Ratio**

Two factors determine whether an 11-speed derailleur is compatible with a 10-speed shifter and cassette – the derailleur’s capacity and * rear shift ratio*.

The rear shift ratio indicates how much the derailleur moves per 1mm of gear cable movement triggered by the shifter.

**Indexed shifters (the most common type) move a predetermined amount of cable per 1 click. Therefore, the derailleur also moves a pre-determined distance per click when coupled with an indexed shifter.**

The rear shift ratio of an 11-speed Shimano MTB derailleur is 1.1. This means that the derailleur moves 1.1mm per 1mm of cable movement triggered by the shifter.

The pull of a 10-speed Shimano MTB shifter is 3.4mm. Thus, the shifter moves the cable 3.4mm per click.

When such a shifter is combined with an 11-speed derailleur, the derailleur moves:

**3.4mm (cable pull) x 1.1 (rear shift ratio) = 3.74mm**

However, an actual 10-speed Shimano MTB derailleur has a 1.2 rear shift ratio and moves 4.08mm per shift.

A difference of 0.34mm may not sound like a lot, but it’s enough to cause less than ideal shifting on a cassette with lots of cogs.

The second requirement for compatibility is **capacity**. The derailleur has to be able to cover the entire range of the cassette. This could be problematic if the user relies on aftermarket 10-speed cassettes with very large sprockets (e.g., 50t).

**11-speed Derailleurs Compatible With 10-speed Cassettes and Shifters**

Some 11-speed rear derailleurs have the same rear shift ratio as 10-speed derailleurs.

SRAM’s 10 and 11-speed Exact Actuation Rear Derailleurs have a 1.3 rear shift ratio. Hence why it’s possible to use an 11-speed SRAM derailleur from those series with a 10-speed SRAM shifter.

Campagnolo 10 and 11-speed derailleurs have a rear shift ratio of 1.5 and fit the bill too.

**Reference Data Table **

The table below contains the rear shift of 10 and 11-speed derailleurs:

Brand | Number of Speeds | Rear Shift Ratio (MTB) | Rear Shift Ratio (Road) |

Shimano | 10 | 1.1 | 1.7 |

Shimano | 11 | 1.2 | 1.4 |

SRAM Exact Actuation | 10, 11 | 1.3 | 1.3 |

Campagnolo | 10,11 | – | 1.5 |

As you can see, only SRAM and Campagnolo’s 11-speed derailleurs match the rear ratio of 10-speed derailleurs.

**Friction Shifters = Universal Compatibility **

Unlike index shifters, friction shifters are not engineered to move a predetermined amount of cable. They’re unrestricted and move as much as the user wants them to. This freedom can compensate for different rear shift ratios.

**If you have a friction shifter, you can combine any 11-speed derailleur with a 10-speed cassette as long as the range of the cassette doesn’t exceed the capacity of the mech.**

This makes friction shifters a logical choice for people who want to combine road and MTB parts as well as drivetrain components designed for a different number of gears.

The downside of friction shifters is that they are slow and not user-friendly. The average cyclist is very likely to find friction shifters annoying. Hence why they’re absent even from the cheapest retail bikes.

The low demand for friction shifters greatly limits the number of available models on the market.

**FAQ: Can I combine an 11-speed derailleur with a 10-speed shifter from another brand?**

**In the case of indexed shifters, the answer is negative because different shifters come with a different pull. **

If the cable pull of the shifter does not coincide with the one of the original 10-speed system, the derailleur will not move to the right place, and the shifting experience will be poor.

Therefore, you will need a SRAM shifter for a SRAM drivetrain and a Campagnolo shifter for a Campagnolo drivetrain. Mixing the two brands will result in inaccurate shifting performance.

The table below contains the cable pull of 10 and 11-speed shifters:

Brand | Number of Speeds | Shifter Cable Pull (MTB) | Shifter Cable Pull (Road) |

Shimano | 10 | 3.4 | 2.3 |

Shimano | 11 | 3.6 | 2.7 |

SRAM Exact Actuation | 10 | 3.1 | 3.1 |

SRAM Exact Actuation | 11 | 3.1 | 3.1 |

Campagnolo | 10 | – | 2.8 |

Campagnolo | 11 | – | 2.6 |

Conversely, if you rely on a friction shifter, the brand becomes irrelevant.

**Related Question: **Do 10-speed Derailleurs Work With 11-speed Cassettes?

I don’t understand the situation with SRAM: If the rear shift ratio for both 10 and 11 speed derailleurs is 1.3 and the shifter cable pull for both 10 and 11 speed shifters is 3.1 mm, then how are the derailleurs making the different sized movements required for cogs that are differently spaced in 10 and 11 speed cassettes? What am I missing? Thanks

You’re right and B.Writer (author of this article) is absolutely wrong.

Shimano makes 10/11s derailleurs and as the casette has the same width, means smaller distances betweeen cogs, you can use either 10s shifter with 10s casette or 11s shifter with 11s casette. This is why a cable is pulled by another ratio, equals lenght per click.

And that’s why Sram derailleur works only with the same speed shifter.