Compatibility [04] Rear derailleurs

Compatibility [04] Rear derailleurs

Updated: 27/01/2019.

This post explains bicycle rear derailleur compatibility, i.e. what derailleurs can work with which number of rear sprockets (cassettes) and which rear shifters. For explanation of other rear derailleur functioning and limitations, such as chain wrap capacity, read this article: Rear derailleur.


Basic terms and what to pay attention to

Most modern bicycles have index shifters, that work with a certain number of clicks. One click per gear change. That is moving the chain from one sprocket/chainring to another with each click.

In order for this to work, these things need to be in tune:

  • Length of cable that shifter pulls/releases with each click. This is called shifter cable pull.
  • Distance that rear derailleur (RD in the remainder of this text) moves laterally per 1 mm of cable movement. This is called rear shift ratio. E.g. if RD moves for 2 mm for 1 mm cable movement (pull or release), then the rear shift ratio is 2.
  • Rear sprocket spacing.

When RD compatibility is mentioned, it is all about it’s tune with the shifter cable pull and rear sprocket spacing. When it is all set up correctly, one click of the indexed shifter shifts exactly and correctly one gear (i.e. one sprocket) at the rear. Compatibility will be explained per number of gears and per manufacturer. If it is not noted otherwise, it is understood that shifter make and number of gears match the RD make and the actual number of rear sprockets. There are three major RD and shifter manufacturer standards:

  1. Shimano
  2. SRAM
  3. Campagnolo
  4. Rotor’s hydraulic derailleurs


1. Shimano

6, 7, 8 and 9 speeds

Rear shift ratio is 1.7, that is for 1 mm of cable pull/release, RD is moved left/right by 1.7 mm. Shimano calls this 2:1 ratio for marketing reasons.

All these RDs are compatible and any 6 to 9 speed RD will work perfectly with either 6, 7, 8 or 9 speed shifter. Regardless whether it’s a MTB, or road shifter, or RD. They are also compatible with Shimano 10 speed road shifters, except the Tiagra 4700 series.

Shimano Dura Ace from 1984 to 1996 period (6 to 8 speeds)

Rear shift ratio is 1.9. They are compatible only with Shimano Dura Ace shifters from the same period (that is for 6, 7 and 8 speeds).

10 speed ROAD RD

Rear shift ratio is 1.7, so it’s compatible with all the 6 to 9 speed shifters, as well as road 10 speed shifters. Same rear shift ratio. MTB 10 (and 11 speed) shifters won’t work well.

Exception is Shimano Tiagra 4700 10 speed road RD – it has the same shift ratio as Shimano road 11 speed RDs, so it will work only with Tiagra 4700 shifters and Shimano 11 speed road shifters.

10 speed MTB RD

Rear shift ratio of this RD is about 1.2. It is only compatible with Shimano 10 speed MTB shifters and nothing else. Shimano calls this system Dyna-Sys.

11 speed ROAD

Rear shift ratio is around 1.4.  Only compatible with Shimano 11 speed road shifters.

The same shift ratio is used for Tiagra 4700 10 speed groupset, so it’s compatible with it as well, but not with other 10 speed road groupsets.

Rear shift ratio of 1.4 matches old Campagnolo ratio, but I haven’t tested this in practice.

11 speed MTB

Rear shift ratio is around 1.1. Compatible with Shimano MTB 11 speed shifters. Shimano calls this system Dyna-Sys, same as 10 speed MTB, but they’re not compatible!

It has similar rear shift ratio to SRAM 1:1 standard (explained later in this post), so it should match it as well, but I haven’t tried it yet!

11 and 12 speed MTB – Hyperglide+ (XTR M9100)

From summer of 2018 Shimano introduces a new Hyperglide+ 11 and 12 speed MTB standard. It comes with a new XTR M9100 rear derailleur, that only works with a matching shifter (which has an integrated 11, or 12 speed operation switch!) and Hyperglide+ 11 and 12 speed cassettes.


2. SRAM

SRAM has four RD families, with 4 different amounts of RD movement per cable movement (actuation ratios). So the only thing to pay attention to is actuation ratio. As long as the RD matches shifter’s actuation ratio (and vice versa), it will work fine.

First, less popular family of SRAM RDs are the ones compatible with Shimano 2:1 standard. Rear shift ratio of 1.7 means they will work with Shimano (and SRAM 2:1) shifters for 6 to 9 speeds (both road and MTB) and road 10 speed ones, except Tiagra 4700 10 speed road shifters.
RDs made in this standard were marketed as 6, 7, 8 and 9 speed models, though this is determined by the shifter – RD doesn’t care how many rear sprockets there are.

Second, more popular SRAM standard is 1:1, with rear shifter ratio of 1.1. This shift ratio is the same as Shimano MTB 11 speed RD (and shifter), so they should be compatible, but I haven’t tested this yet.
RDs made in this standard were marketed as 7, 8 and 9 speed models.

Third, newer standard is Exact Actuation. Rear shifter ratio is 1.3.
Marketed as 10 speed road and MTB , as well as 11 speed road.

Fourth family is X-Actuation, with 1.12 ratio.
Available as 11 and 12 speed MTB RDs 


3. Campagnolo

Campagnolo has two standards of rear shift ratio. Old 1.4 and new 1.5. Also, not every shifter pulls the same amount of cable with each click. With 10 speed for example, there is more cable pull for “slower” speeds, than there is for the others.  2.5 mm pull five times (from smallest 1st to the 6th sprocket), 3 mm for 7th and 8th, then 3.5 mm for 9th and 10th. 2.83 mm average cable pull per click.  🙂

Apart from that, as of 2014 (don’t take my word for the exact year), campagnolo introduces another 11 speed standard. Previous Revolution 11 and the newest Revolution 11+. They are not compatible.

Since Campagnolo cassettes sprocket spacing differs from other manufacturers’, it is hard to combine Campagnolo RDs with anything but the appropriate Campagnolo shifters and in most cases cassettes too.

Table of rear shift ratios for various standards:

Shimano standard – 1.7SRAM 2:1 – 1.7Campagnolo old – 1.4
Shimano 10 MTB – 1.2SRAM 1:1 – 1.1Campagnolo new – 1.5
Shimano 11 road – 1.4SRAM Exact Actuation – 1.3Campagnolo Revolution 11+ – N/A
Shimano 11 MTB – 1.1SRAM X-Actuation – 1.12 
Shimano Dura Ace 6 to 8 speeds – 1.9  


4. Rotor

Rotor’s hydraulic rear derailleurs are only compatible with their hydraulic shifters.

Related post – Bicycle rear hub compatibility:

Compatibility of bicycle rear hubs - which can accept what kinds of sprockets (cassettes)
Compatibility of bicycle rear hubs – which can accept what kinds of “sprockets” (cassettes)

Compatibility posts are also available in eBook (printable and Kindle) and paperback editions on Amazon:

Bicycle Drivetrain Compatibility on Amazon
Bicycle Drivetrain Compatibility on Amazon
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12 thoughts on “Compatibility [04] Rear derailleurs”

  1. Thanks for great article. How about chain compatibility? Is a 10-speed RD compatible whith a 8-speed chain? Does the cage width and pulley wheel design differ between 8 and 10 speed or is it the same?. Thanks again for good work ☺

    • Since all the multi speed chains have the same inner (roller) width, special pulley design won’t know what kind of chain goes over the pulley wheels.

      As for cage width, differences aren’t enough to cause problems. Especially from 10 to 8 speeds. Haven’t tried a 6 speed chain with an 11 speed RD, but I doubt even that would cause problems.

    • “… more popular SRAM standard is 1:1, with rear shifter ratio of 1.1.”
      If it’s 1:1, shouldn’t the ratio be 1.0?

  2. @fhfr436
    It makes perfect sense technically to call it what it is, but SRAM’s marketing department obviously didn’t think that is a good idea. 🙂

  3. This article implies that only Campagnolo has variable cable pulled per shift, when this is actually true for everything that I’ve taken the time to measure. The shift ratio is derived from the average cable-pull per shift, not the individual measurements.

    If you look at the appropriate wikibooks page where those variables are listed, I think I posted the individual pull measurements I’ve taken in the comments/edits-log.

    • Thank you for posting this. Any corrections are more than welcome. I’d check the data, re-measure and correct the info after it’s confirmed.

      In terms of compatibility, with other brands (Shimano and SRAM) using a different speed count shifter than derailleur (8 speed shifter with a 9 speed RD, or vice-versa, for example) works fine, as long as the RD pull ratio is the same and matches the shifter’s “original” (intended matching) RD pull ratio.

      From my measurements, the amount of cable pulled by the shifter is the same for each click, or at least not an easily measured difference.

      What are your measurement results (and which systems have you measured)? Have you measured cable directly as it exits the shifter, so any housing play, or RD limit screws don’t affect the measurement?

      Also, if you have any relevant links confirming otherwise, I’d be happy to include them in the article(s). I’ve sent you the direct e-mail, in case the reply gets completely blocked by the spam-filter (it usually notifies me to double check relevant comments from spam, but just in case – links in a comment are “spam-red-flags” for the filters).

  4. Thanks for the great article.
    I want to ask about mixing RD with cassette,
    Will 11 speed Shimano 105 5800 rear derailleur work with 10 speed Shimano Tiagra HG 500 11-32 cassette?
    Thank you.

    • As long as a compatible 10 speed shifter is used – in case of 105 5800, it would need Tiagra 4700 shifter to work with a 10 speed cassette.

      Shimano claims the short cage (SS) 105 derailleur won’t take more than 28 teeth, so you’d need a medium cage one (GS). However, I’ve had good results with short cage ones for up to 34 tooth cassettes – though this depends on RD attachment position. Also, a thing to watch out for is chain wrap capacity. If you have a triple, or “compact double” cranks, short cage won’t be able to take up all the slack chain when using small-small (front and rear) chainring combinations.

  5. This is a great article, but, the Tiagra 10-speed compatibility is still confusing for me. My wife’s bike has Tiagra 10 speed shifters, cassette, and derailleur. I wanted to change the derailleur out to an XT/XTR in order to accommodate a larger cassette. On my Ultegra 10 speed I used a 9-speed XTR which has worked fine. If I understand this article correctly it seems that the Tiagra shifter is not going to work with a 9 speed XT/XTR of which I have another one available. What would be the compatible XT/XTR derailleur for the Tiagra 10 spd shifter?

  6. For all I know, Tiagra 10 speed (4700 model) will work with the 4700 rear derailleur (of course) and with Shimano road 11 speed rear derailleurs.

    In my opinion and experience, It works better (more precise) than the old 10 speed stuff (including Ultegra and Dura Ace). But it is not compatible with any MTB and older road rear derailleurs.

    The upside is that chain wrap capacity and largest rear sprocket the new RDs can take is very close to those of older MTB ones – so one can use a MTB cassette with them, if lower gearing is needed.

    • Thanks – upon further inspection of the small print I realize it is a 4600 derailleur which should be compatible with the 9 speed XTR derailleur if I read all this correctly. Thanks-you!

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