Bicycle rear derailleur compatibility - which rear shifters, cassettes and chains can it be combined with

Compatibility [04] Rear derailleurs

Updated: 06/10/2019.

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.

Not directly related to shifter-derailleur compatibility, but it is also crucial to use proper cables and housing. I wrote a post explaining shifter (and brake) cable and housing standards.

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.

Another exception is the new “gravel” group (with hydraulic brakes): Shimano GRX. Caple pull wise it’s the same as Tiagra 4700.

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 

EDIT: Based on this comment (on this very article) and provided links to SRAM’s website, Exact Actuation and 1:1 are the same thing. Will have to measure, check and confirm this.


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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61 thoughts on “Compatibility [04] Rear derailleurs”

  1. Keep in mind that shifters cable pull measurement can only be used to approximate with a rather large error and is only ok just for having an idea about it, because the err % is huge at that small dimension (unless you have extremely high end tools for measurement with very very good calibration )

    I have 1×12 sram eagle on my both MTBs (one HT and one FS) so i`v been extremely interested in SHIMANO – SRAM 12 speed cross compatibility. I spent ALLOT of time googling, reading forums , watching YT movies about hybrid setups etc.

    No official data from SHIMANO 🙁 . But lets take a look at the new 12speed SHIMANO. They should be pretty close to SRAM Eagle as ANY combination of casette + RD + shifter (SRAM+SHIMANO) seems to work ( some better than other, but all combination are usable)

    When using SRAM casette and SHIMANO RD and shifter the only dimension that maters is the cassette pitch.

    The only thing that seems to be generally accepted is the shimano 12 speed cassette pitch: 3.55 (a full 0.1mm lower than SRAM Eagle’s 3.65 pitch ).That explain why a shimano 12 speed RD + SHIMANO shifter perfectly aligned on center of a 12 speed SRAM Eagle cassette seems to not shift perfectly on cassette ends ( there will be an misalignment of about 0.5mm on both ends….but still seems to work well enough for most ppl )

    But when combining SRAM shifter with SHIMANO RD or when combining SHIMANO RD and SRAM shifter and it still work the things become more interesting. That means SHIMANO numbers must be verry close to SRAM (most likely both a bit smaller because of cassette pitch being a bit smaller)

    I`v seen quite a few measurements for the SHIMANO 12 speed shifter cable pull and the errors seems to be kinda big…ranging from less than 3mm to more than 3.5mm, but seems that most people are closer to 3.20-3.25 (pretty close to SRAM 3.26)

    pitch / shifter pull = RD pull ratio
    3.55 / 3.20 = 1.11
    3.55 / 3.23 = 1.1
    3.55 / 3.25 = 1.09

    HERE IS WHERE I REALLY WANTED TO GET when I start writing this post: See how much the RD pull ratio error is ? for only a 0.05mm error in shifter cable pull measurement there is a 0.02 difference in the RD pull ratio (as big as the the difference from 1:1(1.1) to X-Aactuation(1.12))

    lets use some of the values: 1.1 and 1.11 RD pull ratio and 3.23 and 3.2 shifter cable pull for SHIMANO 12 speed

    SRAM shifter + SHIMANO RD and SHIMANO shifter + SRAM RD seems to working abysmally better with a SRAM cassette than pure SHIMANO RD + SHIMANO shifter with same SRAM casette

    possible SHIMANO 12 RD + SRAM eagle shifter ( RD pull ratio * shifter cable pull = cassette pitch )
    1.1 * 3.26 = 3.586
    1.11 * 3.26 = 3.62

    SRAM eagle RD + possible SHIMANO 12 shifter ( RD pull ratio * shifter cable pull = cassette pitch )
    1.12 * 3.23 = 3.6176
    1.12 * 3.20 = 3.584

    All values are bigger than 3.55 and closer to SRAM cassette pitch (3.65) so ALL OF THEM MAKE SENSE , DIFFERENCES ARE SO SMALL THAT we have no idea which MEASUREMENTS are closer to the REAL THING, but we already made too many assumptions, used to many bogus measured and approximated data, and then used some logic to round it the way it will make sense for the facts we observed in practice.

    I MEAN IF WE MEASURE A 3.23mm SHIMANO 12 speed shifter cable pull, IN REALITY IT CAN ACTUALLY BE BOTH 3.20 OR 3.25

    I do hope we will find soon some “official” SHIMANO data for their 12 speed RD pull ratio and shifter cable pull ( and maybe a confirmation of 3.55 cassette pitch) , so people can better understand and tune the hybrid setups.

    PS: in previous posts I used ” x ” instead of ” * ” for multiplication and ” : ” instead of ” / ” for division

    Reply
    • For me, since I’m not planning to manufacture any shifters, or derailleurs, rounded up/down numbers are fine, since it’s easier to logically compare. As long as the same value is used always for the same system.

      I have used manufacturer stats and published literature (Leonard Zinn’s to note one) to cross-check and compare. However, as far as manufacturers are concerned, of course, compatibility is usually restricted to using their complete groupsets from the same generation, most of the time (from what I could gather).

      And, just to make things even more interesting, take a look at this, a combo that “shouldn’t work”, but has been working perfectly fine for months now: 🙂

      https://www.youtube.com/watch?v=TCmQZzeH_aU

      It is my personal impression that it’s all marketing, with very little engineering – manufacturers are fighting among each other and, at the same time, trying to practically “force” people into buying new stuff. Taking my city (flat, like Amsterdam) for example, most people are served perfectly fine with 1×6 friction shifting drivetrains. Yet I have to source 2nd hand Shimano friction shifters, since they aren’t making/selling any new ones. Works in the summer, works in the winter – works always. With next to zero worrying about maintenance. While the newly made systems are all (at least “officially”, “on paper” incompatible with other systems, even from the same manufacturer).

      For one example: while SRAM’s 1:1 (1.1 RD movement ratio) is a great improvement – making shifter cable less susceptible to any housing/cable imperfections (with a lot more cable pulled per shift), the X-Actuation 1.12 is just nonsense in my opinion – should have been made to fit the 1:1 standard, if it wasn’t for marketing and pushing people to buy new stuff.

      Same goes for Shimano, with the 10 speed MTB going for 1.2 RD movement ratio, instead of at least trying to be compatible with SRAM.

      It’s a disservice to the customers, mechanics, even ecology – making it harder to combine and re-use older stuff.

      They are all (not just Shimano and SRAM) either silly, trying to “re-invent the wheel”, or (more likely in my opinion) trying to sell new, “revolutionary” equipment at all costs. Can’t say I blame them – they have to make a living. Just calling it out for what it is – excellent marketing, not excellent engineering.

      P.S. The main use for all the compatibility pages is to help me with mix-matching, for myself and the customers. Writing down combinations that have worked and having easy to compare reference charts. Still, I think it’s outright silly that it is that way in the industry, without a commonly used standard. Same goes for headset bearings, bottom brackets, through axles – needlessly many different standards (better named “standards”).

  2. https://www.youtube.com/watch?v=TCmQZzeH_aU

    I have already seen your YT video, kinda surprising …if you used the 11 speed road RD and shifter without any “hacks” ( like altered RD cable attachment point to increase the RD pull ratios) and not altering the 11speed MTB cassette in any way (like using few narrower spacers from the road cassette for the smaller cogs for example ) you should have a full 1.6mm wider cassette space to cover. With the RD perfectly aligned on cog number 6 there will be an misalignment of about 0.8mm on both ends, which is actually bigger than 0.5mm misalignment of 12 speed Shimano RD+ Shimano shifter on SRAM Eagle cassette. Counting that 11 speed chain is 0.37mm wider than 12 speed chain, this it may also help allot with the shifting to bigger cogs by better engaging the “glide” gates machined onto the outer cog surface.

    Great to know that still works 😀

    Reply
    • Worked straight “out of the box” – to both the bike owner’s and my surprise.
      The only “trick” used was derailleur hanger extension (Chinese copy of Wolf Tooth), to make the road derailleur fit an MTB cassette.
      Chain inner widths are not that much different – so I have no idea why it works, it shouldn’t! 🙂

  3. Hi,
    One big doubt: What is the shift ratio for the trekking XT derailleur RD-T8000 SGS ? Is 1,2 or 1,7?

    Reply
  4. Wow this post is amazing.

    I’m switching my SRAM 1×11 drop bar setup to horizontal bars. I have a SRAM Rival 11 speed RD – Exact Actuation. I bought the SRAM GX 11 speed shifter (X-Actuation) before reading this article. I have been having trouble setting this up, and this is why!

    Is there a horizontal bar shifter that will work with my SRAM Rival RD? I’m tempted to buy a Shimano 11 speed MTB shifter based on your conversation with Adi T above. Do you think this might work?

    Thank you so much!

    Reply
    • Thank you for the kind words. The post (as most other on the website) is primarily intended to help me keep track of all the catches and gotchas of the cycling industry and mechanics. But all the others are welcome, to both use it and add suggestions, corrections, additions…

      For your setup, it boils down to RD and shifter having matching cable pulls / cable pull ratios.
      So it’s either X-Actuation shifter and RD, or Exact Actuation shifter and RD.

      Note: Adi T’s noticing SRAM’s claim (on previous comments page) that 1:1 and Exact Actuation are the same seems viable, but I haven’t confirmed that yet, so can’t claim that too will work (Exact Actuation and 1:1 combo of shifter-derailleur).

      So, in your position, I’d see the local shops and/or google and swap whichever is easier to find (or cheaper) – either getting a shifter that matches RD’s cable pull ration, or get a new RD that is compatible with the shifter.

      An additional “trick” is that 11 speed MTB and road cassettes aren’t compatible. So, if changing the RD to match the 11 Speed X-actuation MTB shifter, should not work perfectly. The tested combo that did work, to my surprise, is Shimano’s. Haven’t tried that with SRAM. You could give it a go, but don’t be amazed if you end up needing to replace the cassette as well (and add a spacer before mounting the cassette, since 11 speed road cassette freehub is a bit wider than needed for 11 speed MTB cassettes). Explained that (spacer) part here:
      https://bike.bikegremlin.com/1259/bicycle-rear-hub-compatibility/#8

  5. Hi Relja

    Fabulous site. Wonderfully clear and precise. I have a question which I hope would be easy for you to answer but which I cannot solve (not a bike mechanic or indeed a mechanic of any sort!).

    I have a 1×11 Dolan gravel bike with a 170 Force1 bb30 42t x-sync crank set, rear derailleur Force1 long cage type 3.0 and a 11-42 11-speed (11-42) cassette. These are linked to SRAM Force 22 mechanical shifters.

    The question is relating to the rear cable. On my bike, for the cable not to be overly acutely angled, I have a large loop extending behind the frame. This is not normally an issue but when I pack the bike to travel (about twice a month) I must either bend the cable sharply or remove the front forks to fit it into my case. None of my other bikes require this.

    This is not ideal, for obvious reasons.

    The SRAM 22 shifters have 1:1 Exact Actuation (I understand from my reading) but most of the SRAM RDs I’ve seen have either a 10sp description or have an X-actuation description which seems to be different. As I feel that the cable loop issue is related to the position of the cable entry point on the derailleur, I wonder if I can use any of the other derailleurs which have either a pulley offset or some other attachment point which would not require the loop to avoid cable pinching. Ideally I do not want to change any of the other equipment fitted to the bike. The choices seem to be extensive across both road and mtb and thus confusing!

    Any guidance is gratefully received.

    Reply
  6. Thank you for this page !
    I’ve found very interesting and I’m looking forward to knowing all the movement ratios, cable pull etc. in order to choose components independently of what manufacturers would want us to do 🙂

    I have no measure, but I can confirm that a road 11s Exact Actuation shifter (Apex flatbar) works OK with a “10s” EA MTB RD. I’ve done this on 2 bikes, one with a 11-40 HG 11s cassette (and GX 2×10 RD), and the other with a 10-42 XD 11s one (and X7 2×10 RD).
    I just thought that “exact actuation” components were compatible, but it looks that I’ve mistakenly forgotten to take into account different pitches for 11s road and MTB cassettes ?

    Reply
    • It can get a bit complicated, that’s for sure. The easiest way for me to comprehend it all is dividing into “logical groups” to put it that way.

      Cassette is the most “stupid” component in the whole drivetrain “stack”. It has a number of sprockets and the pitch (distance at which they are lined up relative to each other).

      Derailleurs are a little bit “smarter”. Their job is to move left-right when the control cable is pulled-released. The only thing they need to “worry” about is by which amount they will move per (1 mm of) cable pull-release. However, the number of speeds printed on the derailleur is more a marketing thing (to put it simplified, without going into fine details that don’t make much of a difference anyway). Since the number of speeds is not something derailleur needs to “think” about. Hence we come to the next link in the drivetrain chain (pun not intended 🙂 ):

      Indexed shifter. The “brains” of the whole operation. It has a bit more complicated job. It needs to pull-release an exactly pre-defined amount of cable per each “click” (shift) to make sure that the derailleur (with its pre-defined movement ratio per 1 mm of cable travel) moves exactly the same amount, to match the cassette’s pitch.

      So both the cassette pitch, cassette number of cogs and the derailleur movement ratio are what shifter needs to “have in mind” when doing its job (pulling/releasing the shifter cable).

      10 speed road and MTB cassettes, for example, have the same pitch. As long as the shifter is a 10 speed one, it only needs to match the (rear) derailleurs movement ratio and one single pitch and number of cogs.
      With 11 speed cassettes, on the other hand, since MTB and road ones have (very slightly) different pitch, in addition to matching the RD movement ratio and the number of cogs, shifter also needs to “know” whether it’s working with road, or a MTB cassette.

      This is why 11 speed ExactActuation road and MTB shifters don’t pull/release the same amount of cable per shift.

      Having said all this, the difference in 11 speed MTB and road cassette pitch is not very large. Tested with a Shimano drivetrain, 11 speed road shifter and RD combo worked fine with an 11 speed MTB cassette (to my surprise). Haven’t tested this with SRAM though.

  7. Thanks for that 🙂
    Yeah, I knew that the “number of speeds” of a derailleur had no technical meaning, it was just marketing. Hence my builds with 11s shifter and so-called “10s” RD’s.
    And I also have two other “Frankensteins” : 1st with a Dura-Ace “10s” road RD & 9s SRAM Plasma twister “2:1” and the 2nd with a Gevenalle 10s CX shifter & 9s Hone RD.
    I had heard of many builds with 11s MTB cassettes plus road shifter/RD, so I didn’t even considered that the cogs were not spaced the same distance. My bad 🙁 But it works OK !

    So that would be so great if 3 tables with data for Cassettes pitches / shifter cable pull / RD ratio could be set up. I know it’s hard work because manufacturers don’t want that their nebulous marketing argumentation could be scratched and reduced in so simple figures 😉

    Reply
    • Yes, that’s clear since you had mentioned the “Frankenstein” (like that 🙂 ) builds. The answer was made “more thoroughly” then necessary for two reasons:

      1) In case anyone else with a similar dilemma, but less experience, reads it.

      2) For my own reference, since I think, as you have suggested, that an article that explains how all that stuff works together, but in a simplified way, needs to be added (still not sure how to put it to not miss anything important, but still not be too complicated).

      I’m happy to hear that MTB-road cassette swap works with SRAM as well. 🙂

      The suggestion you made is great by the way. Thank you.

      For now, I have made tables with all the data (cassette pitch, shifter cable pull etc.) – each post in this Compatibility section has the relevant table.

      Combining it all in one table would not look too nice on most screens, but I could make a separate article that has all the tables/charts in one place.

      I could start with 3 tables:
      – Cassette pitch
      – RD movement ratio
      – shifter cable pull

      All one below the other.

      Then add the rest of the tables (chain width comes to mind first).

      How does that idea sound?

  8. I don’t know exactly how to show that as simple as possible…
    Maybe a table with Shifers standards listed horizontally (or vertically) and RD standards listed vertically (or horizontally), and in the matrix, showing the calculated pitches and the possible matching cassettes standards ? (with colours, for instance to distinguish “official” compatibility and other degrees of compatibility)

    Reply
    • That sounds like a perfect candidate for a small database. To pick shifter and derailleur options from a drop-down list, then it would show the closest matching cassettes.
      But there is a problem there, most of my data is rounded (up/down) to make it easier to see and refer to.

      Table would have to be nicely designed and thought of.

      Anyway, this is added to my (rather long 🙁 ) to-do list.

  9. this article and #7 rear shifter gave me the courage to mix the following:
    SRAM X0 9s shifter
    Taiwan 11-46T 9s cog
    shimano deore 10s RD with clutch

    worked like a charm

    Reply
  10. Just wondering, to make use of my very light SRAM X0 9s RD with a 12-36T 9s cog hanging around, can I use a shimano 11-speed rear shifter? it will be for a weight weenie bike build.

    Reply

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