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Compatibility [04] Rear derailleurs

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.

Before you start, to avoid any misunderstanding:
please take the 5 minutes needed to read the compatibility articles use instructions.

Table Of Contents (T.O.C.):

  1. Basic terms and what to pay attention to
  2. Shimano
  3. SRAM
  4. Campagnolo
  5. Rotor’s hydraulic derailleurs
  6. Table of rear shift ratios for various standards
  7. Problems preventing you from EVER tuning your derailleurs properly – video
  8. BikeGremlin’s comment – explanation


0. 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 (and at least one exotic – by Rotor):

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

– T.O.C. –


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.

There are a few caveats here. See below, my comment on 10/11 Shimano MTB RDs.

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.


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– T.O.C. –


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 for 11 speeds, and 1.01 for 12 speeds.
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.

– T.O.C. –


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.

In 2018, Campagnolo introduced their own 12 speed standard – not compatible with any other.

– T.O.C. –


4. Rotor

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

– T.O.C. –


5. 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 – 1.4
* Including Tiagra 4700 10 speed road
SRAM Exact Actuation – 1.3Campagnolo Revolution 11+ – N/A
Shimano 11 MTB – 1.1SRAM X-Actuation
11-speeds – 1.12
 
Shimano Dura Ace 6 to 8 speeds – 1.9 SRAM X-Actuation
12-speeds – 1.01
 

– T.O.C. –


6. Problems preventing you from EVER tuning your derailleurs properly – video

Problems preventing you from EVER tuning your derailleurs properly
Common derailleur tuning problems that often get overlooked

– T.O.C. –


7. BikeGremlin’s comment – explanation

This was originally posted as a reply to a comment, but there are almost 200 comments to this article now, so I’m moving it here:

Due explanation:

I had managed to get some things working OK, even though they don’t match looking by the manufacturer’s specs.

When it comes to specs, this is what Shimano says:
First they say (said) 9, 10 and 11 are all non-compatible with each other.
Now, on the very same page, they claim otherwise, under 10 speed rear drivetrain compatibility section.

Their Zee (RD-M640-SS), and Saint (RD-M820-SS) RDs are noted as 10 speed only.
While the Deore you noted does say 10/11 speeds.
To make things more interesting (and confusing), Deore 11 speed series has:
RD-M5100-SGS that says 1×11, and RD-M5120-SGS that says 1×10, 2×10, and 2×11.

My goal when writing this series of articles was to help myself, by having all the combos that work (in spite of the manufacturers’ specs. stating otherwise) in one place.
The no-go stuff was written down to help when mix-matching, to know what to rule out from the start.

A problem I face is, even when I make a combo from this no-go zone to work, I can’t say with enough certainty that it works on most bicycles.
Like here, when pairing an 11 speed MTB cassette with an 11 speed road groupset.
For me, it would take at least 5 more bikes, tried and (field) tested to be able to say: 11 speed MTB cassettes work with road 11 speed shifters & RDs, in spite of the obvious and measurable differences in pitch.

The above noted Shimano tech. and product specs. certainly don’t make things less confusing (at least for me).

Also, with so many what/ifs and gotchas (by Shimano), it seems the only thing to do is make a database driven app where you enter your shifter, and cassette models, to get a list of RDs that work with those.
Same goes for other combos (cassette, and RD to get a matching shifter model).

Because stating all the possible combos on one page would make it very, very long and almost unreadable (shifter models x cassettes x RD models… it grows exponentially for each new combo, even if only listing the combos that work).

Bottom line:
Combos that are noted here to work – do work, i.e. I’m yet to find a case when they don’t (poor tuning by the user/mechanic aside, of course).
Combos that are not noted to work – sometimes they work, more or less perfectly. If the differences are slight enough, it’s usually worth giving it a try (as we did with the MTB cassette and 11 speed road shifters, noted above).

Having said all this, I do try to keep this as correct and up-to-date as possible. So will add notes regarding 10/11 MTB RDs (and shifters) in the matching sections/articles. Even if not providing a definite answer.


Adi’s comment, regarding SRAM:

This too was originally a comment to this article, but now there are almost 200 comments, so it got “lost” and I’m copying it here:

SRAM Exact Actuation is actually 1:1 as stated by SRAM on their web site on almost all EA RD products.
Just a few examples:

MTB RD 9s,10s
https://www.sram.com/en/sram/models/rd-x7-a1
MTB RD 10s
https://www.sram.com/en/sram/models/rd-gx-t21-a1
ROAD RD 10s
https://www.sram.com/en/sram/models/rd-apx-a1
ROAD RD 11s
https://www.sram.com/en/sram/models/rd-riv-b1

From one of their product description page…don’t remember exactly which one:

Technologies

1:1®
1:1 Actuation is superior by design. Every unit of cable you pull moves the derailleur the same amount. Actuation stays precise and fluid slogging through mud, bouncing off rocks, rutting through roots wherever you find yourself, whatever conditions you’re in. It’s dependable. Tolerant. Easiest to set up. Easiest to adjust. And, not coincidentally, the top choice of the top MTB riders. Got it? Good.

Exact Actuation™
When we launched our road technology from scratch we reapplied our MTB proven SRAM 1:1 actuation ratio (shifter cable travel : derailleur movement) for 10 speed rear shifting. EA helps to simplify/stabilize the uneasy act of balancing rear derailleur hanger design, tight cog spacing and exact cable tension. The result: the easiest index shifting system to set up and it stays that way.

I can’t find any 1.3 pull ratio SRAM RD…it seems that Exact Actuation is just some marketing BS for their medium / high end 1:1 RD (non eagle X-actuation).


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 book
Bicycle drivetrain compatibility book

– T.O.C. –

178 thoughts on “Compatibility [04] Rear derailleurs”

  1. i have widened the cages on some 9 or ten speed rear mechs to fit a wider 6 or 7 speed chain,you just need a longer steel bearing and a longer bolt,i have a few older rear mechs laying about and i modify those shimano ones all the time.

    Reply
  2. and dont forget to put in the slightly wider jockey wheels,they do vary in thickness,the jockey wheels should have a very slight movement side to side,its not much movent its very very slight just enough to make the jockey wheels go round,if there is no play they wont spin

    Reply
  3. Really want to turn my mtb into drop bar with brifters. Has a 1×10 slx derailleur. Is the possible while keeping my derailleur?

    Reply
  4. What an amazing resource you are! Thank you Relja!! I just found your site. I’m considering buying a secondhand bike with SRAM Red:
    Chainrings: ROtor 46/36
    Shifters: SRAM Red 22
    Cassette: SRAM Red 22, 11-speed:11-28
    Front Derailleur:SRAM Red 22
    Rear Derailleur: SRAM Red 22

    I’d want to have an 11-34 or 11-36 for rear cassette – can you suggest any compatible ones? Will I have to change any other part of the drive-train to achieve this?

    Reply
    • Hi Margie,

      2 things to consider here: finding a compatible cassette, and, as you’ve mentioned, drivetrain considerations.

      Before I dive in, I’ll give a very brief answer:
      Any Hyperglide Shimano or SRAM 11-speed cassette with 34 or fewer teeth on the largest sprocket should be fine, just avoid shifting to the largest two rear sprockets while on the larger front chainring.

      Now, for a more detailed explanation and options:

      1) A compatible cassette

      I would expect any Shimano 11-speed cassette (including their MTB cassettes) to work fine.

      SRAM XD cassettes will not fit a road freehub (different mounting standard – see the article on rear hub compatibility for more details).
      The “normal” (Hyperglide) SRAM cassettes should work fine.

      Likewise, any other Hyperglide 11-speed cassette should work fine – SunRace, microSHIFT, Miche etc.

      If one is not concerned with weight, choosing the cheapest matching cassette available is perfectly fine in terms of function and durability – apart from the really cheap “Chinese”/”No-name” models.

      2) Drivetrain considerations – again, two things 🙂

      2a) Chain length
      If your chain is optimally sized, with a larger cassette, you’d need to either get a longer chain, or avoid shifting to the largest few rear sprockets while on the larger front chainring (otherwise, the rear derailleur could get damaged).
      I’ve explained this in the article about the optimal chain length for bikes with derailleurs.

      2b) Rear derailleur capacity
      Not every rear derailleur can handle a 36 T cassette sprocket.
      Most road bike RDs are labelled as up-to-32 teeth.
      In my experience, 34 teeth cassettes are often fine in practice, but 36 can be a stretch and require a derailleur hanger extender.

      Here’s what a road bike RD with a hanger extender looks like, paired with an MTB cassette (my YouTube channel link):
      Pairing Shimano 11speed MTB cassette with a road groupset

      I hope this has helped you more than it has confused you. 🙂

      P.S. I was reluctant to list any particular cassette models because I’m not sure which bike shops or online stores offer good prices (and cheap/free shipping) in your area. And my vote always goes to supporting your local brick & mortar bicycle shop. However, just to be on the safe side, here are a few models from Amazon (affiliate links):
      Shimano 11-34
      SRAM, with an 11-36 option
      If you happen to be in Europe, here’s a lower price from a German online store – Shimano CS-HG700 Cassette 11-speed – 11-34 Teeth

  5. Question on Campagnolo. I believe Campagnolo 1.5 rear derailleur ratio was introduced in 2009 when Campagnolo issued its first ever 11 speed groups with Super Record, Record and Chorus. But all 10 speed group’ rear derailleurs are still Campagnolo 1.4 till the end of 10 speed era in recent year. Is it correct?

    So, all 8, 9, 10 speed Campagnolo Rear Derailleurs are interchangeable. Correct?

    Reply
    • Hi Bill,

      As far as I know, there is some overlap.
      Old (1.4) was built for 8 to 10 speeds.
      New (1.5) was built for 9 to 11 speeds.
      Revolution 11-speed is different from those.

  6. Great article and video, Relja. I have a 1989 Trek 420 road bike, 3 x 7 speed with Shimano Sport LX derailleurs, original cassette, and friction shifters on the down tube. I’d like to convert the down handlebars to flat bars. Is there any kind of index shifters that will work with my derailleurs?

    Reply
    • Update: I installed the Microshift TS39 3×7 shifters. The rear shifter is working well. But I’m having problems with the front. The shifter seems to pull more cable than the front derailleur wants. Shifting to a bigger chain ring, the “big” thumb lever needs to travel a long way before it moves past the “little” lever and clicks it into the next gear–and it hurts my thumb to push it hard that far! I can get the derailleur to go from the small to the middle chain ring and stay there. But to get it to go up to the big ring and have the shifter travel far enough to click into 3rd gear, I have to adjust the derailleur H-limit screw pretty far out, and sometimes the chain falls off onto the pedal crank.

      Going back down, sometimes the “little” thumb lever moves the derailleur from the big to the little chain ring all in one click (instead of two). And sometimes the cable housing just gets pushed out of the socket on the shifter, and the derailleur doesn’t move off the big chain ring at all.

      Do you have any suggestions of what to try?

    • Hi Brian,

      The first thing on my mind is to check the cable and housing routing and cable tension.

      For me, tuning derailleurs usually boils down to an elimination process. Starting with the most obvious (and/or the easiest to check).

      If it helps, I wrote articles about high-quality shifter (and brake) cables & housing, and how to route cables and housing.

      I also made videos about the most common derailleur tuning pitfalls, followed by a very long, in detail video about how to tune the derailleurs.

    • Hi Chris,

      I believe not.
      I think RS700 is a “road” standard shifter, just designed for flat bars (so should work with a Tiagra, 105, Ultegra etc.).
      Saint requires a MTB shifter.

  7. “Their Zee (RD-M640-SS), and Saint (RD-M820-SS) RDs are noted as 10 speed only.
    While the Deore you noted does say 10/11 speeds.”

    Is the Zee noted a 10 speed only because in the Shimano MTB range, 11 speed cassettes have bigger range than 11-32 which is what Shimano advises for Zee?

    The Altus M310 derailleur is specced for 8 speeds 11-32 and yet, I run several of them on 9s 11-34/ 9s 11-36 an 9s 11-40 (Really on the limit).

    I want to try a Zee derailleur with road shifter and a jtek adaptor but, I have yet to find a 10s shifter other than R4700.

    Reply
  8. Hi, and thanks for the great article.
    I am considering converting my 3×9 setup to 1×10, while keeping my rd-m592 (for a mountain bike).
    I think I am left with the only option of buying a Shimano 10s Tiagra sl-4600, as it is the only road shifter that I can find for a flat handlebar currently. Do you think it will work out?

    Reply
  9. Hello Relja,

    Greetings from Slovakia 😊

    I am speculating again how to get lower gears into mine gravel bike and I find by chance this chinese producer : S-Ride.
    https://www.s-ridebike.com/mtb-rear-derailleurs.html or https://www.s-ride.net/gavel-bike.html.

    They also received nice review on this rather known magazin : https://road.cc/content/review/s-ride-rear-derailleur-over-long-cage-290037 as well on Youtube.
    I was attracted by them by „incredible „ official capacity of 49T, that might enable me to use 11-48 or even 11-50 cassette keeping current 46-30 chainrings, if they limits are conservative…as Shimano’s are.
    I am using now complete GRX 10 speed groupset (cassette 11-42 pas used even Shimano „allows“ 11-36 only.)

    Query: could I use instead mine GRX RD RX400 derailleur a chinese RD-GR580C Rear Derailleur 12/11-spd (Formerly named RD-M520c) ?

    They say : Compatible with Shimano 105 ST-5800 and GRX 600/810 road shifters.

    However, what I have studied on Your site and other sites :

    • GRX 10 speed shifter shall pull the same amount of cable as 11 speed and Tiagra 4700 ones
    • Shimano 11 speed and Tiagra 4700 and GRX rear derailleurs have the same translation of cable pull from shifters
    • Shimano 10 and 11 speed „road and MTB“ cassettes have the same width and about the same pitch of
    • 10 speed chain is only about 0,5 mm wider than 11 speed one, so derailluer has much more play on pulleys, so it shall work as well

    So, it shall work I think ! 😊 or, is there logical trap I miss ?

    Thank You in advance for Your kind help here.
    Kind regards, Eduard.

    Reply
    • Hi Eduard,

      If that RD says it is “compatible with Shimano 105 5800” – I would expect it to work fine with Shimano GRX 600 and/or 810 shifters (if using an 11-speed cassette, as those shifters are designed for 11 speeds).

      I would also expect it to work with a 10-speed GRX 400 shifters, if paired wit ha 10-speed cassette.

      The things to consider are:
      How much a RD moves per 1mm of cable movement (on average) – that’s the same for Shimano 11-speed road and Tiagra 4700 (10-speed).
      How much cable does a shifter move per click – that differs for 10 and 11-speed shifters, and needs to match the cassette’s pitch and the RD’s movement ratio (as stated above).

      Hope I’ve helped you and haven’t confused you. 🙂

      Relja

  10. Thank you for this. I want to figure out what my options for upgrading the derailleur on my “frankenbike” are and you are the only one with clear and concise information on this!

    Reply
  11. What’s the full cable pull required for the 11speed dynasys? I have converted an old 8 speed bar end shifter to a friction shifter but would like to calculate the entire cable pull required before fitting.

    Eg cable length required to get from 1st gear to 11th gear… TIA

    Reply
    • Hi Scudders,

      I haven’t got an 11-speed RD at hand to measure that.
      But you could easily measure that upon mounting the friction shifter – mark the cable at one end of the cassette, shift to the opposite end, and measure the length.

      Relja

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