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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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96 thoughts on “Compatibility [04] Rear derailleurs”

  1. Shimano MTB 11 speed RDs have the same movement ratio as SRAM 1:1 (according to my information).
    Hence, I would expect a Shimano 11 Speed MTB shifter to work with SRAM 1:1 RD on a Shimano 11 speed MTB cassette. Though I haven’t tested this yet.

    However, on a 9 speed cassette, it should not work. Since you’d practically be using an 11 speed shifter with a 9 speed cassette. I.e: derailleur movement ratio should be close enough, but the shifter is “all wrong”.

    Shifer’s cable pull per click should move the derailleur to match the cassette’s pitch (cog spacing).

    So the formula is:
    – Shifter’s cable pull per click – call it P
    – RD’s movement ratio – call it D
    – Cog spacing – call it C

    P*D = C

    Or whichever way you want to mathematically transform it (depending on what’s known). For example:

    D = C / P, or
    P = C / D

    To make things more complicated, most of my info is rounded to one, maximally two decimals – for easier noting which ones are the same. However, when using the rounded up/down figures, the results don’t match exactly. While not even I can now tell (from the calculation alone) whether the mismatch is because a combo is incompatible, or because of the number rounding.

    But it is not all black! 🙂
    I have listed for each standard what it is compatible with. Most of the noted compatible combos have been tested (when that is not the case, I explicitly note it – as is the case with the beginning of this comment).

    Reply
    • woah.. thanks for the elaborate reply and explanation.
      It is all clear to me now. .
      If i have same pull ratio rear shifter and rear derailleur (RD):
      rear shifter count = cog count, with RD capacity >= cog count, thats why my set-up work.

      The SRAM X0 9s shifter + Taiwan 11-46T 9s cog + shimano deore 10s RD with clutch.

      Guess i found a $10 solution for my spare SRAM X0 9s RD and 12-36T 9s cog. I found a Taiwan brand “LTWOO”, that has 9 speed rear shifter model “A5” with 1:1 pull ratio.

  2. If this statement is true: “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.”

    Then would you also safely assume that Tiagra 4700 shifters will work with an 11 Speed Shimano Road Rear Derailleur? Specifically looking at the R8000 RD – GS model. Thanks!

    Reply
    • Yes. To avoid any misunderstanding – for Tiagra 4700 rear shifters to work properly, you need:

      1) A 10 speed cassette – they generally won’t index properly with 9, or 11 speed ones.

      2) An appropriate matching rear derailleur. Either Tiagra 4700, or a Shimano road 11 speed derailleur. They have matching movement ratios.

      So yes, R8000 (Ultegra, 11 speed) should work fine, as it is a Shimano 11 speed road derailleur.

      It all boils down to matching the RD movement ratio that a shifter has been designed for, as well as matching the cassette cog pitch that the indexed shifter was designed for. Mismatching either one will cause poor performance.
      With one theoretical exception: if both cassette cog pitch and RD movement ratio are misaligned in a way to match what’s being used, it could work fine.
      That is: Shifter cable pull times RD movement ration must match the pitch of the cassette being used. For many users, getting the match close enough (not 100% exact) gets the system to work acceptably well (for their use).

  3. Hi Relja
    Thank you for great article.

    I have 2007 specialized epic 3×9 model. quite old 26in MTB
    Trying to change 1×9 by using with 11-50T chinese cassete.
    Still using SRAM X7 shifter and X9 RD. it’s required to use hanger extender.

    I can imagine it would be misery situation, when its changing on high gear due to gap becomes wider, and also increased risk the long-gauge extended down will hit the stone… So I am wondering to know whether it works 11 or 12 speed RD(50 cog capacity) with using exist 9s shifter and chinese 9s large cassette.

    On your article per my understanding, it’s said that Shimano MTB 11s RD like deore or SLX/XT serires (M8000/7000/5100) should be compatible with SRAM standard 1:1 (x7,x9,x0 etc..).

    So does it work on this combination?
    1. SRAM X7 shifter + chinese 9s 11-50T cassete + Deore M5100 (or 11s 2018 XT RD)

    addition, I have little doubet to use folowing combination…
    2. SRAM X7 shifter + chinese 9s 11-50T cassete + SRAM NX Eagle RD(12s)

    This poses a challenge for gradual component upgrade (27.5in wheels with hubs, 12s XD Hub or MSpline or 11s FreeHub and 11s or 12s cassette and shifter corresponds to its) and investment in the future.

    Reply
    • Hi, what i used is deore m6000 the 10s and a SRAM x0 9 speed 1:1 on a China 9 speed 11-50T cog.

    • 1. should work – but, I haven’t tested it personally.
      As @PJ Sinohin said – he tested with a 10 speed MTB RD (if I understand correctly) – 11 speed MTB have cable pull that is even closer to that of SRAM 1:1, so, again, I would expect it to work.

      2. NX Eagle uses X-actuation, which is quite close to 1:1 – it could work.

      3. Third option/opinion:
      2x and “even” 3x drivetrains are quite cheaper, and tried & tested.
      I wouldn’t even bother with 1x systems without a good reason – especially if a wide range of gearing is required.
      My opinion & experience on 1x drivetrain systems pros and cons.

    • yeah it was a
      Shimano Deore M6000 RD 10s
      SRAM X0 9s shifter (1:1)
      China 9s 11-50T cog

    • Thank you for your prompt reply. It will be very useful.
      It’s amazing that 10s Deore can be used, especially it is applicable to 50T cog size without extender.
      The difference between 1.2 mm of Dyna-sys and 1.1 mm SRAM 1:1 standard looks just insignificant error.

      My priorities considered in discarding 3×9 are as follows.

      1.Avoid drop chain, when jumping, drop-off, sudden change in descending or climbing
      2.Requires outer/second gear ratio level with 3×9 in high speed
      3.Requires gear ratio of around 0.7 at low speed

      My style is mainly going to trail, fun, sports ride and join marathon race like exterra.
      Now I am using 36t front single with the rear is 11-34t “default” 9s standard. The chain/gear mechanism system is very stable and very comfortable, I love narrow wide chain ring.
      However sometimes it’s still difficult to climb.

      Maybe if I can chose 9T cog, I can use a 32T front single and I can make it lighter and high speed as I wish. my best setting 32T/9T-46T would be my ideal. In current cassete market and my option is 11T as smalllest, then I can use 50T on the rear, and use 36T on the front to achieve my ideal gear ratio.
      Wide ratio chinese cassette is likely to have reliability problems such as back pedal and unusual practice of extender. I don’t think to need up to 12s as cross ratio per me, but may be, I want about 10s or 11s after wide ratio 9s experienced.

      I will try the cassette with default group set currently being transported on the china post, first. then if there is stablitity issues, will consider 50 cog supported RD with 1.1 compatible.

      Really appreciade your advice!

    • Thank you, PJ
      It is very good to know your experience, it would be my good reference.

    • Hi
      I have tried to use SRAM x9 (9s)RD with extension for 11-50t Chinese cassette. It does work. However shifting performance was poor. Slow changing on higher cogs, and sometime skip down to 3rd from lowest cog even though carefully configured. So I try to buy Shimano RD-M8000 (11s) XT RD for it, and have tested to work with following sets;

      SRAM x7 (9s)Shifter + Shimano RD-M8000 (11s)RD + Chinese (9s)11-50t cassette + 9s Chain
      Looks working well with those index and derailleur movements. However, it should be required to use extension due to (shadow type) cable puller interference with 46t 8th cog. I’ve offset the extension diagonally back to avoid this. Shift feeling is more than better old SRAM x9 RD.

      Pros
      No delay of changing on higher range of cogs, performance is back.
      Cheaper upgrade: Chinese 11-50t 9s cassette $50, narrow wide chain ring $10, 9s Chain $10, Shimano RD-M8000 $80, total $150
      No chain drop when back-pedal chain on the lowest cog using 9s huge cogs, unlike 11s’s lowest.
      The clutch helps reduce the inertial rotation of the huge cog cassette when the pedaling sudden stop on the top/2nd cogs chain
      Also clutch can be expected to contribute to be stabilize chain line preventing chain drop.

      Cons
      Chinese cassette is little heavy, 520g
      RD-M8000 (250g) is 50 grams heavier than old style (no clutch) SRAM x9 (200g) for clutch

      Summary
      Good enough, but not a perfect. Choose all 11s group set may be better. I thought the Shimano free body for 11s and the free body for 9s would be different lengths. (So I thought all hub, wheel should be changed for 11s) However it looks same, seemed my misunderstanding with difference of 11s free body for Road against MTB’s. So it had been better to replace it with an 11s group set from the beginning. but I am satisfied with this upgrade, like #9isfine that is premium 9speed group sets, and as a cheap Franken Set.

    • Cool and informative feedback – definitely appreciate it, thanks. 🙂
      Still haven’t tried personally, but would expect (as noted in the article) for Shimano 11 speed MTB RDs to work with SRAM 1:1 shifters (and vice-versa)
      – as long as the shifter’s number of speeds matches the cassette’s number of sprockets.

  4. Hi,
    if you’re considering buying a new cassette and new RD (possibly 12s), IMO that wouldn’t be a great expense to buy also a new 12s shifter (along with a 12s cassette)… You would have a proper and all new 12s drivertrain with less big gaps throughout the cassette than with a 9s 11-50. Shimano SLX is pretty good, cheap and reliable. For the cassette, something like a 11-50 Sunrace for HG body or another chinese equivalent.

    Reply
    • From my experience, an X9 RD (albeit 10s), can cope easily with a 42T big cog (11-36 cassette + 42T range extender), so with a hanger extender, a 50T cog should be OK with your existing X9 RD (I also have experience with such hanger extender with a DuraAce GS RD + 11-34 XTR cassette). Then you’ll be only buying a cassette and a chain (and a hanger extender but that’s just 3$)

    • some just like to keep it simple & stick with the 9s. some don’t mind the gaps or cadence unconscious.

    • Hi Fbi
      Ideally, it is best to have a complete group set of 12s with avilable 9t. A little grading down and the NX 12s set would be nice too. Deore 12s also come up! so it’s excited. But I don’t feel like investing that much in my old MTB 13 years ago. It’s also interesting to make it considering configure in less budget…

      Thank you for sharing your experience. It’s good to know. Yes, I ordered 9s 50t cassete with hanger extender and new chain. 🙂 I’m waiting for those. also I will consider SLX for future set!

  5. Hi Tettera,
    indeed, full 12 speed is an investment, by not by so far expensive than mixing&matching components if you consider to buy everything but a shifter 😉
    I would avoid the NX cassette, it’s made of lead 😉 The Chinese market has cheaper and lighter alternatives.

    On the other hand, the solution with only a wide range 9s cassette and a hanger extender (with your existing RD and shifter) should work and would be on a reasonable budget.
    If you ordered those, I’m sure you won’t be disappointed ! For the budget, it’s a great upgrade.
    Also consider a narrow/wide chainring for the front, it’s only about 5$.

    If I were you, I wouldn’t be so focused on 9t sprocket.
    IMO, upgrading to a proper 12s drivetrain, even not high-end, will perform already really well. Ultimate top speed when pedaling downhill isn’t a major point, and a 9t has a low efficiency. Better stick to 11t with your existing wheels and freewheel body, and fit high volume/low rolling resistance tyres. Upgrading from 26″ to 27.5″ makes a really small difference (26 = ETRTO 559 ; 27.5 = ETRTO 584 ; 29 = ETRTO 722… that’s a bigger gap)
    Cheers 😉

    Reply
    • Typo obviously, but in case anyone else reads it: 29 = ETRTO 622.

      For the 9t part, I’d add: sprockets below 13 teeth are less efficient, while 10 and 9 toothed ones are even more so.

  6. On my bike I have sram 7.0 esp 8 speed grip shifter with shimano 10 speed rear der. m610 (dynasys) on a classic shimano 8 speed cassete (11-34 megrange). It works perfectly.

    Reply
    • Thanks for the feedback – it is appreciated. 🙂

      Sram 1:1 cable pull ratio is close to dynasys (1.1 compared to 1.2).
      8 speed cassette has 7 shifts across it. With good tuning, it can be set for RD position to go from -0.35 mm to +0.35 mm, compared to dead-centre over a sprocket. But the two most outward postitions can be limited using RD limit screws – practically making the “tollerance” vary from -0.25 to +0.25.

      8 speed chains are 2.38 mm wide in the middle (between the inner plates). Sprockets are 1.8 mm wide. So enough “room” for it to fit in spite of a bit of mismatch.

      Chain outer width is 7.1 mm, while sprockets are spaced at 4.8 mm (having distance between adjacent ones at 3 mm). So the chain gets caught by the adjacent sprocket when shifting with no problems.

      So it might not be perfect, but it makes sense for it to work.
      I was more surprised to see the 11 speed stuff, with less margin for error, work when mismatched – in this case it was a cassette mismatch, of 0.16 mm!
      https://www.youtube.com/watch?v=TCmQZzeH_aU

      I included widths and cable pull ratios in all the compatibility articles – so these things can be compared and experimented with. Things that closely match can work OK, especially depending on one’s criteria of OK and their riding conditions.

  7. Here is a video i made (https://easyupload.io/hdifn1). It s not perfect (i have to hold a cellphone in my hand so i can t turn pedal and shift simultaneously). I have this setup for about 4 years and it never let me down. It shifts uphill no problem. Doesn t need adjustments after short or long period of time. Works in winter, summer, etc. This setup is cheap, reliable and funky.

    Reply

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