Tinkering: Shimano XTR Di2 & Road Di2 Shifters – Perfect for CX & Monster CX

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Carbon fibre construction features in the XTR Di2 derailleur.

Ardent fans of the Gravel Cyclist Facebook page may have noticed our recent teaser photo about the Shimano XTR Di2 parts we acquired recently. Some may be asking, “Why the heck would you want to use MTB specific parts in conjunction with a bicycle intended for gravel cycling?”

For those who have ventured to the East coast of the United States, where the Ultra Cross courses are tough and the gravel is gnarly, a machine with the option to run uber low gearing normally associated with a mountain bike, but on a rig with drop bars is the answer to that question. Also, there are the occasions when heavy rain falls, turning a gravel ride / race into a boggy quagmire, where wider tires (tyres) and mega clearance are the order of the day.

These parts solve an issue that cropped up when JOM converted his Lynskey Monster Cross bike to 11 speed – all in the name of gaining an extra 36 tooth cog. Financially, that 36 tooth cog ended up costing some serious cash. Don’t ask.

In reality, JOM’s Monster Cross bike is a 29’er mountain bike frame with rigid fork and drop handlebars – what we call Monster Cross around here. The bottom bracket shell is 73mm wide, versus a regular road bike bottom bracket shell which measures 68mm in width. The Lynskey was originally built with Shimano Ultegra Di2 10 speed front and rear road derailleurs, 10 speed chain, running in conjunction with a 10 speed Shimano XTR MTB crankset.

When shifting the chain from the small to the big chainring, a front derailleur needs to move a certain distance up and to the right for that change to happen. In the case of a road derailleur involving an MTB width bottom bracket shell, a road derailleur needs to move further to the right than planned by the manufacturer – remember, 68mm road bottom bracket shell versus 73mm MTB bottom bracket shell.

XTRDi2Tinkering2015-2When the Lynskey was originally assembled with its 10 speed road drivetrain, the chain shifted perfectly between chainrings, in both directions. However, an 11 speed chain is narrower, narrow enough to make a difference in front derailleur shifting performance. What does this mean? Simply put, the chain will not always catch cleanly onto the shifting ramps of the big chainring, and hence, front derailleur shifting becomes unreliable.

In JOM’s situation, once the Shimano Ultegra Di2 11 speed rear derailleur and matching chain had been installed (with an Ultegra Di2 10 speed front derailleur still in place), the chain would only climb onto the big chainring if positioned on four of the eleven cogs on the rear cassette, closest to the spoke side. The rest of the time, the chain would clang around the place trying to shift to the big chainring, and sometimes fall off the small chainring altogether – not optimal.

Then, Shimano XTR Di2 became available.

This meant, Dr. Pain and I (JOM) spent some time playing with various combinations of cranks, bikes and cassettes, to figure out what works and what doesn’t with Shimano XTR Di2 – and, we’re using road Di2 shifters. Some of this information may be old to some and new to others, but we hope you find it helpful.

Another helpful resource is Shiman’o eTube compatibility chart – this takes a lot of the guesswork out of which components work together, and which ones don’t.

 

XTR Di2 Firmware Updates

Before you can think about mixing Shimano’s XTR Di2 MTB derailleurs with the company’s mechanical brake or hydraulic brake road Di2 shifters, some firmware needs to be updated using Shimano’s eTube software. Namely the battery, SM-BTR1 for external or SM-BTR2 for internal; they need to be on Version 3.0.10 – at the time of this article.

Technically, the external battery contains no chip, rather, the holder that seats the battery contains the chip that stores the firmware. The internal battery hides a chip somewhere inside its casing. The road shifters, hydro or otherwise, will not recognize the XTR Di2 derailleurs until this battery update has taken place.

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SM-BTR2 at top, with SM-BTR1 at bottom (battery ejected).
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eTube screen – Internal battery SM-BTR2 is on firmware version 3.0.10.

Other components such as Junction Box A – part SM-EW90-A (3 port), SM-EW90-B (5 port), front and rear derailleurs, road shifters, climbing switches and even the SM-PCE1 or SM-BCR2 modules for system configuration / battery charging should have their firmware updated, if available.

 

Known Incompatibilities – X

  • Road Di2 derailleurs and XTR Di2 derailleurs cannot be mixed and matched. For example, you cannot use a Di2 road front derailleur in conjunction an XTR Di2 rear derailleur – Shimano blocks this with the system firmware. Some people will claim it can be done, but we’ve yet to see a working example.
  • If Battery update V3.0.10 has taken place, you can no longer mix and match 10 and 11 speed Di2 road derailleurs – note, the firmware which prevents this may be an earlier version – Shimano isn’t forthcoming with information on their website. Incidentally, they play well together until this, or a slightly earlier firmware upgrade has taken place.
  • Junction Box A, part number SM-EW67-A-E – the original junction box for Ultegra 10 speed Di2 does not work with Shimano’s XTR Di2 derailleurs.
  • If using a double chainring crankset, aka 2 x 11, when XTR Di2 is shifted to the small chainring, the system WILL NOT shift beyond the 8th cassette cog. In other words, you will not be able to use your 11, 12 or 13 while on the small chainring. Why? This is to prevent issues with cross chaining. However, similar gear ratios can be attained by shifting to the big chainring, and a bigger cassette cog on the rear derailleur.
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Original Ultegra Di2 junction box at right – NOT compatible with XTR Di2.

 

XTR Di2 Tinkering – 1 x 11 System – ✔

The XTR Di2 system works flawlessly as a 1 x 11 system with regular or hydro Di2 road shifters – in either case, the front derailleur is not required. Because the XTR Di2 derailleur has a clutch, chain tension is kept consistent to avoid slapping against the chainstay, etc. Keep in mind the clutch does add some drivetrain drag in certain gears. Thankfully, the clutch is easy to disengage, although Shimano may frown up on this during normal pedaling operation.

 

XTR Di2 Tinkering – Road Cranksets – 2 x 11 System – ✔

This scenario involved Dr. Pain’s Monster Cross bike, which is a full custom rig featuring a 68mm road bottom bracket shell and compact road crankset. In his case, 48 / 34 tooth chainrings are fitted to the crankset.

The Good – Even though the XTR Di2’s front derailleur cage is about two centimetres shorter than its road equivalent, it shifts flawlessly between 48T and 34T chainrings.

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Dr. Pain’s fancy test rig, wires and stuff hanging everywhere.

The Bad – When the chain was on the small chainring, the inner front derailleur cage would rub against the chain when the rear derailleur was shifted to one of the three cassette cogs closest to the spokes. This is due to the decreased bottom bracket width; the derailleur cannot move far enough to the left.

The special XTR Di2 front derailleur mount (the low mount in our case) left a 5mm gap between the seat tube and the mount itself – I (JOM) don’t recall the seat tube size of Dr. Pain’s frame, but it required us to use the thicker of the two spacer sets supplied with the XTR Di2 front derailleur mount. If a custom, ovalized spacer set could be fabricated, the problem would be solved, allowing the derailleur to sit further left, relative to a road crankset.

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Note the large gap. Disregard the Di2 wire we slung next to the derailleur 🙂

On the original Gravel Cyclist Facebook teaser post about XTR Di2, Brantley Smith reported he has the XTR Di2 front and rear derailleurs working perfectly on a Raleigh cyclocross bike. Normally, cyclocross frames utilize a 68mm road bottom bracket shell. So, it seems the XTR Di2 front derailleur may work with some road type frames, and possibly not others.

Considering Shimano “allows” the road type Junction A boxes / road Di2 shifters to work with XTR Di2 derailleurs in their firmware, this indicates the system was designed to cater for road bike use, or more appropriately, cyclocross / gravel bike use. Do your research before purchase – mounting the front derailleur is key.

 

XTR Di2 Tinkering – MTB Cranksets – 2 x 11 System – ✔

At the time of writing, the largest chainrings offered by Shimano on their XTR 9000 11 speed series of cranksets is 38 teeth for a double, 40 teeth for a triple and 36 teeth for a single. JOM’s Lynskey rig utilizes an XTR FC-M985 10 speed crankset, with 42 / 28 chainrings. Shimano don’t recommend mixing 10 and 11 speed parts. Rules are meant to be broken! :mrgreen:

Cassettes:

  • With a SRAM PG1170 11-36 11 speed cassette installed, the drivetrain shifts flawlessly on both derailleurs. You will need to place close attention to the rear derailleur B-screw – this needs to be set appropriately to allow for clearance between the top derailleur pulley and the largest cassette cogs.
  • With a SRAM PG1170 11-26 11 speed road cassette install, the derailleur pulleys need to sit closer to the cassette, accomplished by turning the rear derailleur B-screw counter-clockwise. Otherwise, shifting will be hesitant on some cogs, especially during the downshift. On JOM’s bike, the drivetrain shifts flawlessly on both derailleurs. However, with a chain cut to length for a larger cassette, such as the 11-36 referenced above, you will see some chain slack on the small chainring with some of the smaller cassette cogs, such as the 14 tooth. Ideally, if switching wheels or cassettes semi-regularly, it is advisable to switch to a second chain to account for optimal chain length and shifting.

Finally, a brief video demonstration of the Shimano XTR Di2 2 x 11 system in action – on a SRAM PG1170 11-26 road cassette. Don’t mind the suspect Di2 wiring hanging all over the place, I’m not quite finished with everything.

Thanks for reading!

90 comments on “Tinkering: Shimano XTR Di2 & Road Di2 Shifters – Perfect for CX & Monster CX

  1. I’m finally in the process of upgrading the Ultegra Di2 groupset on my gravel bike to give me bluetooth configurability and Synchronised Shift: If I’ve read the Shimano documentation, I should be able to do that (in this case) by replacing the Junction A with the SC-MT800 and swapping batteries for the BT-DN110. Will know in the next couple of days. And it does indeed appear that the Bluetooth battery doesn’t actually have a BT radio in it, just the upgraded memory and firmware needed: the actual radio is in the SC-MT800 or the EW-WU101 units.

    1. Nice! Good luck with the installation, keep us posted how it goes. I have played with synchro shift on an MTB, but not a gravel or road bike.

      1. That went well: once I’d worked out that you can’t activate the Bluetooth LE setup if the charger is plugged in, I managed to get the SC-MT800 set up with the BT-DN110 battery in mere minutes: after upgrading the firmware on all components, I now seem to have synchronised shifting working perfectly with Ultegra shifters & mechs. I say “seem to” as I’m just waiting for a slightly longer E-Tube cable and a new circlip plier to turn up, to secure the battery into the seatpost. So I’ve got the opportunity of full synchronised shifting, partial or full manual by cycling through the button on the display, without having to reprogram the whole thing from my phone. Nice.

  2. I can confirm what Richard found. In order to get Syncro-shift to work with XT(R) derailleurs and Ultegra Shifters (and climbing buttons in my case) you have to use the SC-MT800 display/junction. Also you can’t mix EW-90 Junction A/B and the SC-MT800. If you need more than the 3 ports of the SC-MT800, you have to get the dumb SM-JC40 or 41 junction boxes.

    As for custom synchro-shifting, the E-Tube software doesn’t list the gearing you’d find on a gravel bike, so you have to ignore the ratios it lists, and substitute your gearing values in. I’m still testing and experimenting, but so far so good. Right now I’m testing 48/32 with an 11-34t. I have a set of 46/30 rings and an 11-40t cassette on the shelf. I tried the SRAM 11-36t, but just wasn’t happy with how it shifted and gear spacing… I think it would be perfect for a 1x setup though.

    1. Thanks John, I really appreciate you adding this valuable information to the thread. Oh and I’ll say this in the event my friends at Shimano are listening / reading… PLEASE UNLOCK THE FIRMWARE SO WE CAN MIX ROAD DI2 FRONT DERAILLEURS WITH THE MTB DI2 REAR DERAILLEURS! 🙂

    2. John, since you reference XT(R), it would be best to indicate both XT and XTR displays will function to enable synchro with any type of Di2 shifter, not just the XT M8000.

  3. So the current situation is that while using DA or Ultegra DI2 shifters a Dura Ace/Ultegra DI2 FD with a XT/XTR RD will not work due to firmware?

    Assume bike fit for the FD has anyone tried using DA 9170 Shifters, 50/34 crankset, and XTR FD and RD with success? I would go with the 11-40t cassette. I don’t care about syncro shift, just a bigger range.

    I know the current fad is 1x, but lack of cadence options really wears on me on long gravel rides.

    1. Hey Greg, you are correct. Shimano’s firmware prevents the mixing of road Di2 front derailleurs with MTB Di2 rear derailleurs. I have hassled them about this on multiple occasions but to no avail 🙁

      On some bikes, the setup you describe may work, but it will depend on a frame-by-frame case. Generally, the XTR / XT Di2 front derailleur cannot move far enough left without rubbing the chain on the small ring, no matter how it is adjusted.

      With you on cadence options, 2x forever here. BTW, I have a very interesting video coming out involving the new DuraAce 9150 rear derailleur… watch the site / Facebook page for G.C.

  4. Regarding tinkering to accommodate lower gearing than 11×32 for the Di2, there is an interesting letter to the editor in the Dec 2017/Jan 2018 magazine, Adventure Cyclist. Catherine Stewart-Roache used the following setup: a 6870-GS 2×11 Di2 front derailleur and a Wolf Tooth RoadLink derailleur-hanger extension with a Shimano Ultegra 6870-GS, 11-speed medium-cage rear derailleur.

    This is a follow-up to my question that I sent yesterday as to what to relay to my LBS mechanic so that I could go 50-34 and 11-40. Your reply is much appreciated even though it concentrates on XTR or XT components.

    What do you think of Ms Stewart-Roache’s solution? Would it work with any road bike regardless of 68 or 73 mm bottom bracket?

    1. Apologies to all concerned, but the letter should be attributed to Phil Foreman and not Ms. Stewart-Roache.

      1. JOM,
        Thanks again for your reply. Not an article, but a short letter to the editor. In the letter, Paul Foreman details his setup:
        a 6870-GS 2×11 Di2 front derailleur and a Wolf Tooth RoadLink derailleur-hanger extension with a Shimano Ultegra 6870-GS, 11-speed medium-cage rear derailleur; a 50-34 chainring and an 11-40 cassette with the Di2. The letter does not contain any additional technical details.

        Regardless of not reading the LETTER, what is your opinion of the workability of Paul’s setup.

        1. FWIW v1.0 of my build used 6870 Ultegra with a Wolftooth Road link. I started with a 48-32 with a 11-34. I then tried the SRAM 11-36t. I cut about 4 links off the chain orginally and it was STRETCHED going around both big rings. I know you would never run that combo, but I made me think about how much chain I’d need if I tried going bigger on the ring/cog combo. One concern I’d have running that setup (and one reason I went XT/XTR) was the discipline it will take to avoid cross-chaining and chain drop issues with such a long chain and no clutch.

  5. Will xt di2 work with ultegra sti di2. Just tried the xt di2 rear with my ultegra di2 shifters. have 2X 44 and 36 up front and 40 -11 rear cassette. No movement from rear derailleur.

    Is it compatible.

    1. Hi there… XT Di2 does work with the road shifters, but, if you are trying to use an XT Di rear derailleur with the Ultegra Di2 or Dura-Ace Di2 front derailleur, it will not work. Shimano insists that their component groups cannot be mixed, courtesy of firmware. As a side note, if you have an XT Di2 front and rear derailleur set there, you will need to place your Etube software into MTB mode to configure. Good luck!

  6. Very interesting discussion! Here is my situation: I have 6800 Di2 Ultegra GS mechs. I want to have two sets of wheels that I can easily swap out, one 700c road wheels, and one 650b MTB wheels. The road wheels have an 11-32 cassette. The 650b would be either an XT 11-34 or XT 11-40.
    My question is can I run the XT 11-40 without the Road Link? I’m concerned that using a Road Link will not work with my 700c road wheels with the 11-32 cassette very well.

    1. Thread is really about mixing road Di2 with XTR, not if a Roadlink is optimal on a Ultegra RD. Yes it will work with the 11-32, no it is not optimal as the top jockey wheel is moved away from the cogs which will slow engagement a touch when shifting. Degradation in shifting is more apparent as drive components (especially chain) wear. Regardless, if using all road Di2 components, the Roadlink is the cheapest ($20) answer to extending the RD for a 11-40 cassette. Alternative is to get the expensive ($350?) K-Edge cage installed on your RD and that will shift better than with the Roadlink. The K-Edge moves the top jockey wheel rearward but maintains a closer proximity to the cogs which means better shifting.

      1. Jayson, I really wasn’t interested in using a Roadlink. What I was really asking is if I can use an XT or XTR 11-40 cassette with my 6870 gs (long) derailleur without a Roadlink.

        1. This isn’t Jason, or a Di2 issue, and no, the posted max cog capacity for the 11spd Ultegra GS cage RD is only 32t. There is a good reason they provide the max cog spec and it is not internet conjecture. The only way you will get the Ultegra RD to 40t is via extending the RD with a Roadlink or K-Edge type solution.

          1. Thanks Bryan, I’ve been running an 11-36 SRAM cassette with this derailleur for some time and with no modification other than a “B” screw adjustment, thanks in part from this forum. Others have run the new Ultegra R8000 (max cog 34t) with the 11-40 cog set successfully without mods, https://www.youtube.com/watch?v=roUXWvAN-9k

            I just wondered if the 6870 would do it as well. As you know Shimano is notorious for conservative ratings in part because they have to warranty the product.
            After all, this thread was titled “Tinkering” which I interpret as going outside of the “recommended” specification, which this obviously is.

          2. Not all hangers have the same geometry. My setup:

            sw-r600 pave shifter
            5-port junction a
            btr2 internal battery in the btc1 case
            6870gs
            XTR 11-40 11s cassette
            11s SILTEC chain
            Surly Straggler frame.

            Mech was new, I didn’t touch the b-screw. Shifting has been great except when the jockey wheels and mech got filled with thick stiff mud.

  7. The r8000 RD is not the same as the RD-8000 series (you inquire about 8070). The r8000 has a drastically different cage.

  8. Hi – thanks for an awesome post!
    Will this mean that i can use Ultegra Di2 6770 together with RD-M8050-GS. I´m building a c 1×10 cyclo cross and i really want the electronic gear.

    1. You can use the shift levers, but NOT the 6770 front derailleur and RD-M8050-GS.

      1. Shimano prevented 10/11 speed Di2 derailleurs from playing together some time ago.

      2. Di2 Road and MTB derailleurs do not mix due to a firmware block. So, you either run an XTR/XT Di2 front and rear derailleur together with your Di2 6770 road levers, or ditch the front derailleur and do a 1x with a XTR/XT Di2 rear derailleur.

      Good luck!

      1. So if i understand that correct (i will not use any front derailleur only 1x for my) 6770 shift levers goes hand in hand with any xtr/xt rear derailleur. Will it be any problem when the rear derailleur is 1×11 and the shift levers are 1×10?

        Thanks 🙂

        1. Vidar, correct. The shift levers are just switches. They can shift 10 and 11-speed derailleurs no worries at all. You may need to update your firmware for everything to play nicely, and you will need Shimano’s eTube software to be in MTB mode when you set it up.

  9. Hi,
    Can I use the st-6770 shifters with any of the rear XTR/XT derailleurs in a 1×10 or 1×11 setup?

    I have the full ultegra 6770 di2 10sp setup and I want to use the 6770 shifters and buy a rear MTB di2 derailleur to have a larger cassette for my gravel bike. I’m not finding any specific info on this kind of setup. Please help if you know. Thanks!

    1. Oops, just read the comment below… so, my 10 speed 6770 shifters will work with any XT/XTR rear with e-tube. And it’ll be 1×11 because the rear derailleur is 11? Thanks

  10. Looking for advice on setting up Di2 with low gears. So on my Scott Addict gravel / cross bike thinking of upgrading to Di2 using my existing XTR triple front with 46, 34, 22 rings with XTR 9050 Di2 front ( 40tooth version is currently a very reasonable £80 ish) with an XTR medium cage rear. These with 13 – 42 or 13 – 46 cassette. I would want to use synchro shift or cross chain blocking to restrict big to high 7, block highest and lowest on middle and on 22 chainring keep to low 4 to 5 sprockets only. That will limit chain length and cross chaining which I hope will ensure derailleurs are within capacity. Q1 Is this valid, should it work?
    Second question I realise I need a system information display. But can I then use one climbing button to operate synchro shift up and down? That will save changing brake levers till the next upgrade – which likely includes a new frame!
    So third question: Are there any complications in setting up Di2 on this bike and changing to a new, likely internal routing, in a year or so? Thinking if that just entails new cabling shouldn’t cost to much.

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