Shimano Di2 Synchro Shift for road bikes?
So before we even begin to try and tackle this subject, let’s just jump straight to the main question; can I have sequential shifting on my road bike? If you’re reading this only to find out the answer to that question, let me save you a bit of trouble and answer that question up front: No, you can’t. At least not yet.
Now that we’ve got that out of the way, allow me to continue and explain why you can’t, when you can and with a little bit of Di2 history sprinkled in.
School’s in Session; A Brief History of Di2
The subject of sequential shifting — from here on referred to by the official Shimano name, Synchro Shift — is fairly diverse and we have quite a lot to say on the subject from many different points of view. So it seems the only logical place to begin the story is from the beginning. In this case the beginning is much further back than most realize. Most believe that the original Dura Ace 7970 Di2 group released in 2009, announced on August 2, 2008, was the beginning. Actually Di2 is quite a bit older than that. If you go outside the U.S. and look back into the recreational-commuter history you’ll find something called Nexave Di2 C910. Nexave Di2 was first seen 8 years prior in 2001, though it was quite different from the current iteration. In fact this technically makes 2016 the 15th anniversary of Di2. Two years prior to this first iteration of Di2, Shimano was also experimenting with pneumatic shifting in a system called Airlines. Airlines wasn’t successful, and was shelved with few production units making it out into the world. We’re happy about this because we believe the failure of pneumatic shifting was what led to more innovation and development in electronic shifting. We don’t know for sure, but considering we have seen pictures of prototypes from the current versions of Di2 dating to about 2005. We suspect that Di2 development has been pretty much continuous since sometime in the mid to late 90’s, but really only started to take off with the development of the new E-Tube wiring system.
Since the beginning here at FairWheel, we’ve had a strong interest in pushing products to see just how far they can go. Naturally, we’ve had the same mad-scientist urge with Di2. In 2009, thanks to some wonderful friends at Shimano, we were able to score an early production Di2 group for a special project; the first Di2 mountain bike (view on Bike Magic). A special project, yes, but quite possibly the ugliest bike we’ve ever built. The following year with the help of a truly amazing computer genius Jeff Roberson, who still 5 years later we cannot thank enough, turned that into the first sequential shifting mountain bike (View on Cycling News, Cycle Exif, Bike Rumor). The next year we continued to refine the system giving it the possibility of changing from sequential to manual front shifting on the fly in a road setup as well as doing one with wireless shifters. Basically, we did all the things we were hoping Shimano would eventually do. We were totally excited last year when we got to see an advance preview of the upcoming XTR Di2 which featured Synchro Shifting. We hoped this could also be adapted to Synchro Shift the Dura Ace road group with just a few small tweaks.
Well, Can We Synchro Shift Road Groups?
That brings us to where we are today and the main question; can XTR pieces be used to Synchro Shift Dura Ace 9070? The answer as we mentioned in the beginning is no. But there are some things that are possible to do with the system. So before looking at why you can’t Synchro Shift your Dura Ace or Ultegra group, lets take a look at what you can do.
One really cool feature of XTR is the front display. This is basically the same as the A-Junction on Dura Ace, except that it has a screen which displays your current gear, shift mode, and battery life. It doesn’t add anything in the way of performance, but in my opinion having a bar mounted 3 port junction rather than one mounted under the stem as is traditionally used on Dura Ace is a cleaner look. Also, having your current gear selection visible on your bars is a nice bonus. The M9050 XTR handlebar display seems to work perfectly fine with a full Dura Ace or Ultegra setup, at least it did through all of our testing. The front and rear gear indicators work just fine as does the battery level indicator.
Some people have asked about using an XTR rear derailleur on a road or touring bike in order to give themselves a wider gear range with a larger cassette. The answer to this one is a bit tricky. An XTR rear Di2 derailleur will work with Ultegra/Dura Ace shifters, but only if you run it as a 1×11 setup. Which makes for a nice cyclocross rig, but maybe not the best for road or touring. As soon as you try to plug in a Dura Ace or Ultegra front derailleur, the system detects a mismatch and shuts off. In short, this happens because road and mountain derailleurs give the battery different instructions on how to behave. When the battery detects a conflict in these pieces it initiates a defense mechanism that turns everything off to avoid damage. However, if you plug in both XTR front and rear derailleurs with the Dura Ace or Ultegra shifters the system works just fine. Which means you can basically run drop bars on a mountain bike, but you can’t mix road and mountain front or rear derailleurs in any combination. You must use either both road, both mountain, just a single road, or single mountain derailleur with whichever shifters you choose.
At first it irked me that I couldn’t Synchro Shift my Dura Ace, but as I thought about it more and played with some of our previous Dura Ace Synchro setups and then compared them to the XTR, I began the realize the difference between them was pretty dramatic. The Synchro Dura Ace shifts well, but when you’re riding it and a front shift is triggered, you definitely notice that the front has shifted. Functionally it works, but it is far from a seamless transition. However, when I ride the XTR and a front shift is triggered it really doesn’t feel any different than if it were just a rear shift. This is due to several factors including a closer spacing in tooth counts on the XTR front rings, a stouter front derailleur, tighter throw ratios, cog mapping, etc…
Okay, We Can’t, But Why Not?
So now we move into the “why not” territory. Some people on the internet would like you believe that Shimano is this evil entity trying to make everything incompatible in an attempt to monopolize the cycling world. In reality, I think it’s more the other direction. Shimano has been one of the more consistent companies with adhering to standards and not creating something new SOLELY for the sake of having it be proprietary. Just look at how long they stuck with conventional threaded headsets and threaded bottom brackets. Obviously Shimano creates new stuff all the time, I think at one point they were filing 100’s of patents each year. Some turned into successful products, while others never left the drawing board. When they do release something it usually is a performance increase, or an improvement on a design. I think that since we’ve seen Synchro Shift on XTR already, and since Shimano does like to try and keep things compatible, it’s probably a very safe assumption that Shimano is at least looking at Synchro Shift for the road. It may not be in the next Dura Ace update, but I imagine it will be coming down the pipeline eventually. It might be as simple as a firmware update, or it might require new hardware to handle the extra stresses.
Right, But What Does Shimano Have to Say?
It’s at this point where I took some time to chat with Nick Murdick. Nick is the Lead Technical Instructor for Shimano, it’s his job to know basically everything there is to know about the technical side of all things Shimano.
Obviously the first thing I wanted to ask about was why we can’t Synchro Shift with Dura Ace. The answer, while good, was unsurprising;
“Every product we make and every decision we make about those products is heavily influenced by strict (Quality Control) guidelines. We set standards before we even start making a product so that we have a target to shoot for during development. If we can’t meet that standard, we don’t make the product. That’s why we don’t have a quick link, or aluminum rear axle for Saint/ZEE hubs. When you see a combination of Di2 components that doesn’t work, it’s simply because that combination doesn’t meet our QC guidelines. Mixing 10 and 11 speed road derailleurs, mixing road and mountain derailleurs, and using synchro shifting on road bikes all fall into that same category. Like you pointed out, simply writing firmware that makes a road bike synchro shift is possible but it’s not a great result and it’s not something we feel comfortable giving to our customers.”
He then goes on to explain why it’s a different beast than Synchro Shift on an Mountain bike. The large 16 tooth jumps between chain rings on a road crankset creates a small delay when moving the chain up or down. This tooth jump also increases the need for simultaneous large dumps up or down the cassette to get the next sequential gear. So while on an mountain bike you’re only changing the front rings from a 26 to a 36 (10 teeth) only requiring a simultaneous rear change of 1-2 gears. This makes for a relatively smooth and manageable transition. While on a road bike you’re jumping rings from 34 to 50 (16 teeth) on the front and having to trigger a simultaneous change of 3-4 cogs in the rear. Making for a bit of a chunky transition, which is certainly a difference we’ve noticed on our own project bikes.
Nick also pointed out a factor we hadn’t considered in mapping the gears and the function of the shifter. Particularly, how the firmware interprets shifts when there are double clicks on the XTR shifter. A feature which is not present in the current road shifters.
” The mountain shifters have two clicks in each direction. So if a mountain Synchro Shift involves one front shift and one rear shift, we always have the option to cancel the whole synchro thing and just do a front shift by simply shifting all the way through both clicks. XTR Di2 actually reads that double click and instead of doing a front shift and then a rear shift up and then immediately back down, it just cancels the rear shifts altogether. So the lack of a double click in the road shifter is a bit of a factor as well.”
Now that we know this we can readdress what was mentioned earlier about how the road and mountain derailleurs each talk to the battery differently, and how a mix-matched setup causes the system to shut down. This is actually a new thing, and Nick had this to say about it;
“What’s relatively new is the check the battery does to make sure it has instructions to make everything on the bike work properly. Before that firmware update came out, 10 and 11 speed parts worked together but they didn’t work perfectly. Front shift signals still made front shifts happen, and rear shift signals still made rear shifts happen, but the auto trimming and multi-step front shifts didn’t work right. Those instructions were never on the battery. The engineers said they actually didn’t know that 10 and 11 speed components would work together at all before we started complaining that they took it away. There was never a set of instructions on how those components should interact but they could kind of limp along with what they had in common. When mixing 10 and 11 speed road stuff, the consequences weren’t too severe. The chain might rub on the front derailleur in the middle of the cassette because the auto trim was happening at the wrong time. A mechanic might compensate for that by opening up the limit screw adjustments and on some bikes that could lead to occasional chain drop. If we allowed XTR and road parts to limp along with what they had in common the consequences would be much worse. Slow shifting, chain rub in multiple gears, and frequent chain drop would all be huge problems.”
This means some things are specifically told by the computer that they can’t work together, while other components were never envisioned being paired together so no instructions exist for them, either allowing or denying them to work together. A good example of this is that while the XTR display works with Dura Ace the Alfine display does not work with XTR. It’s nothing intentional, it’s just that unless you’re going to try and program for every possible configuration (which would be quite a task) you have to draw a line somewhere. So while someone envisioned that the XTR display might be used with Dura Ace shifters for say a CX bike with a 1×11 XTR group, they may have never foreseen a practical application in which a road rear derailleur was used on a build with a mountain front derailleur. Aside from a handful of strange projects, such as what we do here, there is really no reason an Alfine display should ever need to be mixed with XTR so no instructions were written for those components to talk to one another. I think we can all envision a ridiculous case of mixing XTR, Dura Ace, 10/11 speed, aero bar shifters, sprint shifters, gear mapping etc… to a point where it would be pretty silly and unnecessary to try and make it all work together. Though I imagine with each generation, coding will be changed and added so that over time more pieces will get to a point where they play nicely with each other.
Let’s Just Get a Summary, Maybe A Prediction
So the final question; when can we expect to see Synchro Shift on the road side of things? We never got an answer for this, nor did we expect to. Though I do feel confident in saying that Shimano will release Dura Ace Synchro Shift, if and when they can produce an offering that meets their design and performance standards. It is completely possible that might never happen, but looking at what Shimano has done so far I have to think that they’re going to keep playing with electronic shifting pushing it into territory we haven’t even thought of yet — hopefully further than just Synchro road. The latest version of Di2, the E-tube version, is only a few years old and has already come a long way. I expect at the rate they’re developing, we’ll all be surprised by where they’ve taken it in another 5 years.