Technical FAQ: The intricacies Di2 Synchro-Shift

How do you tune the new Shimano Di2's Synchro-Shift settings? And if you don't want it, how do you keep it in manual mode?

Dear Lennard,
I am in the process of converting a bike from Shimano Dura-Ace 7900 to Ultegra 6870 DI2. I have the BT-DN110-1 internal battery, a EW-RS910 handlebar end junction, and the SM-BCR2 battery charger. I have used the E-Tube software to update the firmware on all of the various components and everything seems to be operating just fine. I am still waiting on a rear wheel that can carry the 11-speed cassette, so I do not actually have the bike on the road yet.

My question is, how do I make sure the synchro-shift functionality is completely disabled? I just want the bike to shift normally with no auto shifting assistance. I looked around in the E-tube software setup but I was not able to see where/how this would be done. There is quite a bit of information on the internet about how to set up synchro-shift, but there does not seem to be much info around on how to disable it, so maybe this would be something good to cover in your column.
— Steven

Dear Steven,
As I discussed in this post, there are three shift modes: M, S1, and S2 (Manual, Synchro-Shift 1, and Synchro-Shift 2). You want M mode, so all you have to do is put it in M mode. On a road bike, if you have not enabled Synchro mode, you won’t get it. You do have a battery that supports Synchro, so you can get it if you want it; to disable Synchro, you simply need to make sure that you are in M mode.

If you have the possibility of Synchro-shift enabled, you can toggle through the three modes with your mode button on your Junction A (in this case, in the end of your handlebar).

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When you simultaneously push both shift buttons on one lever, the LED indicator lights on Junction A will tell you what is going on. They will first tell you the battery level by only illuminating the battery LED (in the proper color to indicate your battery level). If you have the option for Synchro shift, this will be followed by both lights simultaneously glowing or flashing. If the battery LED glows green and the “+-” LED glows red, with neither of them flashing, the bike is in Manual shift mode. If these green and red LEDs flash twice, then S1 shift mode is operational, and if they flash three times, the bike is in S2 shifting mode. If on the other hand, only the battery light glows and is not followed by both lights coming on, then your bike is not currently set up to even go into Synchro mode at all, and you are simply in Manual mode.

If your bike is set up so that you could go into Synchro mode, you cycle from one of the three options to the next with two quick pushes of the mode button on Junction A. The pair of LEDs glow or flash red and green after every time you give the mode button a double push. Since you want Manual mode, if the two lights flash more than once, give the mode button another two quick pushes; do that until the red and green lights just come on briefly together and don’t flash. That indicates you’re in Manual mode, and you’ll stay there until you do another double push.

Since adjusting the system only requires holding the mode button down and not pushing it twice, there is no reason that you will go out of Manual mode in regular operation of the system; you will have effectively disabled Synchro.
― Lennard

Dear Lennard,
I have this setup and have two technical question for you:

1. In S2 mode, I would prefer that the rear cassette advance before the front chainring does. I think most riders do this naturally when in manual mode. Having the front drop from the big ring to the small ring before advancing the rear cassette is very jarring since you instantly spin out. At a minimum, this should be a configuration option. Is it? I don’t see that.
2. I have sprint shifters installed, which is also very nice when in S1 mode. It would be outstanding if they behaved as they do with the eTap system: hitting both sprint shifters could change the front derailleur. Presently, hitting both sprint shifters in S1 mode does nothing. Could this be programmed somehow? Then, S1 would essentially be eTap when sprint shifters are installed.
— Michael

Dear Michael,
While I have heard from Shimano that being able to change the S2 shift order is under consideration, there is currently no such option to change the order in which the system performs the shifts in Synchro-shift mode. Furthermore, I think you are mistaken when you say most riders shift the rear before the front on a downshift; they’re seeking an easier gear, so they drop to the inner chainring first, and then they drop the chain in back as quickly as possible to a smaller cog to reduce the sudden increase in cadence. Furthermore, if they were to go up in gear first and then drop to the front chainring, they will have bogged down and made the front shift much more difficult to accomplish, thus losing more momentum.

Shimano does not offer the option of doing eTap-type shifting in S1 mode with sprint shifters and has no intention of doing so. Why would you even want to shift in the front from the drops anyway? I suppose you could move the sprint shifters up so you can get to them from atop the lever hoods, but then you will have lost the benefit of them, namely having them right by your thumbs when you’re sprinting in the drops. Currently, as you said, if you hit both sprint buttons simultaneously, nothing happens. Makes sense; it doesn’t know what you want, so it doesn’t give you anything. On the other hand, if you were to have them set up like you want and were to accidentally push both of them while in a sprint, you would suddenly drop into the small chainring. I’ll bet you would not be happy about that.
― Lennard

Dear Lennard,
I have several Campy 10-speed record and chorus wheelsets. Are campy 11-speed cassettes compatible with the 10-speed free hubs?
— Robert

Dear Robert,
Yes they are.
― Lennard