Below is a post from another forum. My DN-1101 arrives tomorrow so I will have some first hand experience over the weekend.
"I updated my 6870 derailleurs to the latest firmware and set up sychro
shift. Before I start, if you hate motorized derailleurs or are going to
be snarky and say "hey, why don't they just make it telepathic?" or
something like that, this isn't the thread for you. If you love Di2 like
I do, you might like this thread. Luvahs gunna love. I'm not going to
try to sell anybody on Di2.
I think synchro shift is awesome. I've only had one ride out on the road
with it because the storm hit the next day. But I have also done a
couple of indoor workouts. I am running 36/52 and 11/28. The way I have
mine mapped is it will go to the 25 while in the 52, but instead of
shifting to the 28 with one more click, it shifts down the the 36 up
front and down to the 21 in back. You do notice the shifts when going in
this direction. It shifts the big ring and then the two shifts in back.
But it does not feel any different than what I usually do manually. And
since you are rarely attacking and going one gear easier at the same
time, it feels normal to me.
Going in the other direction is where I really like the system. My
mapping is that it will drop down to the 17 while in the 36, but instead
of dropping to the 15 with one more click, it will shift to the 52/21.
That shift feels totally seamless. It feels like the front and rear
shifts occur simultaneously. In other words, it feels like you shifted
to the 15. It's that smooth to me. I tried it while going hard up a
steep hill and doing some flat sprints and it is so smooth. I haven't
touched the left shifter since setting up synchro and haven't even
thought about it.
You can change these mapping points. You can use more of the cassette
while in the little ring if you want. You can also change which cog it
shifts to since some riders might want a slightly harder or easier gear
with the shift. It's all customizable to a point, but some combos (ones
that just don't make sense anyway) are not available.
There is also semi synchro mode. I didn't really understand this mode
when I first read about it. Here is what it does. You still use the left
shifter and no auto shifting occurs as you move through the range in
the back. What semi synchro does is shift the rear when you shift the
front. You can set whether it shifts 2 or 3 cogs when you shift up
front. For instance, if I have it set for 2 cogs change on both upshift
and downshift and I am currently in the 36/15 and then I shift to the
big ring (using the left shifter), it will shift the back to the 19. Or
if I am in the 52/21 and shift the front, it will shift the rear to the
17. You can set the number cogs independently for the upshift and
downshift. You might want it to go 2 cogs bigger when shifting to the
big ring and 3 cogs smaller when shifting down the to the little ring.
It's up to you. Note that your options are limited to a change of 2 or 3
I liked the full synchro enough that I didn't try the semi synchro out
on the road yet. But I plan to at least try it. If you have 6870, 9070,
or R9150, I encourage you to at least try snchro.I did not think I would
like it. The reason I thought that was when I shift up front, it's
usually because I want a bigger jump in the gearing. At least, that's
how I've trained myself over the years. Now I just shift when I want and
don't "plan" that shift up front.
Keep in mind that you can manually shift the front in full synchro mode.
The question becomes "what happens to the mapping after I do that?"
There is no great way to describe this but I'm going to try. If you do
shift the front, the system will not do a double shift until the mapping
is "back on track". For example, and bear with me here while I try to
explain. My map is set to shift to the big ring when I am in the 36/17
and click for a harder gear. So instead of shifting to the 36/15 it goes
to the 52/21. Now, if I am in the 52/15 and manually shift the front
derailleur to the 36/15, I can now shift to the 36/14 and 36/13. I am
"off the map". It will not double shift until I get back on the map and
go back to the 36/17. Then if I try to go back down to the 36/15, it
will then double shift to the 52/21.
I'm sure it is the same in the other direction too. But the way I have
mine set up (double shifting to the 36/21 instead of going to the
52/28), the only manual front shift to the big ring that would be "off
the map" would be if I shifted from the 36/28 to the 52/28. Not a smart
idea to begin with and as soon as I shift to the 52/25, I'm back on the
I hope that helps"