You can set it to manual shifting.

That actually depends on the shifters installed. With the newest single button TT shifters you only have one button, which usually programmed to do the rear shift only.

In my opinion you have three options:
1. Reprogram the synchro protocol such that you can stay in the small ring for longer.
2. Program either the bar end or brake shifters to shift the front derailleur and move to manual gear change using the junction box.
3. Move the chain to the small chainring and go out of full synchro. Now you’re only capable of changing gear on the rear.

It’s been a while since I programmed mine but I’m pretty sure you can make synchro shift do almost anything you want. I think you could even let it go to the small/small if you wanted.

You just need the Shimano software and the cord to plug into your computer.

The image in this thread shows how you set it up and it’s pretty close to the way I have mine. You can move the shift points anywhere you like.

https://forum.slowtwitch.com/.../?page=unread#unread

The one Thing I did not say this a tri bike with one button shifting. Button on left handle bar is for harder one one right is easier gearing. Do not see how manual is possible.

You need the E-Tube software to configure your Di2 to literally do whatever you want it to do within the context of the 4 buttons (total) you have.

Option 1
You can program the point at which Synchro would shift to the big ring, so you can select it so that it will generally stay in the small ring. (Personally, I wonder if you are on the small ring so often on a tri bike, do you have the right gearing for you and your riding conditions?)

Option 2
Semi-synchro
Allows you to control when it changes to big/small ring,

Option 3
Full manual. You just have to figure out which button you want to do what. (e.g. right brake shifter moves the rear to harder gear, right bar end moves rear to easier gear)

You can select amongst which option you want through the button on the junction box, believe it is a double press, and then each mode is confirmed by a different flashing light sequence. (but you can't change any of the parameters of each mode without the app)

If you have a D-fly wireless adaptor installed in your Di2, you can do all of this from an Android or IoS device,

Thanks for the reply. Most my training is in heavy wind conditions open farm land. I also do climbing workout once week. I am using the big chainring most the time on the Felt IA because that is what synco does. My other four bikes are the old Di2 double button. Spend most of the time in the 36. What I really hate on the IA is not knowing during out of the saddle climbing when big chain is going to drop causing a dead spot. I like to climb and it is nerve racking. Also knees do not like big chainrings on 100 mile rides shorter rides no big deal. I really appreciate your help trying to understand my options. So here is the kicker I am almost 80 already Kona Qualified. Still punch out 200-300 bike miles, 20 +running miles and a bunch of swimming every week. It is called staying in the game....thanks again

Congrats on Kona!

The wind training will help...especially on the way up to Hawi where it's been a head wind every year I've done it!

I suggest you talk to you LBS and get the Shimano D-Fly unit if you Di2 is relatively recent. It can connect to your Garmin and give you an audio warning when it shifts the front ring.

Been to Hawaii many times the wind in 98 was so hard on Q K a few riders were blown down. Hawi it is the down hill run in cross winds on wet roads that causes the most excitement. Going to bike shop going to see if I can do a up shift at 36/14 to the big ring. My Omni is going Hawaii again

As I discovered a couple of weeks ago, even "Full manual" isn't always really full manual.

If you tell the software you are using any front crank size less than -- I believe it is 53/39 -- the eTube software will simply not let you use the smallest two rings in back when you're in the small ring up front. If you're in the very biggest gear on the bike and you downshift up front, it will automatically shift the back a couple of rings as well to enforce this. Even in full-manual mode.

According to ST poster "Di2Terry" this is "gear protection control". They call it a "feature"

So if you are running a smaller crank up front you end up having to lie to the software about your crank to truly get full manual

That info is really helpful. The bike is now setup at the extreme it will allow in the 36. Have not tested it yet but if I do not like the shifting there is a plane B. Two button is available for the extensions for the 8000 derailleurs but not the brake levers. Going to change those. Go full manual. Brake lever buttons will control the rear derailleurs the extensions will work like the old normal setup setup.......thanks

I would think that you would want the buttons on your aero bars to control the rear derailleur.

Changing the shifters on the aero bars to 2 button gives you front and rear derailleurs full function up and down ...I have one button on them now so manual shifting mode does not work.