Shimano Di2 – the dark side of the metrics

Shimano Di2 Metrics

This is a short article highlighting some of the wonderful things you can do with Di2.

I’ve used 2017 Ultegra R8050 derailleurs and DuraAce R9150 shifters which offer more capabilitites than earlier models.

Apologies in advance if you already have Di2 and I give you false hope of newly supported functionality for your existing (old) hardware 🙁 If, however, you are considering Di2 for a new bike or even a less-likely upgrade then here are some of the features now in Di2 that you might find useful or just simply want to have.

Head Unit Display Metrics for Di2

You know how to choose data fields, you’ve done it before many times. You are a data field guru.

Now you are now faced with more data fields to choose from thanks to Di2.


Shimano Di2 Edge 820 GarminThese are the choices:

  • Di2 Battery Level, Gear Battery
  • Di2 Shift Mode
  • Gear Combo (Front Gear, Rear Gear), Gear Ratio, Gears

So that’s all cool enough. As you can see, you can even display a pictorial representation of the cog you are in to save you from looking down and back to check (Gears data field).

Di2 Internal Configuration – change how you shift

A simple lever and a piece of tensioned wire used to be enough in the good old days. Who would have thought there was much that could be configured with a simple gear change?

Well, there is.

  • Shift Mode (synchronised/semi-synchronised) – here you can set the back derailleur to automatically change to a similar ratio when you shift at the front OR you can control both front and rear derailleurs with one gear lever.
  • Gear shift speed – faster speeds seem to work better for me and slower speeds are supposedly more reliable. I find slower speed shifting doesn’t work if your gearing is not well aligned.
  • Max gear shifts per press – I can’t see why this shouldn’t be unlimited but if you want to limit the effects of a miss-press then you can limit the maximum number of changes to 2 cogs (or whatever other value you like)

If you think about it, on those occasions where you are selecting a gear by moving both derailleurs it might be possible to have the exact same gear ratio in each of the front rings. However, that clearly depends on which front rings and rear cassettes you have. So to automate changing around that point you have to tell Di2 what cogs (rings and cassettes) you have. Hence you use the app, as shown above!

If you change your cassette or front rings then you will need to tell Di2 you have done that. It’s much easier to change a wheel (with a different cassette) than to re-configure Di2. So you may want to save different gearing profiles if you change wheels/cassettes often.

For those of you who inadvertently shorten the life of your chains by twisting it as much as you can between small-front and large-rear gears; Di2 can also be programmed to stop those gear choices. Indeed Ultegra stops you from using the smaller two rear cogs when in the smaller front ring. So really a 22-speed Ultegra bike is a 20-speed!

Switch A External Configuration

Switch A is the button on top of the newer shifters. An action on your head set can be assigned to: a single press; a double press and/or a press-and-hold. So that’s 3 actions on two buttons…6 in total.

The Shimano app, sort-of, implies you can configure SWITCH A in the app. But you can’t, so don’t try to look for that option. In the Shimano app, all you are doing is assigning a communications channel to the switch – as shown below this is the D-FLY Channel 2. There are 4 channels.

Shimano Di2 Config
Shifter Buttons/Levers


The meaning of what happens when you press the top button (switch A) is handled on the head unit. Thus there will be variation between new head units. Here are some of the options you get with the Garmin Edge 820.

Just like with your mouse/tablet there is more than one kind of click that the SWITCH A will react to. Hopefully, this slideshow will give you an indication of where to find the options to configure what happens with SWITCH A and some of the MANY options you have, at least with a half-decent Garmin.

You can configure all these actions: Next Page; Previous Page; Record Lap; Start and Stop Timer; Start Timer; Stop Timer; Turn Backlight On; Show Map; Show Compass; Show Elevation Profile; Show Lap Summary; and Show Virtual Partner. I can certainly see several scenarios where I would find those useful, had I already preconfigured the right one 🙂 Still, it’s all very clever.

On all older shifters, you probably have the ability to swap the ‘change up’ or ‘change down’ functionality over from one lever to the other ie from Switch X to Switch Y -I’ve done that as it seemed more sensible to me to have the bigger lever, Switch Y, to move to the bigger cog. No doubt I will come to regret that choice in the future when I borrow someone else’s bike :-(.

One Final Consideration

You will need to program the exact chainrings you are using. I’m not entirely clear to me if you need to do this in one place (the app) or in two places (also the head unit, I think so). Once you have correctly done this then your FIT file will record ALL your gear changes and you can then spend hours analyzing it on Clever stuff but not that interesting for any more than 30 minutes.

Finally, keep an eye out for these boxes near Christmas. If you see one, you’ll know that Sants is being very kind and that you have been on the ‘nice’ list all year. Well done.

Shimano Di2





Reader-Powered Content

This content is not sponsored. It’s mostly me behind the labour of love which is this site and I appreciate everyone who follows, subscribes or Buys Me A Coffee ❤️ Alternatively please buy the reviewed product from my partners. Thank you! FTC: Affiliate Disclosure: Links pay commission. As an Amazon Associate, I earn from qualifying purchases.

3 thoughts on “Shimano Di2 – the dark side of the metrics

  1. So, that’s like 3 (single, double, hold) x 2 (left, right) = 6 separate functions that can be controlled using button A on both sides?

    1. Sounds right.
      you could configure one screen to show a CIQ data field that pops up a reminder mid-ride to tell you how you configured the other 5. I’d never remember.

  2. Does anyone know if using a Garmin 1000 with Di2 components will shorten battery levels more than without the Garmin connected via bluetooth?

Comments are closed.