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Di2 for Dummies - beginner's guide to Di2

Published March 30, 2020 by BetterShifting, Last updated November 17, 2020

When you buy a Di2 bike it generally does not come with a Di2 manual. And even when it does it is usually horribly outdated or full of information you just don’t need right now. On this page I’ll explain the Di2 basics – everything you need to know to use your Di2 bike to its fullest potential.

Di2 basics

There is a lot of Di2 information out there, but it’s all very fragmented. This guide is meant to help you get started. Some things I think every Di2 owner should know are:

What does Di2 mean?

Di2 stands for “Digital Integrated Intelligence” – Shimano’s version of electronic shifting. DI2 gives you instant, accurate, lighting-fast shifts the first and every time, at the push of a button. Even in the most extreme conditions, shifting is precise and controlled. You can change gear even under heavy load while climbing or accelerating. With DI2, you are in complete control.

Di2 is available on road bikes, mountain bikes, e-bikes and since 2019, gravel bikes.

How do I shift a Di2 bike?

So you may or may not have found the buttons on top of your shifter hoods, but those don't actually change the gears. So how do you shift a Di2 bike? How do you change gears with Di2? Simple! Just press the buttons on the side of each brake lever as shown in this image:

Shift the Di2 Front derailleur

In order to shift the front derailleur you use the left lever and press either switch X (the bigger button) or switch Y (smaller). If you find it hard to remember which button shifts up or down, think of it this way: pressing the larger button will shift to a larger chainring. Pressing the smaller of the two buttons will shift to the small ring - an easier gear.

Shift the Di2 Rear derailleur

Shifting the rear derailleur works just like shifting the front derailleur - you press either switch on the side of the right shift lever. Pressing switch X (larger button) will shift to an easier gear - a larger cog or sprocket. Pressing the Y button will shift to a smaller cog or sprocket - a harder gear.

How often do I charge my bike? And how?

A modern Di2 battery is said to last between 2000 and 5000 kilometers per charge. This depends a bit on how often you shift and also your shifting style. The front derailleur has to work harder than the rear derailleur and thus also consumes more energy. This means that if you use the front derailleur a lot your battery will run out a bit quicker – don’t let this stop you from using the front derailleur though. It takes most people months to ride 2000-5000km and most Di2 users don’t charge their bikes more than three times a year.

Once the battery level reaches 10% the front derailleur will stop working. This way the most battery-hungry operations are disabled and you should be able to finish your ride using just the rear derailleur.

So how can you tell the battery level? If you’ve got the EW-WU111/101 Wireless Unit or a mountain bike with a System Information Display – just look at your Wahoo/Garmin or the display.

Don’t have either of those? Press and hold any of your shifter buttons for half a second. The left LED on your junction box will illuminate to indicate the charge left in the battery. Shimano recommend charging the battery when the level gets below 25%.

How do I charge the battery?

First, unpack that SM-BCR2 charger! One end of it plugs into your bike, the other (USB) end goes into either a laptop or an AC adapter with USB port (mobile phone charger adapter for example). The order in which you plug your devices in does not matter. Just connect the bike to the charger and leave it in until the orange charging indicator switches off – this can take up to 1.5 – 3 hours.

Can’t find the charging port? Its location depends on your bike configuration. If your bike has an internal battery you’ll have to plug the charger into the junction box – either below the stem/handlebar or integrated into the frame. It has a little cover that you can open using a screwdriver or knife.

Does your bike use an external battery? Then your charger will most likely plug directly into the battery. Have a look at the image below for some example charging port locations.

Important: Shimano recommend you use an AC adapter with a voltage of 5.0 Vdc and with a current equal to or higher than 1.0 Adc. If you use an adapter with a current lower than 1.0A it may “heat up, potentially causing a fire, smoke, overheating, destruction, electric shock, or burns“. Also, it could result in a poorly charged battery.

If you have to use a computer or laptop to charge your bike, use a USB 3 port (usually blue) if you’ve got one – the (maximum) current on USB 3 ports is higher and it’ll charge quicker.

What does the button on the Junction box do?

Both the current and the previous generation Di2 have a button on the Junction box. Depending on what battery you use, the button does different things. If you use it combined with one of the old batteries (external SM-BMR1, SM-BMR2, or internal SM-BTR2) it:

  • Enters adjustment mode if you press-and-hold the button for 0.5 seconds
  • Enter rear derailleur crash protection reset mode if you press-and-hold the button for 3 seconds

The modern Di2 batteries allow you to enter Bluetooth LE connection mode. Note that this Bluetooth connection only works if you have a Wireless Unit on your bike. With a BT-DN110 or BM-DN100 battery installed:

  • Press-and-hold the button for 0.5 seconds to enter Bluetooth LE connection mode
  • Press-and-hold the button for 2 seconds or more to enter adjustment mode
  • Press-and-hold the button for 5 seconds or more to trigger rear derailleur crash protection reset

Also, if you have a synchro-shift enabled bike, pressing the button twice will let you switch shift modes.

Depending on what mode you’re in different lights come on. Confused? Read on..

What do those lights mean?

When you check your battery level different lights come on depending on the charge levels:

  • Green for two seconds: 100% battery
  • Blinking green five times: 75% – 50% battery
  • Red for two seconds: 50% – 25% battery
  • Blinking red five times: 25% – 0% charge left

Modern Di2 builds will switch on additional lights right after displaying the battery status. These show you the currently selected shift mode:

  • Green and red lit for two seconds: manual shift mode
  • Green and red blinking two times: shift mode 1 semi synchro shift
  • Green and red blinking three times: shift mode 2 (full) synchro shift

Pressing the button can trigger other modes, as described above. The corresponding lights are:

  • Adjustment mode: red led illuminated while in this mode
  • Bluetooth LE connection mode: green and red flashing in alternating order (15 seconds)
  • Rear derailleur crash protection reset: red fully lit and then blinking red (after 5 seconds)

Why doesn't my mobile phone connect to my Di2 bike?

If you've read the little bit of paper that is the Junction A manual then you may have seen that you can connect your mobile phone or tablet to your bike. The document shows you how to enter pairing mode and how to make connections.

However, on road bikes this wireless (BluetoothLE / ANT) functionality is only available if you've got a D-Fly or Wireless Unit installed. No matter how much your bike cost, it most likely does not come with a D-fly. These units are installed afterwards.

On mountain bikes and e-bikes this wireless functionality is included in the display.

Shift modes / Synchronized shifting

All road Di2 builds that use the modern BT-DN110 battery support different shift modes and synchro-shifting. Mountain bikes also need an Information Display (SC-M9050, SC-M9051, SC-MT800).

This means the system will switch the rear derailleur when you change chainring, or shifts the front derailleur automatically when you shift the cassette to a certain sprocket.

I've written posts on synchronized shifting before: Synchroshift: how does it work and How to customize Synchroshift settings, so feel free to read those if you want to know more about synchronized shifting. You can also set up synchronized shifting using the mobile app, if you have a wireless unit installed.

You can change between the shift modes by double pressing the button on your junction box. When you do this the bike cycles through three modes:

  • Manual mode - Indicated by solid red/green leds. This is traditional, full-manual shifting.
  • Shift mode 1 (S1) - Indicated by both red and green leds flashing twice. The default S1 mode is semi-synchro: automatically shift the rear derailleur when you shift the front derailleur.
  • Shift mode 2 (S2) - Red and green leds flash three times. By default this is full-synchro and this automatically shifts the front derailleur as you shift the rear derailleur.

More information on these shift modes can be found on the Synchroshift: how does it work page.

How can I change settings?

If you're on Windows you can use E-Tube Project software to connect your bike to your computer and change a variety of settings:

However, if you are a Mac user then you're out of luck. Shimano haven't made the software available for Mac. GPLama has published a video on running E-Tube Project in VirtualBox. Have a look at his video on that and also his Di2 playlist for some more nice videos.

Also, if your bike has a D-fly installed you will be able to change settings using your mobile phone (Android and iOS) or tablet.

How do I update firmware on my bike?

Sometimes a firmware update is required in order for features to work, or to fix issues. One example is synchronized shifting. Synchro shifting is enabled on older generation Di2 if the firmware is up-to-date and the other requirements (see above) are met. You can read how to update your Di2 firmware on this page.

There are buttons on top of the shifter hoods?

If you have a current generation road or gravel Di2 system press the top of your shifters and you’ll see there’s a button on top of each shifter. The series that have these buttons are: Ultegra R8050/R8070, DURA-ACE R9150/R9170 and GRX. Do you have and older generation bike but want to have buttons on the shifters? You probably can – have a look at the compatibility charts and see whether your system is compatible.

Even if you do have the buttons, they probably don’t do anything. They are set up to control your Wahoo/Garmin by default, even if you don’t have an EW-WU111 Wireless Unit. You can use the e-Tube project software to change the button functionality.

Should I take special care washing my bike?

When it comes to washing your bike don’t worry about the Di2 components. Your bike won’t electrocute you when riding in torrential rains and it also won’t explode if you get it wet washing your bike.

Just like you would with a mechanically shifted bike, use water and soap or any other cleaner. Using a garden hose is fine, but high-pressure washing your hubs or bearings is not encouraged.

How do I safely transport my bike?

Not much can go wrong transporting your bike. The only thing you should keep in mind is that a Di2 derailleur will try to shift and keep trying when a shifter button is pressed. This means that if you puts your bike in the back of your car you should take care that your bike is not trying to shift all the way to your destination – that would mean getting there with an empty battery. Speaking of empty batteries – it’s a good idea to bring your charger with you, even if you just charged your battery.

Shimano manuals and other resources

There is a lot of other information on Di2 out there, you just have to know where to look. Carlton Bale has an excellent page with in-depth Di2 information, GPLama / Shane Miller has a bunch of videos up on Youtube and of course there’s GCN and GCN Tech as well.

If you’re looking for more information you could of course visit the Shimano Tech website – si.shimano.com hosts all of Shimano’s manuals and even exploded views of most components they make. Simply search by keyword or series and then look for the ‘Dealer manual’ – those contain the most information on how to adjust or configure your bike. I’ve also uploaded them to BetterShifting.com:

Yes, but how do I…

Looking for something I forgot to mention? And it’s not in the Frequently Asked Questions? Don’t hesitate to contact me – I’ll try my best to help you with any issues you have!