Congratulations on your new bike equipped with 12-speed Di2! If you’re like most new owners, you probably have a lot of questions about how this advanced electronic shifting system works. While the manuals that come with your bike can be a bit lacking, this guide is designed to walk you through everything you need to know about your 12-speed wireless Di2 system.
If you are instead looking for information on 10-speed or 11-speed Di2 systems, please refer to our 10/11-speed Di2 beginner manual.
This comprehensive guide covers the following topics. Click on any link below to jump directly to the section that interests you:
Understanding 12-speed Di2 Basics
What Does Di2 Really Mean?
Di2 stands for Digital Integrated Intelligence. This is Shimano’s term for their electronic shifting technology, which has been innovating cycling since the release of the first DURA-ACE Di2 7970 series groupset in 2009.
That original 10-speed system used a unique wiring setup, different from all subsequent Di2 groupsets. With the introduction of Ultegra 6770 in 2011, Shimano standardized on EW-SD50 wires and the E-Tube system. Later, the even smaller SD300 wiring standard was introduced.
But what exactly is E-Tube? Essentially, E-Tube is Shimano’s name for their electronic communication network. All Di2 systems (except the initial 7970 series) use E-Tube for communication. While Shimano hasn’t officially stated what it stands for, “Electronic-Tube” is a logical interpretation.
Di2 Software and Essential Tools
Shimano provides software to customize and update your Di2 system. The Windows software is called E-Tube Project, and for mobile devices, there’s the E-Tube Project Cyclist app. Additionally, the E-Tube RIDE mobile app transforms your smartphone into a cycling computer, though with limited sensor compatibility.
For a deeper dive into Di2 software, check out our dedicated page: Di2 E-Tube Software & Tools.
My Recommended Di2 Components
To support our website, please consider visiting my Amazon storefront. I’ve curated a list of my favorite Di2 components and tools there. Purchases made through this link help support the site at no extra cost to you.
My Amazon storefrontAmazon page
Accessing Shimano 12-speed Di2 Manuals
While this guide aims to be extremely comprehensive, it’s impossible to cover every single detail. For the most in-depth information, Shimano’s official documentation site, si.shimano.com, is an invaluable resource. Here you can find Exploded Views (EV), User Manuals (UM), and, most importantly, Dealer Manuals (DM) for all Shimano components.
Regular user manuals can be basic, but the Dealer Manuals (DM) are incredibly detailed. To find a DM, simply enter your Di2 series code into the search box and look for files labeled “DM“. For example, for 12-speed Ultegra manuals, search for “R8150“. For hydraulic shift levers, the code is “R8170“.
Similarly, for 12-speed DURA-ACE manuals, search “R9250“, and use “R9270” for hydraulic shift lever manuals.
For your convenience, we’ve also uploaded the 12-speed Di2 manuals directly to our site.
To learn more about navigating Shimano’s documentation, visit our guide on using the Shimano documentation site: si.shimano.com.
Powering Your 12-speed Di2 System: On or Off?
One of the great features of Di2 is its simplicity. There’s no need to manually switch the system on or off. It’s always ready to go.
For traditional wired Di2 systems (like rim brake setups), the system remains constantly active. The only component that enters standby mode is the rear derailleur’s BluetoothLE/ANT connectivity to conserve battery.
However, most modern 12-speed Di2 bikes use hydraulic disc brakes and wireless shift levers. These systems require a slight “wake-up” action.
The very first shift after a period of inactivity will wake up the system. You only need to do this once per ride or after longer breaks like a coffee stop, as the system enters standby after 30 minutes of inactivity.
Mastering 12-speed Di2 Shifting
If you have a DURA-ACE, Ultegra, or GRX 12-speed Di2 setup, you might have noticed buttons on top of your shifter hoods. While present, these are typically configured for auxiliary functions, not gear changes by default. However, they can be customized for shifting if desired, as explained in our guide on enabling buttons on Di2 shifter hoods.
So, how do you actually change gears? It’s intuitive! Use the buttons located on the side of each brake lever, as illustrated below:
Understanding Di2 12-speed Shifter Buttons: A guide to front and rear derailleur controls on Shimano Di2 electronic shifters.
Front Derailleur Shifting Explained
To operate the front derailleur, use the left lever. Press switch X (the larger button) to shift to a larger chainring (harder gear). Press switch Y (the smaller button) to shift to a smaller chainring (easier gear).
A simple tip to remember: larger button for larger chainring, smaller button for smaller chainring.
Rear Derailleur Shifting Made Simple
Shifting the rear derailleur is similar to the front. Use the right shift lever. Press switch X (larger button) to shift to an easier gear (larger cog). Press switch Y (smaller button) to shift to a harder gear (smaller cog).
Utilizing Hood Buttons on DURA-ACE / Ultegra / GRX
As mentioned, DURA-ACE, Ultegra, and GRX Di2 levers feature buttons on the top of the lever hoods, while 105 levers do not.
By default, these hood buttons control wireless functions, set to ‘D-fly Ch.1’ and ‘D-fly Ch. 2’.
D-Fly is Shimano’s wireless communication protocol for accessories like bike computers, cameras, and lights. These default settings often allow you to navigate screens on compatible bike computers.
However, these buttons are fully customizable. Our guide on setting up hood buttons provides detailed instructions, especially in the ‘using the mobile app’ section.
Many riders find it useful to set the left hood button to “function“. This mirrors the button on the rear derailleur, enabling on-the-fly adjustments to synchro shift mode or entering adjustment mode without taking hands off the bars.
Ultimately, the best setup is what works for you. Experiment to find your ideal configuration.
Wireless Functionality of 12-speed Di2
Yes, 12-speed Di2 systems offer wireless shifting, but primarily for hydraulic disc brake bikes. Rim brake Di2 setups are fully wired.
Shift signals are transmitted wirelessly from the levers to the rear derailleur, which acts as the central BluetoothLE/ANT hub.
However, the system isn’t completely wireless. Both derailleurs are still connected to the main battery, typically located in the seatpost, with individual wires. The battery used is usually the BT-DN300.
Wireless Di2 shift levers are powered by CR1632 batteries. These batteries are designed to last approximately two years for DURA-ACE and Ultegra levers, and up to four years for 105 Di2 and 12-speed GRX levers (two batteries per lever).
Replacing these batteries is a quick and easy process, taking just a minute. For step-by-step instructions, see our guide on replacing wireless shift lever batteries.
Interestingly, even with wireless-capable levers, you have the option to run them fully wired (except 105 levers). This wired configuration can extend the main battery life by up to 50%.
If using wired levers, and a wire becomes disconnected, the system intelligently switches to wireless mode within about 10 seconds, ensuring uninterrupted shifting.
The primary drawback of wireless hydraulic shift levers is the slightly more complex firmware update process, as detailed in our guide on updating wireless shift levers.
Di2 Security: Addressing Hacking Concerns
In mid-2024, security researchers highlighted potential vulnerabilities in wireless shifting systems, including Shimano Di2. They demonstrated replay attacks and jamming techniques.
Shimano promptly addressed these concerns by releasing firmware updates for all 12-speed rear derailleurs and wireless shifters.
While there’s no evidence of real-world bike hacking incidents, Shimano’s proactive firmware updates are a welcome security measure. It’s recommended to install these updates, either yourself or through your local bike shop.
More details on these security updates can be found in Shimano’s firmware update FAQ.
Connecting to Smartphones and Bike Computers
The rear derailleur’s wireless connectivity allows seamless pairing of your 12-speed Di2 bike with bike computers (Garmin, Wahoo, Sigma, etc.) and smartphones.
Connecting with E-Tube Cyclist Mobile App
To connect to your smartphone, download the E-Tube Cyclist app from your app store.
Enable Bluetooth on your phone and open the E-Tube Cyclist app.
On your rear derailleur, press and hold the button for 0.5 – 2 seconds. The LED will flash blue, indicating BluetoothLE connection mode.
Then, use the E-Tube Cyclist app to register a new bike or connect to a previously added bike.
Pairing with Bicycle Computers
Connecting to bike computers is generally straightforward. “Wake up” the Di2 system by shifting or pressing the rear derailleur button.
Your bike computer should then detect the Di2 system and allow you to connect.
The exact pairing process varies depending on your bike computer model. Consult these helpful guides for popular brands:
- [Garmin Support](Link to Garmin Di2 pairing guide)
- [Wahoo Support](Link to Wahoo Di2 pairing guide)
- [Sigma Support](Link to Sigma Di2 pairing guide)
Special Note for HammerHead Karoo users: Due to past conflicts, native Di2 support was removed from Karoo devices. However, a third-party app restores Di2 functionality to Karoo and Karoo 2 devices.
Troubleshooting: Bike Not Working After Mobile App Connection?
It’s a common concern for new Di2 users: connecting to the mobile app and then finding the bike unresponsive. Don’t worry, your bike is perfectly fine.
While your phone is actively connected via the E-Tube Cyclist app, the Di2 system intentionally blocks external commands. This is normal behavior, but can be initially alarming.
To regain control, simply reconnect to the mobile app and press the disconnect button within the app. Your shifting should immediately return to normal.
Monitoring Shifter Battery Levels
For bikes with wireless shift levers, battery replacement is needed approximately every two years (four years for 105 Di2 shifters). Checking battery status is very simple: press and hold both shift buttons simultaneously for about 0.5 seconds.
Each 105 and GRX lever contains two batteries, while Ultegra and Dura-Ace levers use a single battery.
Visual guide to Di2 shifter battery levels: Understanding green, red, and no LED indicators for wireless Di2 shifters.
The lever’s LED will then illuminate, indicating battery level:
- Green LED: 11% – 100% battery remaining.
- Red LED: 1% – 10% battery remaining.
- No LED: 0% battery – battery needs replacement.
When the battery level reaches 10% (red LED), you have about a month before replacement is necessary. After this point, the battery will deplete completely.
Replacing the Shifter Lever Battery: A Quick Guide
Battery replacement is straightforward and takes just a few minutes. Refer to the video above or our detailed guide: Replace Wireless Shift Lever Battery Guide.
Main Di2 Battery Life and Charging
Predicting main Di2 battery life can be tricky, especially for newer 12-speed systems. Shimano’s conservative estimate is approximately 1000km per charge.
This estimate assumes frequent front derailleur shifts. In practice, many riders experience significantly longer battery life, potentially up to 1500km or more, depending on riding style and terrain.
For extended battery life, consider wiring the shift levers directly to the main battery, which can increase battery life by around 50%.
Checking Main Di2 Battery Status
Checking the main Di2 battery level is quick and easy. Simply press the button on the rear derailleur briefly (for 0.5 seconds or less).
The LED indicator will display the remaining charge:
- Solid Green: 51% – 100% charge.
- Flashing Green: 26% – 50% charge.
- Red: 1% – 25% charge.
- Off: 0% charge – battery is depleted.
Interpreting Di2 battery level LEDs: A visual guide to understanding solid green, flashing green, red, and off indicators on your Shimano Di2 rear derailleur.
Blue LED After Battery Check?
A blue LED after a battery check is normal. It indicates the currently selected shift mode, not a battery issue.
For more information on shift modes, refer to the Synchronized Shift section.
For a handy reference guide to Di2 LEDs and button functions, download our Di2 Cheat Sheets.
Once the battery drops below 10%, the front derailleur will cease to function, allowing only rear derailleur shifting until the battery is fully depleted.
Charging Your Di2 Bike: Step-by-Step
Charging is straightforward. Locate your Di2 charge cable (EW-EC300), a USB adapter or computer, and find the charge port on your rear derailleur.
The charge port is located on the rear derailleur, towards the back of the bike. Open the port cover, connect the charging cable, and plug it into a power source.
Locating the Di2 charging port: A close-up view of the charging port with the protective cover open on a Shimano Di2 rear derailleur.
The LED on the rear derailleur will illuminate blue during charging.
Charging time typically ranges from 1 to 3 hours, depending on the adapter and battery level. The LED will turn off when fully charged.
If the LED flashes red during charging, try a different USB port or adapter.
Ensure your adapter has a current capacity of 1.0A or higher.
Note: Derailleurs are inactive during charging and will not respond to shift commands. Charging while riding via dynamo hub or power bank is not supported.
Unlocking the Rear Derailleur Button’s Multifunctionality
As you’ve learned, the rear derailleur button serves multiple purposes: battery level check and BluetoothLE connection mode activation. But it does even more.
For a quick reference to all button and LED functions, download our Di2 Cheat Sheets.
Download the Di2 Cheat Sheets.
Double-pressing the button toggles between synchronized shift modes. The LED indicates the selected mode:
- Solid Blue: Manual shift mode.
- Flashing Blue (twice): Shift mode one (default semi-synchro).
- Flashing Blue (three times): Shift mode two (default full-synchro).
For detailed information on synchronized shifting, see the Synchronized Shift section below.
A short press (0.5 seconds) displays the battery level via the LED.
Holding the button for 0.5s – 2s activates BluetoothLE connection mode, indicated by a flashing blue LED.
Holding for 2s – 5s enters adjustment mode, indicated by a yellow LED, used for derailleur adjustments.
Finally, the button can be used to pair wireless shift levers as an alternative to the mobile app.
Crash protection reset is now simplified. Simply shift through the entire cassette range up and down to reset the rear derailleur after a crash.
Exploring Shift Modes and Synchronized Shift (Syncrho Shift 12 User Guide)
All 12-speed Di2 road bikes support different shift modes, including synchronized shifting, often referred to as “syncrho shift”.
Synchronized shift intelligently automates front or rear derailleur shifts based on your gear changes, optimizing gear ratios and cadence.
Two primary synchronized shift presets are available: full synchro and semi-synchro.
- Semi-synchro (S1 default): Automatically adjusts the rear derailleur when you shift the front derailleur to minimize gear ratio jumps for smoother transitions.
- Full-synchro (S2 default): Automatically shifts the front derailleur when the rear derailleur reaches a pre-determined cog, keeping you in an optimal gear range.
- Manual Mode: Disables all automatic shifting. You control both front and rear derailleurs independently.
Customizing Shift Presets
While the E-Tube Project Cyclist app allows for extensive customization of shift presets, your bike can store two presets at a time: S1 and S2.
For a comprehensive understanding of synchronized shifting, read our detailed guide: ‘complete guide’ on Synchronized Shift.
Instructions for setting up synchronized shift via the mobile app are now on a dedicated page: setting up synchronized shift using the mobile app.
Switch between shift modes by double-pressing the rear derailleur button. The LED indicates the active mode:
- Solid Blue (2 seconds): Manual shift mode.
- Flashing Blue (2 times): Shift mode 1.
- Flashing Blue (3 times): Shift mode 2.
More details on these modes are available in our Synchroshift guide: Complete guide to Synchro Shift.
Maintaining Your 12-speed Di2: Washing and Transporting
Caring for your Di2 system during washing is simple. Di2 is designed to withstand wet conditions, just like a standard mechanical groupset.
Use water, soap, or mild bike cleaner. Be mindful of disc brake contamination.
As long as all Di2 ports are sealed with wires or dummy plugs, the system is water-resistant.
Avoid pressure washing derailleurs directly, as they are water-resistant, not waterproof. After washing, wipe down Di2 components with a towel to prevent oxidation.
Safe Bike Transportation with Di2
Transporting your Di2 bike is generally trouble-free. The main consideration is preventing accidental shifting during transit, which can drain the battery if a shift button is continuously pressed.
When placing your bike in a car or bike rack, ensure no pressure is applied to the shift levers.
It’s always wise to bring your Di2 charger and a spare CR1632 battery (for wireless levers) when traveling, even after a recent charge.
Additional Di2 Resources
For further Di2 information, explore these resources:
- Carlton Bale’s Di2 resource page: [Carlton Bale Di2 Info](link to Carlton Bale’s page)
- GPLama / Shane Miller YouTube channel: GPLama YouTube
- GCN and GCN Tech YouTube channels: GCN YouTube, GCN Tech YouTube
- Shimano Manuals: si.shimano.com (especially Dealer Manuals).
Need More Help?
This guide covers the essentials of 12-speed Di2. For more specific issues, consult our installation guides and FAQs.
If you have unanswered questions, feel free to send us a message or leave a comment below. We’re here to assist you!
