Everything you need to know about the Shimano Di2

Mar 4, 2024 10 min

Everything you need to know about the Shimano Di2

The Shimano 12-speed Di2 groupset

For many, the Shimano 12-speed Di2 is the queen of the shifting groups. So that you can also get the full potential out of it, we at buycycle have summarized all the most important tips and tricks around the electric circuit. In Nic's YouTube video and in this blog post you will learn everything about the 12-speed Di2, from the battery check, the different modes and the fine-tuning of the front derailleur, to the E-Tube app!

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Let's start with the function button: it is the alpha and omega of any adjustments you can make and is located on the outside of the rear derailleur on the newer models. On the inside, you'll find a small LED light that shows you all the information you need in the following steps.

1. Battery check.

To check the battery status of your Di2, click the function button once. The battery is charged between 100% and 50% if the LED is permanently green. If it flashes green, it is between 50% and 25%. If the LED lights up red or completely off, you should reach for the USB cable and recharge the battery.

The central battery of the Di2 sits mostly in the seatpost. Still, the cable that was supplied to you in the normal case, you can simply connect to a USB charging cable and plug in the charging socket on the rear derailleur left by folding up the protective device of rubber briefly. However, ensure you insert the plug correctly and do not use force to avoid damaging the charging socket.

The shift levers on the handlebars are not connected to the central battery but are powered by their own button cell batteries. To check their status, press both shift buttons on one lever simultaneously, and as long as the LED on the hood is green, you can cycle and shift with peace of mind. If this LED lights up red, the batteries are only under 10% charged and should be replaced within the next month.

2. Switching modes.

The Shimano Di2 system offers three different shifting modes. In the first mode, you shift manually, using a mechanical shift group, and operate the front and rear derailleurs independently.

The second mode is the semi-synchronous mode. Here, the rear derailleur automatically shifts up or down to a corresponding sprocket when shifting on the front derailleur. This automatic adjustment ensures that you are always in a solid gear ratio and can be configured to shift up to 4 sprockets. However, the default setting of the semi-synchronous shift adjustment is designed for two sprockets.

The third and final mode is fully synchronized shifting. In this mode, the front derailleur automatically shifts up or down when the rear derailleur is shifted over a certain sprocket. Likewise, the rear derailleur automatically moves up or down to compensate for a change in the front derailleur. No matter how and where you shift in the third mode, you are always in the optimal gear ratio.

To switch from one mode to the next, turn back to the function key and press it twice quickly. When the LED is solid blue, you are in manual mode; when it blinks twice, you are in semi-sync mode, and blinking three times means you are in full-sync mode.

"If you want to briefly check which mode you are currently in without changing it, simply press the function key once, and the battery indicator will be followed by the blue light, which will tell you your current mode." - Alice Huot @buycycle

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3. Fine-tuning of the shifting group.

In the finer adjustment of the gearbox, starting at the rear derailleur, you will find the two limit screws and the B-tension screw.

The first step is to check the B-bolt. This can adjust the distance between the rear derailleur rollers and the cassette. However, this is usually already set correctly at the factory. To adjust, shift to the small chainring at the front and the largest sprocket at the rear (i.e. the lightest gear).

The distance between the guide pulley wheel and the largest sprocket varies depending on the cassette used. According to Shimano's user manual, the distance for Dura-Ace and Ultegra cassettes should be as follows:

11-28T - 18mm
11-30T - 14mm
11-32T - 10mm
11-34T - 6mm

For 105-casettes:

11-34 - 10mm
11-36 - 6mm

Once the B-screw is correctly adjusted, the next step is to fine-tune the gears. To do this, shift the chain to the fifth sprocket from the bottom. The chain must lie precisely on the middle sprocket. Then, hold down the function button until the LED lights up yellow, confirming that you are now in adjustment mode. From here, you can fine-tune the rear derailleur by pressing the buttons on the right shift lever.

"When you shift up, the rear derailleur moves inward; when you shift down, it moves outward." - Anja Benson @buycycle

Shift up until you hear the chain rubbing as if it wants to shift to the next sprocket. Now shift down 5 times or press the corresponding rear derailleur button 5 times. Your jockey wheel on the rear derailleur should now align with the sprocket. A final check never hurts. Shift through all gears once to ensure everything is running smoothly. If not, repeat the entire process and downshift only 4 times this time instead of 5.

Now, you can turn to the front derailleur and adjust the upper and lower limit. This prevents the chain from rubbing against the front derailleur and ensures it does not fall off the chainring. Shift to the largest chainring and the smallest sprocket to set the upper limit. Then, go back into adjustment mode and start fine-tuning the front end using the buttons on the left shifter.

"The goal is for the distance between the chain and the outer plate to be 1 mm. Then, click on the function button again to exit the setting mode." - Alice Huot @buycycle

Shift to the smaller chainring and the largest rear sprocket to set the lower limit and repeat the process. At the latest, your gear should run properly.

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4. E-Tube app.

With the E-Tube app from Shimano, you can configure the modes even more precisely and adjust the buttons, check the battery status, and update the firmware. Download the E-Tube Project app and connect it via Bluetooth with the Di2.

To do this, press the function button on the rear derailleur until it flashes blue, and your shifting group is thus ready to be paired. Then follow the steps displayed in the app and once your bike is connected, you can use the full Di2 potential.

So much for the Di2 circuit: For questions about the Shimano shift groups is our team is always there for you and if you need further tips and tricks around the bike you can have a look at our numerous other blog articles! And if you are so enthusiastic about the Di2 now that you want to ride it immediately, then we surely have a suitable used bike for you on buycycle.com. Until then, we wish you first of all: Happy indexing, happy cycling!

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