Brakes and shifters are pretty much essential when it comes to building a bike and Di2 bikes are no different. On a road or gravel bike you’ll probably want to install a Shimano Dual Control lever.

If you’re building a mountain bike, have a look at the MTB Style Shifting Switch installation guide.

This guide applies to all wired Di2 Dual Control levers. At the time of writing that is:

• Ultegra ST-6770
• Ultegra ST-6870
• Ultegra ST-R8050 / ST-R8070
• DURA-ACE ST-9070
• DURA-ACE ST-R9150 / ST-R9170
• GRX ST-RX815
• ST-R785

While there are subtle differences between all of these, they are also very much similar. I’ll ignore the obvious rim brake vs disc brake difference and show you the general process of installing a Di2 Road/GRX Dual Control lever. Also, I will not show you how to install hydraulic disc hoses or bleed the system. There are some links explaining this process at the bottom of the page.

Tools required

• 2mm and 5mm Hex wrenches. I use a Wera set (Amazon / Ebay)
• Torque wrench (5-6Nm). I use a PRO Torque Wrench (Amazon / Ebay)
• Shimano TL-EW02. Di2 wire tool.

Slide the lever onto the handlebar

The very first step is to actually slide the lever onto the handlebar. In order to do this you’ll have to loosen the lever clamp bolt. This bolt is hidden under the lever’s hood cover, so you’ll have to pull that forward to expose the bolt.

Note: if you’re installing a DURA-ACE lever then you may have to peel the cover back from the front of the lever. On most other models though, simply push the lever hood cover to the front.

Take your 5mm hex wrench and loosen the bolt enough so that you can slide the lever over the handlebar to its somewhat final position. I say “somewhat final” because you’ll probably want to spend some time later aligning both levers and fine-tuning your hand position.

Also, if you’re installing hydraulic disc brake levers you may have to loosen and rotate them to properly bleed the system. In that case it’s probably a good idea to set the final lever height and angle once you’ve bled the system.

Repeat the process for the other lever and proceed to the next section.

Set the final lever height and angle

Now move the shift levers to a position that feels right to you. Most people want a smooth transition from handlebar to the lever, but everyone is different and has their own preferences.

Once you’ve decided on your lever position, let’s make sure the levers are aligned and are the same height.

You can do this using a long bar or a piece of string that you run along the levers. The string or bar should be parallel with the handlebar. I realise this may sound a bit cryptic, so this is what it looks like:

Or, using a piece of string (brake cable in this case):

Satisfied with the lever position and height? Next stand over the bars and look down at the levers. They should be parallel to each other and the center of the bike.

Di2 wire length and slack

With the levers set to their final position it’s time to connect the Di2 wires. I won’t go into detail on how to install your Junction A.. I have a pretty good guide on installing the bar-end EW-RS910 junction and installing the below-the-stem junction is pretty straightforward.

What is important though, is the wire length. If your wires are too short you won’t be able to connect the shift lever or run the risk of accidentally unplugging it. On the other hand, if the wire is too long you’ll have excess wire, but you can usually hide most of that in the handlebar or frame.

So.. if you’re in doubt, prefer a wire that is slightly too long rather than too short.

The general Shimano rule of thumb is this:

Measure the length you need by running a piece of string along the handlebar. Then go the next size up and then add 50mm.

So if the measured length is 230mm, the next size up is 250mm and Shimano would recommend a 300mm wire.

Connecting Di2 wires

With the correct length wires in hand it's now time to install them. First run them along or through the handlebar, most likely from your Junction A to the shift lever.

If you’re experiencing difficulty running the Di2 wires through the handlebar, give a routing tool a try (I use the PRO Internal Routing Kit, but Park and Jagwire make them too).

At this point it just comes down to plugging the wires in, but first read these quick tips that will no doubtt make life easier for you:

• The lever Di2 connection terminal can angle outward
• Some levers have dedicated sprint shifters ports
• Make sure there is some slack in the wires

The Di2 connection terminal can angle outward

You can actually plug the wires in by just pushing the lever hood back and then plugging the wire in. However, things get a lot easier when you push the hood back just a bit more, allowing the connection terminal to angle outward:

Some levers have a sprint shifter port

All Di2 rim brake levers have three ports and almost all hydraulic disc brake levers have two e-tube ports (the exception is ST-R785, which has just one port).

The third port on the rim brake levers is a dedicated sprint shifter port. It can only be used to connect the Di2 SW-R610 Sprint Shifter and nothing else will work in that port. Keep this in mind when connecting your wires, as this is an easy mistake to make.

While the sprint shifter port looks different - it has a notch for the ‘fin’ on the sprint shifter wire - there is nothing stopping you from inserting a regular wire into the port. The wire will go in, but it won’t work - this sprint shift port doesn’t have the required logic circuitry to connect anything but simple switches.

Make sure there is some slack in the wires

This is perhaps the most important thing when connecting Di2 shift levers. Make sure there is some slack in the wire. Having a little ‘U’ of excess wire near the shift lever is highly recommended.

This will prevent you from accidentally disconnecting or breaking the Di2 wire when the lever moves or simply by grabbing and twisting the bar tape. Trust me, it happens. And yeah.. a lever does not move on its own.. but crashes do happen.

Even when your bike falls over or when you pull the lever hard enough, this can happen. If there is no slack in the wire at all then even the slightest of movements can be enough to loosen the wire.

Tweak your brake lever reach

You’re almost done, honest. Some people skip this step, but for those of us with small hands it is good to know that you can easily adjust the lever reach - move the brake lever towards or away from the handlebar.

The process is similar for rim and hydraulic disc levers, with subtle differences. In both cases you adjust the lever reach using the so-called reach adjustment screw.

On the rim brake levers you will find this on top of the lever body itself:

The hydraulic disc brake levers feature an adjustment screw on the lever:

In both cases you need a 2mm hex wrench to adjust the screw. Set up the reach so that you can easily use the brakes and then that’s it - you’re all done!

Except when you’re installing a hydraulic disc lever…. sorry. One final thing you can do is to adjust the free stroke - the amount of “empty” pull before the brakes engage. Once again, use a 2mm hex wrench to adjust the free stroke as you see fit.

This is what Shimano say on the free stroke adjustment:

• Stop loosening the free stroke adjustment screw when the free stroke stops increasing. (loosening the free stroke adjustment screw excessively may cause the screw to be removed from the bracket unit)
• Do not forcibly tighten the free stroke adjustment screw. Otherwise, the adjustment screw may be damaged.
• Do not remove the washer from the free stroke adjustment screw.
• Position the free stroke adjustment screw so that it does not interfere with the bracket cover.

Brake wire or hydraulic hose

That concludes this Di2 wired lever installation guide. As I said right at the start, I’m intentionally leaving out the process of installing the brake wire or hydraulic hose.

This could be an entire page on its own, but fortunately you can also figure out how to do this by reading the Shimano Dealer Manual or the Park Tool guide.