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Each shifter has **two** buttons, and they're **not** 12-speed compatible. If you want to build a 12-speed time trial bike, please read the [building a 12-speed

di2-dealer-manual-dura-ace-9070

DURA-ACE 9070 Dealer Manual

These shifters are compatible with carbon fiber handlebars (but only with aluminum inserts where the brake levers are installed) or aluminum handlebars. The **handle inner diameter** is 19.0 – 22.5mm.


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Building a 12-speed Di2 Time Trial (TT) or Triathlon bike isn't as straightforward as you might think. This guide shows what components you can use, and how to connect the SD50 type shifters and SD300 drivetrain to each other.

Build a 12-speed Di2 Time Trial / Triathlon bike

Ever since [I built that Cinelli](/build-log-cinelli-veltrix-disc-di2/) a few years ago, my 6870-series Di2 has been on Zwift duty - installed on my dedicated indoor bike. It worked great, but I didn't use the front derailleur all that much. Mainly because I just did a lot of ERG mode workouts. 

At the same time, my commuter bike was restricted to 1x, and there were times when I wanted more gears. 

When I spotted Profile Design's [Aeroport adapter](https://www.profile-design-eu.com/products/aeroport-di2-rs910-adapter) I could no longer resist - it was time to move my old Di2 gear to the commuter bike! Not only would I gain a front derailleur and therefore more gears, it would also let me experiment with the [7972 series satellite shifters](/component/dura-ace-10-speed-sprint-shifter-sw-7972/) my [local bike shop](https://koers.cc) gave me.

![SW-7972 box](https://assets.bettershifting.com/aeroport_commuter_0_box_6fe06eb23a.jpg)

## Aeroport? What's that?!
The Aeroport is a [Profile Design product](https://www.profile-design-eu.com/products/aeroport-di2-rs910-adapter) that will let you secure the [EW-RS910 junction](/component/frame-handlebar-junction-a-ew-rs910/) as well as the [BT-DN110 Internal Battery](/component/internal-battery-bt-dn110/) in your aero bars. 

Why would you not just put the [EW-RS910](/component/frame-handlebar-junction-a-ew-rs910/) in one of the drops? 
Well, time-trial bikes generally don't have drops. Sure, you could use the older [SM-EW90-B below-the-stem junction](/component/below-the-stem-junction-a-sm-ew90/) instead, but that is hardly aerodynamic, and it looks a bit messy.

And yeah… my commuter isn't really a time-trial bike. It does have a regular road handlebar with drops. I thought it'd be a fun experiment to put the battery in the aero bars, and that's what I did!

## SW-7972 and Ultegra 6870 are not compatible
If you've ever played with older Di2 components, you may know that the SW-7972 10-speed DURA-ACE shifters and 11-speed Ultegra 6870 [are not compatible](/in-depth-guide-on-upgrading-your-old-di2-bike/). 

The 7970 series has a different plug and will only work with other 7970 series components. It does not work with anything other than 7970 Di2.

<LImage alt="7970 plug vs SD50 plug" src="https://assets.bettershifting.com/upgrade_7970_plug_8027f19974.jpeg" width="900" height="385" caption="EW-SD50 wire on the left, 7970 Di2 wire on the right" />

However, these SW-7972 satellite shifters are very much like [SW-R610 sprint shifter](/component/remote-sprint-shifter-sw-r610/) and the [12-speed SW-RS801 satellite shifters](/component/dura-ace-12-speed-satellite-drops-sprint-shifter-sw-rs801-s/). 

They are *dumb* shifters, without any firmware. Plug them into the dedicated satellite shifter port, tell E-Tube Project/Cyclist that you're using satellite shifters and that's it, they'll work.

*Any* ‘dumb' button will work in the satellite shifter ports, as long as the plug fits.

Obviously, the 7972 plug doesn't fit my [ST-6870 shift lever](/component/ultegra-dual-control-lever-st-6870/) *satellite shifter port*, but there is a way around that. You see, regular [SD50](/component/di2-electric-wire-ew-sd50/) plugs *do* fit into that port… 

To make the SW-7972 shifter work I simply took one of my spare [SD50 wires](/component/di2-electric-wire-ew-sd50/), cut it in half, and then spliced the SW-7972 wire into that. 

When done correctly, you end up with two SW-7972 shifters with [SD50](/component/di2-electric-wire-ew-sd50/) connectors.

Let's walk through the process step by step. This is what I started with, [the SW-7972 sprint shifter](/component/dura-ace-10-speed-sprint-shifter-sw-7972/).

<LImage alt="SW-7972 sprint shifter" src="https://assets.bettershifting.com/aeroport_commuter_1_SW_7972_23fcf720fd.jpg" width="1150" height="602" />

It was given to me by a local bike shop, [Koers.cc](https://koers.cc). It was of no use to them anymore, and they figured I could use it somehow.

So yeah… I cut it up.

<LImage alt="SW-7972 sprint shifter cut up" src="https://assets.bettershifting.com/aeroport_commuter_2_SW_7972_8d4811b5e6.jpg" width="1150" height="631" />

Even though the 7970 series uses a 5-wire system, each of the sprint shifter wires has just two tiny wires inside. 

See that "**KG**" sticker on the shifter? That means this component was made [July 2012](/frequently-asked-questions/how-can-i-determine-a-shimano-component-manufacturing-date/). 

Next, I took an [EW-SD50 wire](/component/di2-electric-wire-ew-sd50/), and cut that in half.
<LImage alt="Cut up an EW-SD50 wire" src="https://assets.bettershifting.com/aeroport_commuter_3_cut_SD_50_35e6922add.jpg" width="850" height="687" />

Inside were - no surprise here - two small wires.

<LImage alt="Splice two wires together" src="https://assets.bettershifting.com/aeroport_commuter_4_sd50_7970_209c1313d6.jpg" width="1150" height="639" />

The SD50 wire is shown on the left, the [SW-7972 shifter](/component/dura-ace-10-speed-sprint-shifter-sw-7972/) and wire on the right.

Stripping the wires was the hardest part of the process. They may look pretty beefy in the photo above, but keep in mind that the diameter of an SD50 wire is just **2mm**.  Each of the small wires inside is *less than* 1mm in diameter.

It took me a couple of tries to get it right, but eventually, I stripped the wires.  

All that was left now was to splice the wires - connect the two together. There are [several methods of doing so](https://www.youtube.com/watch?v=r7GlDBge_WU). I went with the soldering method, but the others would probably work well enough too.

<LImage alt="Test the levers" src="https://assets.bettershifting.com/aeroport_commuter_xy_three_images_levers_dc3f040021.jpg" width="1150" height="500" />

I repeated the process for the other sprint shifter and other half of that SD50 wire, and made sure to test the end result before I actually installed it on my bike.

<YouTube videoId="md9iKYdozNY" />

## Installing the battery and junction
With the sprint shifters working just fine, it was time to unpack the Aeroport and see how that would fit. I decided to put the [EW-RS910 junction](/component/frame-handlebar-junction-a-ew-rs910/) in the right aero extension, and the [BT-DN110 Internal Battery](/component/internal-battery-bt-dn110/) in the left. 

Why not the other way around? Ultimately this is up to the user, but the [EW-RS910 junction](/component/frame-handlebar-junction-a-ew-rs910/) is usually installed in the right handlebar drop. It just feels natural to me to have it on that side, so that's where I put it.

<LImage alt="Aeroport commuter boxes" src="https://assets.bettershifting.com/aeroport_commuter_box_6b17da75d7.jpg" width="1150" height="486" />

The Aeroport comes in a little box, and inside you'll find two pieces of plastic/rubber - the battery/junction holders.

<LImage alt="Profile Design Aeroport" src="https://assets.bettershifting.com/aeroport_commuter_6_on_stone_004a86460f.jpg" width="1150" height="637" />

You essentially slide these over the battery and the junction box. That looks something like this:

<YouTube videoId="f19kebNx1mA" />

Note that even though I've used the older [SM-BTR2 battery](/component/deprecated-internal-battery-sm-btr2/) in the image above, that is not the best battery for this bike. With only one button at the end of each aero extension, that means I won't be able to shift the front derailleur. 

This **BTR2** battery does **not** support [synchronized shift](/di2-synchronized-shifting-the-complete-guide/), but the newer [BT-DN110](/component/internal-battery-bt-dn110/) does. 

I may still swap out the battery at some point, but for now, just being able to shift the rear will suffice. It *is* my commuter, after all. I'm not going to ride time trials using this bike.

## Wiring up the battery, junction, and shifters
With the Aeroport figured out, I decided it was time to install everything on the bike and connect the [shifters](/component/ultegra-dual-control-lever-st-6870/), [battery](/component/deprecated-internal-battery-sm-btr2/), and [EW-RS910 Junction](/component/frame-handlebar-junction-a-ew-rs910/).

This should be a piece of cake. After all, the satellite shifters plug into the regular shift levers, and you can then choose from [a number of methods to connect everything to the EW-RS910 Junction](/component/frame-handlebar-junction-a-ew-rs910/).

However, since I'm installing both the battery and *and* the main junction in the aero bars, things got a little complicated… and I decided to draw some wiring schematics first.

Each [ST-6870 shifter](/component/ultegra-dual-control-lever-st-6870/) has two SD50 type ports, and one satellite shifter port. The [EW-RS910 junction](/component/frame-handlebar-junction-a-ew-rs910/) has two ports as well, and the battery has just one port.

<LImage alt="Aeroport commuter wiring schematic" src="https://assets.bettershifting.com/aeroport_commuter_7_schematic_633a94ddb2.png" width="1150" height="746" />

You can definitely get this to work, but it takes careful planning. For example, you could

- Connect the left shifter to the battery
- Connect the left shifter to the [EW-RS910 Junction](/component/frame-handlebar-junction-a-ew-rs910/)
- Connect the left shifter satellite shifter to its dedicated port
- Connect the right shifter to the [EW-RS910 Junction](/component/frame-handlebar-junction-a-ew-rs910/)
- Connect the right shifter satellite shifter to its dedicated port
- Connect the right shifter to the rest of the system using a long [EW-SD50 wire](/component/di2-electric-wire-ew-sd50/)

Or any other combination of the above. As long as all components are connected, they will work.

In my specific case though, I had only a limited set of [EW-SD50 wires](/component/di2-electric-wire-ew-sd50/) to work with - the ones in my big "*Di2 stuff*" box. They didn't match my situation perfectly, so came up with an alternative wiring setup. 

Besides, I didn't really like having three wires come out of each shifter, and I wanted to have a spare E-Tube port… just in case. 

So I added a second [SM-JC41 internal junction](/component/internal-junction-b-sm-jc41/) to the system. 

That looks like this:

<LImage alt="Aeroport commuter wiring schematic" src="https://assets.bettershifting.com/aeroport_commuter_8_schematic_connected_d005cb0b82.png" width="1150" height="883" />

This seems alright, but I'm not done yet. 

I haven't connected the satellite sprint shifters yet, so let's do that now. I placed the satellite shifters at the end of the aero bars, letting me shift the rear derailleur at all times.

This means I have to run a Di2 wire from each aero extension to the closest shift lever, adding yet another wire to the handlebar:

<LImage alt="Aeroport commuter wiring schematic" src="https://assets.bettershifting.com/aeroport_commuter_9_schematic_full_94f70c4526.png" width="1150" height="811" />

This looks OK, right? Tell me it's not just me going crazy here. 

Most of the wires should be completely hidden from view. They'll be in the aero bars, or underneath the handlebar tape. 

With the wiring all thought out, let's actually install the components. A diagram is nice, but it won't make the derailleurs shift.

## Installing the components on the bike
Before installing the battery and all the wires, I checked whether or not I would actually be able to route the Di2 wires the way I intended. My main worry was the battery - it's 15cm in length, so would I actually be able to access the aero bar's wiring port?

Well…. It turns out I can!

<LImage alt="Fit the battery into aero bars" src="https://assets.bettershifting.com/aeroport_commuter_10_battery_fit_31dae360ac.jpg" width="1150" height="747" />

Only just, but yep - looks like we're all good. Let's go!

With a wiring setup this extensive, where do you start? I decided to start where everything comes together - that [SM-JC41 junction](/component/internal-junction-b-sm-jc41/). 

I used the [PRO Internal Routing Tool](/component/pro-internal-routing-tool/) to run all wires through the aero bars, and connected these to the JC41 junction. This meant connecting the battery, as well as running a Di2 wire to the left shift lever.

<LImage alt="Junction and battery installed in the aero bars" src="https://assets.bettershifting.com/aeroport_commuter_11_battery_jc41_going_in_875a2bf84e.jpg" width="1150" height="810" />

Here is an image of the battery right before I connected it and inserted it into the aero bar. 

On the right side of the stem, you can see the [SM-JC41 junction](/component/internal-junction-b-sm-jc41/) sticking out of the aero bar, with the battery wire and left shifter wire already plugged in.

There was a bit of room for the JC41 junction to bounce around, and that's not surprising. It's only 30.5mm long, 14.5mm wide, and 8mm high.  I wrapped it in a bit of tape to stop it from moving around. No one likes noisy bikes.

Next, I connected the [EW-RS910 Junction A](/component/frame-handlebar-junction-a-ew-rs910/) to the B-junction and the right shifter, and installed the [Profile Aeroport holder](https://www.profile-design-eu.com/products/aeroport-di2-rs910-adapter). I shoved it into the aero bar, and that was that. All done!

<LImage alt="Both battery and junction completely installed" src="https://assets.bettershifting.com/aeroport_commuter_12_battery_junction_installed_0e84efc21d.jpg" width="1150" height="883" />

Well, not really.

While this looks okay at first glance, those two wires crossing over from left to right look problematic. This is a commuter bike, and it'll probably see some above. I definitely don't want these wires to get caught in someone else's handlebar, and damaged in the process.

Besides, having the two wires just hanging there looks pretty bad. 

<LImage alt="Aeroport commuter wires crossing over" src="https://assets.bettershifting.com/aeroport_commuter_13_wires_are_crossing_9442df1d82.jpg" width="1150" height="688" />

Looking at my wiring schematic, these wires turning out this *messy* isn't a surprise at all. In fact, I saw this coming and thought of a solution before I even got started. 

## Profile Design Aerobridge
Not only do Profile Design make an [Aeroport](https://www.profile-design-eu.com/products/aeroport-di2-rs910-adapter) to securely hold the Di2 battery and main junction, they also created the "*[Aerobridge](https://www.profile-design-eu.com/products/ucm-aerobridge-1)*".

<LImage alt="Profile Design Aerobridge" src="https://assets.bettershifting.com/aeroport_commuter_14_aerobridge_4a790d4921.jpg" width="1150" height="592" />

What's this? Well, it's basically another piece of plastic that you secure to both aero bars using two clamps and bolts, *bridging the aero* between them.  
(sorry)

The Aeroport is a "*multi-purpose computer mount that can be positioned on any round section of the aerobar*".  This is exactly what I'll do - and at the same time, it's a neat bit of camouflage for those wires. 

Before I show you the finished bike, here's one last work-in-progress image.

<LImage alt="Aeroport commuter from the front, almost done" src="https://assets.bettershifting.com/aeroport_commuter_15_almost_done_63bd6dfcb7.jpg" width="1150" height="615" />

The Aeroport is in place, but there's still a lot of exposed wire in the shot. At this point I decided to wrap the handlebars and aero bars, hiding all of these wires from view.

(and don't worry, I also installed the brake cables)

<LImage alt="Aeroport commuter from the saddle" src="https://assets.bettershifting.com/aeroport_commuter_16_done_from_saddle_804492c15e.jpg" width="1150" height="705" />

This is what it looks like from above. Pretty neat, right?

<LImage alt="Aeroport commuter finished - from above" src="https://assets.bettershifting.com/aeroport_commuter_17_from_above_854032562e.jpg" width="1150" height="989" />

And finally, here's the view from below. You can see some exposed wires, but unless you look underneath the handlebar, they're all hidden from view.

<LImage alt="Aeroport commuter from below" src="https://assets.bettershifting.com/aeroport_commuter_18_from_below_3d54f8973d.jpg" width="1150" height="764" />

## What's next?
That's it - the bike is all done. I've ridden it to work a couple of times, and it rides just like any Di2 bike should - perfect and immediate shifting.

So what's next for this bike? 

Well… I'd really like to upgrade that battery to the [BT-DN110](/component/internal-battery-bt-dn110/) someday. That'll let me enable synchronized shift so that I no longer need to take my hands off the aero bars to shift the front derailleur.

This being a commuter bike though, I'm not in any hurry. If I run into a discounted [BT-DN110](/component/internal-battery-bt-dn110/) battery I'll probably buy that, but it can definitely wait.

How about you? Have you ever hacked your Di2 components to complete your special project? I'd love to hear about that, so be sure to [send me a message](/contact/), or leave a comment below.

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I installed SW-7972 Dura-Ace satellite shifters on my 6870 commuter bike by doing some cutting and soldering, as well as some creative wiring. Enjoy the build log!

Installing the handlebar junction and battery in aero extensions

The previous generation DURA-ACE components is still a very good choice for a modern bike – especially when paired with a set of new shifters and the bar-end junction box.

Time Trial/Triathlon Dual Control Lever

DURA-ACE ST-9071

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Specifications

Related components

Related pages

Build a 12-speed Di2 Time Trial / Triathlon bike

Installing the handlebar junction and battery in aero extensions

Manuals & other documents