What is inside a Di2 Front Derailleur?

Published August 29, 2021 by BetterShifting Terry, Last updated August 30, 2021

The 10 speed Ultegra 6770 series was the first Ultegra Di2 groupset, and in fact, the first Di2 system to use the two-wire E-Tube (CAN BUS) standard that is still in use today. And yes, it was not actually the first Di2 groupset - that was 7970, way back in 2009.

When it comes to compatibility though, the 6770 series is a huge step forward compared to the older 7970.

Even though it was released ten years ago, all 6770 components can be used with any shifters and batteries. The only thing you cannot do is mix 10 speed and 11 or 12 speed derailleurs.

Curious about Di2 compatibility? I wrote a page on Di2 compatibility and reading the compatibility charts provided by Shimano a while ago.

FD-6770 normal front and back

Now... I happen to have a 10 speed FD-6770 front derailleur. I don't have a 10 speed rear derailleur and I don't think I ever will own one.

So what am I going to do with this FD-6770 front derailleur?

Let's take it apart.

A few months ago I visited the Shimano Experience Center in Valkenburg, The Netherlands. This is where you can rent bikes or fishing equipment.. or just have a good cup of coffee and enjoy their little Shimano 'museum'.. or experience.

Here they showcase their components, from Tiagra fishing to DURA-ACE Di2 bike parts. You can also see some of Peter Sagan's road bikes and Mathieu van der Poel's MTB, cross and road bikes.

They also have cut up some Di2 components, just like this:

Shimano Experience Center

Pretty cool, right?

Since I"m never going to use this FD-6770, let's try to do the same!

Take the side cover off

Looking at the derailleur, three small screws can be seen on the front. Besides these three, I couldn't really spot anything to take apart... so I guess this is where I start.

FD-6770  first cover off

Taking the screws off let me take off the front cover and that exposed more than I expected. You can now see how the derailleur cage is moved: using a servo motor and a large lever.

FD-6770 with one of the covers off

At this point, I got a little stuck. The lever is holding the rest of the top (housing the actual servo motor) in place. In turn, the lever itself is secured using two very tiny retainer rings. After a trip to the local hardware shop though, that came right off.

FD-6770 with both covers off

On the left you see the lever and the retainer rings, while the right hand side of the image shows the main body of the front derailleur: the circuit board and servo motor.

As you can see in the image, the circuit board with E-Tube connector and servo motor just slides out of the black outer casing.

Close up shot of the servo motor

.... I wish.

It wasn't actually that easy. You see, Di2 components are sealed against water.. people do ride their bikes in the rain and getting water in here would definitely be fatal.

Because of this, the black outer casing and the white plastic holding the circuit board are bonded together, creating a pretty good seal. Something that isn't easy to take apart.

So I cut it.

No, you can no longer ride this derailleur in the rain :).

What is it like on the inside?

Let's take a good look at the insides of this derailleur then, since that's what you came here for. First I'll show you all of the individual parts I've taken off.

FD-6770 fully exploded view

That's all! Simple, right? The circuit board, servo and the gears are definitely the most interesting.

Close up shot of the servo motor

You've seen the image already, but this time I'll tell you what you're looking at.

The cylinder-shaped thing on the right is the E-Tube connector. This is where you plug in the EW-SD50 wire.

From that, two wires (red and white) connect to the circuit board, and the black and white wires run to the servo motor. On the bottom left you see some cogwheels or gears.

FD-6770 servo motor

Neat! That is definitely my favourite part of the derailleur.

The only thing I didn't like - there was no "FD-6770" printed on the circuit board! Bummer!

But wait.. there are two very tiny screws holding the circuit board in place. Let's take those off.

FD-6770 is printed on the PCB

There we go: FD-0111_6770"!

You can also see the tiny ribbon cable connecting this circuit board to the other one, on the other side of the derailleur.

Can you put it back together? Does it work?

Sort of! I'm going to answer both yes and no to this.

Yes, you can put it back together - apart from the part that I cut through to get to the insides of the derailleur.

Yes, it does still work.

No, I wouldn't use this outside. Not only do I not have a 10 speed rear derailleur.. it is also no longer sealed or actually safe to ride.

This is also a good time to remind you of Shimano's warranty. There is a two-year warranty on all components, except DURA-ACE and XTR. These last two come with a three-year warranty.

If your component breaks, Shimano will generally just replace it, free of charge. Note that if you tinker with the component yourself, you void the warranty.

That said, let's get back to my specific derailleur. I never intended for it to be ridden again, so I put it back together without the cover. That way you can see what is going on.

FD-6770 drive side shot

The front cover helps hold the rest of the derailleur in place, so I did put that back on.

The FD-6770 front and back

Does it work? Does it work?

Ok.... ok.

Yes, it does.

Pretty cool, right?

Here is another video, this time shot from above:

Thanks for reading

If you made it this far, thanks! I had a lot of fun taking apart this derailleur and putting it back together. Compare this ten-year-old tech to the newer DURA-ACE derailleur seen at the top of this page. Things sure have gotten a lot smaller since 2011!

I don't plan on doing this to other derailleurs any time soon, but you never know.

Any questions, suggestions, or comments? Leave them below or send me a message.

BetterShifting Terry

About the Author - BetterShifting Terry

I enjoy playing with bike tech - both bike building and wheel building, bike maintenance and of course, Di2. Besides writing content and working on the technical side of BetterShifting, I also work as a Software Developer in The Netherlands.

Read more on the About this site page.

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