Alex: Over the past month or so, I've made quite a few videos featuring Shimano Di2
groupset. It has got me thinking about just how impressive the groupset is in terms of the way it
communicates between all the different parts. Now, whilst most of you might have seen Di2 in action,
have you ever wondered how it works exactly? In this video, we're going to cover just that and
explain how the Di2 system works. [music]
Before we get going, I want to know how many of you use Di2 shifting on your bikes or
stick to mechanical shifting. Head over to the GCN app and vote on
the poll. [music]
Di2 has been around for some time now although the early systems
do communicate in a bit of a different way to what this current setup uses. For today,
I've got the current existing Di2 groupset to use, but rumor has it there is a new Dura-Ace groupset
somewhere around the corner. Keep your eyes peeled for that too. First off, we're going to need to
lay all of the components out on the workbench in the sequence that they would be on a bike,
which isn't too complicated, and most of you will know what order to put these components out.
Today, we're not focusing on the brakes. I'm not going to be including those in the components when
we lay them out. Once we've got that all that in place, we can look again to connect it up,
and making sense from this pile of cables that we've got. Let's get on with that first.
[music] We've got all our components laid
out in the correct order. That wasn't too tricky. To make this a working functioning groupset,
we're going to need to link it all together using our selection of cables and junction
boxes. This is the point when it can seem a little bit confusing but fear not because it's
not as confusing as you think. Many people will assume that each cable and connection
is specific to the component that it's going to. That isn't the case. I've pointed it out
in the previous video. All of the cables are interchangeable. The only difference between them
is the length, and that is dictated by the two components that it's trying to link together.
Shimano have a specific tool to aid installation of these little plug connectors on your Di2
system. It's this, which is called the TLEW02 tool. It's quite a quirky-looking tool,
but it makes life super easy clicking the plugs into place. When they're clicked in place,
they have a nice positive engagement so that you know they're nice and secure.
[music] That's everything connected
together. I've tidied it up a little bit as well as you can see here. I've coiled the cables up
so it doesn't look quite as confusing as it would've looked otherwise. It gives a nice,
clear simple layout. With the front of the bike here, you've got your shifters,
your left and right shifters, which are connected in a single cable up to a junction box,
and this would be mounted inside the stem on the bike that this comes off of.
Then you've got a cable that runs down through by the head tube to our first junction box here.
This is located on the down tube, but it can be located in different positions on different bikes.
Then from the junction box, we can back out. We've got a cable coiled all the way up
down to another junction box, which would be sat down by the bottom bracket. From this point here,
we've got a cable that runs down to our front derailleur. Then from the same junction box,
we've got one cable that comes out and up to the seat post here, which houses the battery.
The battery can be housed in different locations, but on this example,
we're using a seat post mounted battery. Then back down from the same junction box that is located by
the bottom bracket, you've got another cable, the last one which comes out at the back of the bike
and then loops to our rear derailleur. This is all plugged in and should be
working correctly. I guess let's give it a little test. Nice. See the rear derailleur is working.
Back down, let's test out the front one. We've got the shifters into the big ring
and shift back down. That's all working perfectly. [music]
I've already said all of the cables are interchangeable on the Di2 system. We need
to understand how that is. In simple terms, it's because all of the cables here only
contain two wires inside of them. The plugs on the ends are all the same. The only difference
is simply the length between the ends of the plugs, which is pretty basic to work
out. All you need to do is choose the cable length relative to the position you're going to use it.
[music] If within these
cables there are only two wires to link up all of these different components parts and the buttons,
you might be wondering how on earth the relevant parts move when you push the right button.
That is the slightly more complicated part. Shimano use the high-tech communication
protocol called a CAN bus network. CAN bus stands for Controlled Area Network.
Most people will have not heard of a CAN bus system before but having previously
worked as a car mechanic, it's a system that I'm fairly familiar with because
almost all cars use a CAN bus system to link all of their electronic components together.
CAN signals use a binary code to communicate through all these networks of cables and
units. A binary code consists of just two symbols; symbol one and symbol zero. Those are in a unique
sequence to give a specific code to the button or action that's required. Binary code is the
most basic way that a computer operates. You can convert text into binary code, just how a computer
would use it to communicate with the different sections inside it. Here's an example of Global
Cycling Network written in binary code. [music]
Whilst that all might sound a little bit confusing when we apply all those
principles to our bike components, it makes a lot more sense. One button
is identified with a specific binary code. As that travels through the network of components,
each unit will recognize it and decide if it has to perform a set action. To give an
example of this on our bikes. As I press the shift button at the front of our bike, a unique coded
signal travels through the network of cables and goes to each individual component on the bike.
Crucially, it's only the rear derailleur that recognizes that signal and then operates
accordingly. Those are the basic principles that make the entire system work seamlessly as a very
effective and efficient method of communication. [music]
As impressive and high-tech as all of this seems, the CAN bus system was actually invented by Bosch
way back in 1980. Over the years, it's developed and evolved into the robust communication system
that it is today. You could go on forever, talking to endless details about the CAN bus system
but in terms of a bike, that's as much detail that we would need to go in to have an understanding
of how it works. [music]
There you have it. Shimano's Di2 system and the CAN bus system explained. I want to know,
are you interested in electronic shifting or are you going to stick with your mechanical gears? Let
us know in the comment section down below. I hope you enjoyed this video. I'm going to have to build
my bike back up soon so I can actually ride home. See you later.
[music] [00:07:37] [END OF AUDIO]