- Bicycle derailleur gears were first seen in 1905
on a French two-speed setup.
115 years later, though, we're still using the chain,
the cassette, and the derailleur
because they're the most efficient way
of having multiple gears on a bike.
Early designs, though, were quite crude,
and modern day transmissions are very different.
They're lightning fast, they're very, very smooth,
and they're very efficient.
How do they work though?
Let's have a closer look, shall we?
To make this video,
Shimano has sent me a 12-speed transmission.
It's a one-by system as well,
which, actually, you could credit one-by
with giving frame designers more freedom,
and essentially, it is probably the best way
of having gearing on a mountain bike.
It's an easy way of having a huge range
of gears on an off-road bike
with none of the limitations that you could get
with a double or even a triple setup.
The reason for that, basically, is the fact
that, on a triple setup,
you would find the main pivot could be off skew,
could be asymmetrical, and you're trying to cram in
all those chain rings to get optimum chain line
depending on which gear you're having at the back,
and of course, you got to get front derailleur
in there as well.
The one-by system is where mountain biking is at right now.
So first up, let's look at the chain.
We're going to work our way around the transmission
and show you what everything does
so you can get your heads round it.
Quite simple, really, actually,
but it's very clever, what they do.
Modern day chain, this is a 12-speed Shimano XT chain,
and what you're looking at in a chain is,
you have these outer plates, you have these inner plates,
you have the rollers, and you have the pins
that go through them.
That is why, when you lubricate a chain,
you have to leave it enough time
for the lubricant to actually get inside the rollers
to make sure the rollers can move around those pins.
That is what needs lubricating,
not the entire outside of those chain links.
Now, most chains will have the same inside spacing.
It's the outside spacing
that actually changes across chains.
We're talking eight-speed, nine-speed, 10-speed,
11-speed, and now, 12-speed,
and this is the reason you can't just put any old chain
on any chain cassette.
They really are quite specific,
although there are some patterns.
10, 11 are kind of compatible.
12-speed though, you do have to use 12-speed
with 12-speed, and the reason for that is,
there's a lot of special features built into these chains.
Okay, so we're going in closer now,
and what you might see, if you look very close, is,
the inner plates here protrude
a little bit more than the outer plates.
This is a design exclusive to Hyperglide+.
This is what you see on Shimano's 12-speed setup,
and the reason for this is,
it has better contact with the chain ring.
Now, minimizing friction is a bit of a strange thing.
It might not work the way you think it does.
By having more contact with the chain ring,
you're actually reducing friction,
you're reducing any movement, any rumbling around
or anything like that.
That all translates to increasing friction,
so this reduces that by having a better holding pattern,
basically, to keep it in place
on a very specific chain ring design.
You also might notice, on the outer plates here,
they've got chamfered edges here.
That is because the chain has to, obviously, stretch
as it is moving through the range of gears,
and instead of having a square edge on the edge of these,
by having a chamfered edge,
it just means it's that bit quieter,
and in fact, you'll find
a 12-speed setup will be much quieter
than its 11-speed counterpart.
If you take a closer look at the inside here,
you'll see that these bits are also chamfered,
almost to a degree that it feels flat on the inside
and it chamfers in, so it's actually quite a defined,
it's almost a sharp edge there,
and the reason for that is,
there are special teeth on the cassette,
which we're going to show you,
and they basically hook the chain up onto the next sprocket
and pull it back down again.
It's a very specific system.
In the old days, to join the chain,
or to break a chain, you would use the pins.
You'd push those out.
These days, you have a specific quick link.
It's a very good system, they're very strong,
and also very convenient to carry spares with you
out on the trail as well
in the event if you break in a chain.
Let's say you take your derailleur off
and everything gets chewed up,
that's what you would need to rejoin your chain.
Super easy to use, and really safe as well.
Working directly in conjunction
with the Hyperglide+ chain,
the very specific Dynamic Chain Engagement+ chain rings.
Bit of a mouthful, I know, but it's very specific
because of the technology involved.
If you look at the profile of the teeth involved here,
you'll see there's some slightly taller ones,
and you'll see also, some are narrower than others.
Reason for that is they fill the void
in between the chain, so you're looking
at male and female chain links, essentially, there.
You notice that the bigger chain ring teeth
actually fill out the bigger void there.
The reason for that is, it's about reducing friction,
it's about removing the chance
that the chain can move around.
If the chain can move around on that chain ring,
there's a good chance it can come off.
Not only is it more efficient, it's quieter,
it's going to last longer, and the chances
of having your chain actually come off
while you're riding is very minimal,
so minimal, in fact,
that many riders don't even use chain guides anymore.
Next up, let's look at the cassette.
Now, this really is the standout item
where you're talking about a 12-speed transmission.
When I first started mountain biking,
I was using a five-speed block on the back.
Now we're up to 12-speed here.
It's got a tiny little 10-tooth on the bottom,
a massive 51, like, that is absolutely enormous.
The range of gears you have for this
with just a single chain ring is far greater
than anything I ever grew up having.
It's absolutely amazing, the technology you have today,
and given that this is a consumable item,
the work that's gone into this is incredible.
It's really intricate.
You got this spider beam design on the back here,
and basically, the ring's also riveted together,
and this is dual material as well.
So you notice that there's steel bottom half
of the cassette, and there's an aluminium top half.
This is to save weight, but also bearing in mind
that aluminium does wear to faster than steel,
but you don't use those gears all the time,
so you may as well chop some of that weight off.
The daily driver gears down the bottom here,
they're all made of much harder-wearing steel.
Very smart design.
This is where the magic happens,
and this is where Shimano's Hyperglide+ system stands out.
Now, if you look closely, I mean, really closely here,
you can see that some of these teeth are very different
in shape, some are like a shark's tooth,
some are flat, and if you look at them in line,
you'll notice, some angle out, some angle in.
This is so they can hook the chain on.
You'll see these ramps and gates,
so this area here is stepped back slightly
from the rest of the sprocket.
Now, that, when you watch in slow motion,
that is where the action happens,
and it's only from here to here
that the chain will jump up, and it'll jump down.
It's immensely fast.
In fact, it's so fast
that you can actually keep pressure down
the whole time when you're shifting
on these Hyperglide+ cassettes,
which, to me, seems a bit alien
because of the fact I'm used to having
to sort of ease up very slightly as you change gears
so you don't crunch your way through the gears,
but they really are, you can just crack through those gears,
no problem, and just keep on mashing round the pedals.
It's amazing technology,
but the thing that's really standout as well
with Hyperglide+ is, not only does the chain pull itself
all the way back up, but it does it the opposite way.
Now, the reason that this is so impressive
from my point of view is,
the rear derailleur is under tension
when you're shifting into a bigger sprocket like this,
and because it's under tension,
is going to pull itself in quicker.
When you release that tension on the shifter
for it to jump back down again,
traditionally, there'd be a minute delay.
I mean, we're talking a small amount here,
not enough to really be an issue
unless there was any sort of drag
in the system, but with Hyperglide+,
the chain physically pulls itself back down again
just as fast as it shifts up.
This is really impressive stuff
because it means, no matter what's going on
anywhere else on the bike,
you know that the chain, when you hit that shifter button,
(imitates chain clinking)
down through those gears.
This is the rear derailleur.
Now, this really is kind of the hub of the system.
This is where the action happens from.
Now, you need one of these in combination
with the ramps you see on the rear sprockets
and those chamfered edges that you see on the chain
to get that really smooth shifting.
Now, essentially, all rear derailleurs have some kind
of parallelogram design to them.
This enables them to move in and out.
Of course, that is at a slight angle,
and it does differ on the different derailleurs available.
They all have a number of different features on them.
So, they all have a sprung lower cage.
This sprung lower cage you see on them as two sets
of wheels on them, sometimes known as pulley wheels,
sometimes known as guide wheels,
sometimes known as jockey wheels,
so there's various different names for them.
These ones on a 12-speed are much bigger.
They're 13 teeth, bigger than the older variety.
It just means they're a bit smoother,
and they put those forces out there a bit more.
The chain doesn't have to pass
at such an acute angle, so therefore,
it just rolls a bit smoother.
Keeping things smooth is the key
to keeping things friction-free and reliable.
Now, there is a difference
between the one-by setup rear derailleur you'd see
and the one you would see
on a multiple chain ring option,
and that is the pivot point here.
So the upper wheel on a multiple chain ring setup
would actually be here.
On the bigger setup, for the one-by,
which means you can use them with that huge 51-tooth,
they have to stagger this slightly
in order to cater for the range of gears.
You got to think, that is a lot of chain
you have to take up the slack for from 10 to 51.
It's a huge amount.
It's also why you see the cage is quite long.
When changing gear into the lower gears,
that is the bigger sprockets,
it has to compensate for that, and to do that,
it can move all the way forwards,
but then, when you change into the smaller sprockets,
this is why you have these two sets of wheels,
they roll all the way back
to take up the slack in that transmission.
Now, there's various points of adjustment
that all rear derailleurs have.
They all have limit screws, high and low,
and they all have a B screw,
sometimes called the B tension.
Now, the B tension is just responsible
for adjusting the height of that upper wheel
in relation to the cassette itself
just to aid your smooth shifting.
More essential one are actually the limit screws.
Now, these adjust the position of these guide wheels
in line with that cassette
in the small position and in the large position.
You only need to adjust these once,
when you set up your derailleur.
One correlates to the lower position,
one correlates to the higher position.
You can actually see them doing their job here
on the inner and outer plate.
So you see here that the inner one is actually
already on the plate, and if I manipulate this,
you'll see this one will hit in the outer position there.
But why would you want a clutch
on a derailleur like this to start with?
Well, it's all about keeping equal chain tension.
If you keep equal chain tension,
i.e., the chain's not flapping around all over the place,
the chain is going to stay in place on those chain rings,
and that, in combination
with the Dynamic Chain Engagement+ technology means
you're very, very unlikely to lose the chain.
The clutch itself, though, is actually really cool.
If I just reach over here and get an Allen key,
and I'll just take the cover off
so you can see it on the inside.
You can actually adjust the tension of the clutch
from the outside, but I want to take the cover off
so you can see here.
Take this off, and you can see the clutch design itself.
It's a roller clutch.
It's a one-way system, kind of along the same lines
as a sprag clutch, and when you move the lever up,
you can see it adjust this cam right here,
and basically puts additional tension in place.
Quite cool out it works.
So, if I undo it first,
and then I move that lower cage
you'll see the one-way clutch moving like so,
and then, if I engage the cam on there,
find it'll be very hard to move that,
and you can increase that as well,
and the whole point is,
it keeps good chain tension on your transmission there.
That basically means you're going to be able
to smash through those gears on rough terrain,
you're not going to lose your chain.
Again, this is adjustable,
and this is something that you do need
to put a bit of lube in from time to time
just to make sure it's working as well as it should be.
And why would you want to turn the clutch off?
Well, being able to turn the clutch off means
it's going to be easier for you to manipulate
the lower part of the derailleur
in order to remove your rear wheel from the bike.
If you try and fight that with the clutch on,
it's just going to be hard work,
so it's a really smart system
to be able to turn it on and off, as easy as that.
The last thing you need to know is
where the cable comes from.
So, the cable comes from the shifter,
which we're about to take a look at,
passes through the back of the derailleur
into the stop here, and it runs around,
and is secured in place by that cable clamp.
Securing the cable is obviously really important
because it relies on the indexing of those gears.
If there's too much cable tension,
you're actually going to be over-shifting.
If there's not enough cable tension,
you're going to be under-shifting.
Although it's not rocket science,
it is important to get it set up right.
When set up right, they work like a dream.
Now, lastly, of course, is the shifter,
so you're going to need one of these
in order to change gear.
Now, way back in the day, there use to be thumb shifters
on top of the bars.
Completely not ergonomic in any way at all.
These days, they sit in a very natural position.
You can downshift using your finger like a trigger,
but you can also push it away from you as well,
and you can upshift using your thumb
on the paddle at the bottom.
There's multiple shifts available.
To downshift, you shift two at a time,
and you can dump through a few gears at a time
on the way up.
Now, something important to say,
along with the various chains you get on the market,
10, 11, 12, et cetera,
you get the same with shifters,
and the cable pull is not always the same,
and in fact, with the Shimano 12-speed setup,
the cable pull actually differs as you're shifting,
so it does mean that Shimano 12-speed off-road stuff
isn't compatible with other stuff on the market.
I'll tell you what, it's kind of hard
to see what's going on here,
so I'm going to actually take the cover off to show you.
(snaps fingers)
Ah, that's better.
So, I've taken off the housing here
so you can actually see inside.
Now, there's only really three main things
you need to know about one of these shifters.
So, essentially, it's just a ratchet
and a spool system.
Works one way, and you have a release trigger.
So, as I move this, you can probably see
on the inside here, it is moving that cable around.
It's pulling it in.
The other way, when there's a bit
of tension on it, you release it.
Very simple, very effective, and to be honest,
you rarely need to actually do anything to a shifter
unless you're changing the cable,
although I do recommend, from time to time,
making sure you put some water displacer
through one of these because they can harbor,
because of the shell on them, a bit of water on the inside.
Now, the one other thing you need to know is
about the barrel adjuster.
This is where you do the fine tuning of your gears,
and you can do this from the trail
because it's at the handlebar end.
Well, there we go.
That's kind of the inner workings of a one-by transmission.
It's a deceptively simple setup,
and all that's required is to get it fit correctly,
set up the base, you can set up the stops
on a derailleur, get the chain the correct length,
and there you go, it's a very simple process.
I'm amazed, actually, we're still using something similar
115 years later from when we first saw a derailleur.
I mean, a derailleur's kind of king.
Kind of love them.
What do you guys think of derailleurs?
I'd love to know, actually.
Let us know in those comments,
and there's going to be a few more videos floating around
for you to see on setting up and indexing your gears.
That's a bit more specific.
This video is showing you a bit more
about the inner workings, and what it means
when you look at those cassettes
and you find yourself a bit puzzled, maybe,
looking at those spiky teeth
that are not so spiky when you actually think
about what they do.
Clever stuff, eh?
See you later.