- This is the GMBN Tech essential series
Our easy to follow series of maintaining
and looking after your bike.
Now, although the transmission
drivetrain of your bike
does look quite complicated,
it's actually pretty simple
when you take a good look at it.
Now in last week's video, we
took a look at the derailleurs
on a bike and the shifter.
Trying to take the complication out of it
and just show you how they worked.
This time around we're looking at
everything you need to know about cables,
how to replace them, how to
get them to the correct length,
and how to adjust them
once they're in place.
(tools clanging)
Now firstly,
let's just take a look at
the cable system on a bike.
This particular one just has a
single derailleur at the rear
so there's a single set of
cables running from the shifter
on the handlebars to the
derailleur at the back of the bike.
Now on some bikes you get a
single length outter housing and
inner cables like this one.
It goes all the way direct to the shifter.
On some bikes you'll have
internally rooted cabling.
This is obviously external,
you can see it all the way.
And on other bikes you'll
have a series of different
cable-stops on the outside.
You'll have shorter
sections of outer cable
and you're about to see
the exposed inner cable
in between those stops.
So the cabling system on a bike
relies on the minimal friction.
And the reason for that is obviously
you're pulling that cable using a shifter
which toggles the cable all
the way through that housing,
to actuate the derailleur.
And the derailleur as we
explained in the previous video
is quite a precise part of the bike.
It has to move very
precisely to get engagement
for all of those gears.
Especially, when you're
returning back down
into the gears where
there's least tension.
If your cable can't move freely,
inside the outer housing,
then you're never gonna get those gears.
Now if you're unlucky enough
to ride in a wet climate,
you'll have to be changing
your cables more frequently
than someone in a dry climate.
Likewise, if you have one
piece housing all the way
to the bars, then you're
going to be changing cables
a little less than someone with
multiple pieces of housing.
The reason for that is the
fact that water can get into
the housing and in those cable stops
and that of course can
get surface rust in there,
it can get any lubricant
that's in there out,
and generally add more friction.
So these are things that
you're gonna need for the job.
Now firstly, you're gonna
need an inner gear cable.
No fuss items, you can get
them from any bike shop,
you can get them in singles, double-packs,
even big reels like you
see in the bike shops.
It's a good idea to have a few of these
in your supply at home,
they'll always come in handy.
Next up is some outer cable.
Now the amount you need
will vary depending
on how big your bike is and the routing
you've already got on there.
If you're unsure about this,
the best thing is to actually
take your old routing off,
measure how long it is
and then you'll know the length you need.
Now you can buy kits with
the inner and outer and
all the ferrules and bits
you need in a single kit
or more often than not if
you're buying this stuff
from a bike shop, they'll
have it on a big reel
which they'll dispense
the amount that you need.
That's a really good way
of doing it 'cause it's
not wasteful using exact amount.
In addition to that, you're
gonna need some kinda spray lube
because it's always a good idea to flush
out the housing first.
You're gonna also need some
kind of very light grease.
If possible a spray grease
'cause you're gonna be able
to get this into the
shifter nice and easily.
And you're also gonna need
shop towel just to make sure
everything's nice and clean afterwards.
Possibly some cable ties if
like me you have cable ties
to hold your outer housing to the frame.
If you have reusable ones
or have reusable clips
on your bike, you obviously
won't need to have cable ties
for that.
Also, you're gonna need the
relevant Allen key or Torx key
to undo the cable clamp
on the derailleur itself.
And then most importantly,
you're gonna need some
quality cable cutters.
Now, if you're any sort of home mechanic,
you probably will have
a set of these already.
And if you haven't, I can't
recommend buying a set enough.
Get a good set 'cause they
will last you a very long time.
I have a set of these at home,
they're probably about 15 years old.
They keep on going if you treat them well
and you just use them for cutting cables,
which as you'll find out
over time of doing this
on your bike, you can be
doing this quite a lot.
You'll also need a
selection of cable ferrules.
These will go on the
outers of the end basically
and they stop the inner
part of the cable migrating
out of the cable and they
also act as a dirt and a
moisture guard to stop the
stuff going into the cable.
And then, you're also gonna
need some cable end caps.
These are soft alloy caps that crimp
over the edge of the cable there,
just to stop it fraying and
becoming messy with time.
Now, I can't emphasize the importance
of cable ferrules enough.
Now the whole cabling system on a bike
relies on these to remain as accurate
as possible for a long time.
Now the construction of
outer cables is you have this
outer black sheath.
On the inside of that
you've got the metal strand
and then there's an inner sheath,
in which case, the inner
cable passes within that.
Now when you trim these down
using a set of cable cutters,
you're obviously exposing the end.
Over time if you didn't use the ferrules,
part of those inner cables can actually
start migrating out the end
of this and a direct result
of that is you're never
gonna have or be able to get
correct cable tension on your system.
When you have the ferrules in place,
everything is compressed together.
They're compressed into the cable stops
and you're gonna get very
smooth and accurate shifting.
So it's really important to
make sure you have all the
correct components to your
cables before you get started.
(mellow music)
So first thing's first, you
wanna make sure there's as
little tension on the rear
derailleur as possible.
That means shifting it
into the smallest sprocket.
That is normally a finger control
or your thumb pushing away from you.
Make sure it's in that
and then you wanna start
loosening off the cable clamp.
This is sometimes a Torx
key or an Allen key.
In this case it's a 4mm Allen key bolt.
You wanna loosen this off and then
you're gonna need to remove
the cable end cap on there.
Sometimes, you can get
away with taking these off
and reusing them which
of course is a good idea.
Other times, if they've been
crimped a few times like
this one has, it's gonna be a no so that's
off to be recycled unfortunately.
When you take the cable end cap off,
you're gonna see if the
cable's gonna fray or not.
If it's a nice clean bit of cable,
this is gonna be okay to pull
backwards through this system.
If it's frayed, though, it can
be quite tricky to do that.
So at this stage you
wanna trim the cable down
using the cable cutters
just to make sure it's
gonna pull backwards through the system.
And at that point, then
you're gonna be able to free
the cable from the
derailleur and pull it away.
With the inner cable loosened off from the
rear derailleur end, now is the time to
pull it back through the whole system.
In order to do that, go
to the front of the bike,
you might want to just
loosen off your shifter a bit
just to make this a bit
easier like I have here.
In which case, you
might need to loosen the
Allen key bolt that secures it.
Sometimes it's a 4 and
sometimes it's a 5mm.
Gently, whilst holding the
shifter itself, pull the
outer housing away from it
exposing the inner cable.
You can then pull the inner cable
back through from that point.
Now at this stage you have to identify
which style of shifter you have.
More modern shifters tend
to have a little rubber cap,
sometimes a little crosshead
screwdriver head you undo
and the cable then, you can literally
pull the nipple straight
out from that point.
Some other ones you
need to actually remove
the shifter from the
bars and remove the whole
top cap in order to
access the cable nipple
and pull it out from the shifter.
Now, even though this
cable is effectively done,
it's been used on the bike,
the condition of it is
not too bad so I'm just
going to trim off a bit of the end so
I've got a nice neat cut on it.
I'm gonna save this 'cause this could
come in handy elsewhere
or on another bike.
It could be used in places
like the drop of remote
cable system which is a
slightly shorter route
than having to get all
the way to the derailleur.
It could be used for fork or shock lockout
on a friend's bike perhaps.
Or it could even be used as a little hack
to get you home from riding on the trails.
That's gonna video you can be able to see
in the link underneath this one
and you can see what I'm talking about.
Now, if you're just
replacing your inner cable,
it's a really good idea to
flush out the outer housing,
make sure it's all nice
and clear on the inside.
Multi-purpose lubricant, WD-40,
anything like that is ideal.
Something nice and thin and runny.
You don't wanna be putting a
thick congealing kind of lube in there.
Now, just one thing to point out
if you're using spray lubes
anywhere near your bike,
make sure no part of that
lube can get anywhere
near your brakes: front or rear.
The best way to do that would be to
have a rag over the end of the cable here
and you spray it in and ideally
at the other end where the
lube is gonna come out as well.
So now it's time to
replace the outer housing.
There's a few things that's
worth pointing out here.
Now, it could be very
easy to just throw this
in the bin, get your new one out
and just chuck it on the bike.
But it's really, really
important to get it
the correct length and also make sure it
has the path of least resistance
from shifter to derailleur.
The point of outer housing
is to minimize the friction
on the cable on the inside,
so your gears start working
perfectly and lightly for a lot longer.
Now if you've got acute
angles on the outer housing
it's gonna be a lot more
friction on the shifting
and obviously it is gonna
interfere with things.
So you want any curve to
be as slight as possible.
Take that into account when
you're routing your cable
especially if you've
got a suspension bike.
If you've got a suspension bike,
it's a really good idea
to sit on the suspension,
compress it a few times and
observe how far cables move.
They're gonna move around as
the suspension compresses.
You wanna see that it's got
enough movement to do that
and it's not gonna pull on the cable stops
in any way at all or compress it in a way
that pushes it to an acute angle.
It's all about giving
the cable enough room
to do its own thing and then your shifting
will stay working smoothly
and accurately a lot longer.
Something else you must
factor in is enabling you
got enough cable that it
won't snap or tug on anything
in the event of a crash.
So, spin your bars around
and look at the length
of your other cables on there.
So you kind of want to match the same
sort of length as those,
enabling the bars to
basically do a full turn in either way.
Now because my outer housing
was already a correct length,
I'm literally gonna hold up my
new housing against the old,
so I can get the correct
length for trimming it down.
Nice easy way of doing it.
You get like for like,
you know it's gonna work
as well as it was when it was
first installed onto the bike.
If you've already got rid
of your outer housing,
you're gonna need to figure
this out for yourself.
But it's not a bad thing to do.
If anything, you can go
a little bit too long.
You can put the outer housing into place
before putting the inner in there.
You can try it for length and if need be
trim it down a slight bit each time.
Nice easy way of doing it.
Now because this bike has
a continuous length of
outer cable that runs from the derailleur
all the way to the
shifter, I'm just gonna pop
a few cable ties through,
join them up and leave
them loose enough to
just support the cable.
I can just check then
that my outer housing
is the correct length
before I commit to it.
Now as I emphasized a minute ago,
the cable routing is
really, really important
to get right on your bike.
Now it doesn't make a
difference if you have
your front brake on the right or left
in the way that your cable
routing's gonna look as well.
But just have a little think about it.
For example, so my rear
shifter is on the right
and I've got the luxury
here of using the cable stop
on either side here so you might think,
"oh the closest route is
actually on this side".
If you're forced to turn
the bars all the way
to the left in a crash, it's
gonna pull a lot on that
which means in order for that to work
there's gonna have to be a
substantial amount of cable
flopping around at the front of that bike,
which you don't really want.
What you wanna do is minimize that.
So I'm gonna go around from this side
which means you can
closer to the bars here.
It means that I only have to allow it
to pass through this amount.
It's gonna keep it nice and neat
and still pass through
the cable routes there.
The cable stops as I want them to.
Now is the time to pass the inner cable
into the shifter itself.
But just before you do that,
I recommend just spraying
a bit of light spray
grease onto the inside.
You don't wanna be spraying
anything like WD-40
or any sort of degreasing
type spray or solvent in there
'cause it's gonna take anything
out that's already in there.
But very fine, light spray grease is great
'cause it stays in place in there
and it doesn't hamper the
action of the shifter.
Of course the shifter
is something we barely
ever need to maintain on a bike.
If there is a little
bit of grease in there
it can help fend the water away
then it's always a good thing.
Something else just to take into account
as well is the barrel adjust on there.
Now the job of a barrel adjuster is to
take up that slack that
happens in the cable system
over time, known as cable stretch.
You may get some minute
amount of inner cable stretch
but it's gonna be barely anything.
The actual sort of movement that happens
is the cable outer
settling into the ferrules
which settle into the
cable stops on our frame.
These are all slight movements.
They need a tiny bit of slack taken up.
That is the job of the barrel adjuster
and it helps insure that your cabling is
nice and taut and the indexing
of your gears remains true.
So just wind this all the
way back into the shifter.
And a little tip I like
to do is just rotate it
back again so counterclockwise
one full turn.
That just gives you a
little room for error there,
in case you pull your
cable through too tight
or your shifting doesn't go
down into the smallest sprocket
it means you've got a turn to play with,
without having to
unclamp that inner cable.
If you clamp that inner cable up once,
it's gonna be nice and secure.
The more times you have
to interfere with it,
the more chances of
fraying that cable has.
Sometimes, you'll be
lucky enough to aim it
in the right place and
it'll go straight in.
Other times, I actually
have to look in line
with the hole and try to see
the daylight from the back
of the barrel adjuster there
in order to get the cable in.
Before you move on, you wanna make sure
that the cable nipple is
just settled into place.
A gentle pull on the cable.
If you just actuate the
gear you should feel it
pull the cable away from your
hand and put it back again.
Couple of times so you will know
it is seated in there correctly.
Now although the ferrule
needs to go on the end
of the actual cable outer...
You might find it tricky
to get the cable in
line with it in the sheath
with that cable outer.
So a good thing to do is to actually
thread them on separately
just to make sure
that you get a nice fit and it goes in
the first time into the outer housing.
And just push that onto the outer,
make sure it's firmly in
place and it bottoms out,
before pushing it all the way through.
At this point it's a good
idea to just to secure
your shifter into a preferred position.
That's gonna make indexing
your gears a lot easier.
Now just before you put the
inner cable into the derailleur
and secure it, it's a
good idea just to check
your limit screws and make
sure that the derailleur
is set up well.
If you want the full
description on how to do that,
click the link below this video,
it's gonna click you straight through
to last time's video where we looked at
all the adjustments you need
to make to do that correctly.
Essentially, there's just
the two limit screws.
The inner one controls the outer limit.
The outer one controls the inner limit.
Now for this stage it's
a good idea if you have
a SRAM derailleur to just apply the lock.
Which means manually
moving the lower case down,
pushing that lock in until it secures it.
Just makes it a little bit easier
so you can see what you're doing here.
Now something that's very essential
is making sure the cable is itself
accurately follows the guides on
the back of the back of
the derailleur itself.
Now these are different
on different models
of derailleur so it's
really, really important
that you just take time to
look before you put it in.
Because sometimes they
have a little loop they
have to follow around.
In this case it has a little
guide it has to follow around.
And then where the cable secures there's a
little channel that would
indicate we just have to sit into.
Make sure there's no slack in
your system before you do this.
Make sure the ferrules are at both ends
or if you've got multiple
stops on the frame.
Make sure those ferrules are
seated into the stops correctly.
Then pull the cable taut.
Don't pull it too tight
otherwise you're gonna start
moving the derailleur in the direction
of shifting its first gear.
Just pull it 'til it's
taut and then you wanna
secure it with the pinch bolts.
Again, making sure it sits
into the correct channel.
This does vary from
derailleur to derailleur.
But it's often easy to
understand by taking a good look.
Now some people like to go straight into
trimming the inner cable
down but what I like to do
is just coil it up first
and then we're gonna
index gears and then
I'll do this afterwards.
The reason for that is if I
need to make any adjustments,
I don't need to cut the cable twice.
And obviously, the more you cut the cable,
the more chance you have of fraying it.
So try to minimize that part of it.
Okay so with the cable loosely in place,
here it's been pinched
nicely by the pinch bolts.
What I'm gonna do is shift
the gear once at the lever,
turn the pedals round an hopefully
it's gonna hop up one gear.
You wanna repeat this process up to
the first three sprockets
and then make sure
it comes back down again
one click per gearshift.
If it doesn't jump up the first time,
you'll need to do a little
bit of counterclockwise
adjustment on the barrel adjuster.
If it goes up and it
doesn't come back down,
you have to do the opposite.
So there we go, that is the new
cable installed to the bike.
The cable ties are
holding on have been cut.
Leaving them nice and flush so they're not
gonna snag my leg if I accidentally
brush against the bike.
The gears are nice and indexed.
Again, if you wanna know a bit more
about that and go into a bit more detail,
make sure you check out
our derailleurs video
that we featured last time.
All there is to do now is
to trim the inner cable down
and fit the cable end cap on there.
The reason you want the end cap on there
of course is to stop it from fraying.
I'm just gonna make a nice neat cut
and install the cable end cap.
These can be fiddly, you can
fit these using pliers or
if you've got a steady hand you can use
the end of your cable cutter tool here.
Just by simply pushing into place
and crimping it on the end.
Don't need to go crazy, just
enough to hold it in place.
And it's nice and neat.
So there we go, that is how you replace
the gear in and outs cable on a bike.
So fairly simple process
you just basically have
to reverse what's already on there.
And how often should you do this?
When your gears are playing up,
if your cabling feels incredibly tight,
or if you ride in wet conditions a lot
it's a good thing to do annually.
But you will know when the time comes
because your gears will be playing up
and you'll hopefully have
got everything else adjusted
and you're gonna be able to
understand that it's the cable.
For a couple more useful
videos, if you wanna see
everything about adjusting
your derailleurs,
how to adjust them, and
what those adjustments do,
Click down here.
And if you wanna see the rest
of our essentials videos,
Click up the top there.
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