– 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. As always, click on the
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