I think it is important to change everything at once when dealing with shift cables. I mean the supplies aren’t expensive and you’re in there anyway, might as well do it all. The most expensive part of cables/housing is the labour you have to pay to get it done. Even with labour and parts we are not talking about a lot of money here. There are a few reasons why you might want to learn how to do this yourself. You could be dealing with a very short time frame, it’s good to be self sufficient, you like to know how to service your bike properly, most shops employ terrible bike mechanics (sad but true).
Okay so whatever your reasons I’ll show you how to do it like a superstar. This how-to will illustrate the replacement of a rear derailleur cable/housing. The steps would be the same for front derailleurs.
---------->On a note before we start. Frayed cables, damaged housing, broken cables……..all of these things are extremely sharp and pose a very serious threat. I can’t tell you how many times I have poked my fingers with cable strands or pieces of old housing. I had a strand go right through my thumb, it sucks! So whenever you are cutting cables/housing or disposing of old cable/housing make sure you do it properly and leave nothing behind. You don’t want to find a 1” strand of razor sharp steel cable with the bottom of your bare foot!
Housing – Anything that is pre-lubed. It means there is grease all along the inside which makes shifting much smoother. Jagwire makes really nice stuff and is the best bang for the buck. 4mm thickness is best for shift. It is smaller and handles bends much better. 5mm housing is typically used for brake cables and is constructed differently.
Housing end caps – Make sure you get the sealed type. They have little rubber o-rings which keeps dirt out of your greased housing. Also make sure they are the appropriate size for the diameter of your housing.
Cables – spend the extra dough and get stainless. They never get contaminated which is a major source of friction. Teflon cables are overrated but still get the job done. Shift cables are around 1.2mm and brake around 1.5mm thickness.
End caps – anything goes here. You can solder the ends, buy fancy caps……whatever you do make sure the ends are sealed or they will fray very quickly. Ditch the electrical tape and do it proper-like.
Tools required (left to right):
1 - cable end caps
2 - housing end caps
3 – cables
4 – housing
5 – side cutters
6 – Allen key(s)
7 – screwdriver
8 – flaring tool
9- cable/housing cutters
Shift your derailleur into the smallest cog and loosen the cable pinch bolt on the derailleur with your 5mm Allen key.
Cut off the old derailleur cable end cap so that you can easily slide the old cable out of the old housing.
Remove the plug in your shifter to gain access to the cable. This plug is very easy to get out but it does vary from shifter to shifter. Send me a message if you need help figuring out how to get access to your shifter cable. Keep in mind all (99%) of shifters will have a superficial cover that does not require you to disassemble the shifter mechanism to gain access to the cable.
*Set your shifter plug in a safe place so you don’t lose it.
Push the old cable through the shifter. Sometimes the head of the cable gets stuck in its little cradle in the shifter and you have to jiggle it to get it out. Make sure your shifter is still set on the smallest cog or you will not be able to remove or install your cables. **If you have an old “rapid rise” style rear derailleur then you need to be in your largest cog in the back. Pretty much the rule with either style is that your derailleur/shifter needs to have all cable tension released.
Throw out your old cable. Best way is to spool it up like in the photo and tuck the end through the middle of the spool a few times so that it wont unravel. *Remember this stuff is seriously sharp!
Take a look at your old housing. Is it the right length? You should be able to rotate your handlebars freely without the housing being so short that it pulls on the shifter, or so long that it can get snagged on a tree. Rear suspension should be able to compress through its entire stroke without straining the housing. Rear derailleurs should be able to float freely.
Remove all of your old housing. Use your side cutters if there are any zipties holding things in place. *Remember, old housing ends can be sharp too!
Set these pieces aside and arrange them in order. Assuming they were the right length, you will be using them as templates for cutting your new housing.
Using your old lengths of housing as a guide, cut your new housing to size.
Cutting the metal housing will leave it ovalised. Using the inner portion of most cable cutters (or flat pliers), squish the housing so that it is round again.
Cutting your housing might make the inner plastic sleeve crimp shut. Take your flaring tool and round out the inner sleeve so that you can easily pass the new cable through. If it is really crimped shut you can use a sharp pin to open up the plastic sleeve before flaring (or push the cable through the other side to open up the sleeve).
Thread your new cable through your shifter. Remember your shifter must be in the smallest cog, if you look though the plug hole you should see the light at the end of the tunnel which gives you something to aim for. Sometimes the end of your cable can get hung up as you try and push it though. It might take you a couple tries.
Make sure the head of your cable is seated properly in its cradle in the shifter. You might have to jiggle it a little for it to sit in place.
Step 12Pop on your new cable housing end caps. Make sure they are the sealed type, it is worth the extra money since they will keep your shifting smooth much longer.
Install your new segments of housing onto the bike. If you were ever wondering, the proper order for your shift and brake housing to lay in place from your handle bars it goes like this:
Looking at your bike from the front, outside to inside-
Slide the new cable all the way through the new housing segments.
Step 13Re-install the shifter plug.
Step 14Screw in your barrel adjusters. There might be one at your rear derailleur and one at your shifter. Turn them in as far as they will go (like a screw) and then back them off a ½ turn.
Step 15Tighten down the shift cable at the derailleur. It is very important that you thread the cable on the correct side of the bolt. Usually there is a give-away, like a notch or slot milled into the derailleur. Also make sure the pinch bolt plate is orientated correctly so that the cable won’t slip.
Keep medium tension on the cable when tightening the pinch bolt so that the cable is taught.
Step 16Ohh baby this is one very important step! This separates the slackers making $10/hour at the shop to the pros making $11/hour at the shop…..
Check the tautness of the cable, it shouldn’t have too much slack. This is how the cable should normally sit when you are in your smallest cog on the back.
Now we are going to stress the system and alleviate most of the “stretch” that may occur.
Grab your derailleur very firmly so that it cant move. Now shift a bunch of gears on your shifter (holding the derailleur in place) so that it puts a bunch of pressure on the cable/housing. Should be about an 8 or 9 on the firmness scale. Now release the gears and repeat a few times.
After you are done stressing the system check the tautness of the cable. You can see that there is probably a lot more slack in the system than there was before. Better to get this over with now instead of having to continually adjust your derailleur out on the trail while the system beds in.
Comprehension (oh boy)
So conventional thought would be that your cables are stretching. This is pretty much completely false. Any decent cable is pre-stretched at the factory. What is happening is the housing is compressing and pushing into the housing end caps. The more segments of housing you have, the more slack you will get in the cable after stressing the system. If you ever change the cables on a bike that has full length housing (like a Scott Spark) you will see that there is still very little slack in the system even after stressing it. The fewer the housing segments, the less the system is affected by load. Not to say that full housing is better, once any system is initially stressed (properly) there will be very little housing compression in the following weeks/months. With our barrel adjusters turned all the way in we have lots of room to take up any small amounts of slack in the cable that might develop by turning them out. Phew!
Holding the derailleur very firmly in place, stress the system by shifting up a few gears.
There will be slack after stressing the system. Loosen the pinch bolt and take up the slack by holding the cable taught then tighten the bolt.
Loosen the derailleur cable pinch bolt and take up any slack that may have developed by stressing the system. Holding the cable taught, re-tighten the pinch bolt. Check the tension once more, it should be as it was before we stressed the system.
Cut off the excess cable. Leave enough extra in case you need to make an adjustment but not so much that it can get caught on something.
Install your cable end cap. I can pinch the end cap with the inside of my cable cutters. Since these are brake end caps on a derailleur cable they are a little too big so I extra-secure them with a final two pinches with the side cutters.
That’s it, you’re done! Enjoy your buttery smooth shifting.
Post in the comments if you have some extra tips!