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HOW TO: FIT INTERNAL CABLES

Cables and hoses are something that are often overlooked when building a bike, not all are created equally. Choosing good quality cables and outers, as well as routing them properly, will massively improve your shifting but also give your bike a tidy, stylish look for those all-important coffee stop Insta pics. This guide will run through how to determine cable outer lengths, cutting and the types of hose/outer. We’ll be covering gear and brake setup or bleeding in other guides but there is some useful information at the bottom of the page.

The key thing to remember for routing cables is not too long, not too short. This might sound obvious but what works on the stand may not work in real life; short tight curves for gear cables coming off the bars look great, but does the cable still move freely? Can you still turn the bars without the cables pulling tight? What about that rear brake, does it rub when you turn left?

The main three types of outer housing you’ll come across are:

Mechanical Brake Outer: Spiral wound steel - coated in plastic - This is designed to resist the large compression forces induced under hard braking. It can still resist high loads even when curved.

Mechanical Gear Outer. Linear steel wires run parallel to the inner, coated in plastic: Gear cable is almost entirely compression resistant - as linear cables won’t compress along their length, ensuring perfect index shifting. Under high loads it can be prone to bursting.

The different load levels between brakes and gears mean that for safe, effective use, you should not mix outers across shifting and braking applications.

Hydraulic Hose – specifically for hydraulic brakes, this airtight woven hose is often specific to a manufacturers brakes and requires specific fittings.

Ferrules – these usually fit each end of a piece of outer and allow the cable to pass through a small hole. As standard they come in 2 sizes; 4mm for gear and 5mm for brake outer. Sometimes a ferrule is not required when the outer goes into a brake/shifter but check your manufacturers fitting instructions on this.

To get started make sure you have all of your cables, outers and ferrules to hand, aswell as some electrical tape, scissors and some good cable cutters, sharp side cutters can be used but may deform the outer and cable. If you have hydraulic brakes you'll also need 2 sets of brake olives and inserts.


Step 1.

Starting at the right lever put the gear outer into the shifter and offer up the piece of cable outer to the bar. Trace the curve of the bar, then a line down to the cable port in the frame, don’t cut yet and make sure to allow a slight curve in this routing to allow for steering.

 

Continue on from the port running the housing parallel to the outside of the frame, determine the length needed by running down the downtube and along the chainstay, then form a loop around to the barrel adjuster on the rear derailleur. Follow the mantra of not too long, not too short, mark this point by pinching between thumb and finger, then cut.

Step 2.

Repeat this for the front derailleur, following the curve of the bar, down the outside of the downtube, then create a small curve under the bottom bracket shell and upto the stop on the back of the seat tube, or directly into the derailleur on newer Shimano models.

Step 3.

Remove the cable ports from the frame and thread your freshly cut outer housing into the hole in the frame. Internal cable routing kits are available but if you don’t have one, these things will make this much easier:

  • A headtorch or posable lamp
  • A seal/dentists pick or an old spoke
  • Needle nose pliers
  • Another pair of hands

Step 4.

Now that you have both sets of gear outers in the frame slide the cable port covers onto the outer but don’t bolt them back on just yet, we still need to thread the brake hose/outer later.

Next you'll need to thread your inner gear cables into the shifters, if they didn’t come preinstalled this can be a bit tricky on some shifters so check the manufacturer’s instructions on how to install for your shifter:

Shimano: Si.shimano.com

SRAM: Servicearchive.sram.com/service

Campagnolo: Campagnolo.com/UK/en/Support/support

Step 5.

Thread the inner cables through the outer housing adding ferrules to the outer as you go (it will be easier to thread them onto the cable). Seat the ends of the outer housing into the shifter and the derailleurs. If the ends of the outer are pinched closed from cutting make sure to open them back up with a bradawl or a small Philips screwdriver. At this point leave the inner cables at full length, it will help when setting up the gears.

Step 6.

Check that the end of the gear outer is seated properly into the shifter then hold the outer firmly so it follows the shape of the handlebar, and use electrical tape to secure it tidily in place.


Depending on whether you have mechanical or hydraulic disc brakes the next steps are a little different, for mechanical disc brakes that use a cable to actuate, you’ll need to cut the brake outer to length, following the same steps as for the gear outer:

Step 1.

Trace the curve of the bar from the lever to the port on the frame, down the outside of the downtube and along the chainstay to the caliper. Again make sure to leave a slight curve in the routing to allow for steering, by holding the cable in position and turning the bars to 'full lock'.

Step 2.

Thread the cut down brake outer into the frame as you did with the gear outer and reattach the port covers.

Step 3.

Thread the brake inner cables through the lever and into the brake outer, adding ferrules as you go. If the cable feels rough or won’t go into the outer use a bradawl or screwdriver to open the ends of the outer. (Remember: Brake ferrules are a different size to gear ferrules.)

Hold the brake outers in place on the bar and secure them with electrical tape like the gear outers. Leave the cables uncut for now as this will help with setting up the brakes.

For hydraulic brakes you’ll need to detach either the caliper or the lever from the hydraulic hose (see links below on which one to do for your brake). You'll need to cut the olive and insert from the end of the hose and slide off the shroud nut. Make sure you have a spare olives and inserts before starting this. Don't pull the brake lever while the caliper is detached and have some rag handy to wipe and drips.

Step 1.

Offer up the hose to the downtube, and along the chainstay to the caliper from lever as you did with the gear outer (but without the extra loop) and cut to length.

Step 2.

Thread the hose through the frame as you did with the gear outer, (starting from whichever end you haven’t detached the caliper or lever) and reattach the port cover. Then follow the instructions for connection and bleeding from your manufacturer (below).

Step 3.

Hold the brake outers in place on the bar and secure them with electrical tape like the gear outers.

That's all of the cable routing done, time to get the gears indexed and the brakes setup, we’ll be covering this in further guides but for now check out these great links for more help:

 

Front and rear derailleur setup

https://www.parktool.com/blog/repair-help/front-derailleur-adjustment

https://www.parktool.com/blog/repair-help/rear-derailleur-adjustment

Caliper fitting:

https://www.youtube.com/watch?v=6_T9lAufgUo

Sram hose fitting and bleeding:

https://www.servicearchive.sram.com/sites/default/files/techdocs/95-5018-024-000_sram_hrd_bleed_manual_rev_a.pdf

Shimano hose fitting and bleeding:

https://si.shimano.com/pdfs/dm/DM-RADBR01-06-ENG.pdf

Campagnolo Bleeding:

https://www.youtube.com/watch?v=WQk-pUPKOqk

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