How to Fit Internal Cables on a Bicycle

Updated 8 November 2026 · Standard formula, shown below

Fitting internal cables routes brake or gear-control cables through a bicycle’s frame for a neater finish and less exposed cable. The job is manageable with the right cable and housing, but the routing method depends on the frame: some have guide tubes, while others require a temporary guide to pull the cable through. Check your frame and component instructions before starting, and do not ride until every control works reliably.

What You’ll Need

The correct inner cable and compatible housing for your brake or shifting system. Use the specified cable type and diameter; brake and gear cables are not interchangeable in every setup.
Bike-specific cable and housing cutters, plus a sharp pick or awl to reopen a cut housing end.
Hex keys and other tools needed to remove controls, stops, or frame covers, as specified by the component maker.
A cable-routing guide, magnet-based routing tool, or a length of thin guide wire. A small piece of tape can secure a guide to a cable.
Ferrules, frame grommets, and end caps that fit the frame and housing. Have replacement parts ready if the existing ones are worn or missing.
Work stand, clean cloth, and eye protection. If the bike has hydraulic brakes, use the manufacturer’s bleed kit and fluid only if the work requires opening the hydraulic system.

Step-by-Step

Identify each route before removing anything. Look for labels, frame diagrams, access ports, and existing cable paths. Photograph the current setup and note which entry and exit ports serve the front derailleur, rear derailleur, and each brake. Follow the frame maker’s routing diagram; do not assume that a port’s location tells you its purpose.
Make the bicycle safe to work on. Shift to a position that reduces cable tension where applicable, then secure the bike in a stand. For rim brakes, release the brake cable if needed to make removal easier. For mechanical disc brakes, follow the brake maker’s instructions. Do not disconnect hydraulic hoses as though they were ordinary cables; opening a hydraulic circuit can require a proper bleed.
Remove the old cable carefully, if replacing one. Loosen its clamp bolt and detach it from the control or derailleur. If the old cable passes through the frame, attach a routing guide to its end before pulling it out. A purpose-made guide is best; a secure, narrow connection reduces the chance of the guide separating inside the frame. Pull gently and stop if it catches. If there is no usable old cable, use the frame’s internal guide tube or a suitable routing tool.
Choose the correct entry and exit ports. Confirm the intended route for each control and whether that route uses bare inner cable, full-length housing, or short housing sections. Some frames require a liner, specific grommets, or a particular sequence through the bottom bracket area. Never force a cable into a port or drill, file, or enlarge a frame opening.
Feed the guide through the frame. Insert a routing tool at the correct entry port and guide it toward the exit. With a magnetic tool, move the external magnet slowly along the frame to steer the internal guide. With a guide wire, use a light, flexible wire that will not scratch or damage internal parts. Keep it away from sharp edges and moving components. If the frame has a continuous guide tube, feed the cable through that tube without adding an improvised liner.
Pull the inner cable or housing into place. Attach the new cable or housing to the guide securely, keeping the connection slim enough to pass through openings. Pull the guide from the exit while gently feeding from the entry; avoid kinks and sudden force. For full-length housing, use housing made for the specific control and cut it to a length that allows steering or suspension movement without tight bends. Confirm the housing is seated in its stops and frame grommets.
Prepare housing ends and fit ferrules. Make square cuts with cable-and-housing cutters, not general-purpose scissors or pliers. Open the liner with a pick if it has collapsed, then fit the correct ferrule where the system calls for one. Some housing or frame systems specify no ferrule at particular ends, so follow their instructions. Check that the cable slides freely and that no sharp strands are exposed.
Connect and adjust the control. Route the cable through the shifter or brake lever and its housing exactly as the component instructions show. Pull out slack and fasten the cable at the specified clamp point and tightening torque. For gears, set the derailleur limits and indexing according to the derailleur and shifter instructions. For mechanical brakes, set pad or caliper alignment and cable tension. Do not guess at torque values; use the component maker’s specification.
Check movement and secure the finish. Turn the handlebar fully left and right, compress the suspension if applicable, and check that the cables do not tighten, snag, or rub. Operate each control repeatedly. Trim excess inner cable with cable cutters and fit an end cap. Refit covers and grommets, and make sure the cable cannot touch a wheel, rotor, crank, chain, or suspension linkage.
Test before riding. With the bicycle stationary, check that both brakes engage firmly and release fully, and that the gears shift through their intended range without cable binding. Spin the wheels and verify that nothing rubs. If braking or shifting is uncertain, do not ride; correct the setup or have a qualified bicycle mechanic inspect it.

Common Mistakes

Pulling out the old cable without leaving a guide. This can turn a straightforward replacement into a difficult routing job. Attach the guide before removing the cable, and use a frame-compatible routing tool if the route is already empty.
Using the wrong cable or housing. Brake and gear systems can require different construction. Match the cable, housing, ferrules, and end caps to the control and frame specifications.
Forcing a cable around a bend. Tight bends or damaged housing cause friction and poor control. Re-route it or use an appropriately sized housing section rather than pulling harder.
Cutting housing with unsuitable tools. Crushed ends can obstruct the inner cable. Use proper cutters, make a clean square cut, and reopen the liner if necessary.
Ignoring cable movement at the handlebars. A route that looks tidy with the bars straight may pull tight at full lock. Check steering and suspension travel before trimming or fastening everything permanently.
Treating hydraulic hose like a mechanical cable. Hydraulic lines carry fluid and need compatible fittings and bleeding procedures. Do not cut or disconnect one unless you have the correct instructions, parts, and tools.

Tips

Work on one route at a time and label each guide so cables do not get crossed.
Keep the guide-to-cable connection smooth and compact; cover a small connection with tape if needed, but do not create a bulky lump that can snag.
Use a light source at the opposite port to help locate a guide, and move magnetic routing tools slowly so you can track the guide’s position.
Leave enough housing for full steering movement, but avoid unnecessary loops that can rub or catch.
Keep the frame’s drainage openings clear. Do not seal ports or openings unless the frame instructions specifically call for a plug or grommet.
After the first short ride, recheck cable seating and mechanical fasteners. New housing can settle, changing brake tension or gear adjustment.

Troubleshooting

The guide will not reach the exit port: Confirm you are using the correct route and entry point. Try a flexible routing wire or a magnet-based tool, and move it in small increments. Check the frame diagram for internal guides or obstructions. Do not push a stiff wire blindly into the frame.

The guide separates from the cable: Stop pulling and inspect both pieces. If the guide remains inside, retrieve it with the routing tool or a suitable magnet if the guide is magnetic. Reattach it with a slimmer, secure connection and pull gently while feeding the cable from the other side.

The cable moves roughly or will not slide: Look for a kink, crushed housing, misaligned ferrule, or a tight bend. Remove the cable if needed, replace damaged housing, and verify that the housing ends sit squarely in their stops. Do not lubricate lined cables unless the cable maker allows it.

Shifting is inconsistent after fitting: Check that the cable is clamped in the correct groove or position, housing is fully seated, and the cable runs freely. Then reset indexing and limits using the component instructions. If the derailleur or hanger is bent, cable adjustment alone will not fix the problem.

A brake feels weak, sticky, or fails to release: Do not ride. Check cable routing, housing seating, clamp position, and brake adjustment. If the system is hydraulic or the cause is unclear, arrange an inspection by a bicycle mechanic.

Frequently Asked Questions

Can I fit internal cables without a special routing tool?
Sometimes. A continuous guide tube or an existing cable can provide a path, but a routing tool makes empty or complex frames much easier. Use a method that will not damage the frame.

Do internal cables need to run inside housing for the whole frame?
No. Some frames use full-length housing, while others route bare inner cable through a guide or liner and use housing only at the ends. Follow the frame and control instructions.

Can I reuse the old inner cable?
It may be possible if it is undamaged and the correct type, but replacement is sensible when the cable is frayed, corroded, kinked, or difficult to remove. Never reuse a cable with damaged strands.

Can I route brake and gear cables through the same port?
Only if the frame is designed for it and the routes do not interfere. Follow the frame’s routing diagram; cables should not rub against one another or moving parts.

When should I take the bike to a mechanic?
Get help if you cannot identify the frame route, a guide is trapped, the frame or cable is damaged, or you are unsure that the brakes work correctly. Hydraulic hose work also requires compatible parts and proper bleeding.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.