Bike cables and housing: wear signs, types and replacement

Why cables and housing wear out

Cables and housing are the "nerves" of your bike — they transmit every braking and shifting action. But they endure tension, friction, corrosion, and crushing over the kilometers. A fatigued cable means spongy braking or imprecise shifting.

Wear signs you should not ignore:

• Frayed cable: one or more strands are broken, visible near the pinch bolt
• Cracked or crushed housing: visible compression, often near tight bends or attachment points
• Spongy braking: the lever sinks more than usual despite new pads
• Skipping gears: the derailleur no longer indexes correctly, even after adjusting the barrel adjuster
• Resistance when pulling: you feel friction when operating the lever — the cable is sticking inside the housing

Rule of thumb: replace cables and housing every 2 years in normal use, or every year if you regularly ride in wet conditions.

Stainless vs galvanized: which cable to choose?

• Galvanized cable: the basic, affordable cable. The steel is coated with a thin zinc layer that temporarily protects against corrosion. But this layer wears quickly, and the cable ends up rusting from inside the housing. Avoid if you often ride in rain.
• Stainless steel cable: more expensive (2-3 euros more per cable), but does not rust. The surface is also smoother, reducing friction inside the housing. This is the recommended choice for any regular use.
• PTFE (teflon) cable: stainless cable with a PTFE coating. Minimal friction, but the coating can get damaged at cable clamps. Reserved for demanding setups (long internal routing, road racing).

SIS compression vs spiral housing

This is the most important and most often overlooked distinction:

• SIS housing (compression): structure of parallel longitudinal wires wrapped in a plastic sheath. It resists axial compression — essential for shifting. Each shifter click pushes or pulls a cable, and the housing must NOT compress under load.
• Spiral housing (coil): structure of a steel wire wound in a spiral. It is flexible and handles bending well, but it compresses under load. Used exclusively for mechanical braking.

The rule: SIS housing for derailleurs, spiral housing for brakes. Never swap them — spiral housing on a derailleur will give imprecise indexing and mushy shifting.

Internal routing: the pitfalls

Modern bikes with internal routing (cables running inside the frame) add an extra challenge:

• Use a magnetic guide or a guide cable to thread the new cable through the frame. Without a guide, you can spend hours looking for the exit.
• Never cut the old cable before attaching the new one — tape the new cable to the old one and pull the old one through to guide the new one through the frame.
• Check the housing end caps: internally routed frames have specific stops. A wrongly sized end cap can create play or prevent the housing from clicking in correctly.

Cutting and finishing

• Cut the housing with a dedicated cutter (like the Shimano TL-CT12 or Park Tool CN-10). Universal pliers crush the housing and deform the inner liner.
• Deburr the inside of the housing after cutting with an awl or needle — burrs slow down the cable and wear the PTFE liner.
• Add a housing end cap (ferrule) to each cut end. Without a ferrule, the housing gradually deforms and cable movement degrades.
• Crimp a cable end cap onto the cable after clamping to prevent fraying.

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