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Smooth-running shift and brake cables are extremely important for the function of a road bike. Worn or damaged cables should therefore be replaced - here's how.
Check Bowden cable
Check the cables regularly for damage, especially near the stops. Crushing, kinks, torn ends or dirt in the sheaths increase friction, making shifting and braking sluggish and imprecise.
Lubricate Bowden cable well
The best lubricant for Bowden cables is grease. It also seals the ends against water and dirt. In sleeves and cable stops, it protects against corrosion and cracking noises. Pull the well-greased cable back and forth in the sleeve several times so that the grease is well distributed.
Invest in the quality of Bowden cables
It is worth spending a little more money on high-quality cables. The coated Shimano cables improve the performance of all Shimano groupsets enormously. The original Campagnolo cables are also good. We do not recommend special, sealed cable sets for road bikes because they tend to increase friction.
Do not mix up shift and brake cables
Shift and brake cables are different and must not be confused or mixed. Shifter cables are thinner than brake cables and have a smaller head. Attention: There are different versions from Shimano and Campagnolo! The Shimano heads are slightly larger and can seize up in Campagnolo shifters. Shifter cables are slightly slimmer than brake cables and are reinforced lengthways so that they are not compressed when shifting. Outer brake cables have a spiral reinforcement, which makes them somewhat more flexible when routing.
Only use special tools
Always use a good quality cable cutter to shorten the cables. Bowden cable pliers (top image). The sleeves must be cut cleanly and at an exact right angle. Do not cut the cables or sleeves with side cutters or pliers, as these will crush the cables too much.
Prepare the ends of the Bowden cable
Smooth the ends of the cut outer sleeves with a file so that they sit firmly and flush in the stops and end caps. Also widen the cable duct after the cut with a pointed object. (see picture)
Prepare caps
Make sure that you have enough end caps available. The caps for shift and brake cable housings are different. The crimp cap on the cable end is very important, as the cut wire cable splices open quickly and can easily injure you. A spoke nipple or adhesive tape is suitable as a makeshift solution; if you want to be really classy, you can also solder the ends.
Bowden cable: Professional tips
- Avoid tight bends when routing the cables; the cables should run in gentle curves to minimise friction. SRAM specifies a relatively large bend on the rear derailleur to ensure that the derailleur functions perfectly.
- For mechanically actuated disc brakes, special pressure-resistant outer brake linings are recommended. They provide a more defined pressure point and increase braking performance.
- The PTFE-coated Shimano cables (from 105 upwards) improve the function of all Shimano and SRAM drivetrains. Although they are sensitive to fit, they run very smoothly and remain supple for a long time.
Cables and wires
Cables and lines are usually routed through the frame. This poses a number of challenges - TOUR provides tips on how to overcome them.
5 tricks for getting the cable through the frame
1. leave the trains in
If the cables are still fitted, do not pull them completely out of the frame. First replace the inner cable only, then pull out the old outer cable housing over the inner cable and thread the new one over it. If the cables are routed inside the frame without a housing, a long, thin inner cable housing (liner) helps to hold the position of the cable (left image).
2. dismantling
If possible, unscrew all stops and cable guides from the frame and only thread them loosely onto the cables. When routing through the bottom bracket shell, it is usually worth removing the crank and possibly also the bearing.
3. threading aid for Bowden cable
A brake cable with a slightly curved end is a good choice for re-routing. It is somewhat stiffer and heavier than a shift cable and is therefore easier to thread. A long, pre-bent wire (approx. 1 mm thick) is also a good threading aid, e.g. for the cables of hydraulic disc brakes.
4. magnet
A strong magnet can be used to guide cables in the frame from the outside. With carbon frames this works well along the tube wall, with metal frames you can at least "catch" the end of the cable.
5. hoover trick
If edges and tight radii make installation difficult, you can try using woollen thread and a hoover. Seal the remaining frame openings a little, thread the woollen thread through the pull opening and try to suck it back in at the other end. You can then use the thread to pull a liner or inner pull through the frame.
Control centre - the handlebars
All cables arrive at the handlebars, so it is particularly important to lay them properly. What you need to bear in mind.
Narrow gear lever
Make sure you know how to thread the shift cables into the levers. In the relaxed state, this is usually done through an opening, either on the side (Shimano, SRAM) or from below (Campagnolo) under the grip rubber. The channels are narrow and rarely run straight. It is best to use new inner cables with unsoldered ends. It may help to bend the ends slightly.
Temporarily fix trains
First stick the outer covers tightly to the handlebars with adhesive tape before wrapping the handlebar tape. Make sure that the sleeves are firmly seated in the stops and run tightly in the handlebar bends and in their guides. Only cut the sleeves to length after you have pulled the inner cable out far enough. The handlebars must be able to turn freely and the cables must not interfere with each other.
The pitfalls of integrating trains
If the cables run through the handlebars and stem, the length must be correct to the millimetre. If possible, leave the outer casings and brake lines fitted to the handlebars during the work. If they have to be replaced, memorise their exact route and the sequence and orientation of the individual parts, especially the headset.
Handlebars: Professional tips
- Shorten the cables when the handlebars are in the highest position. This leaves some room for manoeuvre to change the height later.
- With small frames, it can be useful to cross the derailleur cables in front of the head tube - then they do not kink as much when turning. The rear derailleur cable then runs to the left-hand side of the frame in the direction of travel, the front derailleur cable to the right. Cross the cables again in or under the down tube.
- Some handlebars offer the option of routing both cables at the front or one at the front and one at the rear of the handlebar. Which is the better option depends on the gear lever and the shape of the handlebars.
Electric shifting and hydraulic brakes on road bikes
With electronic shifting and hydraulic brakes, changing cables is no longer a routine job on a road bike because they do not wear out. However, there are other things to consider with modern transmission lines.
Brake lines
New connection
Each time you disconnect the cable from the brake body or handle, use a new, suitable connector. To do this, the cable must be cut cleanly at the corresponding end.
Leave the brake line long
If you disconnect the brake hose, cut off as little of it as possible. A few millimetres often decide whether the line can be used again or whether a new one has to be fitted. It may help to first pull the connection piece out of the line and then cut the line cleanly - this can save a few millimetres.
Deflate the brake
Use the brake lever to pump the brake as completely empty as possible. This prevents any leaking oil from causing damage.
Electric cable
Check the plug
Many malfunctions can be traced back to faulty connections. If the cables are all in perfect condition, it may also be due to the plugs: they are comparatively stiff and must engage noticeably. Loose plugs can sometimes be pulled out of their seat, especially on the gear lever. We recommend using the right tool to apply more force.
Troubleshooting
If a component does not work, it is often difficult to localise the fault in electrical circuits. Wire the individual connections externally with a long, securely functioning cable. This makes it easy to find the faulty cable or component. Caution: With modern wireless circuits, the entire system does not work without the switching mechanism.
Sensitive Di2 cables
Di2 cables are susceptible to damage: If they are crushed or rub against sharp edges, a cable break can happen quickly. Therefore, make sure you provide sufficient protection, e.g. an axle sleeve in the bottom bracket.
Jens Klötzer
Editor
