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How to install cables on a road bike

Stu Bowers
12 Mar 2021

Cables are often overlooked, but their quality and installation are paramount to the long-lasting performance of your bike

It’s easy to overlook the cables that connect up mechanical gears and brakes on a road bike. But a bit of grit or an excessive amount of wear in these crucial lines of communication can play havoc with how your bike performs.

So if your brakes are feeling a tad sticky, or your gears are a little hesitant to shift, odds are it’ll be their cables that need replacing. 

If you’re looking for specific instructions on how to change your gear cables you can find more information here, while instructions on how to freshen up your brake cables can be found via this link

How to install cables on a road bike

1. When deciding how much cable length you need, allow just enough length for the bars to turn fully

2. Measure twice, cut once. Be precise about the length of outer cable – too much will create an unnecessary bend and add friction in the system; too little will cause imprecise function as it will be overstretched

3. Use good-quality cable cutters so as not to crush the casing and to achieve a flat, smooth end with no burrs. Good mechanics will often grind or file the ends after cutting for the perfect fit with the ferrule

4. Fit the correct ferrules (correct diameter for outer) and make sure they are snug, tight and pushed on all the way

5. Avoid inner cables running directly on metal or plastic where possible

6. Make sure you use the correct cables for the components. Brake and gear cables are different, but also there is a difference between cables for Shimano, SRAM and Campag fitment. If in doubt, check

7. It's often best to replace inners and outers together. A new inner cable in an old piece of outer will sometimes not perform as well as it should

8. Although greases and oils can free up rough cables, the chances are you'll just add to friction troubles longterm. Replace instead

9. If you lose a cable in a frame while trying to route internally, a magnet can often help to guide it to the exit point

10. Finish inner cables neatly with a ferrule to avoid fraying

How do bicycle cables work? 

Until very recently it hasn’t been possible to have a road bike without cables. Now that Shimano has combined hydraulic disc brakes with its electronic Di2 shift system, a cable-free bike is a reality, but we’re still a long way off resigning cables to the history books. 

With the current trend being to route cables internally, tucking them away from view inside frame tubes, these thin steel strands are like the tendons of our bikes, dutifully controlling the precise movements of our braking and gear shifting components, practically unseen.

Yet out of sight shouldn’t be out of mind: our safety and enjoyment depend on them more than most riders realise.  

‘One thing is for sure – poor quality or badly fitted cables are guaranteed to ruin any bike,’ says lifelong bike mechanic Andy Phillips of Ride bike shop in Poole.

‘It doesn’t matter how expensive the parts are, the cables are what makes them work… or not. I get so many people telling me their mech or shifter isn’t working, but most of time the reality is that their cables have had it.’

All are not created equal

The correct terminology for the type of cables used on bicycles is Bowden cables. Like most things in history there is some dispute over who to credit for the invention.

Some attribute it to Sir Frank Bowden, founder of the Raleigh Bicycle Company, who began using them in the early 20th century to replace the solid steel rods that applied brakes at the time. Others credit Ernest Monnington Bowden (no relation), an Irishman who took out a patent for the Bowden cable mechanism in 1896.

Regardless of origin, the Bowden cable is essentially a system of an inner cable running through a flexible outer casing, and more than a century later nothing has surpassed it for simplicity and effectiveness when it comes to operating brakes and gears. But that does not mean that all cables are created equal. 

Mild steel is often used for simplicity of manufacture and cheapness, but has the drawback of being prone to rust and corrosion, so stainless steel, while pricier, is preferred for the inner wires instead, although non-metal alternatives have also been explored, such as Kevlar.

The highest-quality steel cables can also be die extruded – a process that takes away a tiny amount of surface material to ensure the cable is entirely uniform and completely smooth – plus they can be coated with friction-reducing polymer layers such as PTFE. As always, good quality costs extra. 

You want an inner cable to be as slick and free-running as possible. Usually if we want to reduce friction then grease or oil come to our rescue, but where cables are concerned extra lubricants can actually increase the drag inside the housing, and risk attracting dirt and contaminants. Most cables are designed to run clean and dry.

It’s important to remember that brake and gear cable outer casings are task-specific, so not interchangeable. A brake cable outer is spiral wound, so that it is flexible and can withstand the large forces that are applied under braking.

A gear cable outer by contrast is made of stiff, parallel linear strands of wire (originally invented by Shimano) as it does not need to withstand such high forces, but it mustn’t stretch under tension to deliver a crisp and precise gear shift. 

Equally important are the ferrules (the cap ends for the cable outers). They aren’t just decorative; they are responsible for the neat and efficient union of the end of the cable with the component.

It’s really what makes a Bowden cable system work. As Sir Isaac Newton recognised, ‘For every action there is an equal and opposite reaction,’ and when you pull a cable, the ferrule’s job is to push back against the component to cause its movement.

One myth to dispel is that cables stretch over time. Some may do a tiny amount, but really any changes in performance are down to all of the components of the system individually ‘settling in’. 

The quality of the cables will have a huge bearing on how well your bike functions. Good quality cables will improve the function of poor components, and conversely you’ll decrease the performance of expensive parts by fitting poor quality cables. But most important of all is to take care when fitting them.

The key thing to avoid is bends causing unwanted friction, so always look for the smoothest possible curve. Shoddy fitment will result in shoddy performance. 

As the late, great Sheldon Brown said, ‘Care in cable installation is much more important than having the latest titanium doo-dads!’