The Importance of Internal Cable Routing on Bikes

The Importance of Internal Cable Routing on Bikes

With the increasing popularity of modern bikes, most new bikes (27.5″/650B and 29″/700C) come with the feature of internal cable routing or cable routing inside the frame. Due to their fold mechanism, Folding bikes require more flexible cable routing and are mostly still placed outside the frame, although there are already folding bikes with internal cable routing.

Bikes with hidden cable routing make bikes with external cables look messy and outdated. In this article, we will see that internal cable routing also has many drawbacks and causes problems, as well as the components that can affect cable routing on bikes.

Why use internal cable routing

Making internal cable routing requires additional labor costs and parts, making the price of a bike or frame with internal cable routing slightly more expensive. What benefits and advantages can we get from this extra cost?

Aesthetics

It cannot be denied that bikes with internal cable routing look cleaner, simpler, modern, and elegant. Almost all high-end to mid-range modern bikes offer this feature of cable entering the bike frame. There are no dangling cables, protrusions, or cables that obstruct the frame’s shape, making the frame look sharp. And the absence of cable guides and cables makes the bike easier to clean, all parts can be rubbed until clean.

Aerodynamics

Another reason for the advantage of bikes with internal cable routing is the aerodynamic factor. Bike frames with internal cable routing do not have protruding cable guides on the frame, reducing air resistance/wind due to less friction with the air, which should make the bike faster. It is difficult to quantify the benefits of internal cables to speed, but based on experience, the benefits of aesthetics are greater than the aerodynamic factor.

Safer cables

Cables that are neat reduce the potential for cables to get caught on trees, branches, or other objects around the biking area. The cable routing that enters the frame can also avoid cables from hitting rocks, roads, and other objects, reducing the potential for cable damage, abrasion, and other damage. But this hidden and unseen cable position can also cause many problems, which will be explained below.

The Disadvantages of Internal Cable Routing

Because there are no other bike options, we often do not know whether internal cable routing is necessary, and what the disadvantages of having cables inside the bike frame are. This is not widely recognized by bike users that bikes with internal cables have significant drawbacks. Particularly those who want to change from external cable routing to internal, need to be aware of the risks they will face.

Frame Structure

In bike frames with internal cable routing, there are usually 6 or 8 additional holes in the frame. The presence of these holes will weaken the bike frame structure, although it may not be significant. This becomes significant when we make more holes, incorrect drilling, holes in the carbon frame can become sources of cracks or cracks that can spread if not done correctly. Some frame brands add two holes to the fork or chainstay to hide cables that are about 15 cm long. This will also affect the strength of the frame to some extent, plus other problems due to the addition of holes.

Holes become the entry point of water and dust into the frame

Many internal routing frames do not provide good protection. Usually, on the cable holes, there are additional rubber protectors that not only protect the cable from rubbing against the frame, but also prevent water, dust, and mud from entering the bike frame. The position of the open holes upward and the cable route into the holes will become a way for water/dust/dirt to enter the bike frame. Not all cables inside the bike have casings (covers). Except for hydraulic brake cables, shifter cables, and mechanical brake cables, many are open inside the frame.

Water and other contaminants can cause this steel wire to rust and reduce its lubrication. This includes water and dirt that settle inside the bicycle frame. The inside of the bicycle frame is not coated with paint, especially for iron bicycle frames, which are highly susceptible to rust from the inside of the frame that is difficult to inspect. Usually, at the bottom of the bottom bracket of the bicycle there is a hole for the cable route or as a hole to drain water that enters the bicycle frame. Because the cable position is inside the frame, it is difficult to know its condition.

Just because it is not visible does not mean it is safe, until we feel the performance of the shifter or brakes start to change. Another example is when we lean the bicycle on a rack mount, bicycle support on the car, parking, installing bicycle locks, the pressure of these objects on the brake or bicycle shifter cable can affect its performance, make the cable more slack, bent, or even broken.

Maintenance

One of the biggest factors that distinguishes internal vs external cable routing is in cable maintenance or service. Cable outside the frame is indeed more prone to dirt and friction/impact, but to see its condition, maintain (clean, add lubrication), and replace it is very easy and fast.

Conversely, in internal routing, it takes more patience and time when working with cables. Inserting cables and expecting them to come out of the hole we want is not easy. Some bicycle tools are also made to make this job easier. One of the easiest bicycle tools is to use a magnet, where iron is attached to the end of the cable, and pulled by a magnet from outside the bicycle frame to the desired hole.

Bicycle components with internal cables

There are several bicycle components that use cables, including mechanical cable (bowden), hydraulic, or electrical cables, that can make different cable routing options.

Frame with internal cable

Most modern bicycles already use a bicycle frame with internal cable routing, including folding bikes, and this trend is likely to continue, even for cheap bicycles. Carbon, alloy, titanium, and other materials can all be customized to pass cables from inside the frame. The position of the holes also varies between brands and models, it can be located in the head tube, fork, top tube, chainstay, and others. There are also some that are combined with external cable routing.

Bicycles with neatly arranged external cables do not actually look much different from internal cable frame bicycles at first glance. However, the most cluttered cable parts on the bicycle are usually the cables that go to/from the handlebars.

Handlebar with Full Internal Cable

For bikes that aim for a clean and streamlined look with minimum visible cable routing, the solution is a handlebar with full internal cable routing. Bikes that integrate the cables into the head tube, stem, and handlebar will have a vastly different appearance, similar to a fixie bike with a simple and exotic look. The internal cable system in the handlebar also ensures proper cable length, position, and setup that allows the handlebar to rotate freely to the left or right, like a motorcycle.

Stem and Handlebar with Internal Cable Routing As shown above, the difficulty level of cable routing within the handlebar is much higher. To work with the stem, such as changing its length, the cable must be removed from the brake lever, shifter, or brifter. If using a hydraulic brake system, the brake fluid must be bled. Compatibility between the stem and handlebar must also be considered, and currently, the options for these components are limited.

Not only for road bikes, but mountain bikes also have handlebars with internal cables. A popular example is the MAGURA Cockpit Integration (MCi). This Magura brake has a clean and modern design, with a cylinder in the grip area that also serves as the brake fluid reservoir, making the brake lever minimalist and cables hidden inside the handlebar.

Seatpost

As we know, bike seatposts can also be adjusted for height. A remote-operated seat post or lever is mounted on the handlebars so that we can position the saddle height without having to feel around or look at the saddle. This lever controls the spring (air) pressure within the seat post. Dropper seat posts also have the option of routing the cable through the seat tube, down tube, head tube and to the handlebar.

Di2 frame & electronic groupset

Bicycle components and groupsets (with cables or wireless) are constantly evolving and are beginning to replace mechanical components and groupsets, particularly in high-end groupsets. Shimano with Di2, SRAM with eTap, Campagnolo with EPS (Electronic Power Shift) all have different systems and workings.

At present, unlike SRAM eTap, Shimano Di2 (Digital Integrated Intelligence) does not use a wireless system to connect the shifter to the RD or FD, but uses a special electrical cable, and on the FD/RD there is a motor/machine that will move the derailleur position according to the button/lever on the shifter. So in terms of cabling, the Shimano Di2 electronic groupset is still similar to the mechanical bicycle cabling, only with different cable shapes and sizes, so bicycle frame manufacturers make specific frames to support Di2, which we often see referred to as Di2-compatible frames.

Di2 frames have different cable hole sizes, along with specific brackets to position the external battery, junction box, and additional holes in the frame and bottom bracket to facilitate cable routing and internal battery storage.

However, to use the Shimano Di2 groupset, you don’t have to have a Di2-compatible frame, and conversely a Di2-compatible frame can also be fitted with a mechanical/hydraulic groupset/cable. It just requires more setup and additional parts due to the different hole sizes/shapes and cable stops.

The era and wireless (cable-free) technology are developing rapidly, including for bikes. Electronic component and wireless technology is at a different level, with many advantages and disadvantages. Perhaps someday, we won’t need cables on bikes anymore. But for now, the choice of cable and mechanical/hydraulic is still the cheapest and simplest for bikes.

Which do you prefer, internal or external cable?

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