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i was replying to fronesis who had said "no ferrule at shifter". that's all. ferrules on derailleur housing serve an important function.

the tech manual starts with the usual dire campy warnings about being used by professional mechanics only. hence my little joke.
 

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"Ferrules or no ferrules, that is the question."
~ the internet

Brake cables:
Spiral brake cable housing has a pressure point where it was cut - the end of the spiral's tip rests against the stop, be that on the frame, caliper, brake lever block. The steel itself has certain deflection characteristics, a certain tensile strengh, and if you don't surpass that, it won't permanently deform. During braking, there is some deformation happening at the end of the cable, where the spiral wants to unravel as it's being pushed against at that pressure point. When braking stops, it springs back. (note that we don't know what to expect of cheap chinese cables as material quality/density varies wildly, so some may actually start to get permanent deformation. but in absense of consistency, this would be rather hard to predict).
Without a ferrule, braking may feel slightly softer/"mushier" (while it is one of the contributing factors, it is not the only one. other factors such as the steel used (alloy and density (quality)), precision of the wind (how tightly), brake pad material, caliper flex, lever and lever housing flex...)
Brake cable ferrules serve 3 purposes: to provide structural support to prevent that temporary expansion at the ends. It distributes some of that pressure around a larger general area covered by the ferrule along the housing. Braking can feel a bit crisper with ferrules. And lastly, it helps prevent the cable from twisting when you use the barrel adjusters to adjust housing length.

Shifter cables:
Most shifter cable housings have straight wire strands arranged to form a cylindrical structure, to reduce compression. The plastic envelope around it provides enough support to keep them aligned, but is considered insufficient at the ends. The use of cable cutters inevitably results in some of the strands being every so slightly longer or shorter than the others. This causes some to get more pressure, where they flex, others less pressure.
Ferrules provide that needed reinforcement so the housing maintains it's shape and integrity by holding it all together, and by transferring some of the force from the higher pressure points, to be more evenly distributed into the housing.
Leave out the ferrules, and shifting may be affected slightly. Cable housing integrity over time may also be affected, especially the plastic envelope that holds it all together.
Shifter housing ferrules provide structural support and contribute to crisper shifing.

You can leave any and all ferrules out if you want. Your cable ends will deform slightly as pressure increases. It is one of the factors, in a chain of variables, that affect how crisp and how sharply your cables react to your commands. If a cable's envelope is so thick and strong that it is considered to have "integrated" ferrules, a ferrule can still be of help with regards to that pressure point where the spiral is cut. Unless you have a tool to plane it.


As for some cables requiring ferrules and others not, you may debate that all you want: a ferrule will never harm.


PS: my apologies for reviving an old thread (surely someone will jump out and slap me in the face for it). I hadn't looked at the dates - only doing so after composing my reply.
I stumbled upon this while researching something about some Campagnolo brifters I was working on. I had found some of the comments here to be entertaining, or simply stating ways of doing things without appearing to having a good understanding of a ferrule's purpose. So, as others may stumble on this thread just as I have, I thought this information could be helpful to past commentators and future visitors alike.
 

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"Ferrules or no ferrules, that is the question."
~ the internet

Brake cables:
Spiral brake cable housing has a pressure point where it was cut - the end of the spiral's tip rests against the stop, be that on the frame, caliper, brake lever block. The steel itself has certain deflection characteristics, a certain tensile strengh, and if you don't surpass that, it won't permanently deform. During braking, there is some deformation happening at the end of the cable, where the spiral wants to unravel as it's being pushed against at that pressure point. When braking stops, it springs back. (note that we don't know what to expect of cheap chinese cables as material quality/density varies wildly, so some may actually start to get permanent deformation. but in absense of consistency, this would be rather hard to predict).
Without a ferrule, braking may feel slightly softer/"mushier" (while it is one of the contributing factors, it is not the only one. other factors such as the steel used (alloy and density (quality)), precision of the wind (how tightly), brake pad material, caliper flex, lever and lever housing flex...)
Brake cable ferrules serve 3 purposes: to provide structural support to prevent that temporary expansion at the ends. It distributes some of that pressure around a larger general area covered by the ferrule along the housing. Braking can feel a bit crisper with ferrules. And lastly, it helps prevent the cable from twisting when you use the barrel adjusters to adjust housing length.

Shifter cables:
Most shifter cable housings have straight wire strands arranged to form a cylindrical structure, to reduce compression. The plastic envelope around it provides enough support to keep them aligned, but is considered insufficient at the ends. The use of cable cutters inevitably results in some of the strands being every so slightly longer or shorter than the others. This causes some to get more pressure, where they flex, others less pressure.
Ferrules provide that needed reinforcement so the housing maintains it's shape and integrity by holding it all together, and by transferring some of the force from the higher pressure points, to be more evenly distributed into the housing.
Leave out the ferrules, and shifting may be affected slightly. Cable housing integrity over time may also be affected, especially the plastic envelope that holds it all together.
Shifter housing ferrules provide structural support and contribute to crisper shifing.

You can leave any and all ferrules out if you want. Your cable ends will deform slightly as pressure increases. It is one of the factors, in a chain of variables, that affect how crisp and how sharply your cables react to your commands. If a cable's envelope is so thick and strong that it is considered to have "integrated" ferrules, a ferrule can still be of help with regards to that pressure point where the spiral is cut. Unless you have a tool to plane it.


As for some cables requiring ferrules and others not, you may debate that all you want: a ferrule will never harm.


PS: my apologies for reviving an old thread (surely someone will jump out and slap me in the face for it). I hadn't looked at the dates - only doing so after composing my reply.
I stumbled upon this while researching something about some Campagnolo brifters I was working on. I had found some of the comments here to be entertaining, or simply stating ways of doing things without appearing to having a good understanding of a ferrule's purpose. So, as others may stumble on this thread just as I have, I thought this information could be helpful to past commentators and future visitors alike.
Aside from the mechanical properties of materials, lever "feel" can be affected by installation. This is why I always prep the casing ends by ensuring that the strands/coils are squared with a quick hit to a shop grinder, and trimming the outer casing back just a bit to optimizes the contact surface to the ferrule/stop.

I am not convinced that ferrules improve the "feel", especially when they become worn and deformed. Anytime there is another "interface", deflection occurs and tends to soften things. Rather, I believe ferrules mainly serve as a way to keep the moisture out of the casing as the exposed strands have capillary actions that can cause problems.

Ferrules are used on frame stops because of dimensional variations from one brand to another that are difficult to account for. On locations where this is can be better controlled i.e. the hood/shifter, caliper, derailleur, etc., ferrules are not necessary, this is likely why Campy do not use them at these locations.
 
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