Cable Issues.

One of the most common problems modern bikes develop and, one of the easiest fixes, concerns indexed gear shifting. Modern derailleurs, especially rear ones, are nothing less than engineering marvels and we have all grown quite accustomed to the flawless and smooth gear changes that grace all today’s bicycles. As with most things, the more refined and technical something becomes, the easier it is to disrupt its operation. Here we come to the easiest way to upset a derailleur; friction.

When you push, pull or twist a gear shifter you are pulling an exact amount of cable that stays constant all the way to the derailleur, which in turn moves the derailleur in or out the perfect amount to facilitate a perfect gear change. Any time you are pulling on the cable for a gear change you will overcome any friction or resistance in the system because we can exert any extra pressure required to move said shifter. However, when we are releasing cable at the shifter end all that is pulling on the cable is the relatively small return springs in the derailleurs themselves. Now we have a problem.

So, what causes a once perfectly operating system to become a non functioning, frustrating, irritant that drives you to the edge of insanity. In short, contamination. Dust, water, sweat and mud. If you look closely at a bicycles cabling you will notice that there are sections of bare cable and also many sections of housing, the stuff the bare cable disappears into to navigate a bend in the system. Some systems have lots of bare cables and short runs of housing and others will run long lengths of housing. It makes no real difference, one is no less susceptible to contamination in the long run, (no pun intended.) Dust and moisture always gets dragged into the housing and will build up friction and stop the cables sliding gracefully in and out.

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On the left a standard mtb brake cable. Above a standard shift cable.

Now we come to the fix. There are a few things you can do to get things moving again, loosen the cables and slide off the housing and flush with a light weight lubricant such as Tri-Flow. After flushing wipe the cables down and apply a thin coating of bicycle grease. This will get things loosened up again but in my experience is a short term fix. The best way to deal with the problem is to replace. Cables and housing are relatively cheap and just replacing them will make the shifting like new again. Whenever we do a tune up and most any full overhaul, will see us replace the shifting cables and housing and usually the brake lines as well. Whilst on the subject of brakes, they suffer exactly the same issue but tend to cause less problems when the release slows down, therefore people tend not to notice the issue as much as with the shifting.

It amazes me how bad things will get before people seek a solution. I have had systems seized completely and the bike has effectively become a single speed. Many times the force that has to be exerted on the shifter has resulted in a complete failure, expensive. More often than not people just quit shifting, which is sad and a little silly honestly. So if you are experiencing these issues get it fixed.

At this point, having been informed of the benefits of new cables and housing, I will issue certain caveats to be aware of when choosing replacements. Not all cables and housing is created equal. Standard derailleur cables are 1.2mm in diameter, brake 1.5mm. The cables are made of smaller wires in a standard twist bringing it up to the required diameter. At the ends are the various different slugs which interface with the brake, shifter etc. A cheap inferior cable will stretch easily and can be quite rough on the exterior, which defeats the object of replacing it. There are many different makes and our favorite brand in the store is Jagwire. We have found their slick sport cables to be superior to others in every way. They are pre-stretched which removes a lot of the initial bedding in stage and they are also mandrel drawn. This is a process of smoothing the ridges on the exterior of the cable formed by the smaller wires. They make the cables in both stainless steel and a zinc coated steel. Both are highly recommended. The housing we prefer is also by Jagwire and has a superior inner liner to what we find on other brands. It also comes in all manor of colors for those of you who like to have a touch of style and coordination. Bottom line, this housing will let your cables slide around in there like a greased penguin on pack ice.

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A zinc coated cable is the shiny one of the three above. Stainless steel tends to be a little darker and dull. Both work well, the stainless are a little more expensive than the zinc coating. The zinc will eventually wear away to reveal a bare, unprotected steel but, by that point, the housing would be gummed up and locked solid anyway.

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The above picture shows the two common housing types, brake at top and derailleur at bottom. I have revealed the individual layers to each. The exterior protective layer, the main wire arrangement for strength and the inner slick guide tube. The inner tube is the key to the performance of the system and it is this component that causes the problems when it gets clogged or wears through. As I mentioned earlier, the Jagwire liner is my recommendation but it will wear out eventually too.

Other manufacturers that are worthy of a mention are.

Sram Gore, Shimano, Promax. Nokon. All these are good brands and produce fine cables and housing, we have used all of them, however Jagwire still has the edge. Whilst on the subject of recommendations I will give you a big one. Never, ever, ever and one more time EVER use a cable that has an exterior coating on it, apart from zinc. Many years ago now some idiot woke up in the morning and during the course of frying his eggs and bacon in a frying pan with a Teflon coating decided, that if Teflon made his egg slide onto the plate without sticking it would do the same on your shift cable. On paper this sounds like a fantastic idea, however in the real world rarely has there been a worse one. Any bike mechanic that has been at his post a while will regale you with stories of Teflon coated cables. The worst thing about them is the fact that they are still being produced in vast quantities. I often open a box of new shifters and find a pair nestled in the corner for my delectation, honestly I’d rather find a severed thumb. What, I hear you cry, is the problem, well I’ll tell you. Teflon may be great on your frying pan but on a cable it just peels right off in a fuzzy birds nest immediately wedging itself in the housing, causing more friction than dust ever could.

This is a brand new, unused coated cable. I’ve seen less hair on an Aberdeen Angus.

This is a brand new, unused coated cable. I’ve seen less hair on an Aberdeen Angus.

This is what they look like in there natural habitat. You will see them in various colors, Regardless of hue, avoid them like the plague.

This is what they look like in there natural habitat. You will see them in various colors, Regardless of hue, avoid them like the plague.

This tumble weed was dug out of a piece of derailleur housing

This tumble weed was dug out of a piece of derailleur housing

Over the years plain Teflon coatings have progressed into all manor of wonderful concoctions and exotic blends and all are equally bad. I cannot overstate how abysmal these things are or, explain why they are still being made and recommended for use by such big names in the industry. I can only imagine that it is like the Emperor’s new clothes, nobody wants to tell them they have been an idiot. Anyway, bad ideas happen and Teflon cables won’t be the last and they certainly are in good company. Two that spring readily to mind are; Nikola Tesla’s earthquake machine and, my personal favorite, Alexander Graham Bells six nippled sheep. What kind of mind must you have that segues from inventing the telephone on a Thursday to deciding that Friday would best be spent increasing, by four, the nipples on a sheep. These are the questions that keep me awake at night. And, for anyone thinking I made up these last two ideas; I did not, they are absolutely true, you need to look them up, Quite fascinating…

Posted on January 31, 2019 .