: Got cables?

By: g | No Comments » |

Since the weather’s turned nasty, maintenance on bikes has become somethingmother than blowing dust off them. One of the ways to improve shifting/braking [1] performance is to keep your cables clean. While cleaning and lubing is possible, eventually the cables will need replacing.

Equipment needed:
Cable cutters.
New cables + end caps
File
Soldering iron/solder or superglue.
Dremel (every job needs a Dremel!)
A small spike (needle, tack, etc.)

First up, use cable cutters. It’s technically possible to use side cutters or a dremel, but it’s very hard to get a nice clean cut. That nice clean cut affects how easy it is to get the cable through the outer, and the various devices to which you attach the cable. A slight fray at the start can catch and result in having to replace the cable again.

These instuctions deal with conventional cables – Gore “Ride-On” cables are similar, but any instructions here dealing with lubrication should be disregarded in favour of the manufacturer’s advice.

Replacing outer cables

Generally you’ll only need to replace the inners, but occasionally the outers will be sufficiently rusty/dirty to require replacing as well. The easiest way to test this is to try pushing a bit of clean inner through – if it feels “grabby” or “gritty” you should replace the outer as well. The tight arse option is to try flushing the outer with WD-40 or an aerosol silicon lubricant. This can extend the life of an outer, but not indefinitely.

Choose the right kind of outer cable. This is very important! Under the plastic coating, the internals of brake and gear outer cables differ considerably. A brake outer has a helical (like a corkscrew) wrap of relatively thick metal that is reasonably incompressible, with very strong sidewalls. Gear cable outer has a series of thin wires running the full length of the wall. This is extremely incompressible, but the sidewall can split if excessive force is applied. Since gears need precision changes with not much force this cable is suitable, while brakes need much higher amounts of cable tension. Using brake cable outer in place of gear cable lead to sloppy shifts (if you can make it shift). Using gear cable outer in place of brake cable outer could be lethal. Be aware that very old gear, cable had a similar construction to brake cable – this may still be available in some areas, but should be thinner than brake cable.

Cut the cable to length. Any bends should be as wide as possible without the cable needing to curve back (imagine a question mark). Too tight a curve and there’ll be extra friction. Too long a curve and the cable will bend back, as well as having extra friction due to being longer. Also remember that you’ll need to allow for the handlebars to turn freely. As a guide cut the outers to the same length as your previous outers, but be aware that these may well be slightly too long or too short.

If you don’t have proper cable cutters, cutting outers is reasonably easy with a Dremel, or similar tool. If you use anything else, like side cutters, you’ll definitely need to file the ends flat. This isn’t a bad idea to do anyway, since it’s a really easy way to clean up the end of a brake cable, where the end of the helical wrap tends to form a small hook when it’s cut. After cutting, and optionally filing, use a small spike to open out the inner plastic sleeve. A small strand of old cable can be useful for this.

Put an end cap anywhere it’s required (note that some bikes have “special” end caps for various locations, or are designed to simply have the cable put in without a cap), thread the cable in through the cable stops, and you’re ready to run the inners. It’s possible to get end caps with a small o-ring that helps to keep the inners gunk free. A small amount of grease in the end cap can also help the cables move freely, though it can also hold dust in place.

Running a full length outer.

One way to help prolong the life of a cable is to wrap the entire length in an outer. Some people find this makes for increased cable compression, or that gunk tends to kill an entire outer rather than a small length, but it’s certainly an option to consider. It’s also trickier to push an inner cable back through since there are no exposed lengths to grab mid way, but this is generally not a major problem. Running a full length outer generally involves drilling out the cable stops to turn them into cable guides. Since this is an irreversible change and potentially a warranty voiding exercise, try zip tying the outer in place until you’re sure you
want to proceed.

The first stage is to drill out the cable stops. This is easiest with a small grinding attachment on a Dremel – the flexible neck helps to get parallel with the tube. It’s also possible with a conventional drill, or even a rat tail file. Be really careful not to take too much material, and not to drill into the tube/stay. Once the stop is opened out, ensure the inner surface is free of any burrs or ridges that could catch the outer – if these are the wrong shape they can act as a ratchet, and pull the outer through as it vibrates. Eventually you end up with a tiny loop at one of the cable and a huge on at the other, and woeful shifting.

If you are running a full length outer, it’s worth using o-ring end caps, and/or putting a small amount of grease in the end cap to stop water getting in to the main length of cable.

Replacing Inner cables

Inner cables are sufficiently cheap some people treat them as a throw away item. Whether you try to clean your inners or simply replace them, they’re worth maintaining regularly. A quick wipe with a lubricant soaked rag, or a touch of a “dry” lubricant often helps. Wet lubricants and grease are commonly used, but can attract dust. Some cables are teflon coated so as
not to require lubrication.

Brake cables and gear cables differ in their thickness and the swaged on ends. Brake cables tend to have a large low cylinder with the cable coming out of the side. Gear cables tend to have a small high cylinder with the cable coming out one end. Road brake cables tend to look like a larger gear cable with an extra, larger cylinder on the end. The easiest way to get it right is to look at your existing cables, or ask your local bike shop for the right type.

Most brake levers have a slot through which you can remove the cable – unhook the brakes and pull the cable out. Now unbolt the cable from the clamp. Gears require the cable be detached first, then pushed through. This normally requires the shifter to be at one extreme, and generally the removal of some kind of cover. If you can’t determine the access method by inspection check with the manufacturer or your bike shop. Once the cable is removed, check it for any major rust patches or kinks – these could be signs the outer needs replacing as well.

Once the old cable is out, thread the new cable through. Pull out any slack, then loosely clamp the cable. Ensure that the outer is correctly routed and through all stops, and that the inner is correctly threaded. Now adjust the gears/brakes until they’re working correctly and clamp the cable properly. Two good resource for adjusting gears and brakes are sheldonbrown.com and
Parktool.com. Cut the cable about 3-5cm from the clamp. Most cables are provided with crimp on end caps. These stop the end of the cable fraying. A more elegant solution is to solder or superglue the last 3mm or so of the cable. This stops the cable fraying while leaving the end thin enough to pull back through the outer for maintenance. Be careful not to glue the cable to your frame, or melt various components with a soldering iron – if you’re a bit fumble fingered end caps are probably safer.

Dave – who probably could have just pointed out the two URLs for everything, but snuh.

[1] Assuming your shifting [2] and/or braking system uses cables.
[2] Shimano Airlines, or this hack:
http://weightweenies.starbike.com/articles.asp?ID=28

 

Tags:Brakes,cables,gears


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