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Bicycle Cable Installation and Maintenance
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by Sheldon "Do It Right" Brown
revised by John "Routing" Allen
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Good Cable Installation For Good Braking And Shifting

Please read this article in connection with our main article about cables. That article describes the different types of cables and cable end fittings.

Gearshift and brake cables often show the difference between a hastily assembled bike and one which has been assembled by a mechanic who cared what he or she was doing.

Especially now that new handlebar designs seem to come along every week, a good mechanic must understand the theory of routing cables. One can no longer rely on a couple of rote "rules of thumb" for routing cables correctly.

Although people pay a lot of attention to what kind of derailers and brakes are fitted to a particular bicycle, good cable installation practices are more important than most differences between different brake and shift systems. The most expensive brakes and derailers will work poorly if there is excessive friction or play in their control cables. Even cheap brakes and derailers can usually be made to perform satisfactorily if care is used in installing the cables.

The great majority of service problems with brakes and gears results from cable friction or misadjustment, not deficiencies in the levers, calipers or derailers.

Cutting Housing and Preparing the Ends

A very common source of excessive cable friction or "sponginess" is improper cutting or failure to shape the ends of the cable properly, allowing actual compression.

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Cable Replacement

To replace a derailer cable, you want to start out with both the derailer and the shifter in whichever position has the cable slack. This will usually be the position corresponding to the smallest chainring/rear sprocket.

If you disconnect the cable (or if it broke) and pedal the bike a couple of times, the derailer will automatically go to the correct position.

While operating the shifter to get it to shift to the loosest position, you may need to pull on the cable. If the shifter indexes, it will stay in that position. If it is a friction shifter with a return spring, you may have to tighten the friction adjustment to get the shifter to stay in the loosest position.

Once the derailer is disconnected from the derailer's anchor bolt, pull the housing (if any) away from the shifter, and then push the exposed inner cable into the shifter. The moulded end of the inner cable should then pop out of the shifter. If it's a simple lever shifter, such as a down-tube or bar-end shifter, the cable end is readily visible.

If it's a more complicated ratcheting type shifter, there will usually be an access hole where the cable end can pop out...but this access hole may line up correctly only if you remembered to shift to the loosest gear position first. In case a Shimano STI shifter does not release to this position, please see advice on another page.

Hole for cable insertion is visible after releasing the shifter to the loosest position and squeezing the brake lever. Cable insertion into STI brake-shift lever. Arrow indicates forward motion of cover plate when brake lever is squeezed.
Cable insertion hole in STI shfiter cable insertion in STI shfiter

 

Twist-grip shifters such as SRAM GripShift are typically the most difficult for cable changing, and these commonly require disassembly.

Generally, the derailer limit stops should not require any adjustment when you replace a cable, but you will need to adjust the indexing.

Before connecting the cable, screw the adjusting barrel all the way in, then back it out maybe a turn or a turn and a half. This will give you the opportunity to loosen the cable a little or to tighten it a little or a lot.

Front Cable Replacement

Thread the cable through the shifter and any housing. Check the condition of the housing and particularly the open ends. Replace or trim if needed. See also my Cables Article. Pull on the cable and operate the shifter until you have the slackest position. The chain will normally be on the smallest chainring.

Run the cable under the anchor bolt hardware and secure it. If it's an indexing system, and particularly with triple chainrings, you will need to fine-tune the indexing to get it to shift well and run smoothly on the middle chainring.

Rear Cable Replacement

Thread the cable through the shifter and any housing. Check the condition of the housing and particularly the open ends. Replace or trim if needed. See also my Cables Article. Pull on the cable and operate the shifter until you have the slackest position. The chain will normally be on the smallest rear sprocket.

Method A:

Use a pair of pliers to pull the cable really tight and secure the anchor bolt. Use the adjusting barrel to correct the indexing adjustment.

Method B:

(This is how I do it. Only works if you have the bike in a work stand of some sort, unless you have three hands.)

Hand pedal forward with your right hand while manually pushing the rear derailer inward until the chain engages the 3rd smallest sprocket. Stop pedaling, then let go of the derailer. The derailer spring will try to move the derailer outward toward the smallest sprocket, but the stopped chain won't let it go all the way.

Pull fairly firmly on the end of the cable to take up the slack and secure it with the anchor bolt. Then you can pedal and check the indexing adjustment. I find that this usually gets me quite close, with only a minimal amount of fine tuning needed to the indexing adjustment.

Cable Routing at the Handlebars

Drop Handlebars Upright Handlebars

Special brake cable routings for unusual frames and forks -- see the section about this on our page about caliper brakes.

Brake Cable Routing

The segment of cable that traverse a pivot or telescoping joint must be run in housing. The cable to a front hub bracket with a rigid fork also must run in housing. Flexing of the fork during braking can tighten an open cable and lock the wheel.

The Four Commandments of Cable Routing:

  1. The handlebars must be able to turn as far as they can in both directions without being limited by a cable pulling taut. Instead, the turning limit must be set by the handlebar bumping into the top tube or by the brake arm or reflector bracket bumping into the down tube.
  2. No wrong direction bends (For example: as the rear brake cable leaves the top tube and makes the bend down toward the caliper, it should make a smooth transition from parallel to the top tube to parallel to the seatstays. If the cable bends up from the top tube before bending down toward the seatstays, it is probably too long. If the cable curves out past the caliper, then bends back at an angle more vertical than the seatstays, it is certainly too long.
  3. Bends that cannot be avoided should be made as wide (gradual) as possible,
  4. Cable housings should be as short as they can be without violating the above rules. If a housing is attached to a part that moves, test it at the extreme positions it will take when in use. Apply a brake; shift a derailer to the positions where the cable is tightest and where it bends the housing the furthest in each direction. Be especially careful with front and rear suspension, which reach their limit positions only under load. A cable to a front hub brake should run in housing even with a rigid fork: the fork's slight flex can tighten the cable.

This cable housing is too long -- there will be unnecessary friction and slop:

Sheldon Brown photo

This cable housing is correct:

Sheldon Brown photo

This cable housing is too short -- when the brake is applied, the housing will not reach:

Sheldon Brown photo

Someone didn't read our advice on cable routing.
DO NOT RUN AN OPEN CABLE TO A FRONT HUB BRAKE!
The rear cable is maybe just a bit long too.

Open drum-brake cable. Do not do this!

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Gear Cable Routing

More often than not, shifting problems are due not to any problem with the derailers, but to excessive friction in the cables that control them. The usual effect of cable friction is to make the derailer move sluggishly when the return spring is pulling it toward a smaller sprocket.

The most common area for this problem is the short loop of cable housing that leads from the rear stay to the derailer. The front end of this housing is exposed to road spray from the front tire, and the resulting rust can seriously degrade shifting. This cable loop should be fairly long, so that it makes a very gradual curve. Many bikes have too short a housing loop here.

And as already described, index-compatible housing should be cut when bent into the shape it will take when in use.

You must have a ferrule at each end of each piece of index-compatible housing. This keeps the housing from falling apart and hleps keep the hole in the housing aligned with the cable stop.

Another problem area is the cable guide where the cables run under the bottom bracket. In addition to sluggish upshifting, friction in this area can cause spontaneous upshifting under load.

Some newer front derailers are designed with a choice of two cable attachment options. If the cable is run on the outside of the anchor bolt, away from the parallelogram pivots, the cage moves less far for a given cable movement, providing a lighter action, and easier fine trimming.

If the cable is run on the inside of the anchor bolt, toward the parallelogram pivots, the cage moves farther for a given cable movement. This is often necessary to provide correct functioning with indexed shifters.

Over or Under the Bottom Bracket?

Autoshifting

Cable that runs either over or under the bottom bracket can sometimes contribute to "autoshifting", spontaneous upshifts of the rear derailer under heavy load. This issue is addressed in a separate article.

"Criss-Cross" Cables

Most bicycles with handlebar-mounted shifters run the rear cable on the right, the front on the left. This causes some awkwardness in routing housing from the shift levers to the frame stops. Because these housings have to be long enough to permit the bars to turn all the way back and forth, the housings often wind up making a reverse bend--for instance, the rear will go from the shifter, which is on the right, swing forward and cross over past the centerline of the bicycle, then back over to the right side of the head tube, before heading down the down tube. These extra bends increase friction, and the fairly forcible contact between the housing and the side of the head tube can damage the finish.

A neat solution to this is to run the cables "criss-cross" style: The rear runs from the lever, (on the right) around the head tube, and to the cable stop on the left side of the downtube! The front cable crosses over similarly from the left side of the handlebar to the right side of the downtube.

The bare cables then cross one another under the middle of the downtube, making an "X". The cables may touch where they cross, but t very lightly, since they are both straight...the tiny bit of friction at this crossing is more than offset by the reduction in friction in the smoother-flowing cable housings.

This technique does not work with over-the-bottom-bracket cable routing, but is doable with most newer bikes that have under-the-bottom-bracket cable routing and cable stops mounted toward the bottom side of the down tube.

This site also contains an extensive article on Derailer Adjustment.

Square knot in cableCable too short? Too long? Broken?

New cable too short? This problem can occur when you can't get a long cable for a tandem or when you need to re-use a front cable at the rear. Don't necessarily throw away cut-off inner wire. It can be spliced in open runs.

There are commercial cable splitters for bicycles with separable frames. Two cable anchor bolts in a strip of metal drilled at both ends also can splice cable. In an emergency, two lengths of cable can be spliced together with a square knot. Bend each piece into a tight "U" shape a couple of inches from the end, then loop them together to form the knot and pull hard on the cable with the lever to tighten it up. You may have to readjust the cable more than once. Highly flexible braided cable may need to be bent into a "Z" shape so it can be knotted once more in order to hold. This is an inelegant bu trelable repair with a shift cable, probably not so reliable with a brake cable.

You probably don't want to carry a cable cutter with you as you ride. You can store excess cable temporarily by coiling it and weaving the end around the coils.

looping cable

And -- if a cable breaks at the lever end, as is usual, and you have left some excess, many shift levers will work if you tie a knot in the cable. Yes, you could prick your fingers, but then also you can continue your ride and have the use of the gearing. This repair might also work with a brake lever if you tie a larger knot, but we haven't tried it and it is strictly for emergencies. It's really better to carry spare cables.

knotto keep cable from pulling through shifter

 

Cable bootThese Boots are made for Cabling

Where a cable end faces upwards, rainwater can run down inside the housing. The water can rust the cable, but worse, in cold weather, the water can freeze and disable a brake a few minutes after taking the bicycle outdoors. The boot used where the cable of a direct-pull brake crosses between the brake arms can be used here to keep water out. Pack the boot with grease to keep water from running down inside. Oiling the cable also helps.

Lubrication

Cable Lubrication

In the old days, before the development of plastic-lined housing, it was necessary to coat the inner cable with light grease or heavy oil.

Modern plastic-lined cables have made the use of grease inappropriate, because the viscosity of the grease makes for sluggish cable movement. This is a more critical concern with modern brake and gear systems that use weaker return springs, and with indexed shifting in general.

Many manufacturers now recommend against using any lubrication on cables. It certainly should be avoided with sealed systems such as Gore-Tex ®. Bicycles used in wet conditions, however, will often benefit by the application of a bit of oil, more as a rust-preventive than as a lubricant. The area of particular concern is the short loop of housing which carries the rear derailer cable around from the chainstay to the derailer.

Some bicycles provide awkward cable routing which forces housing to enter cable stops/adjusting barrels at a fairly sharp angle. This is particularly common on rear cantilever brakes. It often helps to put a bit of grease on the bit of cable that runs through such fittings.

Hardware Lubrication

Much of the hardware associated with cables requires lubrication on assembly.

Take The Trouble To Do It Right

At the risk of repeating myself, let me again urge you to pay careful attention to all aspects of cable routing. Care in cable installation is much more important than having the latest titanium doo-dads!

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Articles by Sheldon Brown and Others


Reports of the demise of this Web site are greatly exaggerated! We at sheldonbrown.com thank Harris Cyclery for its support over the years. Harris Cyclery has closed, but we keep going. Keep visiting the site for new and updated articles, and news about possible new affilations.

Copyright © 1997, 2008 Sheldon Brown

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