To The Point - Shift Cables and Housing

Feb 12, 2013 at 0:07
Feb 12, 2013
by Mike Levy  
 
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Given that they control the shifting (and often the braking as well) of your bike, cables and housing most certainly don't get the respect that they deserve. We often take it for granted that a shift cable will almost never fail during a ride, or that, barring wear and tear, its housing will assuredly never come apart. That feeling of security comes from many decades worth of manufacturing experience and has resulted in the relatively inexpensive cable becoming an unsung hero of the modern mountain bike. Jagwire's Tech Support Specialist Ben Oliver has been working with cables, hoses, and housing for the past fifteen years, including wrenching for professional cycling teams around the globe, and here he sheds some light on this often overlooked subject.




What exactly are a shift cables and housing made of?

Shift cables are typically made using nineteen steel wire strands, either galvanized
or stainless. An inner core is created using seven strands with an additional twelve
wrapped around the outside in a slight spiral.

Shift housing features four layers. From the inner-most layers out, they include:
• a polymer inner liner, which may or may not be lubricated
• a shell made of linear steel strands
• another polymer layer that stabilizes the linear shell
• and an outer layer of housing that faces the elements

Jagwire shift cable and housing detail

A dissected view of shift housing



Is there really a difference between brake and shift housing?

There is a critical difference in the inner shells of brake and shift housing. Brake
housing has a shell of coiled, flat wound wire wrapped around the inner liner. This
wound wire flexes slightly to resist the significantly higher load that brake cables put
on housing. This flexing would wreak havoc on shifting performance because it
doesn’t deliver the precision movement needed for clean shifts.

Shift housing resists this flexing by using linear strands of wire that run the length
of the housing parallel to the shift cable. These wires experience much lighter
loads, but are designed to keep the housing from compressing, resulting in clean,
crisp shifting. If you’ve ever tried to use shift housing in place of brake housing you’ve
seen what a poor substitute it is. The force of braking will either cause the linear
strands of wire to compress and bow out or simply split the housing into pieces.

All this, not to mention the cables and housings for each application are of vastly
different size, are reasons to never switch up the two.

Jagwire brake cable and housing detail

The same view of a section of brake housing.



And why is it that shift cables are made from spiral steel strands instead of a simpler straight wire?

Cables today are made from spiral steel wires to deliver strength and durability, while still remaining flexible. A single or series of straight wires would be extremely stiff and vulnerable to breaking when curved.






We've all seen cables rust, but could this cause them to fail?

Rust can obviously be a cause, but most frequently it’s general fatigue and wear. When overused or installed incorrectly, cables can fray due to movement against cables guides, tight bends in the frame or shifter, etc...





How is the cable "head" attached to the cable, and why is it the shape it is?

The shape of the cable head is dictated by the individual OEM component manufacturers.
Mountain bike brake cables have settled on something fairly standard, whereas road
components have a couple different types of cable heads for both shift and brake.

The attachment of the cable head is accomplished by first cutting the cable, then spot
welding the end. Once complete, the welded end is “punched,” causing the individual
strands of the cable to mushroom out. This mushrooming allows the cable head to be
forged around and through the strands making it extremely strong and resistant to being
pulled off the cable during braking or shifting.


Shift cable used in Crank Brothers Kronolog seat post
Shift cables are often used to control dropper seat posts as well.



Mechanics often use the phrase "cable stretch." What does this mean, and is it all down to the cable or does housing play a part?

In general, cables today are all pre-stretched. The “cable stretch” phenomenon has more
to do with housing compression that occurs after installing new cables.

If you’ve ever put on new brake cables and housing you know the way to finish everything
off is to give the lever several hard squeezes. This compresses the flat-wound wire and
“stretches” the housing. There’s a noticeable change in lever feel once this has been done.

It’s less of an issue with derailleur cables and housing, but it’s still good practice to get any
settling that the cables and housing are going to do out of the way before you send a new
bike out on its maiden voyage. This can be difficult if the bike uses internal cable routing. But
again, it’s usually not as dramatic on shift cables, and if it does occur all it takes is a simple
twist of a barrel adjuster to take up the slack.



www.jagwire.com

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73 Comments

  • + 46
 Maybe this will stop some of the dumbass questions I get at work...! Good article.
  • + 58
 there are no dumb questions.. only dumb people.. Wink
  • + 10
 or dumb answers Smile
  • - 35
 I use shimano dura ace or xtr 1.2 mm housing with sram 1.1 cable.
  • + 12
 maybe in an educational setting but trust me where I work there are plenty of dumb questions from dumb people doing dumb things... and they're gettign paid for it!
  • + 27
 I don't think that there is such a thing as a dumb question. If you go to a doctor you have to know everithyng about diseases? If you work in a bikeshop, you have to answer every question without judging the person, or the question itself. I agree, these articles are welcome, but i'm not an expert in bike mechanics and i prefere to leave some things in an experts hands.
  • - 30
 This is all well and good but I want to know how the shifter cables really work. I mean really how they really really work man. I like want to put a camera inside the cable and see it man. I got to feel man how does this thing really work???????? How they do that???
  • + 12
 Dude... You used "really" five times in one sentance...
  • + 13
 Sentence dude....
  • + 21
 DAMN YOU DYSLEXIA!!!!!!
  • + 14
 rejean and Questrails' sense of humour are underrated
  • + 12
 gota give PB credit for being able to put togather a 6 or 7 paragraph article on cables and housing..... theres really no mystery to it. lol. but they pulled it off
  • + 9
 tried using brake cable once as an emergency shifter cable,................tis true is does not work for shiz

+ it is true that there is no dumb questions only dumb people, and the french
  • + 7
 Why so many negative props? XTR housing has teflon inside and sram cable is a bit smaller so it glides easier. I've gotten some better shifting performance with this setup. Sorry fellow pinkbike users, next time i won't share my opinion!
  • + 2
 maybe if you said that in the first place, your comment would be relevant.
[Reply]
  • + 23
 I never came to appreciate the difference between gear and brake outers/cables until I had to cut them. They are indeed marvels in their own way. I'd say that probably 95% of problems people have with gears or brakes are the cables and not the components themselves.

In answer to 'who runs cable brakes...', the answer is pretty much everyone on the planet except our very small little niche of mountain bikers. Same thing with square taper cranks and threaded headsets, they might be irrelevant for a downhill bike, but not for the common town/commuter bike.
[Reply]
  • + 7
 if any one wants there shifter to feel crisper and more responsive, ive had awesome luck with a company in idaho called "POWER CORDZ" they are a kevlar cord so no stretching and the housing looks normal but instead of stainless steel it uses aluminum making it 2nd lightst housing behind nokon for a fraction of the price, not that housing was to heavy already
  • + 2
 I've been thinking for the last few years how kevlar would do the trick, too bad its so expensive! How long do they usually last for you?
  • + 3
 They last longer than a cable since they do not corrode. They are kinda a pain to cut or work with, but very legit performance.
  • + 1
 dude weight isn't the only thing.... aluminium has half the weight of S/S but also half the strength, it also stretch, bend and breaks much easier.....
  • + 1
 Dang! Those are expensive! I just buy Jagwire for $15
[Reply]
  • + 1
 On my old beater bike when I rebuilt it, I poured Shell marine grade oil into the brake cable housing and my cable brakes felt almost as smooth as hydraulic, and the smoothness lasted for over a year, but nothing beats the actual feel of hydraulic brakes, I wonder what the future holds for bike brakes? Brake by wire systems? lol
  • + 1
 cables are a place where you want lube to stick around, definitely grease territory instead of oil. I use slick honey. using a grease also helps displace anything else that may try to get into your cables. I've seen housing shatter due to water freezing in the line, not cool halfway through a race run.
  • + 1
 The Shell oil I used was very thick, I think it was 70w90, worked great, but I wouldn't recommend it for gear cables.
  • + 1
 wasn't meant as a dig: gear lube is very nearly thick enough to be a light grease, and the additives they put in it are designed to make it act even more like a grease.
[Reply]
  • + 4
 This is definitely an interesting article and it's great to look at bikes from different perspectives.
  • + 12
 Absolutely agree. I can't speak for anyone else, but I loved the details and the spotlight on something I take for granted so often.
  • + 2
 ^^^ I agree aye. It's often the little things like a brake or shifter cable that every cyclist takes for granted and often have a lot of thought go into them in the design process. Good to see an article on these little marvels of the cycling world. I myself use hydraulic brakes though, as I'm an AM, DH/FR biker. Cable brakes just aren't as strong as their hydraulic brothers. Oil doesn't compress as much as the steel wires stretch so the hydraulics are very responsive and brakes can be applied with great control plus they are self adjusting.
[Reply]
  • + 1
 Whilst standard shift housing is unsuitable for braking applications Goodridge housing is non flexible and is made to resist braking forces, thus producing a much more powerful and crisp feel at the lever.
  • + 0
 Yeah, it's possible to get plenty of power out of the BB7 brake. Enough power for non stop runs at Mont St Anne with no arm pump. You just have to have the right cables and pads. Bring on the downvotes, but it's true. And I've never had a bb7 fail, which I can't say for most of the hydros I've tried.
[Reply]
  • + 1
 Never had to lube a cable after it was installed...., i now use a Teflon coated shifter cable Smile no need to lube (and looks cool ).
[Reply]
  • + 3
 Never new there was that much to cables and housings...
[Reply]
  • + 2
 So what about 'linear' brake housings you get for bmxs and the like? surely they are very similar to a shifter housing?
  • + 2
 also, great set of articles so far!
  • + 1
 linear brake housing is the linear cables around the coiled inner. the coiled inner is resistant to brake forces, while the linear inner prevents the coiled inner from compressing.
  • + 1
 ahhhh! Its obvious now you've said it. Cheers!
  • + 1
 Full specs are here:-
www.odysseybmx.com/catalog/braking/slic-kable

They actually work great as gear cable on an MTB too.
  • + 2
 Anyone running mechanical discs would find a major upgrade in using the linear brake housing. It makes the brakes so much more responsive and powerful due to the linear stiffness of the housing. Combine this with a section of stainless tube and you have a great system for mech discs. Avid makes, or used to make, a system like this that worked wonders for their BB discs.
  • + 1
 to add to bogey, nice levers are always a plus.
[Reply]
  • + 1
 LEarned a little bit today...I got a rear mech disc brake on my winter beater...I thought it was just a thicker cable...guess not.
[Reply]
  • + 1
 Remember kids, use a good sheath for protection. Wouldn't want an "accident" now would we?
[Reply]
  • + 1
 Gore ride on cables are the best. Installed them 2 years ago and haven't had to adjust them once. Still smooth and like new.
[Reply]
  • + 1
 Cable oilers are available for motorcycles that will work great on bike cables
www.youtube.com/watch?v=e0w42p1RqbU
[Reply]
  • + 1
 I just stick my gear cable in and on I don't do anythink to it . Fit and forget
[Reply]
  • + 2
 Opinions on lubing shifter cables?
  • - 2
 I do not lube TBH. But I always give an outer a proper blast of GT85 and then lube it before wacking the cable in. I also wash the cable with GT85. But then I keep my cables in the tub with some oil at the bottom so they are pre greased. I found that it actually makes it attract too much dust, etc. when your cable is properly lubed up- if your outer is nice, clean and lubed up there should not be any need for additional lube on cables, right? Or should there?
  • + 2
 lube alllll the cables Wink well outer cables, shit gets messy trying to lube the inners' just flush the outer through with some gt85/tf2 spray, but make sure to de-grease the outside of the outers, dont want dirt sticking anywhere near the entrances to cable outer. Smile
  • + 2
 I reckon it might be just the case of different techniques and similar results... Lubing the inners is way easier I do admit. And it makes sense too as you change the inners more frequently that outers. But unless the outer is prepared than it won't last long IMHO. Any 'correct' procedures?
  • + 1
 I have been using graphite on the cables.
  • + 2
 I allways grease my cables by putting blob of grease on my thumb/finger and as I pull the cable thru the outer the grease is applied along the length of the cable , this also helps ' plug up ' the ends of the outer stopping any crap getting in.
  • + 4
 I use the tube that comes with Tri-Flo and drop a few beads on the opening of the housing, wait till each gets sucked into the housing and then insert the inner. This does attract dirt, but I do my own mechanical work on my bike and I do it often - so no long term problems. I also run full-length housing so there is also less dirt and water getting where it isn't wanted.
  • + 1
 I have used those specially coated cables that claim not to require lube. They work okay, but the coating did wear off after a year of my usage. I lubed my recent build with a light film of grease and cant tell the difference between the grease and the special coatings. I do have several twists in my routing though. Perhaps a roadie would benefit more from the special coating stuff.
  • + 2
 If you run a full length housing then lubing the cables is not a problem. I do it with light oil, dipping it drop by drop in the housing before inserting the cable. And even if you have to change the cables two times a year, they are cheap enough (about 1-2€) for to do that.
  • + 3
 good cabling takes skill and experience, it makes a big difference to the performance (action and feel) of mechanical gearing and braking systems, and can also prevent premature wear to frames, fork crowns and other bike components.


Sometimes running a cable 10mm too long makes a big difference. good cabling is the sign of an experienced mechanic who understands their work Wink


now we are moving to electric shifting systems like Campy EPS and Shimano Di2 it really makes you look at mechanical shifting systems again.

best product I have found for pre-lubing cables is from "Pro-Gold" who even make a syringe-style cable lubing solution, absolutely fantastic, check this: progoldmfr.com/store/index.php?route=product/product&product_id=52

best gear cable I have used in the workshop? Shimano SP-41 for gear cable outer, and Shimano PTFE (Teflon) coated inner cable

for cable brakes? It does not matter so much, as long as its well lubed with a thick wet lube: Jagwire or Clarke's outer works just fine with similar inner cables.

have found the super-expensive Gore-Tex cable systems a complete waste of money! Better off cabling the bike properly and replacing the cabling as and when needed.
  • + 1
 I find that Middleburn Cable Oilers work pretty well on both cable actuated dropper posts and mechs. Use a good blast of GT85 or alcohol if it's cold.
[Reply]
  • + 1
 I love this article -- so awesomely different from the usual. Thanks, guys!
[Reply]
  • + 1
 what are peoples thoughts on JagWire Housing
  • + 3
 probably one of the most well known and best....and relatively cheap. I've run it on all my rigs, even my beater...shifting is as smooth as glass.
[Reply]
  • + 1
 lol, jagwire
  • + 1
 Am I missing something? Why the "lol"? Is there something wrong with Jagwire? Not trying to be smart, I'm just in the market for cable housing - are there better brands out there?
  • + 1
 shimano SP41 is the ONLY shift outer to use, period.
  • + 1
 i find my jaggwire housing is just fine and you can get it in almost any color too not saying the SP41 is garbage just never used it or heard of it till now ?
[Reply]
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