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Old 02-09-12, 09:26 PM   #1
dleccord
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shifter vs brake housings, quick question!

hello,

i bought both from the service dept but forgot to ask which was which, the difference between both housings are soft and hard. which is which?

many thanks,
kyle
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Old 02-09-12, 09:38 PM   #2
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See picture and description in attached. http://urbanvelo.org/issue13/urbanvelo13_p82-83.html. Brake housing is on right, shifter on left. Brake housing is continupous spiral' Shifter is a bunch of wire strands running same direction as the outside cover. You can use brake housing for shifters (although shifting won't be as good because housing compresses slightly). You can't use shifter housing for brakes because it will rupture under the load that braking puts on housing.
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Old 02-09-12, 09:49 PM   #3
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So you're opinion would be to use the harder housing on the brakes?
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Old 02-09-12, 09:56 PM   #4
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Forget "soft" and "hard". Look at the picture DOS provided. If you are still not 100% sure ask someone (in person) who knows. It is important that you get this right. Using shift cable housing on brakes is a hazardous condition which can lead to personal injury. Don't guess.
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Old 02-09-12, 10:03 PM   #5
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Quote:
Originally Posted by dleccord View Post
So you're opinion would be to use the harder housing on the brakes?
I've never really noticed a difference in hardness so I am not usre what you mean; although , intuitively, I suppose, the coiled brake housing would feel harder. But differentiating between brake a derailleur housing is not a matter of opinion, and there is no need to make determination by feel. Look at the the cut end of the housing, if you see what looks like bunched strands all running in straight line, thats shifter housing; do not use it for brakes. If you see a single flat metal coil spiraliing away fromm you, thats brake housing. Also, standard brake housing in 5mm, shifter housing comes either 4mm or 5mm. So if you have 4mm shifter housing, it will be visually thinner than the brake housing. This method of differentiation won't work, of course, if you have 5mm shifter housing.

edited to add: dsbrantjr beat me to response, making same point with fewer words.
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Old 02-09-12, 10:57 PM   #6
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Think of it this way and you'll understand the difference. Brake housing is a fully collapsed coil spring, so each turn lays directly on it's neighbor. As suck it's steel on steel and doesn't depend on the plastic to hold it together under compression.

OTOH in derailleur housing the strands are lengthwise, and kept from buckling under compression by the plastic coating. This is fine for derailleurs because they operate at low tension/compression loads, but not suited for braking where the loads are much higher. There's also a safety factor involved since the cable is most likely to buckle under the highest load, and that's when you probably need the brakes the most. (otherwise why'd you squeeze so hard?)
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Old 02-09-12, 11:22 PM   #7
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Shifter housing: Won't affect cable length when bent (so the derailleurs won't ghost shift), but is weaker (not suitable for the forces generated from braking).

Brake housing: Stronger (needed for braking), but will affect cable length when bent (not enough to affect braking, but not good for shifting).
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Old 02-10-12, 12:46 AM   #8
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brake. is a coil of square wire, gear is a facia.. a long bundle..
the latter, wires all standing on end,
is said to be compression less. index shifting needs minimal compression
Friction shifting, both can be coil housing..
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Old 02-10-12, 01:11 AM   #9
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Originally Posted by FBinNY View Post
Think of it this way and you'll understand the difference. Brake housing is a fully collapsed coil spring, so each turn lays directly on it's neighbor. As suck it's steel on steel and doesn't depend on the plastic to hold it together under compression.

OTOH in derailleur housing the strands are lengthwise, and kept from buckling under compression by the plastic coating. This is fine for derailleurs because they operate at low tension/compression loads, but not suited for braking where the loads are much higher. There's also a safety factor involved since the cable is most likely to buckle under the highest load, and that's when you probably need the brakes the most. (otherwise why'd you squeeze so hard?)
you sound like an engineer.
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Old 02-10-12, 09:18 AM   #10
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Originally Posted by dleccord View Post
you sound like an engineer.
You make that sound like it's a bad thing. Perhaps we can put it in a simpler form. Derailer cable housing for brakes, bad. Brake cable housing for derailer, meh?
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Old 02-10-12, 09:35 AM   #11
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Originally Posted by dleccord View Post
you sound like an engineer.
I try to explain things in a way that people can understand the key points and make sound judgements for themselves. I don't know if that's a good thing or not, but it's the way I do things.

When I teach mechanic courses, I start with the basics and explain the key difference between brake and derailleur cables. Brake cable transmits force, so good tension/compression strength is the priority. Derailleur cable primarily transmits position. so good dimensional accuracy is most important.

The other way people can look at it is to assume that the folks at the major component companies aren't total idiots and have valid reasons for making two different types of housing, and use them accordingly.
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Old 02-10-12, 10:17 AM   #12
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I try to explain things in a way that people can understand the key points and make sound judgements for themselves. I don't know if that's a good thing or not, but it's the way I do things.

When I teach mechanic courses, I start with the basics and explain the key difference between brake and derailleur cables. Brake cable transmits force, so good tension/compression strength is the priority. Derailleur cable primarily transmits position. so good dimensional accuracy is most important.

The other way people can look at it is to assume that the folks at the major component companies aren't total idiots and have valid reasons for making two different types of housing, and use them accordingly.
cool stuff, i'm taking mechanics of materials right now
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Old 02-10-12, 10:22 AM   #13
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cool stuff, i'm taking mechanics of materials right now
one of my favorite courses almost half a century ago. I hope they still have real lab work, and not just computer simulations.
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