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PostPosted: Fri Aug 09, 2013 3:27 am 
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So before I get shredded on this forum let me explain exactly what I mean here;

Basically about 16 years ago Ryders mountain bike was in a shop and upon inspection I realized that he was running Shifter cables as his brake cables, with shifter housing as well, on his xtr v brake set up. They felt amazing and I was blown away. A couple of years later I gave it a shot; using a shifter cable on a xtr lever to bb7 for a few months without any issues.

Now, I've recently acquired 3 sets of Nokon shifter housing and want to run it as brakes.

Does anybody have the engineering specs for specific cables max load? I want to know how much force it takes to snap a brake cable vs. shifter.

Google search comes up with housing tech. and nothing about the actual cables.

Thanks for any info.


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Posted: Fri Aug 09, 2013 3:27 am 


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PostPosted: Fri Aug 09, 2013 9:28 am 
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Joined: Tue Jun 30, 2009 9:04 pm
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Location: Denmark
Not exactly what you are asking, but on my road bike, I have been using 1.1mm gear inner wire with ilink mini for the rear brake. No issues after 2000km and a lot of mountain descents. But MTB braking may put more strain on the cable - I don't know..


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PostPosted: Fri Aug 09, 2013 11:05 am 
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Location: Midlands, United Kingdom
As a road pull ratio levers have a higher leverage ratio they put more tension in the cable than road bike levers (linear for V or MTB cable disc), you won't snap the cable, although (and I'm sure you would) I'd only use stainless as corrosion will have a proportionately faster effect than on a fatter brake cable.

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PostPosted: Fri Aug 09, 2013 10:45 pm 
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Joined: Sun Sep 17, 2006 9:09 pm
Posts: 54
Location: Canada
The last time I used Nokon cables, there wasn't any difference in the housing beads and liner between brake and shifter. So, you should be able to use the housing with brake inner wires without issues.


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PostPosted: Sat Aug 10, 2013 2:08 am 
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Joined: Fri Aug 09, 2013 3:04 am
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Thanks for the info guys

A brake cable will not fit in the liners unfortunately. Alright, I'll give it a shot, it is for a trials bike, but I'll run them on my mtb for a few rides to gain confidence. High end cables only brah.


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PostPosted: Sun Aug 11, 2013 10:57 am 
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If you are talking about the carbon Nokon housing... DON'T DO IT! I tried with very dangerous results. As for the aluminum housing, they are the same between brake and derailleur... only the inside diameter of the liners is different.

The derailleur cables may work for a little while as brake cables, but they won't last long. Also, the smaller heads on the cables will likely tear up the cable stops inside your levers.

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PostPosted: Mon Aug 12, 2013 12:52 pm 
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xnavalav8r wrote:
The derailleur cables may work for a little while as brake cables, but they won't last long. Also, the smaller heads on the cables will likely tear up the cable stops inside your levers.

Because.....?

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PostPosted: Mon Aug 12, 2013 1:48 pm 
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Derailleur cables use a different orientation of the individual wire strands and there are fewer of them. They will stretch considerably with use due to the greater pull and forces associated with braking. Ultimately they will fail.

The heads on the derailleur cables are much smaller than those for a brake cable. They may pull right through the cable stops in your brake levers after gouging them up sufficiently.

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PostPosted: Mon Aug 12, 2013 1:51 pm 
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here is an image and a link which explains the differences...

http://www.bikeman.com/bicycle-repair-tech-info/bikeman-tech-info/1641-cables-a-housing

Image

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PostPosted: Mon Aug 12, 2013 7:50 pm 
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Location: Midlands, United Kingdom
Shifter cable end form isn't much smaller than the road bike end form, road levers have nearly twice the lever ratio of MTB brakes, so in an MTB the cable load is half that of a road bike on that basis you can get away with about 1/2 the seating (actual, allowing for the larger cable hole) area for the end nipple and half the cable cross section. You either exceed the limit of the cable or you don't!

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PostPosted: Thu Sep 19, 2013 12:28 am 
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xnavalav8r wrote:
If you are talking about the carbon Nokon housing... DON'T DO IT! I tried with very dangerous results. As for the aluminum housing, they are the same between brake and derailleur... only the inside diameter of the liners is different.

The derailleur cables may work for a little while as brake cables, but they won't last long. Also, the smaller heads on the cables will likely tear up the cable stops inside your levers.



Not only that, but derailleur cable housing has parallel un-spiralled wires held in place by a jacket. It's designed this way to be stiff in compression, as is required for precision indexed shifting... but at the same time it is low in ultimate strength. Think of it as being brittle. The failure mode is that the jacket ruptures and the wires balloon outward. Suddenly.

Compare that to brake housing which has a continuous spiral wrap of wire. The jacket's only there to keep dirt out, the wire provides all of the compressive strength and it is considerable. Think of it as being tough but flexible. About the only failure mode conceivable would be for one wrap of the spiral to pop outward, which would only lose you a millimeter or two of cable travel.

I'm all for trying to find or build lighter cables, but at least use them the way they were designed: derailleur cables for precision actuation, brake cables for strength. If you want lighter brake cables, research industrial suppliers of Bowden cables, I'm sure they're available in smaller sizes than those deemed safe by brake manufacturer's liability departments, that will still be much stronger, with much more gradual failure modes, than derailleur cables.

References:
http://urbanvelo.org/issue13/urbanvelo13_p82-83.html
http://sheldonbrown.com/cables.html


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PostPosted: Thu Sep 19, 2013 5:43 pm 
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Joined: Tue Aug 30, 2011 7:27 pm
Posts: 36
the housing designs are specific, spiraling for brakes allowing modulation, parallel for derailleur for no compression.
Cables strength, if I recall right a standard for derailleur cable is 250 lbs, brake is 400 lbs. There is probably a safety factor X10 here.
So be careful with what you are doing, it may seems like it could work but you may increase your chances of a long walk home or a free helicopter ride.


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Posted: Thu Sep 19, 2013 5:43 pm 


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