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Ok folks, I'm confused and in need of advice. On my commuter (touring) bike, I just upgraded my BB5's to BB7's. In the process, decided/realized that I also need to replace my cables and housing (@mikes was right in his answer to a past question of mine).

In surfing the 'net I see that I can get compressionless cable housing or "regular" cable housing. Compressionless seems to be preferred by folks interested in higher levels of performance.

That said, I have always trusted Sheldon Brown's advice on a variety of bike related topics. He seems to say that compressionless housing is made for (and should only be used for) indexed shifters and it might be dangerous to use it for brakes. However, there are several vendors (1),(2) who sell compressionless housing made specifically for brakes.

So, is Sheldon wrong? Will I be introducing additional risk in my braking system by using them? Will compressionless cable housings make a significant difference in the performance of my mechanical disc brakes?

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    I dare say the good people at Jagwire tested their cable outers before advertising them as break cables. Both examples you posted have an additional kevlar reinforcement over their gear cable counterparts. – alex Sep 12 '13 at 6:27
  • Sheldon Brown's advice is awesome, but its getting dated. John Allen has been doing updates, but some of it is a decade old now, and obsoleted by tech rolling forward. Someday, Sheldon will return from his current grand fondo brevet world-global mega-ride, and will update all the things. Amen! – Criggie Dec 19 '16 at 3:40
  • I was under the impression that the only advantag cable disk brakes have over hydraulic onse is the price... What would be the benefit of investing in high-end/specialized parts for cable disk brakes? (As compared to just upgrade to hydrolics?) – fgysin Dec 19 '16 at 12:42
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I recently upgraded my brake cables with some Jagwire of the compressionless variety. jm2 is correct in saying the steel housing is reinforced with kevlar to prevent the longitudinal wires from buckling. The performance is very good and my brakes are far more responsive than with the old, traditional spiral-wound housing that was there before.

That said, installation is made a bit more tricky because:

  1. The cable is not as flexy (it's a lot thicker than gear housing) so lengths must be cut appropriatly and secured well with the correct ferrules/end caps.
  2. It is very difficult to cut. I tried first with a proper, full-size hack saw to get a smooth cut and it was immediately blunted. They must use very hard steel. I then just used some high-quality wire cutters which just about did the job and I smoothed up the cuts with a file. Make sure you have decent cutters if you're using compressionless.

It's also debatable whether compressionless is needed for brakes. It's needed for gears as they are indexed so need precise cable draw for a given shifter movement. Brakes have no such need, if you need more caliper movement just squeeze the lever a bit more. It probably gives some finer modulation but I reckon most of the improvements I experienced were just due to new cable vs 8-year-old ropey cable.

  • Great advice, especially about the installation issues. Hadn't considered many of those (I had a hard enough time cutting my old stuff). – D. Woods Sep 12 '13 at 14:32
  • Isn't longitudinal wire housing only for shifters? At least for road I've always been told to use coil for brakes. Or is compressionless brake designed specifically to allow use of longitudinal wires in brake cable housing? – John Doucette Sep 12 '13 at 15:18
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    If you have a dremel that's the way to cut it. Get the thin cut-off wheels. You can get generic packs of 100 on eBay for $12. The benefit is that after you cut you can square it up cleanly. – jqning Jun 14 '15 at 15:54
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I believe Sheldon wrote this before there was brake specific compressionless housing available on the market. My understanding is that brake specific compressionless housing is reinforced with Kevlar, not plastic, and it has certainly been rigorously tested to work as expected.

The folks I know that run compressionless housing on their mechanical disc brake setups seem very happy with it, so if you're not completely happy with your current setup it may be worth a shot.

  • Indeed, compressionless housing for brakes is quite new (post his death, iirc). Regular compressionless housing (e.g. things for your shift cables) will rupture, hence hte need to reinforce. – Batman Dec 16 '14 at 1:03
  • Kevlar is a form of plastic. It is a polyamide, making a cousin of Nylon. (A cousin with much more tensile strength when spun into fibers, albeit). – Kaz Aug 21 '17 at 19:48
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Yes there is a difference between traditional gear & brake housing. And no you shouldn't use standard gear housing for brakes as it can split right down the middle.

The true compressionless housing available for brakes these days is like nokon, i-link and vertebrae. They all use a segmented design and can be used safely for both gears and brakes.

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This can be confusing, especially if you are not new to cycling. Let me explain. Regular brake housing is spiral metal, looks like a compressed spring, with a slick lining. This has been around a long time. But, like the spring it resembles, when you brake and put a load on it it compresses a tiny bit.

With the advent of index shifting, which requires precise cable pull, manufacturers came out with compressionless casing for shifters. The casing is made up of thick wires that are spiral wound, think of a helix, along the length of the cable. When you pull the cable, the wires cannot compress.

In the past you had to be very careful never to use the compressionless housing with brakes as the spiral wound casing was only held together by the plastic outer casing of housing. Shifting did not put enough stress on the housing to split the plastic outer, but braking definitely could cause the housing to split leaving you with no brakes. That could be lethal!

Then someone clever figured out that if you wrapped the spiral wound wire with a material that could withstand braking forces then you would have a braking system that would give better feedback. Now you can buy this as compressionless brake housing. There are also other compressionless housing systems, like Nokon.

My comment about confusing to old timers has to do with being warned to never using spiral wound casing for brakes because it could fail. Now the reinforced spiral wound casing can be used for brakes. You just need to be very careful that the casing is reinforced for use with brakes.

Another thing to note is that compressionless housing is not as flexible as spiral wound casing, so you need to account for that when you route it and cut it.

Given a choice, compressionless is the way to go as there it less slop in the system. You will pay a premium for the housing, but it is worth it. Hope that helps.

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    I fear you have this backwards - it's the linear wires that are compressionless, spiral wound is is the old school cable that changes length slightly when flexed. Over-stressing the linear cables would split them, but a kevlar wrap fixes that in the new linear-wire brake outers. – Móż Sep 13 '16 at 1:03
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Normal fluid driven disc brakes are engineered to use the non-compressible nature of the fluids to drive the caliper. Cable driven disc brakes for bikes use an almost the same mechanisms but instead of driving the caliper by pushing it (compressive force), they pull it (tinsel force) with the cable.

Derailleurs movements need to be more precise than traditional brakes. So, shift cable housing is for bikes is more rigid than typical brake housing for bikes. It deals with much less force than the brakes, so it can be made thinner than on brakes and save some weight.

A shift cable isn't strong enough to handle the forces used with disc brakes and would snap. We need the precision that the rigidity of shift housing with a diameter that can handle the thickness of a brake cable.

Compressionless brake housing gives us that by taking the rigid design of shift cable and scaling it up to handle brake cable thicknesses. But if that was all the cable manufacturers did it wouldn't work. The extra thickness would prevent the cable from snapping but, under these higher forces the steel strands that make up the wall of the housing (housing, not cable) would "mushroom" through the outer plastic jacket like a loose sock.

Imagine holding a fist full of drinking straws. You can balance a plate on top of them and place a lot of weight on top that. If you let go of the straws, they'd collapse. The plate is like the pulling force on the cable, the straws are like the steel strands that make up the housing wall. The wall in compressionless brake housing is wrapped in telfon, kevlar, or steel coil to keep them from deforming, just like your hand keeps the straws together.

Anyway, without this additional rigidity, or more specifically "this lower tolerance for changes in force", the caliper would "float" against the disc and be less efficient. They'd feel squishy and have less power.

I have the BB7 discs like you on one bike and cantilever brakes on four others and compressionless housing (Jagwire Road Pro) on all of them. I definitely do not have the "spongy feel" on the cantis that people often complain about. They are rock solid.

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