What's the deal with compressionless brake cable housing? 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?
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:


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.
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.