Are you sick and tired of people debating the merits of road disc brakes? Me too! So today I'm going to rain all over a different parade: cable-operated disc brakes.
Cable disc brakes are not the best at anything. If you set them up perfectly, they can work pretty well, but proper adjustment is a moving target and in really mucky conditions (like on a peanut-butter-sticky ‘cross course, for example) you may find yourself twiddling a barrel adjuster more often than seems reasonable.
'Traditional', single-piston cable disc brakes are an inherently less-than-wonderful design. With a single piston, only one brake pad moves, pushing the disc rotor against a second, fixed pad. This means that every application of the brake involves bending the rotor slightly, and that the pads will never both make perfect, perpendicular contact with the braking surface. Uneven pad wear is all but inevitable, and you need to keep on top of adjustment for your brakes to work properly.
For many years, this was the state of the art in cable disc brakes, and calipers like the Avid BB7 and its cheaper, slightly less adjustable little brother the BB5 were the benchmark. They worked OK and they certainly offered more outright stopping power than rim brakes, but in the cold light of day they basically sucked quite a lot.
TRP upset the apple cart by introducing a dual-piston disc caliper in 2013, the Spyre. Like all the best ideas, the Spyre was beguilingly simple; the brake cable pulls on an arm that straddles the caliper, controlling a piston on either side of the rotor. Symmetrical braking — hurrah!
The Spyre is a vastly more elegant design than any single-piston brake and if you must have cable discs, there's no question that it rules the roost. (To my knowledge, your only other dual-piston option for the road just now is the Rever MCX1, which I've never encountered in the metal and therefore upon which I cannot comment.)
Curiously, Giant's newest entry-level road bike the Contend has just launched with a stem-mounted mechanical-to-hydro converter
Even so, hydraulic brakes are just flat-out better, principally because of their self-adjusting nature; where a mechanical caliper requires you to make continual cable tension adjustments to account for pad wear, hydros self-adjust and they also self-centre to an extent.
When road hydraulics were in their infancy they were an expensive, niche product that most riders couldn't justify. Now the tech has trickled down to the level of relatively affordable groupsets like Shimano Tiagra and SRAM Rival. It's appearing on complete bikes around the £1,000 / US$1,300 / AU$1,700 mark, the kind of money many of us are quite happy to spend on a machine for riding through wet winters or for commuting.
For this reason, I'd argue that for most of us, the need for cable disc brakes has all but disappeared, if indeed it existed in the first place. I've said before that I don't think everyone needs discs or that discs suit everyone's precise requirements, but with the current state of the market I think that if you do want them, you should go the whole hog and just get hydraulics. You'll notice that I've not mentioned hybrid mechanical/hydraulic systems, like the TRP Hy/Rd and the Juin Tech R1. That's because however useful they may have been, it's hard not to view them as an evolutionary dead-end, an interim measure that we made do with while we waited for pure-hydraulics to become more affordable.
Curiously, Giant's newest entry-level road bike the Contend has just launched with a stem-mounted mechanical-to-hydro converter. I'm going to withhold judgment on this until I've actually tried it, but on the face of things it's a profoundly odd choice given the alternatives now available.
The obligatory caveat
Everyone loves a caveat, so here's one: it's possible that for really remote riding — let's say touring in Outer Mongolia — you may be better off with cable operated disc brakes, although even that is highly debatable.
They do have the advantage that you'll never have to bleed them and of course they're childishly simple, with no perishable seals or fluid to boil on big descents — but does that really matter? You can carry spares for any brake system, so I'm not convinced on that score.
Cable disc brakes served their purpose, but we've got better options now. Rest in peace you unlovely things, I won't miss you.
