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The Fall of Discs: Tips for setting up the TRP Parabox

  • By Michael Robson
  • Published Sep. 19, 2012
  • Updated Oct. 30, 2014 at 10:16 AM EST

Editor’s Note: Disc brakes are here for cyclocross in a big way. Nearly every manufacturer is offering at least one disc-ready frame and many of the sport’s heavyweights are adopting the technology for 2012-13. We’ve been proponents of disc technology for ’cross for years and over the coming weeks, VeloNews.com contributor Michael Robson will explore the burgeoning arena of ‘cross-specific disc brakes, from the new gear to tips on getting your disc set-up dialed.

There’s no doubt that the holy grail of disc brakes in cyclocross right now is a full hydraulic system, right out of the lever, and it may eventually come our way — perhaps even this week at Interbike. But for now, the only option is cable-actuated discs, which have the rider pull the lever, which pulls a cable. In the current melee of cable-actuated disc brakes in cyclocross, it’s easy to overlook some of the more simplified and elegant solutions, namely the TRP Parabox.

The deal here is pretty straightforward: A simple, double-barreled master cylinder that mounts under the stem coverts action at the lever into hydraulic action in the line. The point is to convert the cable pull to hydraulic pressure as early as possible in the process so the brakes feel as hydraulic as possible.

Installation is pretty self-explanatory, but there are a couple of pitfalls. First, the short sections of cable housing coming out of the lever have to be cut to exactly the right length. If you go 3mm short or long, it won’t work, and patience here is key. Best practice is to mount the Parabox master cylinder where it is going to reside under the stem, insert the metal cable noodles provided and then set the housing lengths. At this point, keep an eye on where the cables are going to pop out at the back of the Parabox and be sure they have some room to be cut and capped.

After that it get’s easy. Run the cables and connect them to the Parabox and then attach the hydraulic lines to the frame and cut to length. In the event of too much fluid loss at install, the system comes with a bleed kit. A quick side note: the mounting hardware adds 14mm of stack height, so be warned if you like your stem slammed.

TRP unveiled its new Parabox-R at Interbike’s Outdoor Demo this week and the new system will only fill 5mm of stack height.

And then there’s the good old disc-brakes-in-cyclocross elephant in the room: Weight. At a glance, the Parabox looks involved and heavy, and on paper it is. You’re looking at almost 500 grams of chunky goodness, but that’s not the whole story. A set of Avid BB7 cable-actuated calipers weigh 400g with mounting hardware. When you add to that around 130g of cable with full housing, all of a sudden you’re up to 530g. I weighed the housing and cable required to mount the Parabox at 30g. Add the Parabox system’s 484g and 15g for the cable noodles and the system suddenly starts to look pretty good at 529g total weight. Remove the stem mounting hardware and zip tie the Parabox to the stem and that’s another 40 grams gone! (That move looks pretty rough, though.)

Now that we’ve laid weight to rest, let’s talk ride quality. Lever action is slightly heavier than brand new cable calipers, but the feel and modulation is outstanding. The amount of lever pull and modulation pressure is very consistent and as we all know from mountain bikes, the brakes self adjust as the pads wear. So, the brakes feel exactly the same, all the time. The Parabox’s calipers are front and rear specific, with the front caliper slightly larger and designed for a 160mm rotor for more braking power. The rear is smaller and is designed for a 140mm rotor so that braking is nicely balanced.

So if weight is comparable and this system offers the fantastic feel, modulation and control of a hydraulic system, the Parabox is suddenly very attractive. The price tag of $470 might take a bit of getting used to, but having the advantage of hydraulics on your ’cross bike might be well worth it.

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