New Product Spotlight: TRP’s Parabox Hydraulic Disc Brake System for Cyclocross – Updated

Pin It
The TRP Brakes Parabox hydraulic disc brake adaptor sits below the stem and requires about 25mm of space on the steerer. You could run it above the stem if necessary. © Cyclocross Magazine

The TRP Brakes Parabox hydraulic disc brake system and adaptor. © Cyclocross Magazine

by Andrew Yee

The Sea Otter Classic Expo is just a day away, and there’s quite a number of new cyclocross products expected to be unveiled at the Monterey, California event.  Several of these new products are disc-brake related, whether it is the highly-anticipated new carbon Redline Conquest (assumed to be disc-ready), or the disc-equipped Airborne Delta cyclocross bike, or TRP’s road brake lever adaptor for hydraulic disc brakes.

Well, the gearheads at Cyclocross Magazine couldn’t wait until Thursday to start geeking out with the new cyclocross gear, and thus we camped out and seized an exclusive early opportunity to preview and ride TRP’s new Parabox hydraulic disc brake system. The Parabox is designed to allow your favorite cable-pull road brake lever/shift lever to actuate a hydraulic disc brake system, not unlike Tim Cannard’s 324 hydraulic brake adaptor system we profiled in December, 2010 (Update: see our updated look at Summit Lab’s 324 Brake Adaptor).

Brake cables pull little levers that push plungers and force hydraulic brake fluid down the lines. TRP Brakes Parabox Hydraulic Disc Brake Adaptor. © Cyclocross Magazine

Brake cables pull small levers on the TRP Paradox that in turn push plungers and force hydraulic brake fluid down the lines. © Cyclocross Magazine

The Parabox features a steerer-mounted master cylinder that translates brake cable pull into hydraulic braking power. The unit accomplishes this through two small levers, that when pulled by each brake cable, pushes a plunger in the master cylinder to actuate the fork-mounted front brake hydraulic caliper and the chainstay-mounted (on this Stevens frame) rear hydraulic caliper. Through altering the length of the lever the brake cable pulls, TRP is able to modify and optimize the stopping power of the brake.

The TRP Parabox is designed to work with any road brake lever, whether it’s SRAM DoubleTap, Shimano STI or Di2, Campagnolo Ergopower or even TRP’s own RRL singlespeed lever.

Lance Larrabee,  marketing director for TRP Brakes, expects the Parabox to be ready in time for the 2011/2012 cyclocross season both as an aftermarket unit and as OEM equipment on new bikes. Larrabee told Cyclocross Magazine that at the recent Tapei show, the most common question he received from bike company product managers was “when can we get it?”

The Parabox will come complete kit with TRP rotors, calipers, pre-bled hydraulic brake lines and the master cylinder, is expected to retail for $400-500 and will weigh 450 grams.

One common complaint about disc brakes is the added weight. Larrabee figures the Parabox system will add approximately 250g to the bike, or just over a half-pound. This estimate does not include the added weight found on disc-compatible hubs compared to their non-disc versions, but Larrabee believes racers can then ride on lighter rims that offset any additional hub weight as braking surfaces become unnecessary.  Is 250g a deal breaker? If part of the attraction of a disc brake-equipped bike is the mud clearance, then 250g seems insignificant compared to possible mud accumulation after just one lap on a muddy course.

The unit sits below the stem and requires about 25mm worth of spacers and a stem that doesn’t have significant negative rise to fit. Technically, you could run the Parabox above the stem if you prefer an aggressive riding position and have a bicycle with a tall head tube.

Update: While the Parabox unit is agnostic to the frame’s rear spacing and just needs a disc-compatible hub, it appears that manufacturers like Stevens are moving to the 135mm mountain bike standard spacing from the 130mm road standard for disc-equipped cyclocross bikes  in order to take advantage of the plethora of existing mountain bike hubs and 29er wheels.

Initial Riding Impressions

The Parabox hydraulic caliper mounts on the chainstay of the Stevens disc cyclocross bike. TRP Brakes Parabox Hydraulic Disc Brake Adaptor. © Cyclocross Magazine

The Parabox hydraulic caliper mounts on the chainstay of the Stevens disc cyclocross bike. TRP Brakes Parabox Hydraulic Disc Brake Adaptor. © Cyclocross Magazine

I had the first opportunity to ride this early prototype, and I was impressed. The unit actually mimicked the feel of a decent cantilever brake, with perhaps a bit more power than a typical wide-clearance cantilever, but not quite the power of a well-adjusted low-profile cantilever or mini v-brake. For a traditionalist, this can be welcome and safer, as there is not the fly-over-the-handlebar-with-one-finger-braking danger of some mountain bike hydraulic brakes if you’re not used to the power.

But while the disc design, even without additional braking power, adds mud clearance and can make for a lighter rim, rest-assured TRP aims to also harness the additional power and modulation a hydraulic brake can offer. And while pinky-braking may not be the goal, the company is refining the leverage of the cable-pulled lever.

“We’re going to lengthen that cable-pulled lever to increase stopping power,” said Larrabee. “This [prototype] has similar stopping power to a cyclocross cantilever, but our production models will have more.”

If you’re used to hydraulic disc brakes on your mountain bike, the one thing you may notice with such a setup is that unlike with your pure hydraulic levers, the hand position on the road bike lever seems to matter much more. In the drops, pulling at the bottom of the lever Di2, braking power was quite good, and endos and wheel skids were easy. In the hoods, on this early prototype, it took more effort. Keep in mind that these Di2 levers pull 20% more cable than SRAM, Campagnolo or older Shimano levers, which means roughly 20% less power.

Mud clearance is no longer an issue with the disc brakes. TRP Brakes Parabox Hydraulic Disc Brake Adaptor. © Cyclocross Magazine

Mud clearance is no longer an issue with the TRP Parbox disc brakes. © Cyclocross Magazine

While mud clearance and braking power both are potential benefits of such a system, the other benefit is the removal of brake chatter. Without the cable pull-inducing fork flex, you can slam on the front brake to your heart’s content, without the unpredictable chatter found on flexy forks with steerer-mounted cable hangers.

Larrabee believes the Parabox to be a great solution for cyclocrossers who want to uses disc brakes now, but he fully expects companies like SRAM and Shimano to eventually offer a hydraulic brake / shift lever in a few years.

Based on what we saw and rode, the TRP Parabox is an innovative solution that allows you to harness the benefits of disc brakes this season. We’re excited to try the production units and find some real mud for some real-world testing. Stay tuned.

Photo Gallery:



Cyclocross Magazine, Issue 22, Print and digital subscriptionsHave you subscribed yet? You're missing out if not. Get all-original content and your cyclocross fix throughout the year with a subscription and Issue 23 back copy, with features on Lars van der Haar, Jonathan Page, Elle Anderson and more!
Tagged as: , , , , , ,

I must say that Stevens at least got it right. The rear disc is mounted in between the chain says and seat-stays. It makes it so much stronger for breaking. Van Dessel is about the only one that does that on their Jersey devil. Plus it looks so much better.


And you have to admit, even if you don't like the idea of cross bikes with discs, that the seatstays and fork look reaaaaallly nice - knobbies, all that clearance, smooth surfaces, mmmm.


Fantastic. Someone had to stick their toe in the water and TRP decided to be the front-runners with this incremental innovation. Whether you would run it or not, the story makes sense to a lot of people. I probably wouldn't get this V.1 product but it might make the other brake mfg'ers take notice.


I think I'll wait a while. $400+ is steep!! I don't' even pay that for mountain. Someone's going to come out with shifter disc combo. hopefully it sram before shimano get's their greedy little hands in it.


steveCX said it best: "a solution in search of a problem."

God Bless TPR none-the-less.

Cyclocross Magazine
Cyclocross Magazine

Dylan - agreed that it's unclear on the direction here for non-disc cyclocross bikes in the future. Stevens for now is keeping its normal bike at 130mm. On this disc bike, you couldn't use 130mm wheels anyway if they are not disc-compatible? Unless you rebuild both with new hubs and just use the rims, a normal road hub won't support the rotors unless you mimic the wheel in a pic here:

Perhaps they'd be useful in a bike that has both canti posts and disc mounts...but to use discs you'd need different hubs.

What's not clear is whether companies will move normal canti-enabled cyclocross bikes eventually to 135mm, or whether we'll see all of road stuff move in that direction too and don't have to designate hubs as road or mtb but just disc or not (as we've seen with stems/bars moving to one size).


135mm? So are frame companies going with mtb spacing rather than relying on hub manufacturers making 130mm disc-compatible road hubs?

This is going to be the sticking point for me. Sure, I'd kind of prefer disc brakes. But I've already got a closet full of road wheels that I like to be able to use.

Cyclocross Magazine
Cyclocross Magazine

@Tee, TRP said they will have it ready for cx season and some companies will spec it as OEM equipment. we're already seeing some more disc-equipped cx bikes though. stay tuned for our Sea Otter coverage.

@Brandon - the rear is 135mm spacing. Is that what you wanted to know? Our photos say that but we should probably add to the copy.


What is the OLD of the rear end?


This is really cool. I'm thinking about getting another CX bike this Fall, should I just suck it up with my current rig and wait until disk bikes are more readily available? Can we expect disk options on the market by Fall 2012?

Stay up to date:

Search for a product, review, race or racer:

Visit these cx-loving companies:

Become a CXM Supporter:

Like the content on We're just a tiny two full-time person operation with big aspirations. Help us continue to bring you awesome cx content: Become a CXM supporter today:


What do you do in the off-season?

View Results

Loading ... Loading ...

Support CXM at no extra cost to you: