Cyclocross disc brakes: it gets serious from here on out

cable disc brake.jpg


p> It’s official: the UCI has declared that disc brakes will be legal for all cyclocross competition for the 2010-2011 season. The rumour circulating the interwebs is that Shimano made a push to convince the UCI to make the rule amendment.

Among the advantages of disc brakes is that rims can be made lighter because they wouldn’t need to act as braking surfaces. Riders will be able to brake more effectively in all conditions particularly mud, and there wouldn’t be brake pads next to the rim to pack on mud. However, forks would need to be beefier.

All this has been mentioned for years, but now it seems that with the UCI’s blessing, we are perhaps now on the eve of the next big revolution in bicycle equipment. Cyclocross is the doorway through which disc brake systems integrated into dropbar shift/brake reach the consumer as well as the natural path for discs to reach UCI acceptance to road racing.

That said, there’s a number of design issues which I’m gonna love seeing Shimano and SRAM overcome….

The first issue is whether the brakes will be mechanical (cable-actuated) or hydraulic. Cable-actuated brakes for dropbar levers are already available and have been for years. You can already buy the BB-7 road disc from Avid (a SRAM sub-brand) and also Shimano’s BR-505. But I hardly expect the top pros to convert to those brakes en mass. Those guys are going thru a lot of trouble to get bikes superlight; I’d be shocked if they’d be that willing to readily accept the 1+lbs penalty that currently available disc brake systems would bring. Of course, the current cable discs on the market were not engineered for top-level competition, but in the very competitive mtb market hydraulic is the choice for weight and performance.

Besides, if the rumours about Shimano championing discs to the UCI are true, I would have to assume that they already have prototypes for the next generation disc brakes. According to the story, Shimano had equipped a bike to show the UCI a few months ago. And there’s one thing about Shimano: when they decide to do something they go all-in. Maybe they have developed a new light weight cable disc, but I wouldn’t be surprised if they had a hydraulic brake lever with integrated shifter. After all, STI (Shimano’s term for integrated shifter) actually stands for Shimano Total Integration.

From a more cynical standpoint, if Shimano makes an integrated shifter/hydraulic lever then the consumer MUST buy the entire system: derailleurs, levers, brakes, probably rotors, and possibly hubs/wheels. Cyclocross from its inception has involved parts kit cobbled together from disparate sources; Shimano could potentially create the first true cyclocross gruppo.

The next issue is the design of the lever, assuming that the brake calipers will be hydraulic: where to put the master cylinder for the system. For those not really savvy with the inner workings of a hydraulic system, the master cylinder is a fluid filled tube with a piston. Your hand movement at the lever pushes the piston in, forcing fluid out of the piston and into the caliper at the other end of the system. The caliper has one or more cylinder/pistons. Relative to the master cylinder, the cylinders of the caliper a short length and wide diameter so that the calipers piston (s) move a shorter distance than the master cylinder’s piston but with a lot more force. And the caliper’s piston(s) move the brake pads against the disc rotor.

On a typical mtb lever, the master cylinder is part of the lever body and the lever blade directly drives the master’s piston. This is the most straight forward way to do things. There have been examples where the master cylinder has either been built into the caliper or at some intermediate point between the lever and caliper, in both cases a cable connects the master to the lever. Historically, these systems were used as a way to combine hydraulic systems with existing cable-actuating levers, created by companies that didn’t manufacture shifting systems. In most cases, these systems have fallen by the wayside as better, pure hydraulic systems have reached the market.

So that leaves us with trying to cram a master cylinder into a Shimano STI or SRAM DoubleTap lever and make the master cylinder serviceable. There’s not a lot of excess space in the current lever designs. Magura used to make a hydraulic dropbar lever (for hydraulic rim brakes), but that didn’t have shifter functions. I’ve thought about this off and on, and it seems to me that the previous generation of Shimano STI, as exemplified by Dura Ace 7800, was the best starting point for a shifter/hydraulic-brake lever because the shifting functions were all in the front of the lever, in the lever blades themselves. The levers bodies were mainly empty space. Whether Shimano would take the aesthetic leap backwards to exposed shifter cable routing is another question.

Frankly, I never had much issue with the exposed cable routing of the old STIs. All the latest integrated road levers…Campag, Shimano, and SRAM…are a f*ing bitch to replace shifter cables and housing on now. It’s definitely a case of aesthetics over functionality. And even if SRAM and Shimano don’t intend on consumers or even shop mechanics to be able to service the shifter mechanism, it unlikely that they expect to be able to sell non-serviceable hydraulics. A lot of people keep telling me that the engineers will just make everything small enough to fit as if these things were like other consumer goods. But this isn’t like making a new, smaller iPod…the mechanisms and volumes are largely dictated by the forces that need to be applied. Take a look at side-pull caliper brakes on road bikes: if anything they have gotten bulkier today than in the past, even if careful shaping and materials selection has kept the weight down.

Of course, the ultimate solution might be to have an electronic Dura Ace (Di2) lever incorporating a hydraulic brake system. After all, if the shifting functions can be electronic and thus minuscule, then the braking structures can move into the vacated space. The shifting buttons and wiring are so light and discrete that it would be a relative cinch to make the hydraulics fit. But considering how expensive a regular Di2 shifting system is now, the cost of such a hydraulic version would just be mind-blowing.

So here are my predictions for what happens next:

1) Sven Nijs will be running prototype Shimano disc brakes on some of his bikes.

2) Most of the top amateur and professional cx racers will be racing with cantilevers however, because

3) it’ll be another year at least before the light weight brakes are widely available.

4) there’ll be a 2nd tier cost/weight/performance level product that will cater to the needs of commuters, touring riders, and other non-elite cyclists. It will most likely be cable-actuated.


“Magura used to make a hydraulic dropbar lever (for hydraulic rim brakes), but that didn’t have shifter functions. “

Not true. Magura, in partnership with Edco of Switzerland, created the Edco Competition IGP group in the early/mid 90s. This group featured hydraulic rim brakes and the levers had integrated shifters. Extremely rare but they did (briefly) exist. Wasn’t that long ago that Mel Pinto (or was it Euro Asia?) had a group for sale.

Here’s the group:

Here’s a closeup of the brake/shift lever:

It’s an ergonomic nightmare and as far as I can tell you’d never be able to shift from the drops. Looks like they just took a downtube lever and grafted it on top of the brake lever.

I think you’re right about Di2 being the way to go. Makes a whole lot more sense, especially in cross.

Here’s a 5th prediction: Masters will be the first to adopt them because it’s bound to be really expensive and Masters always seem to feel the need to have better gear than what most pros race on. ;)

The BR-505 pretty much enables #4 already. I’ll be running it myself in another week or so.

you’re right, in addition to making their own brake-only dropbar levers, Magura did make stuff for EDCO.  I had forgotten about them, but it’s not like i’ve ever seen them in person either…

that thing about Masters…so true. 

it’s so odd that 10yrs ago cyclocross was something you did while riding a beat-up touring frame with the old parts off your road bike.

I against anything that makes cyclocross more “serious.”

I’m with Tony; however, I don’t know that the advent of disc brakes in cyclocross could possibly make either the disciplineof cyclocross or the riders genuinely appear “serious.”  There’s always going to be a measure of silliness in a sport that has us intentionally dismounting perfectly good bikes.

That being said, the mountain biker in me is dying to build my drop-bar Di2 29er.

Shimano:  Hook us up, y’all!

Di2 is dramatically overpriced in relation to actual dev costs and manufacturing costs.  Actually, what in cycling isn’t?

Big problem with electronic stuff is you need redundancy and reliability.  Your shifting craps out and it’s no big deal, your braking craps out and you could be dead.  No way shimano wants to embark on having to meet automotive industry levels of safety and standards; it might not even be possible given the single mode fault - the battery pack.

I have trouble believing hydraulics will ever make their way to road riding, cabled systems easily provide ample braking and they aren’t even using the most aggressive actuation ratios they could be.  There is a lot of sexy things you can do with routing and housing design without having to move to fluids too.

How many people use the redundant brifter + bar top brake systems too?  Moving the master cyclinder off the bars and somewhere say clamped to the head tube makes some sense for CX as well and eliminates shifter integration issues.

I think hydraulic brakes for CX makes a lot of sense.  Probably pretty standard in about 3-5 years.  Many of the arguments I have heard are repeats of the same from MTB.

PJ I’m not sure of your point.  Di2 has been used for some time with good reliability.  Current systems are not redundant unless you consider two brakes redundant.  Cables snap, not often, but they do.

Have you guys seen the Canyon 6.8?

Claims to address a lot of the drawbacks of hydraulic discs on road frames.


The reliability requirements for shifting are a lot different from the reliability requirements for braking.  Thats the reason why Di2 only shifts and doesn’t brake. 

Shifting isn’t really “mission critical” but braking most certainly is.  Electronic systems are well accepted to be far less reliable than anything mechanical, especially compared something as simple as a cable system.

Batteries especially crap out due to cell damage, Li ion batteries (the type most likely to be used by a Di2 brake system) aren’t well know for their reliability.

With a vital electronic system you need to thoroughly ensure reliably and this means a whole slew of bits, it also means new safety and compliance standards for the cycling industry (they have those you know).  You need a huge market base to move to a product like that - obsessive cyclists are not a huge market.

Cables only fail after gross abuse, and fraying and rusting (and stainless cables don’t rust) - they are dramatically over designed otherwise.


They aren’t selling me on the 6.8.  That’s a lot of work to put out what is a effectively a disk system that has the braking power of a road calliper (by their admission).  How many people have heating related failures on descents with good pads and alloy rims (carbon rims are a different discussion)?  When it’s wet it’s not your brakes that are going to let you down first, it’s the traction.  Any decent calliper/lever combination will dramatically overpower and lock a rear wheel in the wet.

Rotor brakes are a nice idea for full composite wheels, but so are new resins and pad compounds.

just to clarify, i wasn’t suggesting that the electronic portion of Di2 actuate the hydraulic brakes, only that the Di2 lever would have more room for hydraulic system structures. if you’ve ever held a Di2 lever in your hand, you can see that the it’s just a carbon/resin brake body with a couple spring-loaded buttons attached to the carbon lever blade. for the suggested hydrdraulic-version of a Di2 lever, i was assuming that the hydraulic functions would operate independent of the electronics, and thus would not be subject to any reliability issues associated with the shifting system.  much the same way as when the shifting function of a 8sp mechanical STI might crap out, but the lever still functions for braking.

the 6.8 is an interesting system, but it seems so focused on addressing a few issues associated with road bikes that i think it might not be that suitable for cyclocross. i would like a better picture of the “dome-shaped” access panel on top of the lever…this seems like a natural approach to the servicing requirements as opposed to the conventional rubber hoods.  i don’t know if dual front discs might come into play, but i think something smaller than a 160mm rotor is very likely. and that’s part of the “integrated system” i expect Shimano to bring. if they introduce a groupset along with a few frame/fork manufacturers that sets the standards, they would force every other component maker have to play catch up.

Advertise here

About this Entry

The Next Mobile Social was the previous entry in this blog.

Fremont Solstice Parade: 1/2 Naked Biker is the next one.

Find more recent content on our home page and archives.

About Bike Hugger