At the Cycle Show this year the buzz was definitely about disc brakes for cyclo-cross, specifically hydraulic.
What is all the fuss about? Firstly the UCI made it legal to use disc brakes in competition. Their announcement got the industry whirling. While disc brakes have been around on mountain bikes for years, they can't move over to drop bars because cyclo cross bikes use road STI levers, which house the brake levers and gear shifters within one unit.
Increased braking power at the disc
Canti and V-brake do not have leverage to pull to the rim.
No mud affecting the braking
When a brake is pulled using a rim brake system it must first work through mud and water at the rim before making contact.
Increased mud shedding and clearance, fewer bike changes
Reducing the componentary around the tyre and frame stops mud and leaves collecting. The wheel isn't slowed or jammed. This means less time fighting against resistance or less time making bike changes in the pit.
Improved longevity of the rim
There are all sorts of nasty elements that cyclo-crossers ride through: sand, gravel, bits of wood, and limestone. Mix with watery mud and squish it at the rim with a brake pad and you have a lethal paste that will wear out your rim.
Braking later in the corner allows the rider to be confident that they can pedal on the approach, rather than ease off and prepare to brake. Because braking can be guaranteed and stopping power is greater, it doesn't need to be so soon.
Cable stretch and friction
A hydraulic system doesn't suffer from the same degradation as a cable operated system as cables stretch over time and water-ingress causes corrosion on the cable, which in turn causes friction as the inner slides within the outer.
TRP converter, cable from the lever feeds in and hydraulic cables feed to the brake
The reality of high end hydraulic systems is still a year away. USE, TRP and Hope are the main players in the UK scene. The Hope and TRP system uses a converter that is bulky and sits under the stem. Hope converter boxes are available in November.
There is a weight penalty; the converter plus a metal rotor weighs more than a rim brake system, but only slightly. Numbers from manufacturers say their systems are 250g to 350g heavier.
Space for the converter
Smaller riders with a smaller head tube may not be able to fit the converter under the stem. However, the new brake from USE places the converters at the bar and away from mud flicking off the wheel.
Cable/mechanical brakes aren't top end
If you want all the bling and can't wait, then a cable-operated mechanical brake is the way forward. They aren't top of the range options. Both Shimano Tiagra and SRAM Apex are an option for mechanical brakes. That said, though the compromise is better stopping power for less bling, for new 'crossers it is a great affordable option for the new technology.
Since early May, at mountain bike races (when 'cross bikes are allowed), we've have been trialling the mechanical disc option with a pair of carbon tubular wheels and hubs from USE with lots of positive feedback and success.
Disc builds are available on both the Terra-X and Bivio-X and the framesets for the 2011/2012 season have brake mounts for cantilever and disc.
We matched the Tiagra disc and caliper (£119.99 per bike) with Shimano Dura-Ace levers and we used a Shimano XT wheelset (£399.99) for use with clincher tyres. The options for riders wanting to use tubular tyres start at using Deore centre lock hub (£29.99 each), built onto a pair of Mavic Reflex rims (£43.99 each).
The prototype hydraulic disc bike made in collaboration with USE uses jewel-like XTR calipers, a legendary off-road component. Keep a close eye on riders at the National Trophy Series this year as Condor-sponsored riders are using the brake.
On the bar system from USE, used by Condor-sponsored riders