The Avid Shorty 6
As with any type of racing, powerful brakes in cyclocross actually help riders go faster by allowing them to carry more speed and brake later when entering a corner.
Unfortunately, though, to get good braking in cyclocross you have to sacriﬁce pad-to-rim clearance, which might slow you down on a sloppy day.
Center-pull cantilever brakes, once common on mountain bikes, are now completely gone from the off-road racing circuit. When the summer season ends, however, and the leaves begin to turn colors, cyclocross bikes come out of hiding and center-pull cantilever brakes once again enjoy the spotlight.
To understand what makes a good cyclocross brake, we ﬁrst must touch on some of the basics of cantilever geometry, lever ratios and the concept of mechanical advantage. At the most basic level, a brake and its lever must be matched in terms of mechanical advantage.
A prime example is a linear-pull brake. The brake arms themselves have a very high mechanical advantage, meaning the end of the brake arm moves a long way in relation to the brake pad. In turn, the pad contacts the rim with more force. A linear-pull brake lever, on the other hand, has a low mechanical advantage. It needs to be able to pull a lot of cable, yet doesn't have to pull with a lot of force.
Matching a linear-pull brake to a lever with a high mechanical advantage, like a Shimano STI or Campagnolo Ergopower lever, spells disaster. Most of the time you won't even be able to get it to work in the repair stand.
And for cyclocross, it's a given that an STI or Ergopower lever is the best choice. These levers have a rather high mechanical advantage. They don't pull a lot of cable, but they do exert a decent amount of force. Ideally one would pair a high mechanical advantage lever with a medium or low mechanical advantage brake to achieve the optimal performance, but this is not always as easy as it sounds.
There are three common options to choose from when equipping a cyclocross bike: linear brakes with adaptors, low-proﬁle cantilever brakes and high-proﬁle cantilever brakes. We'll skip the topic of discs to comply with the UCI's arcane rules (disc brakes are banned).
Linear-pull brakes require an adaptor to moderate a standard road lever's high mechanical advantage. In the form of a pulley system, Problem Solvers Travel Agent adaptors increase the amount of cable pulled by a road lever, thus allowing linear brake's compatibility with standard road levers. Linear brakes are not common in the pro ranks because of the need to use an additional cam and because of their poor rim clearance.
The Giant cyclocross team, however, uses Shimano's XTR V-brakes with the Travel Agent adaptors. Since it's ﬁrst and foremost a mountain bike team, its riders spend the summer riding bikes equipped with powerful disc brakes. Their hands are used to smooth one-ﬁnger braking action, and they ride with the habit of braking late before corners -- a technique that requires good brakes. Putting these racers on a bike with wide-proﬁle brakes would require them to modify their style.
Linear brakes are easy to set up, and they have lots of power. Just don't forget the adaptors. If a component company could reﬁne a road brake lever to pull the right amount of cable, this style of brake could become a favorite of mountain bike converts.
The next option and most common found on production cyclocross bikes is the reﬁned low-proﬁle cantilever. The most popular example is Avid's Shorty series, but Shimano and TRP are also good examples. These brakes offer good stopping power, though not quite of the magnitude a linear brake can produce, and they're simple to set up.
With this style of brake, bolt them on and set the pad up to hit the rim correctly. They're almost as easy to set up as linear-pull brakes. Another advantage is that they are some of the most economically priced brakes on the market. The major disadvantage is that the rim clearance is low, and that can lead to problems on muddy days.
At the top level of 'cross, the wide-proﬁle cantilever remains the tool of choice. Common models are Paul's and Spooky. TRP has a new one this year, too. The wide-proﬁle brake splits the difference between power and brake-pad travel, giving them a number of advantages over a low-proﬁle cantilever brake.
First and foremost, they offer two to three times the pad travel of a linear or low-proﬁle cantilever. This is the biggest reason for the style's popularity among professionals. When the rims and wheels pack up with mud, the brake doesn't impede it. In addition, when properly set up, their mechanical advantage actually increases as they travel through their arc. Plus, they are some of the lightest options available for cyclocross brakes.
There is one huge tradeoff, however, and that's the brake's lack of stopping power. Other more minor drawbacks are the complicated set-up and heavy lever feel. Wide-proﬁle cantilevers haven't changed much since the late 70s, so set-up is less than intuitive and some adjustments, like toe-in, require a bit of mechanical ﬁnesse, i.e. bending with a wrench.