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Stopping Progression: Are Disc Brakes Here To Stay?

Will disc brakes be a momentous advancement for road and tri bikes or are they doomed for the dumpster?

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Will disc brakes be a momentous advancement for road and tri bikes or are they doomed for the dumpster? 

My read on things is that road disc brakes may become fairly common on road bikes with time, but it is unlikely they will be the type of revolution that is almost instantly adopted by the entire triathlon industry.

Before discussing the potential merits and challenges of using disc brakes on road bikes, it is important to understand how disc brakes compare to the traditional caliper-style brakes commonly found on road and tri bikes today.

A typical road brake uses a cable-actuated pivoting caliper that squeezes the sidewall of the spinning rim between two rubber pads to slow the wheel. The beauty of the caliper brake is that it is simple, light and fairly universal. The downside is that caliper braking power can vary widely and they will never be as strong as a disc brake. Performance can also be significantly affected by weather conditions (they don’t work as well in rain) as well as rim/pad selection. Carbon rims, for example, do not stop as effectively as aluminum.

A disc brake, on the other hand, works independently of the rim and instead uses piston-actuated brake pads that compress against a rotating disc that rotates around the wheel’s axle. The biggest benefit of a disc brake is consistent braking modulation and performance (even when wet) and potentially exceptional braking strength. They can be driven by cables or hydraulically.

Road disc brakes have been available for a few years in the form of Avid’s BB7 Road mechanical option. This brake has been used on some custom bikes and a few production cyclocross bikes and they work pretty well. However, the BB7 uses a cable, like a caliper brake, and not hydraulic lines like a car, motorcycle or current high-end MTB brakes. This means the BB7 offers some of the benefits of a hydraulic disc brake, but it is not as strong or as well sealed as a hydraulic system.

When discussing how disc brakes will affect road and tri bikes in the future, I’ll focus on the affect of hydraulic systems since these are buzzing right now and introduce additional complexity.

While hydraulic disc brakes on road bikes have the potential to provide more consistent and stronger braking with better modulation than current rim brake options, there are a number of challenges.

Complexity. Hydraulic disc brakes require a complete redesign of current road brake/shift lever design to accommodate the hydraulic fluid reservoir. Outside of electronic shift levers, where there is space available in the lever housing, mechanical shift levers already face internal space limitations.  If the fluid reservoir is not placed in the shift lever, it will need to be externally mounted – potentially creating a bulky appendage. This is less problematic for triathlon bikes, since the brake lever is separated from the bulky shifter internals.

Compatibility. Going to disc brakes requires a new bike; your frame, fork, wheels and shift levers all will need to be replaced. Seeing as many road riders and triathletes have thousands invested in multiple wheelsets and enjoy compatibility between multiple bikes, it is a significant investment to jump to discs, especially if you like to swap wheels between bikes. Road riders tend to like clean and crisp lines and will not want thick and heavy hydraulic lines zip tied onto their frame; internal frame brake line mounting will be requisite.

Along with these challenges, it should be noted that rim braking has improved markedly on carbon rims in recent years and the latest crop of mechanical and hydraulic (TT) caliper brakes work quite well. Carbon braking surfaces and brake pad technology has come a long way in recent years and high-end composite wheels boast braking performance that is vastly superior to versions from five years ago.

Disc brakes have revolutionized mountain biking and are poised to revolutionize cyclocross bikes now that they are legal for racing. However, mountain bikes and cyclocross racing generally have quick and hard braking zones in dirty/muddy conditions and the cantilever brakes used on cyclocross bikes have never worked particularly well. Discs have a significant performance advantage in these applications, but the same has yet to be proven in road riding where braking zones tend to be longer, tire contact patches smaller, and acceleration out of a corner is less dramatic.

Potential benefits include stronger braking, and some product developers in the cycling industry report to have found aerodynamic improvement in wind tunnel testing to disc brakes instead of calipers. There is yet to be a consensus on the aerodynamic implication of using disc brakes.

Hydraulic disc brakes require less maintenance, although when they do need service, it requires more tools and expertise than cable brakes.

Will the braking improvement offered by a disc be worth the weight gain and other challenges?

The industry seems to think so as major players like SRAM and Shimano would not be investing in the concept if they did not think it valid. However, there will be a number of challenges facing disc brake integration in the road market and more time is needed to see how these are resolved by the industry and received by consumers.

This all being said, look for many companies to show disc brake models in their line-up for 2013 at this week’s Eurobike trade show.

Ian Buchanan is co-owner of Fit Werx with locations in Waitsfield, VT and Peabody, MA, offering cycling and triathlon products, specialty bicycle fitting and analysis services. Fit Werx can be reached in VT at (802) 496-7570, in MA at (978) 532-7348 or at”