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ASK RBA: ASK RC: DISC BRAKES ON ROAD BIKES
Road Bike Action
April 12, 2010
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Why haven’t road bikes adopted disc brakes? It seems like they would increase stopping performance – especially in wet weather.
– Rick
Disc brakes for road bikes could be an improvement for cyclist at all levels, however, two factors stand in the way of disc brakes for road bikes: weight and wussies.
I must preempt my answers with the statement that rim brakes are in fact, disc brakes. The advantages of separating the braking function from the rim surface to a separate rotor at the hub is that the rim can be designed to a lighter weight and profiled more intelligently and the wheel would not have to be perfectly true to function. In addition, hub disc brakes can be better optimized with materials that can handle heat, withstand water and grime than a wimpy rim brake. Finally, disc brakes self adjust and do not require the rider to disable the brake to replace a wheel – so they are safer.
The weight issue: Conventional rim brakes use the existing rim as a rotor and the caliper is fixed to a part of the frame and fork. This configuration eliminates spoke wind-up from the wheel and only required the seat stay and rims to be built slightly heavier than their normal function calls for.
To incorporate disc brakes at the hub would require beefing up the frame's left-side seat stays, chain stays and fork blade to handle braking torque – and configuring the spokes to feed the braking torque into the rim. Designing a lighter-weight rim would offset some of the weight, but we would not see this right away because the bicycle industry is so slow to capitulate on new technology.
Naysayers may disagree, but technology and materials are available at present to design disc brakes for road bikes without adding significantly to their weight. Uber-light pro-level disc brakes would cost a lot of money, but judging by the number of $5000 wheelsets out there, money is not the issue blocking their development.
The wussies: Presently, hub disc brakes are not legal for UCI sanctioned road events or cyclocross. Because the Olympic governing body and USA Cycling are too weak to form a separate opinion from the UCI, elite road riders won't be buying disc brakes in our lifetime. Until the anti-technology, former-roller-skating-judges and crybabies at the UCI allow bicycle makers to incorporate aerodynamic and mechanical improvements, there is no compelling reason for companies to spend money to significantly improve the road bike.
Contact Richard Cunningham for questions or comments, or just to talk bikes at: askRC@roadbikeaction.com
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