Disc brakes on road bikes have gained considerable attention in the past few years to the point that the UCI has promised to assemble a panel to discuss their application in UCI world events. Currently, they are prohibited in the professional circuit. A number of reasons make them unsuitable for big race events (heat buildup in long descents and making tire changes slower and more difficult). But what are the benefits of disc brakes on road bikes as a practical option for the average recreational rider and amateur racer?
There is no question that disc brakes increase stopping power and give a rider more control over their ability to apply useful and responsive pressure to the braking surface. The mountain bike community has swore by disc brakes for years now and the trend in that discipline is not going away anytime soon. For roadies, however, weight and aerodynamics are always a concern even to the most casual riders.
Current disc brake systems which have been applied to road bikes are more or less ported over from what is found on MTB bikes and thus are large, bulky and heavy compared to caliper brakes. Even if the disc caliper remained the same weight as a standard rim-based caliper, there is still the disc itself which adds weight. If the technology starts to catch on, we’ll start to see manufactures come up with smaller and lighter compenents cleverly hiding the calipers behind the frame to reduce drag.
But what about the effect this will have on wheel design? As it stands right now, carbon rims that incorporate a brake track require more material thus making them heavier than perhaps they could be. The reason for this is heat dissipation. More material equals more heat dissipation. Without the need for a brake track, wheels could be made lighter by removing the excess material. How would this affect wheel design? Without being hindered by the need for a brake track could this open the door to more aerodynamic rim shapes? Jon Thornham of Flo Cycling doesn’t seem to think so, “From a design standpoint the brake surface can be shaped for aerodynamics in most ways regardless of where the braking takes place.” He also adds that, “When you add a disc brake to a wheel the weight of the hub increases significantly. Often times more than the reduction seen at the rim.”
It seems there are few advantages for aerodynamics and weight when it comes to disc brakes. Removing a brake track likely will not have much of an effect on rim shape design (i.e. improving aerodynamics) nor will it significantly reduce the weight of the bike. The question then becomes, how much more braking power and control does a rider need than what the current technology already provides? Is increased stopping power and modulation necessary for someone cruising the roads at 30kph? Will it make a difference in densely packed criterium races? Preference will likely be a big factor in the switch to disc brakes and I would gamble that most roadies, stubborn as they are, will find disc brakes unsightly and too far outside the accepted traditions of road cycling.