Quora Question: What is the advantage of disc brakes on road bikes?

Someone requested my answer to the above question on Quora. My response can be found here, and copied below.

Disc brake systems offer two main advantages on a road bike.

First, and often overlooked, is that the rim can be manufactured without concern for a braking surface. This enables the rim manufacturer to use different materials, shapes, and in some cases less material than if they needed to include a rim brake track. In many cases, this results in rims that cost less to manufacture, which is very appealing to bicycle makers.

Second, disc brakes tend to work better in adverse conditions. Discs shed water better than rims, and as the surface stays hotter (evaporating water), and the disc is substantially farther from road spray. Metal on metal friction (as in a disc setup) maintains better friction when wet, as compared with rubber and metal (as in rim brakes). Although disc brakes on the whole work better than rim brakes in the wet, they need to be properly configured in terms of pad material in order to perform their best. In some cases, like in a very muddy cyclocross race, a rim brake would perform better than a disc setup with organic resin pads. The disc brake surface coated in mud and grit will wear an organic pad in just a few stops, resulting in an unsafe and unreliable braking system.

A lot of people say that discs modulate better than rim brakes. That’s primarily true in the case of hydraulic disc brakes, which do not have cable and housing give. I find that rim brakes with a higher quality set of housings and cables (like this setup from jagwire) will drastically improve the performance of any brake system with poor modulation. Even a mechanical disc setup will benefit greatly from a change to higher quality brake housing.

For most riders either a rim or disc setup, properly configured and maintained, will perform perfectly well. Disc brakes certainly seem to be the future of bikes, but rim brakes will maintain a market for well into the foreseeable future. Unless you’re riding in the wet on a regular basis and notice brake perform declining, I don’t think there’s a good reason to buy an entire bike for disc brakes.

Happy Riding!