Disc Brakes and Road Bikes (from trekbikes.com)
In recent years, new technologies and adventurous riders have expanded expectations of where and in what conditions road bikes can be ridden. Riders today demand more versatile bikes that retain efficiency and high performance, but are capable enough for extended gravel riding and provide confidence in inclement weather.
The most significant new technology to fulfill this need is disc brakes. Disc brakes have been used on mountain bikes for years, but until recently, they were considered too heavy for road riding. Today, disc brakes are lighter and more svelte, and are now an important consideration when deciding which bike to buy.
Unlike a traditional rim or caliper brake, which slows the wheel by applying pressure from a soft rubber pad directly to the rim, disc brakes employ rotors attached to the wheel hubs, which are slowed by calipers attached directly to the frame. Disc brakes are used on automobiles, motorcycles, and nearly all off-road bicycles, which speaks to their versatility and superior stopping power.