Just as how there are different types of suspension on a mountain bike, there are different brake systems to choose from in the downhill mountain biking world. Rim brakes are a very good, sturdy choice, but disc brakes are becoming more common, especially as their merits are extolled by downhill mountain bike athletes and enthusiasts. Disc brakes are more powerful and more effective that rim brakes, a characteristic that is essential to downhill mountain biking. One must be able to stop at a moment's notice, or ride their brake all the way down a descent without the pad burning out or getting knocked out of place. Downhill mountain bikes equipped with disc brakes are more likely to have successful, safe, and enjoyable rides.
Disc brakes are modeled off of automotive hydraulic brake systems, though there are components on downhill mountain bike disc brakes that are identical to rim, or cantilever, brakes. When the rider wished to slow the bike down, they will squeeze a lever on the handlebar. The lever, attached to a tube of hydraulic fluid, uses the fluid to transfer the force of the pressure aplie don teh brake lever to the brake shoes, where a small piston applies pressure to the fluid in the line. At the actual brake pads, a larger piston, propelled by this brake fluid, squeezes the pads onto the wheel rim. The fluid/piston model allows the forces of the brake lever to be multiplied at the wheel, providing for a much firmer, more powerful brake. The handle of the brake contains a small device that moniters the amount of brake fluid on the disc brake system.
Because of the higher level of technology and refined mechanisms in disc brakes, they run at a higher price than rim brakes. However, disc brakes are becoming more common on all mountain bikes today, and are no longer the ultra-specialized components they were years ago. All manufacturers of downhill mountain bikes, such as Trek, Cannondale, Kona, Jamis, and Mongoose, offer reasonably priced downhill mountain bike models with affordable disc brakes.