One of the choices you’ll make when purchasing a new mountain bike is the type of braking system you want. The top two choices are rim brakes, often referred to as V-brakes, and disc brakes. If you want a lighter bike, you are likely to choose rim brakes, but if you want better stopping power, disc brakes are the better option.
Identification and Design
Disc brakes work via hydraulic pressure that pushes brake pads against a disc mounted on the wheel hub. The best ones use hydraulic fluid to operate the brake system’s caliper. Less-expensive versions incorporate cable-operated portions into the braking system. Most mountain bikes that feature rim brakes use the V-brake system because it’s the most powerful cable-operated rim brake design. It uses two long arms mounted on the bike’s frame to squeeze against the wheel’s rim. Other elements of your bike's design may be a determining factor. If you want an upside-down fork design, your decision on which type of brakes to use is already made. Disc brakes accommodate this fork design, whereas rim brakes do not.
Power and Performance
Disc brakes give you more braking power, which is important when traveling downhill. In fact, disc brakes are popular with downhill riders because they’re more reliable when traveling at high speeds. They also perform better in wet weather. Rim brakes have reduced effectiveness in muddy or wet conditions, according to “The Mountain Bike Book,” by Steve Worland. They also won’t work effectively if the rim’s surface is not flat and true, and they can cause wear and tear on your rim.
Advantages
Disc brakes offer a variety of advantages over rim brakes. They get less contaminated with dirt and other debris because they are at the center of the wheel. That means they’re lower maintenance than hydraulic rim brakes. For example, “Mountain Bike Performance Handbook” recommends bleeding rim brakes weekly to get rid of contaminants, but says you can get away with bleeding the fluid from disc brakes only periodically. On all types of rim brakes, you need to check the pads for embedded objects or wear after every muddy or wet ride. Check them every three to five rides when conditions are clean, according to "Bicycling" magazine. Also, check the centering on your rim brakes prior to every ride by lifting your bike and spinning the wheel. With disc brakes, check the rotor to make sure it’s not loose prior to each ride and inspect the hydraulic system for leaks weekly.
Disadvantages
Disc brakes have disadvantages as well. Wheels dished to make room for the disc brake rotor have an altered spoke tension, which makes a slight weakening in the wheel. Disc brakes also are heavier than rim brakes, so if you are seeking to lighten your load, they’re less desirable. Price also is a consideration. Disc brakes are more expensive, says Worland.
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