There are effectively 3 types of brakes you’ll find on mountain bikes, though really only one type–disc–should be under consideration for most folks. In general, mountain bike frames are set up to handle either a disc or rim-style brake so be sure to determine which mounts you have before choosing an upgrade.
Coaster brakes: Remember skidding your bike in the driveway as a kid? If so, your bike probably had coasters which lock the rear wheel when you back-pedal. The very first mountain bikes had these and believe it or not, they’re making a (very limited) comeback on some bikes.
Rim brakes: There are different varieties of rim brakes, including “V-brakes” and “Y-brakes,” but the basic principle is the same. A rim brake uses two pads on either side of the wheel to grab the rim, slowing the rider down. Rim brakes are no longer in favor due to their limited stopping power, difficulty in wet conditions and with rims that aren’t true, and weight considerations.
Disc brakes: Most modern mountain bikes come equipped with disc brakes so for the remainder of this discussion I’ll focus on those.
Hydraulic vs. Mechanical Disc Brakes
There are two flavors of disc brakes on the market: hydraulic (hydros) and mechanical. Hydraulic brakes utilize a piston-cylinder system filled with fluid similar to the brakes you’d find on a motorcycle or car. Mechanical brakes, on the other hand, use a steel cable to translate a pull on the brake lever into a pull on the caliper at the disc.
Hydraulic brakes generally offer more stopping power and many users report improved modulation over mechanical brakes (more on that later).
Mechanical brakes are less expensive and riders will find them easier to maintain and troubleshoot.
Weight differences between hydraulic and mechanical systems are minimal.
The rotor in a disc brake system is the circular disc mounted to the wheel that the brake caliper grabs to slow the bike down. One of the rotor’s main jobs is to dissipate heat caused by braking so manufacturers often use innovative patterns and materials that seek to maximize airflow and heat transfer (while keeping weight low). A rotor’s diameter also dictates heat transfer so gravity-oriented bikes (DH, AM) tend to use larger rotors than cross-country bikes.
Top-end rotors are made in two pieces to both reduce weight and improve heat dissipation. For example, Shimano’s new Ice-Technology rotors feature an aluminum core and a stainless steel braking surface.
To some degree, the position of the caliper mounts on a bike frame dictate the size of the rotor that can be used. The good news is most brake manufacturers include or make available adapters to fit various rotors. After-market rotors are popular with many riders because it’s an easy and inexpensive way to customize a build.
Disc Brake Pads
There are three basic types of disc brake pads for mountain bikes: semi-metallic, sintered, and organic.
Semi-metallic brake pads are known to produce better stopping power and they don’t wear as quickly as organic pads. Out of the box, most brakes will include some type of semi-metallic brake pad.
Sintered pads are also known as metallic pads and are typically used by gravity riders due to their high friction values. In fact, sintered pads generate more friction at higher temperatures than low so they don’t have as much initial bite as organics but work well in extreme conditions.
Organic brake pads (also called resin) offer improved modulation and generate less noise. But remember, they also tend to wear out more quickly and you’ll want to avoid them for wet rides.
Ceramic disc brake pads are also available and in general they’re similar to metallic pads but with improved heat performance.