Wednesday, 12/2/09 at 3:43 PM
by Sara Jarrell
by Sara Jarrell
All About: Disc Brakes
The two main types of disc brakes used for bicycles are hydraulic and mechanical. Hydraulic disc brakes are characterized by the use of oil in a closed system consisting of a brake lever, a hose, and a brake caliper. When you pull your brake lever the oil from the master cylinder, contained in the lever body, is forced into the brake caliper mounted on the fork or the rear of the bike. This fluid then fills the caliper and pushes on the pistons and in turn the brake pads against the rotor causing you to stop. Mechanical disc brakes are operated using a cable and housing system common to rim brakes. Like hydraulic disc brakes, mechanical systems include a brake lever and a brake caliper. When the brake lever is pulled the cable then pulls an arm on the brake caliper, which pushes the pads against the rotor and causes the bike to stop.
When a disc brake is adjusted properly the amount of stopping power compared to a rim brake is noticeable to say the least. Between the two, hydraulic brakes have a bit more stopping power than their close relative the mechanical disc brake. However, the cost of maintaining a hydraulic braking system is generally more expensive than a mechanical system. The mechanical braking systems require periodic cable and housing changes compared to bleeding the hydraulic system. Both types of brakes will need brake pads replaced periodically and should be inspected for wear at least every couple of rides. Pad wear will vary based on the terrain, weather, and a number of other variables.
Rotors are another component of both the hydraulic and mechanical braking system, and seem to be the most prone to damage. Rotors bend; sometimes because they have been hit by something while riding and other times they can warp when they are exposed to extreme temperature differences very quickly. For example, if you have been riding down a steep grade and have been on the brakes the whole time your rotor will have become extremely hot. Then at the bottom of the steep grade you come to a creek crossing that submerges your rotor in cold mountain water. Well chances are on the other side of the creek you might begin to experience a rhythmic metallic rub coming from your brakes – most likely a slightly warped rotor. A warped or bent rotor can be fixable depending on the how severe the rotor has been bent. With a slight bend/warp it is possible to true the rotor making it straight enough that it does not rub the brake pads. With more severe bends/warps truing may not be possible or advisable, a mechanic at your local bike shop can make that call for you.
Anytime you are having trouble with your brakes whether mechanical or hydraulic having a trained mechanic give them a once over is a great way to ensure your safety and keep that little thought in the back of your head from holding you back on your next mission. As with all components on your bike it is advisable to consult your owner’s manuals, and manufactures specifications when diagnosing or working on your bike.
Best,
Sara
When a disc brake is adjusted properly the amount of stopping power compared to a rim brake is noticeable to say the least. Between the two, hydraulic brakes have a bit more stopping power than their close relative the mechanical disc brake. However, the cost of maintaining a hydraulic braking system is generally more expensive than a mechanical system. The mechanical braking systems require periodic cable and housing changes compared to bleeding the hydraulic system. Both types of brakes will need brake pads replaced periodically and should be inspected for wear at least every couple of rides. Pad wear will vary based on the terrain, weather, and a number of other variables.
Rotors are another component of both the hydraulic and mechanical braking system, and seem to be the most prone to damage. Rotors bend; sometimes because they have been hit by something while riding and other times they can warp when they are exposed to extreme temperature differences very quickly. For example, if you have been riding down a steep grade and have been on the brakes the whole time your rotor will have become extremely hot. Then at the bottom of the steep grade you come to a creek crossing that submerges your rotor in cold mountain water. Well chances are on the other side of the creek you might begin to experience a rhythmic metallic rub coming from your brakes – most likely a slightly warped rotor. A warped or bent rotor can be fixable depending on the how severe the rotor has been bent. With a slight bend/warp it is possible to true the rotor making it straight enough that it does not rub the brake pads. With more severe bends/warps truing may not be possible or advisable, a mechanic at your local bike shop can make that call for you.
Anytime you are having trouble with your brakes whether mechanical or hydraulic having a trained mechanic give them a once over is a great way to ensure your safety and keep that little thought in the back of your head from holding you back on your next mission. As with all components on your bike it is advisable to consult your owner’s manuals, and manufactures specifications when diagnosing or working on your bike.
Best,
Sara
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