What You Should Know About Motorcycle Brake Pads
What Do They Do?
When the rider presses on the brake lever or pedal of a disc brake equipped motorcycle, the brake master cylinder attached to the lever or pedal pressurizes the system and sends hydraulic pressure to the brake caliper(s) at the wheels. The calipers have one or more pistons which are forced outward against the metal backing of the brake pads. As the brake pads clamp against the spinning rotor, they create friction which converts the kinetic energy built up in the motorcycle from speed, into heat energy. This heat passes into the brake rotors, pads and calipers, and finally into the air.
What Are They?
Brake pads are the friction surfaces which contact the brake discs (commonly called brake rotors as well) in disc brake systems. They are made of various friction materials bonded (they used to also be riveted) to a steel backing plate. Most of the older brake linings were made from asbestos, but as the health hazards of the material were recognized, asbestos was phased out and newer, high-tech materials were introduced to replace it. Today, brake pad linings (friction material) are made from a variety of high-tech materials.
Sintered Brake Pads
Sintered brake pads are presently the most popular type of linings. They are used as original equipment on nearly all motorcycles because they handle the widest range of conditions. Sintering is a process of fusing metallic particles under heat and pressure to form a friction material that is very wear resistant. Because of this, sintered linings are well suited for racers, city riders and those on steep hilly terrain. Sintered brake linings provides a stable friction coefficient cold to hot and produce good bite right away. They also handle extreme heat well, are resistant to fade and will typically last longer than other types and perform well even in rain and mud. However, they do have drawbacks. Sintered pads produce more wear on rotors, so if you are a casual rider who wants the easiest maintenance, consider using organic pads, because it's easier and cheaper to replace pads than rotors. Sintered pads are also noisier than organics when brakes are applied, plus they are more expensive.
Organic Brake Pads
Organic brake linings are made from a mixture of fibers and fillers bound together by special resins. Some organic pads now use fiber components such as Kevlar and carbon to increase durability. Organic brake pads have a softer makeup which provides a more varied and progressive feel or feedback when the brakes are applied. That’s in contrast to the more abrupt grab, or initial bite, of sintered pads. His low initial bite provides more control at lower speeds.
Organic pads produce less rotor wear, which is welcome for casual riders who don’t want to replace rotors often. The softer materials in organic pads also make them quieter than sintered. Organic pads produce less brake dust and they’re generally less expensive than sintered linings. But organic brake pads have downsides too. The softer organic pads wear more rapidly and are not as tolerant of high heat. Once they reach their maximum operating temperature the organic linings lose their coefficient of friction quickly and fade. Also in wet or muddy conditions, organic pads don’t perform well and may even form a glaze on their surface which may reduce future braking ability.
Semi-Sintered Brake Pads
There's another alternative for you folks who are in the middle ground and would like features of both sintered and organic linings. Semi-sintered pads, such as those from EBC, combine the long-life qualities of sintered linings with the low rotor wear and progressive feel of organics. The semi- sintered pads use 30-percent copper by weight in an organic matrix designed to fit right in the middle between sintered and organic for durability and performance and are a good compromise for many riders.
Ceramic Composite Brake Pads
Ceramic Composite brake pads are formed using high-strength ceramic fibers and non-ferrous metal filaments bonded at extreme pressures and temperatures. Ductile metal-filaments produce a friction material with moderate base coefficient of friction for good initial "bite", while heat resistant ceramic fibers and polymeric binders reduce thermal pad decomposition and out-gassing, which contribute to high temperature brake "fade." They are also quiet, and deliver strong braking performance over a wide range of conditions. Ceramic Composite material provides good stopping power when both cold, and hot after miles of riding. The non-ferrous metal filament matrix provides high thermal mass and thermal conductivity to quickly carry heat away from the pad-rotor interface for fast thermal recovery. Lower operating temperatures reduce rotor wear and risk of deformation or warping. However, they are not available for all models of motorcycles.
How to Check Your Brakes
Make it a habit to visually inspect your brake pads on the bike, before a ride and during oil changes, etc. You may need a flashlight, but look into the calipers, including the back side as there are inner and outer pads. If the friction lining has worn down to about an eighth inch or less, it's time for replacement. You should also always listen and pay attention to the sounds coming from your brakes. If the sound changes, heed that as a warning and inspect the brakes immediately. A squealing sound may or may not indicate a problem.
Sometimes it’s just a high-pitched vibration which occurs as the pads are clamped onto the rotors. However, a scraping or grinding noise is definitely a strong cause for immediate concern. That’s an indication that the metal brake pad backing is rubbing against the rotor surface. Continuing to ride with metal-to-metal contact will ruin your rotors and may result in a crash because you won't be able to stop as well as you should. Typically and easy, way to tell the difference is that the high pitched squeal will go away as you clamp the brakes harder while stopping. But the grinding noise will get worse.
How To Replace Motorcycle Brake Pads
Fortunately, replacing brake pads on most motorcycles is an easy project which most DIY riders can accomplish in under an hour with just a few basic tools. Sometimes saddlebags and other items are in the way of caliper access, which will add a few minutes to the job.
Brake pads are self-adjusting and as a result, they require no adjusting after they are installed. If you have an older bike with drum brakes however, you will need to make some minor adjustments so keep that owner’s manual handy. Also, do not forget to pump the brake lever or pedal back up until it puts tension on the brakes after installation. If you miss this step and go for a test ride, you will find you have no brakes the first time you try to apply them.
Check rotors for warping, cracks, etc when you replace your pads. If a brake rotor is damaged or grooved, now is the time to replace it. If the brake lever had been pulsing as you come to a stop, it’s an indication that a rotor has become warped or bent. This calls for a replacement at the same time the new pads are installed. Sometimes rotors can be resurfaced but it’s difficult to find a shop that has the ability to do it these days.
Refer to your manual as needed during the installation process. I suggest taking a photo of the brake assembly before you dismantle it so you can have a reference for where the springs, clips and factory brake line routing. This will help you make sure to get it all back together correctly on the first try. If the bike has dual front brakes, you may consider doing one side at a time, leaving the other for reference until you get the procedure down to a science.
Some brake calipers have open tops which allow the pads to be removed without taking the caliper off the fork. In this instance, the retaining pins and hardware are removed and the caliper pistons are retracted to make room for the new, thicker pads. However, most calipers will require you to remove them from the fork tube, in order to replace the pads.
Caliper pistons can be retracted with a large screwdriver, a small tire changing spoon or your hands if you’re tough enough. It is best to open the brake bleeder screw (connect a drain hose that will catch the fluid in a container so it doesn’t squirt all over your bike). This is a much better solution than simply forcing the fluid back through the master cylinder return port.
Clean out any dirt or crud from the brake caliper and rotors once you have the pads removed. Use a spray type brake cleaner, never use petroleum based cleaners in this area. Take this opportunity to inspect all the brake hardware, including spring clips, pins, etc. Replace any parts that are visibly broken, damaged or worn out. I prefer to apply a coating of a product designed to prevent brake squeal onto the brake pad backing surface. Then slip the new pads into place, making sure that any clips or retention springs are properly positioned. This can be fiddly at times, but it must be done properly.
Once the new pads are in place (and calipers reinstalled to the specs in your owner’s manual), make a final visual inspection and then pump the brake lever or pedal until the pads firmly contact the rotors and the lever effort feels normal. When reinstalling the caliper bolts, it is a good idea to apply blue Loctite to the threads and tighten them to the OEM specs.
Now that the brake pads have been swapped, it is time to check the brake fluid. The brake fluid level should be brought to the upper fill mark on the reservoir. Brake fluid should be completely replaced along with a flush of the entire system, about every two years. This is also the perfect time to bleed your brakes using a fluid catch system that keeps the goo from getting all over the bike or your garage.
Before you take the bike for a test ride, be sure to check everything one more time. Make sure the brake levers feel normal. When you do go for the test ride, make sure not to go haul ass or put yourself in heavy traffic right away. Wear full gear too, just in case. Once you are confident that the brakes are working properly, begin the break-in process. During your first 50-100 miles, use the brakes moderately, avoiding hard braking situations unless you are forced to brake for an emergency. This helps to seat-in the ads and avoid glazing.