Brake pads are found inside the calipers. They’re designed to clamp down on the rotor at high speeds, which means their main job (besides stopping your bike) is to hold up under heat and friction.
Resin Vs. Sintered Brake Pads
There are two main types of brake pads. Resin brake pads (also called organic) are composed of organic materials like glass, rubber, and fibrous binders bonded together with resin. Sintered brake pads (also known as metallic) are made of metallic grains that are bonded together at high pressure.
In terms of feel, resin pads are quieter and have a stronger sense of bite. They’re better at managing heat, but they can fade as heat builds up. They also wear more quickly, particularly in muddy conditions. Sintered pads are the choice for riders who do mostly downhill mountain biking. They produce more heat but are less susceptible to its effects; and they last longer under heavy use and in wet conditions.
Resin pads are what most brakes come with, but you should consider switching to metallic if you’re bigger, ride downhill terrain, or ride mostly in wet weather.
Disc Brake Pad Maintenance:
If you’ve checked your caliper and rotor but still hear squealing when braking, it can mean that the braking surface (including pads and/or rotors) is contaminated and needs cleaning.
Detach the wheel and use isopropyl alcohol on a clean rag to wipe off the rotor, then remove the pads and clean them as well. It’s also a good idea to wear disposable latex gloves; you’re trying to get dirt and oil off the braking surface, not add more.
Make sure to let the pads dry completely before reinstalling.
SRAM recommends replacing pads when the total thickness of the backing plate and the pad material is under 3mm. Shimano says that when the pad material alone is less than half a millimetre thick, it needs to be replaced. If you switch pad type (resin to metallic, say), swap your rotors as well; the pads and rotors pair by “bedding” small amounts of the pad material on the rotor, which means an old rotor won’t get optimal performance with a new pad type because it’s already bedded to the other kind of pad material.