The brakes on a car are made up of several components, but the discs and the pads are where the action is at. Brake rotors (or discs) are commonly made from cast iron, which is cheap to make and relatively long lasting.
Sports cars and supercars tend to have carbon discs, which are paired with ceramic pads. These are much more expensive but are more effective at braking the car from higher speeds and for longer periods.
Brake pads use a wide variety of compounds and materials but fall into three broad groups: organic or semi-organic brake pads, ceramic brake pads and metallic or semi-metallic brake pads.
Organic brake pads used to be partly made up of Asbestos, but it’s carcinogenic when breathed in as a dust so many countries around the world have banned its use in cars for more than 10 years now.
The US, however, has yet to ban it outright. It’s important not to inhale brake dust - use a liquid brake cleaner when changing the pads and wear a suitable dust mask.
Organic pads contain compounds such as fibreglass, resins, rubber and Kevlar. They are generally quiet in operation and work well when cold but aren’t so good when temperatures are high after prolonged use and wear faster than other pads.
Ceramic pads are designed to work with carbon discs. They’re made up of copper, bonding agents and ceramic fibres, which do a great job of withstanding hard use because they cope well with high temperatures.
They’re also long lasting but cost a lot to buy and tend to be at their best when they’re up to operating temperature, although modern ceramic pads are better than they used to be.
The majority of road cars have metallic or semi-metallic brake pads. They contain graphite, steel, iron and copper, so are heavier than ceramic and organic pads but last well and resist brake fade better than organic pads. Metallic pads aren’t as kind to the brake rotors (discs), however.
Brake shoes are fitted to the rear wheels of older and less powerful cars. Their braking performance isn’t as strong as that of brake pads and discs and they are mostly made up of the compounds found in organic pads.