Assignment

A good brake pad/lining should be the best suited friction partner for the brake disc or drum, also in the wet, in addition, it should not suffer too much abrasive wear. The performance of the brake is, in all cases, superior to the engine performance, also in the case of super-sports cars. Since they cause deceleration over over a certain speed range much better than the engine can accelerate. The brake pad must withstand temperatures of up to the red-hot glowing point (approx. 800°C) and still, after ten maximum braking applications, deliver satisfactory delay values. This simulates long downhill descents. Careful precautions should also be taken to prevent the brakes from squeaking.

Function

The exact mixture used for brake linings/pads will probably always remain a secret, closely guarded by the manufacturers. Most brake linings/pads are made up of more organic materials. Amongst these are, apart from a small amount of metals and strengthening fibres, the filler materials and antisieze- or binding agents (e.g. resins). Sintered metal linings are nowadays, apart from isolated appearences in sports cars, increasingly reserved for use in motorcycles and in racing sport. More about the materials can be found here.

Sinter materials are generally developed from an exactly co-ordinated mixture of different metal powders. In the case of brake linings, there are metal fibers, silicon-carbide or iron-sulphide with e.g., graphite as the antisieze- or binding agent. In reality, there are up to 15 various materials used, in organic linings, there are as much as 30. Some manufacturers stress that their linings contain no antimony, lead or cadmium. Part of the sintering process is, after mixing, the bonding to a carrier plate, pressing under high pressure, the processing and the long-time heating (300°C). In the finishing process, the tolerances are checked and the burnishing of the surfaces takes place, possibly also the milling of key channels. This avoids, the same as bevels or chamfered edges, possible noise development when braking.

Sinter linings can withstand much higher temperatures, have a higher friction value, cause less grooving of the brake disc and last much longer (except in racing cars). They are also more insensitive to water-spray. Unfortunately they conduct the heat to the brake calipers better, which can be a problem for the brake fluid. Organic linings still need a certain running-in period, sintered linings must only adapt themselves to the brake disc.

Asbestos

The European manufacturers have changed over to asbestos-free linings at the lastest in 1990 (USA 1995).

Important

Organic linings transform about 40% of the actuating force on the linings into braking force ( = 0,4).

In addition

Screeching noises when braking can irritate the driver and the environment.
How to remedy this:
- several pistons on the same side of the disc,
- brake caliper with a vibration damper,
- varnish or other coating on the reverse side of the lining. 09/10