Brake Pads for scooters and mopeds
Brake linings are brake parts mounted on the frame side which bear against the brake disc on both sides. During braking, the wheel is prevented from rotating by the brake pads being pressed against the brake disc. The kinetic energy is converted into heat by friction and the vehicle brakes. The friction forces between brake lining and brake disc lead to wear of both components. Brake pads for disc brakes are, with a few exceptions, made of two parts. The carrier plate is made of full metal (steel or grey cast iron) and is used for mounting the brake lining. The actual friction lining is glued or riveted onto this carrier. Only this lining gets into contact with the brake disc.
Composition and properties of brake liningsBrake linings consist of a complex compound of various friction materials. The exact composition is kept under lock and key by the manufacturers, but most commercial brake linings contain antimony trisulphide and barium sulphate (the resin that cokes during manufacture and characterises the carbon-like appearance of the brake lining). Metals such as copper, iron, brass or iron in the form of fibres or powder are also used. Mineral fibres and sulphides of various metals are also used. Until 1990, brake linings often contained a considerable proportion of asbestos (up to 42%), but this has been prohibited since an EU regulation of 1989. Since then, the manufacture, sale and installation of brake linings containing asbestos has been prohibited. In the case of brake linings for scooters and mopeds, a basic distinction must be made between three different categories of friction:
organic brake padsBrake pads made of organic friction materials. These are often fibres that can be obtained from glass, rubber, carbon or Kevlar and Twaron. In addition, there are various fillers and heat-resistant natural resins. Organic brake pads are quite soft compared to other brake pads and make the least noise during braking. However, they also wear out faster than other brake pads and cause the "popular" black brake dust in considerable quantities. A further characteristic of these linings is that the coefficient of friction deteriorates at higher temperatures, so the braking performance decreases (fading). Organic brake linings have a reputation for protecting the brake discs.
partially sintered brake pads (low-metallic or ceramik)Sintering is a process for changing materials. The fine-grained, metal-containing coating mixture is heated under increased pressure, which compacts the particles of the starting material. Brake pads of the "low-metallic" category contain between 10 and 30 % metal chips (steel, iron, copper, brass, etc.) mixed with graphite, fillers and binders. They are relatively inexpensive with increased durability and good braking properties even with high heat generation (low fading). However, the brake disc wears out faster than by the organic colleagues and it can come to brake squeal. As an alternative to purely metallic brake linings, ceramic linings are also available. A ceramic base is used instead of metallic friction agents. The quite new type called "ceramic brake lining" sounds promising at first, but ceramic and metallic brake linings often cannot be clearly distinguished from each other, as both materials are usually present in certain parts of the linings. A lining can nevertheless be marketed as "low-metallic" or "ceramic" as long as the lining thus designated contains appropriate admixtures of the respective friction agent. However, brake linings with a high ceramic content can be recognised by their lighter colour.
Sintered brake pads (semi-metallic)With 30 to 65 % metal chips, sintered brake linings have an even higher metal content than low-metallic brake linings. Sintered brake pads are extremely fading stable, wear much more slowly than organic brake pads and have a better braking effect. However, the brake pads first have to be warmed up, since full braking power only builds up at certain operating temperatures.
The right choice of brake padsIn recent years, brake discs (e.g. NG Brake Disc) have become harder and therefore more resistant due to new alloys, but the following still applies: the harder the brake lining, the greater the wear on the brake disc. You should be particularly careful with older scooter models and with all those that are equipped with organic brake pads ex works. Some brake disks are too soft for sintered pads and there will be strong wear and possibly hardening (tarnishing), deformation and scoring of the disk. The degree of hardness of the brake disc and brake pads must therefore match. Unfortunately, there is no distinction between "sinterable" and "not sinterable" for brake discs, but at least there are some forums available where you can look at the reports of other scooter riders. If you are satisfied with the standard braking performance, you should stick with organic brake pads, because sintered pads are much harder than organic ones. Therefore they brake better, but make an unsuitable brake disc unusable in a short time. Even good brake discs don't have to and shouldn't be burdened with the extra load if you're only driving in city traffic with the standard scooter.
Brake pad wear and replacementThe thickness of the brake pads must be checked regularly, as brake pads wear over time, similar to the tread pattern. There is also a wear limit for brake pads, which is reached at 1.5 mm pad thickness. If this thickness is not reached, an unmistakable metallic noise could soon be heard because only the carrier plate of the brake lining rubs against the brake disc. It is therefore better to replace the brake pads in good time. If you have to change the brake pads, you should not rely on cheap brake pads, which sometimes have too large metal pieces in their pad mixture and can lead to damage to the brake system as well as poor braking performance. Instead, it is advisable to use brake pads from renowned manufacturers such as Delta Breaking orr Vicma.
Der Wechsel ist nicht gerade kompliziert und auch nicht mit stundenlanger Arbeit verbunden, jedoch sollte man bei Wartungen an der Bremsanlage schon wissen, woran man gerade herum schraubt und etwas Konzentration und Ruhe mitbringen. The change is not exactly complicated and also not connected with hours of work, however one should already know with maintenance at the brake system what one screws straight around and bring some concentration and peace. Normally no other brake parts are removed when changing the brake pads. New brake pads are thicker and you create enough space for them by pressing the brake pistons into the brake calliper before removing the worn pads. Zuvor steht jedoch eine Reinigung der sichbaren Stellen der Bremskolben mit brake cleaner spray und einer feinen Bürste / Lappen an!!! Schließlich will man sich durch Dreck und Bremsstaub nicht die Dichtungen des Bremssattels zerstören, wenn man die Kolben zurück ins Gehäuse bewegt. Anschließend wird meistens einfach ein Führungsstift aufgeschraubt und heraus gezogen, der die Bremsbeläge hält (Vorsicht: Bremsbeläge können evtl. direkt heraus fallen). Die alten Bremsbeläge können dann aus ihrer Führung genommen und die neuen eingesetzt werden. Danach wird der Führungsstift wieder eingetzt und mit mäßiger Kraft fest gedreht.
The new brake pads must now be retracted. In the beginning they have to adapt to the brake disc and do not lie against it with their entire surface. When braking, the brake pads are only subjected to punctual stress and there are higher thermal loads than with retracted brake pads. Sharp braking manoeuvres during the running-in period (at least 50 km) must be avoided at all costs, as this leads to glazing (due to high pressure and excessive heat, the lining hardens and a shiny, glass-like layer forms). The glazing is irreversible and the brake pads no longer perform well. Only a new set of brake pads can help.