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06/03/2012
ORGANIC OR SINTERED?

TWO WHEELS
Brake pads and organic or sintered material. Apart from choosing, wear must also be monitored

Fabio Quinto

If a motorbike or scooter is fitted with organic pads and you decide to replace them with sintered pads, what will happen? On paper, they give better braking, but they could damage the disc.

Before looking into why this should be so, we have to start with the definitions. The “traditional” organic material that is used to make pads is composed of organic fibres, phenolic resins, rubber, reaction accelerators, metals, friction modifiers, lubricants, thickeners. The newer formulas with greater performance may also contain carbon and Kevlar. Sintered material is, instead, a more recent substance and is composed of metals like copper and tin and is distinguished by high friction.

Questioned on the subject, the technicians at Newfren, an important Italian manufacturer of brake components for motorbikes and scooters, explained that, “basically”, when a motorbike or scooter is originally fitted with organic material, it’s better to replace the old pad with another organic one. The reason for this is that the manufacturer probably built the motorbike and its parts around this type of configuration (the technical characteristics of the pistons, brake disc hardness and so on), so for safety reasons it’s unwise to make any changes”. In other words, using a sintered material with second-rate discs could jeopardize braking effectiveness and cause excessive wear of the disc itself. Changing from organic to sintered is possible “only with a good quality disc that can cope with greater aggression and with a calliper that is suitable for use with this type of material”.

Sintered material guarantees greater friction, it is more durable but increases disc wear. On the other hand, “replacing a sintered pad with an organic one is worse, unless a less aggressive product is sought because of problems with brake system modulation, for example”.

Apart from choosing the right material, pad and disc wear must also be monitored; for the disc it is closely associated with hardness, shape and the slots in the disc. The more regular the surface of the disc, for example, the less wear on the pad. A round disc with not too many round slots causes less wear compared to irregular shapes because the pads are less subject to the slicing effect (irregular discs and slots create edges that use more friction material).

With regard to the shape of the disc, according to Valter Barbero, chairman of Newfren, “we have not followed the fashion of irregular-shaped discs because they reduce surface contact between the pad and the disc and decrease the braking effect with a reduction in performance as a consequence. When making its discs, Newfren usually copies the size of the original disc. Only in certain cases (such as for racing) we make discs that are thicker and wider to guarantee better stress absorption. Choosing the type of material depends on the force on the disc. The parameters used by manufacturers are certainly the calculation of weight, mass, braking distance and cost. Newfren has identified two types of high-strength steel; one is used to make discs for scooters and the other for motorbikes. In both cases, they are heat-treated and guarantee maximum braking performance and durability, frequently above the average of products available on the market”.

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