TRW expands its brake disc range with Semi-Compound Discs for Mercedes- Benz Models The decision as to which parts are installed in the independent workshop depends more often than not on economic aspects. As a result, although in most cases prices are compared, the technical requirements of a spare part are not. This situation becomes particularly critical when it concerns safety-relevant vehicle systems. In such cases, it is essential that all components are optimally matched to the respective passenger car and meet the quality of the original equipment. For over 100 years, brake systems for automobile manufacturers worldwide have been developed and produced under the TRW brand. The same experience and expertise are also incorporated into the TRW product portfolio for the independent aftermarket, which is now being further expanded by the semi-compound brake discs. These brake discs are now also available for various Mercedes-Benz C-Class and E-Class models. Additional references for S-Class and GLC models of the Stuttgart premium manufacturer will follow by mid-2021. Two-piece design The two-piece design of the Mercedes-Benz brake Steel hub Friction ring discs consists of a steel hub and a gray cast iron friction ring. This special design optimizes thermal expansion during braking so that the disc is not deformed by thermal stress. The brake disc of this special design was developed to reduce weight, improve safety and performance and to extend the Riveted joint lifetime in more powerful vehicles. Coating for corrosion protection TRW has developed an exclusive design for the independent aftermarket, which has the advantages of Semi-compound brake disc with steel hub and gray cast iron friction ring the OE product, but differs in the connection between the brake disc hub and the friction ring. TRW's semi- compound brake disc uses a specially developed riveting process to connect the disc hub to the friction ring. Due to the change in hub material and riveting process compared to a cast iron disc, a coating is also applied to provide long-term protection from corrosion to the brake disc, especially at the riveted joint. All TRW semi-compound brake discs are subjected to the strict OE-compatible test procedure and are ECE-R 90 certified. Special coating for corrosion protection - especially at the riveted joint ZF Friedrichshafen AG Rudolf-Diesel-Str. 7, 56566 Neuwied, Deutschland/Germany Tel: +49 (0) 2631 912-0, Fax: +49 (0) 2631 912-110 www.aftermarket.zf.com Temperature behavior In physical terms, kinetic energy is converted into thermal energy when a car brakes – in other words, the frictional surface (friction ring) of the brake disc heats up. The temperature development depends on the intensity and duration of braking. The closed design of all types of brake discs causes extremely high temperatures at the transition from the frictional surface and disc hub. Various measures can be taken in the brake disc design in order to prevent disc warpage. The choice of material, type of ventilation and effective disc diameter of an intelligent brake design all play a decisive role. The semi-compound Risk of brake judder caused by brake disc brake disc has proved to be a particularly effective warpage at high temperatures element in managing a brake's temperature. Due to the different expansion coefficients of the friction ring and steel hub, both materials behave differently on heating. The resulting "separation" of materials reduces brake disc warpage as a whole. Service life, performance, comfort and safety remain unchanged, even at high mechanical stress. As a whole, the brake disc works at a comparatively lower temperature. This creates reserves which minimize the risk of brake fade even when the brake is exposed to high stress. This means full braking power is always available whatever the situation. A special design requires special attention Improved temperature behavior with semi- Due to the special design of the brake disc, certain compound brake discs aspects need to be considered in the use and handling of this part. This starts even before the brake discs are installed. The part must not be removed from the packaging by the hub as this has only a material thickness of less than 3 mm. Furthermore, a steering movement required during repair when the wheels are < 3 mm dismounted, should be made by turning the steering wheel and not by pressing on the semi-compound brake disc. All further information regarding the use and handling of semi-compound brake discs can be found in our instructions: XZB900. Disc hub material thickness = < 3 mm ZF Friedrichshafen AG Rudolf-Diesel-Str. 7, 56566 Neuwied, Deutschland/Germany Tel: +49 (0) 2631 912-0, Fax: +49 (0) 2631 912-110 www.aftermarket.zf.com The increasing complexity of presumably simple parts such as a brake disc means that even more attention must be paid to the relevant documentation in the future when replacing these parts. Even work steps which have become part of the routine, such as mounting the wheels, can become a source for error. Due to the thin material of the disc hub on the semi-compound brake disc, it is necessary to follow the special instructions when mounting wheels. The wheels must be tightened in three steps until the torque specified by the vehicle manufacturer is reached. The procedure is described in detail in our service information: XZS183. The wheels must be tightened in three steps Semi-compound brake disc and axle design With the market launch of the Colette brake caliper, TRW made an important contribution to axle designs with negative scrub radius. This development was prompted by vehicle manufacturers in order to meet the growing demands on the vehicle's response during braking. A negative scrub radius ensures that a vehicle stays directionally stable on various road surfaces when braking, in other words it does not break away. The axle design of Mercedes-Benz vehicles also requires a particularly flat disc hub which can only be achieved with one semi-compound brake disc. This means that the rim is moved further in the direction of the vehicle's longitudinal axle, changing the scrub R R radius angle and ensuring a stable vehicle response during braking. Scrub radius (-R) with gray cast iron brake disc (left) and semi-compound brake disc (right). Less weight and CO2 emissions The reduced weight of a semi-compound brake disc, compared to a full cast brake disc, reduces the unsprung masses, which improves driving comfort and NVH (Noise, Vibration & Harshness) behavior. In addition, the weight reduction contributes to the decrease of fuel consumption and thus CO2 emissions. Extensive tests ensure consistently high quality in all product areas ZF Friedrichshafen AG Rudolf-Diesel-Str. 7, 56566 Neuwied, Deutschland/Germany Tel: +49 (0) 2631 912-0, Fax: +49 (0) 2631 912-110 www.aftermarket.zf.com.