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Sachs technology successful in WRC

Teams trust in high-tech from Schweinfurt


The 2003 World Rally champion drives with Sachs shock absorbers. The 27-year old Norwegian Petter Solberg secured his first drivers‘ world championship with four victories this season. Suspension technology from the ZF Sachs marque is used in his Subaru Impreza WRC. If that‘s not enough – the competition also relies on the high-tech from Schweinfurt, the Ford Focus RS WRC, with which Ford works driver Markko Märtin celebrated two world championship victories in Greece and Finland, is equipped with ZF Sachs Race Engineering clutches.

The Sachs Formula WRC Damper played a large part in the success of world champion Petter Solberg. With their dampers, which were used for the first time during the Rally Argentina in May 2003, Sachs once again established a technical milestone: The two 300 PS Impreza WRC cars are currently the only cars in the World Rally Championship with 4-way adjustable dampers. Compression and rebound can each be adjusted in two ranges. The high-tech components are adjustable in the so-called low-speed response range for small road irregularities and in the high-speed range, which is required, for example, when driving over jumps, through pot holes and over large bumps. Theo Rottenberger, suspension expert at ZF Sachs Race Engineering, revealed some details: „The low-speed bump and rebound damping characteristics have a sixteen-position adjustable range. Even in the high-speed range there are twelve settings available. Due to this flexibility, Subaru can find the correct set-up for all road conditions much faster.”

Sachs provides Subaru with two different dampers for gravel and asphalt. While the version for rough surfaces has 200 millimetres of spring travel, 140 millimetres suffice on firm roads. If the spring travel is completely exhausted, a hydraulic bump stop with additional reserves is available to protect the car from being damaged. During the tough day-to-day life of rallying, Sachs dampers put up with a huge amount of abuse: The piston rod in the damping element moves at speeds between three and five metres per second. To compare: A Formula 1 damper takes things a little more leisurely with speeds of one metre per second.

Special dynamometers enable Sachs, as possibly the only damper manufacturer, to simulate every conceivable competition rally terrain. The dampers undergo 100,000 load alteration cycles before being delivered to Subaru. After all, the suspension components in the Impreza WRC guarantee perfect road holding, allowing world champion Petter Solberg to loose exactly this during the shower of champagne on the podium.

Sachs-partner Ford also had reason to celebrate during the 2003 season. With his Ford Focus RS WRC, in which ZF Sachs Race Engineering clutches are used, works driver Markko Märtin achieved two world championship victories on the gravel roads in Greece and Finland, and ended the season as fifth in the world championship. For every clutch, rally competition is a tough test. At the start of a special stage approximately 650 Newton-metre are set free by the driver. As a result, the Ford clutch is loaded more than that of a Formula 1 race car. To compare: In Formula 1 approximately 400 Nm torque is required to spin the rear wheels. Within a millisecond the titanium clutch cradle and the three carbon-friction discs reach several hundreds of degrees, sometimes even a temperature of as much as 1000 degrees Celsius is attained. Under normal operating conditions the clutch reaches a temperature of between 150 and 200 degrees. The spring clamping loads amount to 1.4 tonnes, a maximum of up to 900 Newton-metres torque can be transmitted. In this case the GM FZ 3/140 Y – as the clutch is known internally at ZF Sachs Race Engineering – is a midget. The friction plates are a mere 140 millimetres in diameter, and weigh a total of approximately 1600 grams. To compare: The production car unit for the Ford Focus weighs circa 4000 grams. However, a production car clutch with comparable performance values would weigh-in at about 20 kilograms – the weight of a truck clutch.

Theo Rottenberger explained: „During a rally we always have to expect the unexpected, for example, if a driver slides down a slope and must escape under his own steam. Therefore the clutch must have reserves.” Nevertheless, a clutch lasts the complete distance of a world championship rally with 400 timed kilometres. Afterwards they are only checked for wear and normally used again. Even so, at every service after 40 to 50 competition kilometres, the Sachs engineers expect the unexpected. That‘s why the clutch can be changed within five minutes.

For further information: ZF Sachs AG,
Detlef Reinhart, Director Company Communications
Phone +49 (0) 97 21 – 98 21 41, Fax +49 (0) 97 21 – 98 31 80
E-Mail: presse@sachs.de

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