A complex challengeDamping of a four-wheeled versus two-wheeled vehicle

An innovative damping technology such as CDC (Continuous Damping Control) can be applied to various categories of vehicles if it is adapted accordingly. It has proved considerably more challenging to adapt CDC for motorcycles.

A simple calculation:

One motorcycle with rider weighs approximately 280 kilos. Once passenger and luggage have been added, the same bike can weigh up to 380 kilos – an increase of approx. 36 percent. Such differences in load do not exist with passenger cars. Passenger cars have considerably more space available to design the suspension and damping to offset the differences in load. This is just one of the many differences which the engineers at ZF had to take into account when adapting the CDC damper technology (effectively used in passenger cars and commercial vehicles) for the two-wheeler. "Motorized two-wheelers do have a completely different vehicle geometry than passenger cars", comments Rolf Heinz Rüger, Head of the Suspension Technology business unit in the Car Chassis Technology division at ZF. What is more: Greater dynamic wheel load shifts occur during braking, acceleration, and lean angle cornering. In addition, it is typical for motorcycles to have clearly different vibration behavior in contrast to passenger cars or even commercial vehicles. And finally an optimum distribution of pressure is also extremely important during rebound and compression.

CDC modular system

Different control characteristic maps of passenger car and motorcycle with CDC

ZF developers also profited from the vast experience of the Group – in the design of the CDC modular system. ZF has already solved the problem of how to design a space-saving proportional valve - the key technical element of CDC – as well as the valve inside the damper (CDCi) for passenger cars. The proportional valve restricts or increases the flow of oil in fractions of a second and thus produces a harder or softer damper setting. Alongside the actual damper, the motorcycle telescopic fork system and suspension struts also had to be specifically adapted.

The functioning of the CDC system for motorcycles derives primarily from the control software in conjunction with the hardware. Some motorcycle manufacturers use the proprietary system for their vehicle software including all subsystems. In this case, ZF supports with application development and advises manufacturers in determining control algorithms. Other manufacturers require complete system solutions. ZF responded by developing a controller designed specifically for the motorcycle in 2013. ZF developers again profited from the vast experience of the Group. A complete system is expected to be showcased in the first six months of 2015.

CDC provides motorcycle manufacturers with a wide range of options: They can, for example, offer different driving programs for the driver to choose from while riding. This flexibility and specific adjustment to each motorcycle model are reasons why the CDC system does not feel the same on every motorcycle.

More information on CDC for motorcycles