Comfort & ergonomics
ESA & ESA II.
The electronic suspension adjustment of the second generation, or ESA II for short, allows highly convenient adjustments to the suspension for every riding style and load. The characteristics the rider can select for suspension and damping provide an unparalleled range of tuning and preload settings for all road conditions.
Unique on the world motorcycle market, this system provides the rider with electronic controls that let him adjust not only the rebound damping on the front and rear struts and rear wheel spring rest (“spring preload”), but also its spring rate and therefore “tightness”. All this is provided conveniently in the form of the multicontroller presenting menu navigation on the TFT colour display.
The rider first enters only the load state (“solo”, “solo with luggage”, or “with pillion and luggage”). This greatly simplifies operating the system and prevents unintended misconfigurations. The system then analyses the corresponding spring basis or spring rate and configures them automatically.
Depending on how he wants to ride, the rider can also select the chassis adjustment “Comfort”, “Normal”, or “Sport” that affects how the machine responds to his control. The electronic controller then analyses these specifications and calculates the appropriate damping rates as a function of the optimal parameters. It then actuates an electric motor that configures the spring basis accordingly. There are a total of nine different tuning variants available. The damping rate is modified at the dampers by means of small step motors.
These additional modifications to the spring rate mean that the vehicle level can be adjusted optimally to the various load states for even better riding stability, handling, and comfort. Even under the maximum load with pillion and luggage, the full banking freedom is therefore retained, for a sporting riding style. In addition, these adjustments to the spring rate greatly reduce the risk of bottoming out under extreme load. Also when the vehicle is moving, the damper tuning can be changed very easily (“Normal”, “Sport”, “Comfort”) at the touch of a button. For function and safety reasons, the spring basis can be changed only when the vehicle is stationary. An electric motor with gears is used to vary the spring rate.
The spring rate is changed with two springs connected in series. Here, the compression forces are absorbed by an elastomer element (Cellasto) combined with a conventional helical spring installed below. The outward radial expansion of the Cellasto element is permanently contained inside a steel sleeve. On the inside, an aluminium sleeve is moved electrohydraulically. The position of this inner sleeve affects the inward expansion behaviour of the Cellasto element, and therefore its spring rate. This has the same effect as two springs with different tightnesses. When the inner sleeve comes up against the steel spring, the Cellasto element loses its function, and only the steel spring is acting. When the inner sleeve is then moved further, the steel spring basis, or the “spring preload”, can be varied in addition.
In this manner, the normal static position and the riding geometry retain their optimal values in all load states. The additional adjustment to spring rate over the wide range of 110–160 Nm serves to augment potential configurations for “Sport”, “Normal”, and “Comfort” in ESA II, with considerable effects on the vehicle's characteristics.
When compared with the conventional mechanical adjustment of spring preload and damping characteristics, the advantage of electronic chassis adjustment with ESA lies in the constantly harmonious coordination between all suspension components and in the avoidance of errors for the “normal user”. The rider is also spared awkward and time consuming work with tools. Instead, he can conveniently press a button to make adjustments in just ten seconds. The rider can therefore adjust the suspension in next to no time, for instance before taking a pillion along at short notice or when the surface of the road suddenly changes.