BMW R 1200 RT Rider's Manual page 102

The combination of spring
6
mount, suspension and spring
rate ensure that the suspension
98
geometry is always perfectly
adjusted.
The static normal position is
almost maintained even while
riding.
The different riding conditions
and load statuses are com-
pensated, so that the handling
of the motorcycle remains con-
stant.
It is possible to change the
spring rate electronically by
combining a conventional coil
z
spring and a plastic element
(Elastogran), the lateral expansion
of which can be restricted
electro-hydraulically using
a displaceable sleeve. The
more the sleeve encloses the
plastic element, the more the
expansion of the plastic element
is restricted, causing the spring
rate to increase. The maximum
spring rate is achieved when the
sleeve completely encloses the
plastic element and rests on the
steel spring. By the same token,
the spring rate decreases when
the sleeve allows the plastic
element to expand further.