BMW F12 2011 Technical Training Manual page 16

F12￿Chassis￿Dynamics
3.￿Chassis￿and￿suspension
The￿primary￿objective￿of￿the￿EDC￿system￿is￿to￿increase￿ride￿comfort￿and￿maintain￿a￿high￿standard￿of
driving￿safety￿without￿compromise.￿Greater￿ride￿comfort￿is￿achieved￿if￿the￿vertical￿movement￿of￿the
vehicle￿body￿is￿virtually￿eliminated￿despite￿excitation￿of￿the￿vehicle￿due￿to￿the￿roadway￿(unevenness,
joints)￿or￿cornering.￿This￿is￿why￿the￿adjustable￿dampers￿are￿operated￿using￿a￿soft,￿comfortable￿damp-
ing￿characteristic￿in￿as￿many￿situations￿as￿possible.
A￿high￿standard￿of￿driving￿safety￿is￿guaranteed￿if￿the￿wheels￿never￿lose￿contact￿with￿the￿roadway￿and
deliver￿a￿high￿bearing￿force￿when￿necessary.￿This￿is￿why￿a￿harder￿damping￿action￿is￿set￿if￿the￿driving
situation￿or￿driver￿intervention￿(e.g.￿steering,￿braking)￿is￿required.
In￿addition,￿the￿EDC￿control￿takes￿steering￿operations￿(e.g.￿transition￿from￿straight-ahead￿driving
to￿cornering)￿into￿account￿based￿on￿the￿steering￿angle￿characteristic.￿If￿the￿EDC￿detects￿a￿rapid￿in-
crease￿in￿the￿steering￿angle,￿the￿controller￿deduces￿that￿cornering￿is￿starting￿and￿can￿now￿set￿a￿harder
damper￿setting￿at￿the￿outer￿cornering￿wheels￿as￿a￿preventative￿measure.￿The￿EDC￿therefore￿supports
the￿ARS￿control￿and￿thus￿assists￿in￿reducing￿the￿rolling￿movement￿of￿the￿vehicle.
EDC￿can￿also￿detect￿when￿the￿driver￿is￿braking￿based￿on￿the￿information￿supplied￿by￿the￿DSC￿on￿brake
pressure.￿A￿high￿brake￿pressure￿normally￿causes￿a￿pitching￿movement￿of￿the￿vehicle.￿EDC￿counteracts
this￿by￿setting￿the￿front￿damper￿for￿higher￿damping￿forces.￿This￿also￿improves￿the￿braking￿force￿distri-
bution￿at￿the￿front/rear￿which￿produces￿a￿small￿braking￿distance￿advantage￿(when￿compared￿to￿a￿vehi-
cle￿without￿EDC).
The￿basic￿damping￿force￿level￿is￿adapted￿by￿the￿EDC￿controller￿depending￿on￿which￿damping￿program
is￿selected￿by￿the￿driver￿(comfort/sport).￿Irrespective￿of￿this,￿e.g.￿even￿if￿the￿Comfort￿program￿is￿se-
lected,￿high￿damping￿forces￿act￿on￿individual￿wheels￿in￿critical￿driving￿situations.￿A￿reference￿damp-
ing￿force￿is￿output￿via￿FlexRay￿for￿every￿wheel￿or￿damper￿according￿to￿the￿prioritization￿of￿the￿individu-
al￿controller￿components.￿In￿addition,￿a￿default￿current￿value￿for￿the￿quiescent￿operating￿point￿is￿speci-
fied￿for￿the￿dampers.
3.4.￿Wheels￿&￿Tires
Run-flat￿tires￿are￿fitted￿in￿the￿F12￿as￿standard.
Front￿tire
Rear￿tire
Front￿wheel￿rim
Rear￿wheel￿rim
12
650i
245/40￿R19￿all￿season￿run￿flat￿(standard)
245/35￿R20￿performance￿tire￿(option)
245/40￿R19￿all￿season￿run￿flat￿(standard)
275/30￿R20￿performance￿tire￿(option)
19￿x￿8.5￿(standard)
20￿x￿8.5￿(option)
19￿x￿8.5￿(standard)
20￿x￿9.0￿(option)