BMW F97 Technical Training Manual page 57

F97/F98￿Complete￿Vehicle
5.￿Chassis￿and￿Suspension
The￿diameter￿of￿the￿rear￿perforated￿M￿compound￿brake￿disc￿is￿25 mm￿larger￿than￿that￿of￿the￿G01/G02
BMW￿M40i.￿Apart￿from￿the￿blue￿paint￿finish,￿the￿rear￿brake￿caliper￿including￿the￿electromechanical
parking￿brake￿has￿been￿carried￿over￿from￿the￿standard￿production￿models￿and￿is￿a￿single-piston
floating￿caliper.
The￿characteristic￿maps￿of￿the￿M￿Dynamic￿Stability￿Control￿have￿been￿adapted￿specifically￿to￿the
M￿design.
M￿carbon￿ceramic￿brakes
M￿carbon￿ceramics￿brakes￿are￿not￿offered.
Brake￿noise
• Humming￿of￿the￿BMW￿M￿compound￿brake￿disc￿at￿high￿speeds
• Squeaking￿brakes￿shortly￿before￿coming￿to￿a￿halt
• Cracking￿noises￿from￿the￿area￿of￿the￿BMW￿M￿compound￿brake￿discs￿when￿hot.
Explain￿to￿the￿customer￿at￿this￿point￿that￿such￿noises￿occurring￿temporarily￿or￿in￿specific￿situations￿are
inherent￿in￿the￿design￿and￿do￿not￿represent￿a￿quality￿problem.￿They￿are￿a￿consequence￿of￿the￿special
performance￿of￿the￿brakes￿and￿do￿not￿pose￿any￿danger￿or￿risk￿of￿damage.
Point￿out￿that￿the￿customer￿can￿use￿his/her￿braking￿technique￿to￿help￿prevent￿the￿noises￿occurring￿or
ensure￿they￿quickly￿disappear￿again.￿For￿example,￿after￿washing￿the￿vehicle￿it￿is￿important￿to￿dry￿the
brakes￿out￿by￿braking￿(braking￿a￿few￿times￿from￿50 km/h￿(31￿mph)￿to￿0￿is￿sufficient).￿Or￿that￿the￿brakes
can￿have￿a￿tendency￿to￿squeak￿if￿they￿go￿through￿long￿periods￿when￿they￿are￿only￿exposed￿to￿light
braking,￿which￿is￿why￿braking￿hard￿a￿few￿times￿can￿help￿out￿(=￿higher￿brake￿temperature).￿After￿driving
the￿vehicle￿very￿hard￿and￿subjecting￿the￿braking￿system￿to￿high￿loads￿(high￿brake￿disc￿temperatures)
the￿driver￿should￿try￿to￿make￿sure￿that￿the￿brakes￿are￿able￿to￿cool￿down￿while￿the￿vehicle￿is￿moving
and￿not￿to￿keep￿the￿brakes￿on￿the￿first￿time￿the￿vehicle￿comes￿to￿a￿stop.￿As￿a￿result￿of￿the￿increased
material￿transfer￿from￿the￿brake￿pads￿to￿the￿disc￿after￿very￿hard￿driving,￿a￿humming￿noise￿can￿occur
which￿disappears￿again￿after￿a￿short￿time.
Brake￿dust
Is￿an￿effect￿of￿a￿high-performance￿braking￿system.￿The￿BMW￿M￿models￿are￿high-performance
vehicles￿which￿are￿designed￿for￿fast￿and￿dynamic￿driving￿and￿embody￿a￿racing￿pedigree.￿The￿specially
designed￿brakes￿make￿possible￿the￿high￿braking￿performance￿required￿by￿the￿vehicle￿and￿in￿so￿doing
generate￿larger￿amounts￿of￿dust￿due￿to￿the￿greater￿levels￿of￿friction.￿The￿brake￿dust￿tells￿the￿customer
that￿his/her￿BMW￿M￿vehicle￿has￿been￿driven￿in￿an￿appropriate￿manner.￿What￿is￿important￿is￿to￿ensure
that￿it￿is￿regularly￿removed￿by￿washing￿the￿vehicle,￿as￿otherwise￿it￿will￿eat￿into￿the￿surface￿of￿the￿wheel.
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