B340414

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SI B34 04 14
Brakes
September 2015
Technical Service
SUBJECT
Diagnosis of Compound Brake System Complaints in M Vehicles
This Service Information bulletin supersedes SI 34 04 14 dated December 2014.
Designates changes to the bulletin
MODEL
E46 (M3 Coupe, Convertible)
E60 (M5 Sedan)
E63 (M6 Coupe)
E64 (M6 Convertible)
E82 (1 Series M Coupe)
E85 (M Roadster)
E86 (M Coupe)
E90 (M3 Sedan)
E92 (M3 Coupe)
E93 (M3 Convertible)
F06 (M6 Gran Coupe)
F10 (M5 Sedan)
F12 (M6 Convertible)
F13 (M6 Coupe)
F80 (M3 Sedan)
F82 (M4 Coupe)
F83 (M4 Convertible)
F85 (X5 M)
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F86 (X6 M)
SITUATION
The customer’s complaints may include:
1. Visible cracks in the brake discs can be noticed through the wheel opening or during service.
2. There are temporary vibrations or steering wheel torsional vibrations during braking.
3. After high brake loads, running noises can be heard when applying the brakes.
INFORMATION
1. Visible cracks are caused by
high thermal stresses during
rapid heating and cooling of the
brake discs. Braking from high
speed with cold brake
components (less than 212
degrees F) increases the
likelihood of cracks to form.
These surface hairline cracks are
usually spread over the entire
brake disc friction area, and
have no negative influence on
the durability or braking
performance. The rotors should
not be replaced only for their
appearance reasons.
When performing routine service on the brake system (pad replacement due to wear), the brake
discs should be replaced if surface cracks are found to be greater than 13 mm, or if the brake disc
thickness is below the minimum thickness.
Always replace brake discs in pairs (per axle). Install new brake pads when replacing discs. By
doing this, the service life of the friction pad surface is increased, and an even material loss is
ensured.
2. Vibrations and/or steering wheel torsional vibrations during braking are caused by applying
the brakes on discs with minimal to heavy corrosion. These vibrations are most noticeable
when braking from high speeds with cold brake components (less than 212 degrees F), and
will diminish with normal everyday operation. Parts replacement is not required.
3. After high brake loads, running
noises can be heard when
applying the brakes, and may
also be heard to a limited extent
after the brakes are released.
(See the note in the Owner's
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Manual).
These noises are reduced during
normal everyday operation, due
to further erosion of the brake
pad friction lining.
Visible surface cracks or craterlike recesses on the brake pad
surface are caused by a minor
difference in the material of the
pad lining, which will decrease
with further operation and
should not be replaced due to
their appearance.
WARRANTY INFORMATION
Not applicable.
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