34 00... Assessing the carbon ceramic brake discs (CSiC) for wear

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Use the following image documentation for damage assessment (brake disc wear).

Cracks (tension relief structure) in brake disc friction surface

Cracks in the brake disc friction surfaces must be viewed differently than in grey cast iron brake discs. In carbon ceramic brake discs, these cracks are not a wear indicator. They are already found on new brake discs for manufacturing reasons.

Fig 1: Identifying Cracks In The Brake Disc Friction Surfaces

Courtesy of BMW OF NORTH AMERICA, INC.

The brake discs are equipped with 6 wear indicators each (3 on the inside and 3 on the outside, see arrows).
The wear indicators are attached close to the brake disk outside diameter at an angle of 120° relative to each other and are recognizable by their surface structure and color shading, which differ from the surrounding friction surface.

Fig 2: Locating Wear Indicators
Courtesy of BMW OF NORTH AMERICA, INC.
Each wear indicator is 2 cm² in size.

As the brake disc is used, the surface structure of the wear indicators (1) changes. The change in this surface structure provides an indication of the wear state of the brake disc.

Graphic: New brake disc

Fig 3: Identifying Wear Indicator On New Brake Disc

Courtesy of BMW OF NORTH AMERICA, INC.

Graphic: Used brake disc

If continuous, uninterrupted pits or cavities in the surface are visible at the indicators (1) > 1 cm² or surface pitting >50% (entire surface of an indicator is 2 cm² )

-> Replace the brake disc.

Observe note in REMOVING/INSTALLING/REPLACING BOTH FRONT CARBON CERAMIC BRAKE DISCS (CSIC)

Fig 4: Identifying Wear Indicator On Used Brake Disc

Courtesy of BMW OF NORTH AMERICA, INC.

Checking the brake discs for edge damage

Depending on the degree of wear, edge damage on the brake disc friction surfaces may make it necessary to change the brake discs.
If the friction surface of the other brake disc is still OK, only one brake disc needs to be replaced.

Fig 5: Identifying Edge Damage
Courtesy of BMW OF NORTH AMERICA, INC.
- Max. permissible
  width/depth = 2 mm
- Max. permissible length = 10 mm