Reference sample catalog for assessing visual quality of carbon ceramic brake discs in used condition

Temperature sensor 

Generally, for all fault patterns listed below, brake discs do not have to be exchanged in pairs or sets as long as it is guaranteed that the wear limits have not been reached yet.

Observe Service information ASSESSING THE CARBON-CERAMIC BRAKE DISKS (CSIC) FOR WEAR , and REMOVE FRONT BRAKE DISCS (VEHICLES WITH 17-INCH LOW BRAKE) , REMOVING THE FRONT BRAKE DISCS (VEHICLES WITH HIGH BRAKE) , or REMOVING REAR BRAKE ROTOR .

1. Chipping in the friction layer (delamination): 

   Definition:

   Delamination means a separation of the friction layer through the carrier body.

   A sharp edge (1) on one side as well as the visible fiber structure (2) of the carrier body and the shorn-off area (3) facing it are typical of delamination.

   The affected area of a delamination can take different sizes.

   In case of delamination up to on total sum of areas of 5 cm ²  per side of friction disc  , exchange of the brake discs is not mandatory!

   The separation represents a merely visual defect, but it can lead to the customer's disappointment and insecurity.

   Courtesy of BMW OF NORTH AMERICA, INC.

   Further example of delamination:

   Fiber structure (1)

   Courtesy of BMW OF NORTH AMERICA, INC.

   Further example of delamination:

   Fiber structure (1)

   Courtesy of BMW OF NORTH AMERICA, INC.

2. Chippings from the friction layer 

   As displayed in the illustration, these do not occur with the approved brake pads → check installed brake pads!

   • Characteristic of the chipping:
     • No carrier body visible
     • "Sharp" edges
     • Small area (under 2 mm)
   • Chippings like these do not lead to delamination (see item 1)

     One of the possible causes is the use of a brake pad/friction lining not approved by BMW (supplier, aftermarket, etc.).

   Courtesy of BMW OF NORTH AMERICA, INC.

3. Scoring (1) on the friction surface 

   In the brake disc design used by BMW M, the M Carbon ceramic brake, a highly wear-resistant friction layer is applied to the carrier body of the brake disc. This layer is resistant to almost all media and extremely hard. Industrial machining is

   possible with diamond tools only. Due to the continuous engagement of the brake pad during braking, slight visual phenomena can nevertheless emerge on the surfaces. The illustration presented here suggests the presence of a foreign body in the brake pad, which is to be removed manually from the surface of the pad before assembly. Use of the brake disc with brake pad can continue without concern. This visual phenomenon will significantly improve with increasing mileage.

   Courtesy of BMW OF NORTH AMERICA, INC.

4. Chipped edges at the outer diameter of the friction ring 

   Damage to the outer diameter of the brake disc by improper handling, predominantly by improperly executed wheel and brake pad exchange.

   Chipping at the outer diameter as displayed in the illustration are still permissible in used condition:

   • Maximum width of damage (A) = 4 mm
   • Maximum length of damage: 360°
   • Maximum depth of damage: 4 mm

   In this damage pattern, the brake disc is not functionally impaired.

   Components with damage exceeding the specified limits must be replaced!

   Courtesy of BMW OF NORTH AMERICA, INC.

   Sample illustrations for OK chipping. 

   Courtesy of BMW OF NORTH AMERICA, INC.

   Sample illustrations for not OK chipping (1) 

   Example fault patterns of chipped edges on the friction ring outer diameter due to improper handling = not OK? replace component! 

   Courtesy of BMW OF NORTH AMERICA, INC.