Cracks (Stress-Relief Microstructure) In The Brake Disc Friction Surface

Information 

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Stress-relief microstructure in PCCB brake disc friction surfaces

• Due to the composition of different materials in the friction layer and support body, the friction surfaces have an non-critical crack pattern (stress-relief microstructure). Individual relaxation cracks sometimes run along the perforated bores.
• The stress-relief microstructure results from the way in which the brake disc surface is manufactured and does not pose a risk to safety. There is also no danger of the friction layers flaking off from the support body because the friction layers are virtually free of internal stresses as a result of the stress-relief microstructure.
• The stress-relief microstructure is sometimes clearly visible in new brake discs and can be significantly different on the brake disc hub side and the side opposite the hub.