Description of defect: Formation of cracks on the carrier surface in contact with the hub. This is due to incorrect tightening during fitting. The tightening sequence has not been followed and torque is insufficient. Failure to follow the recommended sequence and tightening torque can cause distortion of the carrier mounting surface even when there are no visible cracks.

Consequences: Distortion of the carrier mounting surface causes vibrations that can be felt immediately after fitting when the brake pedal is pressed.

Advice: Fit another disc, following the recommended sequence and tightening torque.

Description of the defect: The carrier mounting surface breaks away from the rest of the disc. There are clear signs of excessive tightening, above all in the area of the two fixing holes. This is evidence of a failure to observe the recommended torque and sequence during tightening.

Consequences: Pronounced rasping noises and absence of braking torque.

Advice: Fit another disc, following the recommended sequence and tightening torque.

Description of the defect: The carrier mounting surface can easily distort when the disc positioning bolt is tightened too much. This excessive tightening can cause the mounting surface to break as can be seen in the photo.

Consequences: Run outing cannot be kept within an acceptable tolerance. Heavy vibrations occur during the very first kilometres following installation.

Advice: Tightening bolts are only intended to ensure that discs are positioned correctly. Do not tighten them excessively.

Description of the defect: Formation of cracks on the carrier mounting surface. Signs of a poor match between the diameter of the disc centring and that of the hub.

Consequences: Disc contact with the wheel hub is incorrect. This defective installation will immediately cause vibrations due to excessive run outing.

Advice: Check catalogues to determine the correct disc reference: model, year of manufacture. Never force discs when fitting.

Description of defect: The braking surfaces have broken away from the hub. Asymmetrical braking surface wear can be noted: the central area of the external surface in respect of the vehicle and the outer edge of the internal surface. In this case mechanical stress has caused the disc to break and the braking surfaces have come away.

Consequences: The impact of this breakage can be felt when braking. Very loud rasping noises. Safety is compromised.

Advice: Before fitting new discs check the alignment and assembly of the caliper body on the axle.

Description of defect: An exaggerated tightening torque knocks the bottom out of the bearing seat.

Consequences: Braking system functioning is compromised because of disc instability relative to the bearings. Strong vibrations are felt right from the first braking action.

Advice: Replace the hub, bearings and disc. Apply correct tightening torque when installing.

Description of defect: The hub surface was not cleaned when the disc was fitted: presence of rust or dirt. Tightening against this unsuitable surface causes the new disc to run out excessively.

Consequences: This error during installation causes the onset of vibrations after a few hundred or thousand braking actions, vibrations that increase with the distance travelled. Uneven disc wear as a result of the pads causes DTV to increase - this is the origin of the vibrations - and noise.

Advice: Clean contact surfaces very carefully. Check disc run out after installation.

Description of defect: Excessive hub run out causes the braking surfaces to wear as they are not parallel to the plane of the disc. Evidence of localised overheating is indicated by the darker colour of the worn areas. This is due to an alternating rubbing action of the disc and pads as a result of pronounced wheel hub run out.

Consequences: Vibrations can be felt right from the start and progressively increase. Onset of loud noises.

Advice: Check the wheel hub run out and ensure that this falls within the tolerance specified in the disc installation instructions.