Description of defect: The thickness of the braking surfaces measured using a micrometer is less than the recommended minimum thickness etched on the outer disc rim or on the carrier.

Consequences: Performance and comfort decreases.

Advice: Check state of disc wear periodically. The disc should be replaced after every two or three pad changes. Pads must be changed every time discs are replaced.

Description of defect:

a. Disc
The minimum thickness indicated on the outer rim of the disc has been exceeded by more than 1 mm. Furthermore, the disc has been subjected to excessive operating temperatures as a result of the reduced braking surface thickness. This causes cracks of a thermal origin.

b. Pads
More marked wear can be noted in the central area of the disc whereas the area in correspondence with the pads is less worn. This can be attributed to the presence of hard points in the friction material, an indication that the production mixture was not homogeneous. It can also indicate poor functioning of the caliper.

Consequences: Distortion caused by vibrations during braking. In the long run cracks may form that can lead to disc breakage.

Advice: Periodically check disc wear. The disc must be replaced every two or three pad changes.

Description of defect: The disc has been subjected to excessive operating temperatures: in the outer area of the braking surface there are evident signs of overheating. High operating temperatures lead to the appearance of cracks.

Consequences: Distortion and pad "bouncing" when hot that causes vibrations during braking. With time, cracks form and the disc may break.

Advice: The worn disc must be replaced. Check the state of wear periodically.

Description of defect: The disc is extremely worn and has been damaged by the metal pad support, the friction material of which has completely disappeared. The thickness of this disc when new was 7 mm, measured now it is 3.5 mm compared to a recommended minimum thickness of 5 mm.

Consequences: Very loud noises, very long braking distances, caliper functioning is critical.

Advice: Replace pads when they reach wear limits. Check out the pad wear warning indicator circuit.

Description of defect: Braking surfaces show evident signs of overheating due to the considerably reduced mass of the worn disc. This situation has caused the braking surfaces to break away from the hub.

Consequences: Violent impact during braking. A very strong rasping noise when braking. Possible safety problem.

Advice: Always check the disc thickness every time the pads are replaced. Replace the disc before it reaches its wear limit.

Description of defect: Disc thickness less than the limit value. The disc has been worn by the pad support as friction material is completely absent. The metal support plate has come out of its seat in the caliper and has almost entirely cut the disc brake surface from the carrier. The braking surfaces are near to breaking away from the carrier.

Consequences: Rasping noises, loss of efficiency (considerable brake pedal slack), possible rubbing between the disc and caliper, thrust of the caliper is not symmetrical.

Advice: Check and, if necessary, repair the caliper. Replace the discs and pads.