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Fault assessment of disc brake pads

Fault assessment of disc brake pads

Detachment of the friction material due to corrosion

Edge deterioration

Cause:

  • Edge detachment due to the use of new brake pads on extremely worn brake discs.
  • Inadequate spring force of the hold-down spring (off-centre travel).
  • Other mechanical overloading
  • Constant high thermal stress on the disc brake pads
Heavy underlying corrosion
  • Friction material becomes porous (completely or in spots).
  • Friction material has become disconnected due to corrosion.
  • Backing plate has obvious traces of corrosion.
  • Adhesive residue
  • Underlayer and friction material visible on backing plate.
No indication of excessive temperature load (view: cross-section)

Explanation:
The optically visible formulation components are present. The graphite batch containing elastomers, as well as the friction carbon and aramide fibre, are still present up to directly under the friction layer.

Clear traces of thermal stress (view: cross-section)

Explanation:
The graphite batch containing elastomers no longer exists and the friction carbon is now only present up to directly above the underlayer. The aramide fibre is still present under the friction layer (from approx. 4 mm onwards). Corrosion is visible below the underlayer.

Detachment of the friction material due to thermal destruction

Thermal destruction

Friction material decomposes, brakes off in some places and/or the underlayer and adhesive are damaged. Pad detaches completely, coating peels off. Partial colouring of the backing plate. Friction material has hardened, has a hard ring, reddish brown colouring of the friction material, white ash in some places.

Explanation:
Disc brake pads have exceeded the highest permissible temperature for longer than 15 – 20 minutes. During this, constituents that contribute significantly towards stability are destroyed.

Detachment of the friction material due to mechanical influences

Mechanical influences (1)
Mechanical influences (2)

The friction material detaches from the backing plate. Delamination occurs. Disc brake pads are new, separation above the adhesive/ underlayer. Damage visible on the backing plate.

Explanation:
Disc brake pads have been dropped or fitted at a tilt or deformation due to extreme “wobbling” in the brake calliper.

Detachment of the friction material from the backing plate

Detachment due toCauseEffectDistinguishing characteristic
Corrosion1. Edge deterioration due to extremely worn brake disc; inadequate holddown spring (off-centre travel)
2. Constant high thermal stress on the disc brake pads
Friction material becomes porous (completely or in spots), friction material detachment as a result of corrosionBacking plate has obvious traces of corrosion, adhesive residue, underlayer and friction material visible on backing plate
Thermal destruction of adhesive, underlayer and friction materialDisc brake pads have exceeded the highest permissible temperature for longer than 15 – 20 minutes, during this, constituents
that contribute significantly towards stability, are destroyed.
Friction material decomposes, breaks off in some places and/or the underlayer and adhesive are damaged, pad detaches completelyCoating peels off, backing plate is coloured blue in some places, friction material has hardened, has a hard ring, reddish brown colouring of the friction material, white ash in some places
Mechanical destructionDisc brake pads have, e.g., been droppedFriction material detaches from the backing plate, delamination occursDisc brake pads are new, separation above the adhesive/underlayer. Damage visible on the backing plate.

Attention: These faults often occur in combination!

Attention:

  • Detachment can be due to various causes, only faulty production being within our sphere of influence and will, thus, be accepted as a complaint.
  • Basically speaking, a wheel brake first becomes hot, and then the pad is destroyed.
  • A sheared off brake pad is never the reason for a wheel brake to become hot.