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Fault assessment of disc brake pads

Fault assessment of disc brake pads

Introduction

With few exceptions, disc brakes are used as wheel brakes on the front axle of passenger cars. Depending on the load, disc or drum brakes are used on the rear axle. The following remarks are limited to the disc brake.

When you change the pads, check that the contact areas of the caliper are free from dirt and grease.

High mechanical and thermal stress exerted on the brake system

The foot force exerted on the brake pedal, supported by the system, acts as tensioning force in the wheel brakes that presses the brake pads onto the brake discs. As a result of the friction force created by this, the greater portion of the kinetic energy of the vehicle is converted to heat within a short time. The mechanical and thermal stresses acting on the brake disc and brake pads are very high. In extreme cases, the braking power occurring during deceleration can be many times the maximum engine power.

Essential requirements with regard to the brake system

The essential requirements placed on a brake system can be summarised as follows:

  • Minimum stopping distance under all operating conditions
  • Good brake comfort (no judder, no squealing, good pedal feel)
  • Adequate service life of the wearing parts.

As far as brake discs and brake pads as essential co-functioning elements for the braking procedure are concerned, this means:

  • Frictional stability over a very wide temperature range
  • Low dependence of the coefficient of friction on the contact pressure,
    speed and environmental influences
  • Good mechanical strength and resistance to deformation
  • Wear status within the specified limit values
  • Component tolerances within the specified limit values
  • Adequate wear behaviour of the brake pads and brake discs.

Brake discs and brake pads are co-functioning key safety elements. The requirements placed on them can only be met with components developed for/adapted to the vehicle concerned. Safety risks, as well as losses of comfort and a reduced service life can be avoided by correct maintenance.