Diagnosing brake problems

The friction lining has come loose from the lining's base plate, either in full or in part.

• Thermal or mechanical overload 
• Subsurface corrosion between lining and base plate
• Insufficient fitting accuracy of the brake pads
• Damage to the brake pad due to incorrect handling or installation
• Non-compliant brake pads

• Grinding noises when not pressing the brake
• Squeaking during braking
• Deficient braking characteristics
• Breakdown of friction lining due to thermal overload

• Clean the brake caliper and check for proper function ✓
• Check the brake caliper and pad for fitting accuracy ✓
• Replace the brake pads and accessory parts if necessary ✓

Brake pad has been damaged due to overheating. Binder in the pad has been destroyed and the pad material is breaking down. The surface is porous and glazed in parts.

• Sticking or tight guide sleeves
• Brake piston stuck within the brake caliper
• Extreme driving conditions or sustained braking
• Sticking brake pad

•  Noises
• Poor braking function

• Clean the brake caliper and check for proper function ✓
• Check the brake caliper and pad for fitting accuracy ✓
• Replace the brake pads and accessory parts if necessary ✓
• Check the brake discs and replace them if necessary ✓

The pad surface has deep grooves and wear edges.

• New pads have been installed on the old, worn brake discs
• Foreign bodies between the brake pad and disc
• Environmental influences (salt, dirt, etc.)

• Noises when operating and not operating the brake
• Poor or one-sided braking function

• Clean the brake caliper and check for proper function ✓
• Replace the brake pads, accessory parts and brake discs ✓

The friction lining is damaged. The lining material has broken off at the edges.

• Incorrect installation
• Incorrect, non-compliant brake pads
• Lack of freedom of movement for the brake caliper
• Mechanical overload
• Thermal overload

• Noises
• Poor braking function
• Premature wear

• Clean the brake caliper and check for proper function ✓
• Replace the brake pads ✓
• Check the brake caliper and pad for fitting accuracy ✓
• Check the accessory parts and brake discs and replace them if necessary ✓

Brake pads are heavily worn and have worn down to the base plate in some cases.

• Deficient maintenance
• Exceeding the inspection intervals 
• Sustained braking during downhill driving
• Sticking or tight guide sleeves
• Brake piston stuck within the brake caliper
• Extreme driving conditions or sustained braking
• Sticking brake pad

• Noticeable noises when operating and not operating the brake
• Poor braking characteristics
• Damage to other wheel brake assemblies due to thermal overload 

• Disassemble the brake system and check it ✓
• Clean the brake caliper and check for proper function ✓
• Check the caliper guides, dust covers and damping sleeves and replace them if necessary ✓
• Replace the brake pads, brake discs and accessory parts ✓

The brake pads on one side of the wheel brake have been worn down unevenly.

• Sticking or tight guide bolts or caliper guides on the brake caliper
• Brake piston stuck within the brake caliper or brake pad wedged in the caliper slot

• Noises
• Uneven braking characteristics
• Premature wear due to mechanical and thermal overload

• Disassemble the brake system and check it ✓
• Clean the brake caliper and check for proper function of the individual components ✓
• Check the brake caliper and pad for fitting accuracy ✓
• Replace the brake pads and, if necessary, the accessory parts and brake discs ✓

The friction lining has a hard, smooth, polished-looking surface that reflects incident light and is similar to a glass surface. This defect generally occurs on new brake pads with minimal time in service.

• Overload of the brake pads in the bed-in phase
• Repetitive high temperature change on the brake pad at short intervals
• Long braking phases with low pedal pressure

• Loss of friction on the brake pad, leading to poor braking function
• Insufficient or one-sided braking function at the affected wheel brake
• Noises (squeaking) during braking

Replace the heavily glazed or damaged brake pads. Check the brake discs and replace them if necessary. 

Brake pads with short time in service:

• Grind the friction lining surface evenly ✓
• Compare the thickness of all the brake pads and check for reusability ✓

Brake pad has been contaminated by grease, oil or other foreign substances.

• Deficient maintenance work
• Defective drive shaft joints
• Leak in hydraulic brake system

• Insufficient or one-sided braking function
• Braking causes noise

• Disassemble, check and clean the wheel brake of the affected axle ✓
• Determine and correct the cause of the contamination ✓
• Clean brake pads with sufficient thickness and grind the surface evenly ✓
• Replace heavily contaminated or worn brake pads ✓
• Complete the brake system and check for proper function ✓•

The friction ring of the brake disc has vertical cracks running all the way through from the edge to the disc chamber.

• High alternating mechanical and thermal load
• Overload of the brake disc in the bed-in phase due to force or sudden, hard braking
• Use of the brake disc beyond the wear measurement
• Brake discs of unknown origin with poor quality

• Reduced braking function
• Knocks at the steering wheel
• Pulsing brake pedal

• Replacing the brake discs
• Check the condition of brake pads and check for wear; replace if necessary

Always follow the maintenance and repair instructions from the respective vehicle and brake manufacturers in this regard! 

The friction ring of the brake disc has horizontal striations or grooves on the contact surface.

• Contamination or foreign bodies between the brake pad and disc
• Brake pad of unknown origin with poor quality 

• Reduced braking function
• Noises
• Increased wear

• Clean the brake caliper and check for proper function
• Replace the brake discs and brake pads.

Always follow the maintenance and repair instructions from the respective vehicle and brake manufacturers in this regard!

The brake disc has a different disc thickness spread over its circumference. These deviations in geometry are also referred to as a difference in thickness. (DTV - Disc Thickness Variation).

• Poor concentricity of the wheel hub or brake disc
• Erroneous or improper installation of the brake disc on the wheel hub
• Insufficient cleaning of the contact surface on the wheel hub
• Long brake disc period of use with excessive axial runout

• Wobbling motion of the brake disc
• Axial runout with simultaneous low brake load
• Brake judder

• Replace the brake discs and brake pads
• Check the concentricity of the wheel hub and brake disc

Always follow the maintenance and repair instructions from the respective vehicle and brake manufacturers in this regard!

The disc chamber is corroded in places at the contact surface to the wheel hub.

• Installation error
• Insufficient cleaning of the contact surface on the wheel hub

• Poor concentricity and axial run-out of the brake disc
• Difference in thickness of the friction ring
• Brake judder

• Clean the wheel hub and remove any rust
• Clean the contact surfaces on the brake disc chamber and/or remove rust for an even surface
• Replace heavily damaged or warped brake discs
• Check the concentricity of the wheel hub and brake disc

Always follow the maintenance and repair instructions from the respective vehicle and brake manufacturers in this regard!

Damaged or improperly function components in the wheel suspension or steering can affect not just the driving characteristics but the braking characteristics of the vehicle as well. If unusual noises, vibrations or unstable driving characteristics are detected during braking, the potential cause can stem from different vehicle components.

Defective shock absorber and tires

• Degraded traction
• Declining braking function
• Lengthened braking distance

Defective or improperly installed rubber bearings

• Unstable driving characteristics
• Steering wheel or pedal vibrations
• Knocking noises

Lack of damping due to damaged or leaking hydraulic support

• Knocking noises
• Brake judder
• Vibrations
• Unstable driving characteristics

Defective coupling rods, transverse control arms or stabilizer suspension

• Knocking noises
• Unstable driving characteristics
• Vibrations

Defective or improperly installed rubber sleeves at the drive shafts

• Leaking grease contaminates adjacent assemblies