Faulty brakes – faults and common defects
Here you will find useful basic information and handy tips relating to brakes.
Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.
Background information on problems and their causes in connection with disk brakes.
Check, determine and replace as needed: Tips on how to avoid complaints
A basic prerequisite for every repair is that all components are cleaned, followed by lubrication of all necessary spots in the area of the guide shafts for the brake pads and/or at the mounting points of the brake shoes using a non-conductive, high-temperature-resistant, solid-free (non-metallic) paste from our product range that is suitable for ABS vehicles.
Do not use copper paste!
All components which were not assessed as OK must be strictly exchanged according to the guidelines of the vehicle, system, and brake manufacturers. Observance of the notes helps to avoid technical problems and complaints.
Follow the instruction leaflets!
Observe the instruction leaflet in the HELLA PAGID BRAKE SYSTEMS disk brake pad packages. Here you can find notes on special installation instructions, such as
Take care when working on vehicles with an electro-hydraulic brake!
When working on vehicles with an electro-hydraulic brake (e.g. SBC Sensotronic Brake Control), never change the pads and the brake fluid at the same time! Work on the electronic brake system may be performed by trained personnel only.
Follow the instructions from the vehicle and brake system manufacturers!
Always follow the instructions from the vehicle and brake system manufacturers regarding repair and maintenance work.
When carrying out the repair, test procedures such as checking the concentricity (lateral runout) and checking non-uniform thickness (varying disc thickness) of the brake disc may be required.
If hub eccentricity exists, the lateral runout at the outer edge of the disc will be twice as much.
The thickness difference measurement of a brake disc can only be verified using special measuring tools. A micrometer screw provides sufficient measuring accuracy of ± 0.001 mm.
The measurement should be taken at 12 to 15 positions on the circumference and approx. 10 – 15 mm below the outer friction radius. Depending on the vehicle type, judder phenomena can be caused by thickness differences as small as 0.012 mm to 0.015 mm. These values must therefore not be exceeded on new brake discs.