Marginal Column

Disc brakes service Frequently Asked Questions

  • Brake system requires proper operation of all units
  • Wrong opinion on noise or creaking caused by the poor quality of brake pads or inaccurate performance of replacement operations
  • Regular preventative maintenance and service procedures are mandatory in addition to parts replacement
  • Inspection of the brake is necessary at least 2 times a year
  • Adjacent suspension and steering components must be included into the mandatory checking procedure in addition to brake system parts

Bosch has almost 100 years of experience in development and service of brake systems. In 2017 the first brake booster developed by Bosch will celebrate the 90th anniversary. Bosch Training Center arranges different courses in diagnostics and repair of brake systems for automotive service station professionals. On the base of the extensive experience in teaching and communication with users Bosch experts collected the most frequently asked questions related to the disk brake mechanism service. The answers are presented by Aleksandr Kotelnikov, the brake system specialist of Bosch Training Center:

What is the reason of brake system components creaking? Is it true that the noise at the moment of braking occurs due to brake pads?

Yes and no. This is a common, but not the only reason. The noise at the moment of braking occurs due to vibrations and resonance of different components of brake systems, suspension and steering.

Furthermore, if the squeaking appears after a long operation period, this may mean that the special wear indicators integrated into some brake pads signal the need of replacement.

If the noise appears after replacement, does this mean that the new pads are poor quality parts?

Considering that bad, poor quality pads are the reason for the niose is fundamentally wrong. Brake system is a complicated mechanism working as a single whole. It works like an "orchestra". Vibrations are inevitable when braking, and some components of the system may not make any sounds. But when in different spots of the system depreciation has gradually accumulated, the components start vibrating and enter into resonance with other parts. Then the brake system begins to "sound" in full force. It may be the pads, drive rods, bushings, stabilizer, and even the shock absorbers. Therefore, when noise occurs, inspection of all the relevant components is mandatory. Moreover, if the same pad is mounted on different vehicles it can behave ideally or enter into resonance with the other components.

Very often, noise comes from the brake disc, since it has a very large area and acts as a kind of a loudspeaker. However, you should always consider the brake system or brake machine, as it is sometimes called in service centers, in the complex.

Can the problem of brake pads and rotors be solved with replacement?

Only after checking of the entire brake system. If you put a new part on a faulty mechanism, it will not work well.

What are other reasons for noisy operation of the brake system?

Overtightened wheel nuts can be one of the simple reasons. As a result of the constriction the rotor may be deformated that leads to beating on the brake pedal. This may also be the reason for the noise! So telling the exact reason for the noise appearance is impossible. Each case is different and always requires comprehensive diagnostics.

How often visual inspection of the brakes should be performed?

Inspection of the brake system is required at least 2 times a year. It is advisable to carry out routine inspection at the time of seasonal wheel changes. And, of course, the owner should come to a service center, if he hears noises during braking or experiences other problems.

Also regular attention should be paid to the brake fluid. Reduced fluid level in the reservoir is a sign of pad and disc wear, or may indicate other problems in the system. In addition to the main function, the brake fluid protects system components from corrosion, and therefore requires periodic replacement.

Brake fluid replacement interval is specified in the car or motorcycle manual, and is usually from 1 to 3 years depending on the vehicle type. However, objectively evaluate the condition of the brake fluid is possible by checking the boiling temperature. This can be done only with a special tester, for example, Bosch BFT-100.

What is the proper procedure of disk brakes service? What prevention measures are required to avoid screeching?

Even if replacement of rotors or pads is not required, the procedure will prolong their service life. The minimum a service processional should do is to remove the caliper, check the status of all components, clean dirt and after that do the necessary lubrication. In addition to checking the brakes, the details of the suspension and steering (pads, rotor, rods, bushings, stabilizer, shock, etc.) should be checked.

Very often the reason for the noise is the lack of preventive braking system maintenance.

Should copper grease be used?

Despite the extensive use of copper grease by both car owners and service specialists, the use of this or any other grease containing metal is not recommended for brake maintenance. During operation electrochemical reaction occurs between different metals, causing the parts oxidation, and finally corrosion. This leads to wheels sticking to the hub or brake rotor. The wheels, caliper guides and pads lose mobility. In addition, the emerging micro-currents that accompany the process of electrochemical reaction could adversely affect the operation of the ABS/ESP electronic systems. Therefore, to avoid problems it is recommended to use the special Bosch Superfit grease for braking mechanisms. It does not contain acids and metal and protects parts against corrosion.

What are the advantages of coated brake rotors?

The coating on the brake discs of premium segments increases corrosion resistance and heat resistance prolongs the service life of the rotor and the whole brake system. These rotors do not require pre-cleaning of the surfaces prior to installation.

Can ceramic pads which are used on the sports models be used on all vehicles? Are friction materials universal?

Friction materials are not universal and Bosch engineers recommend sticking to the basic specifications of the original parts. Each system is designed to achieve the specified tasks and requirements. If the vehicle is designed to work with traditional pads, after installation of ceramic pads, their rapid deterioration with a high level of dust will lead to damage and malfunction of the system. Conversely, if the original ceramic pads are replaced with normal pads, it will lead to the disadvantages in the form of noise and excessive wear of the rotor. When replacing pads sticking to the principle of the original design is the best practice.

What are the ways to increase the brake system performance?

The best way to improve braking performance - is installation of high-quality pads and discs, for example parts manufactured by Bosch. In addition, high quality service and repairs can restore the brake system performance to the "original" values that ensure braking that meets the high requirements of automakers.

Should the guides or other components of the brake system be replaced in addition to pads and rotors?

If additional components of the brake system designed for mounting of pads, reducing noise and vibration are in good condition, replacement is not mandatory. However, over time the guides wear, corrosion occurs on the surface, and the spring platselose their characteristics. Since the cost of these components is not high, they may be replaced with new ones when necessary.

What are the advantages of Bosch components?

As Bosch produces and supplies components of brake systems as original equipment for many cars, often spare parts by Bosch are exactly the same as the OE parts. Bosch supplies products for primary and post-warranty service to the market and quality and requirements for the products are no different.

In the development of disk pads one of the objectives is to ensure that the level of noise produced by Bosch components is below 70 dB. Therefore, only the correct selection of materials and very precise tuning of characteristics can provide the required comfort for high performance pads. With the help of acoustic testing on special dynamic stands at the Research Center in Karlsruhe (Germany) individual characteristics are determined for each brake system, that provides the maximum level of performance. To simulate realistic operating conditions in various climatic zones around the world the temperature around the test stands can be adjusted from -40 to + 60°C.

There are other advantages that Bosch products feature. For example, for customers who have any questions, we maintain the hot line that can be accessed by phone. The number is +7 (495) 560-9500. For car service representatives we constantly arrange training where explain principles of service of both mechanical brake systems and electronic systems. For more information on the course program please visit the website of the Bosch Training Center.