The brake discs are a part of the disc brake and together with the brake pads generate a braking torque which is then transmitted to the wheel hub and the rim. The kinetic energy of the vehicle is converted into thermal energy by friction between the pads and the disc, so that the speed is reduced. 90 percent of the heat generated penetrates the brake disc and is temporarily stored there. The heat is then transferred to the ambient air. Thus the brake disc serves as a kind of heat exchanger. It is important to dissipate the heat to the environment as quickly as possible in order to avoid overheating damage, as the brake disc can only absorb a limited amount of heat.
The brake discs are therefore exposed to high thermal and mechanical loads. The following environmental influences also play a major role:
Brake discs are subject to natural wear. When the wear limit is reached, the discs must be replaced to ensure reliable functioning of the braking system. Most newer cars have a so-called warning contact for this purpose. On the one hand, there is a cable which ensures that a warning light warns of wear in good time. Alternatively, there are also acoustic wear warning contacts which draw attention to themselves by making loud noises when braking. If no warning contacts are installed, there is still the visual inspection. The wear limit indicates when the brake discs are worn out. The discs have a minimum dimension specified by the manufacturer. The wear limit varies from manufacturer to manufacturer. The defined minimum thickness is located on the outer edge or on the disc cup. Usually this information is stored in the technical data of the vehicle or in the service booklet. Grooves on the disc can also be an indication of wear. Flash rust, on the other hand, is normal and does not impair the function of the brake disc.
The following signs also indicate defective brake discs:
Changing the brake disc is basically not very complicated, but there are a few important points to consider to ensure road safety. We therefore recommend that the brake disc change be carried out by a specialist. In this way many mistakes can be avoided which would damage or contaminate parts of the brake system and reduce the braking force. In order to always be on the road with a good feeling, the brakes should be checked regularly during the inspection. There the thickness of the brake discs is also determined with the help of measuring instruments. When changing the brake discs it is also advisable to use a brake pad paste such as Plastilube to prevent the brake pads from rusting with the brake carrier. This is applied to all guide surfaces on the brake caliper and on the back plate of the brake pads.
It is not advisable to continue using the vehicle with worn brakes. Otherwise the brake discs would crack, which could lead to a sharp reduction in braking efficiency and cause damage to other brake components. When replacing brake discs, the discs should always be replaced together with the pads per axle, i.e. in pairs.
There are different types of brake discs that are used for heat regulation.
Brake discs are made of different materials such as grey cast iron and ceramics. The normal brake discs are made of grey cast iron.The ceramic brake disks are often used as special equipment for highly motorized vehicles and therefore have a higher price. The advantages for ceramic brake discs are the low weight, an extremely long service life and high form stability at all temperatures.
In our shop you will find grey cast iron and ceramic brake discs exclusively from renowned manufacturers who produce in OEM quality. These include Zimmermann, Herth+Buss, Textar, TRW and Brembo, and many others.The brake pads as well as the wear warning contacts should also be replaced as they also wear out. With our inexpensive brake sets you can also save money.
Important in the search for the right brake discs are the key numbers and, if necessary, restrictions on the vehicle, such as the PR numbers for cars from the Volkswagen Group. The restrictions are indicated in the list of vehicles on the respective product page and can also be found in your vehicle registration or in the vehicle service booklet. A small instruction how to read the PR numbers can be found on our help page. Thanks to this information you will also find the brake callipers and the brake pads in the required size. If you need further help in choosing the right brake disc, please contact our customer service.