Brake disc

Since the invention of the disc braking system on cars, the brake disc has been an important part of the automotive industry.

Along with the brake pad, the brake disc forms a friction material pair that is subject to wear and must withstand extreme loads.

Both components provide the braking torque required to slow the vehicle down or stop it.

The brake disc is a disc that is connected to the wheel hub, so it has the same rotation as the wheel and hub itself. When the brake pedal is depressed, the brake pads press against the disc, creating friction that slows the wheels and therefore the vehicle. This process generates a lot of energy, and it is the disc’s task to dissipate it, which is why this component can reach enormous temperatures.

Brake disc material

During braking, brake discs are subjected to high mechanical loads. As well as pressure, tensile and centrifugal forces, they must also cope with thermal stress. To achieve the best possible results in every braking situation, the composition of the brake disc and brake pad material must be adapted. Depending on vehicle type and the area of application, brake discs can be made from materials such as grey cast iron, stainless steel, carbon or ceramic. Most are manufactured from grey cast iron, the characteristics of which are enhanced by the addition of various materials. The presence of molybdenum and chromium helps to increase the alloy’s resistance to cracking under the effects of temperature and wear. A higher carbon content improves heat absorption capacity.

Due to cost considerations, ceramic or carbon brake discs are used in motorsport or on the most expensive cars. Other advantages, apart from low weight, high strength and good responsiveness, are the reduction of fading effects.

Nevertheless, due to their reduced thermal conductivity, these brake discs require special brake pads to compensate for this effect.

Technical data

During braking, friction converts kinetic energy into heat energy. Up to 90% of this energy is absorbed by the brake disc and released into the ambient air.

Consequently, under extreme conditions the temperature on wheel brakes can reach up to 700°C. In addition to physical stress, brake discs are subject to environmental influences, dirt, water and salt. The manufacturers have to consider all of these factors when developing brake discs, which necessitates the production of different variants of brake discs. The basic distinction is between one-piece brake discs and selfventilating brake discs.

One-piece brake discs are manufactured from a single casting and have only one friction ring. As one-piece brake discs give off heat slowly, they are generally installed in the small car segment. They are mainly used on heavy duty or manual vehicles and are mounted on the rear axle which is less exposed to braking forces. They partially replace drum brakes thanks to their improved handling.

Due to their large dimensions, self ventilated disc brakes have a high heat storage capacity and are cooled down quicker due to the radial channels through which the air flows. These radial channels are located between the two friction rings. The rotation of the brake disc causes a “fan” effect which creates a continuous flow of air through the brake disc.

Since the dynamic distribution of weight between the axles results in higher braking forces at the front axle, ventilated disc brakes are normally fitted on the front axle. This enables high braking power even under extreme conditions. Depending on vehicle type, use or vehicle motorisation, self-ventilated disc brakes can be fitted on the front and rear axle.

Furthermore, solid and self ventilated disc brakes can be fitted with grooves or grooves as well as axle drilling. Material removed from the brakes, water and dirt accumulate in the grooves or grooves and are ejected outwards by the rotary movement. Axial holes increase heat dissipation, but have no self-cleaning effect as material removed from the brakes can accumulate in the holes.

The parameters to look out for in brake discs

The following rules apply when a brake disc should be replaced or reground

Simply put: when the disc has worn down. Wear occurs as a result of abrasion of the pad material through contact friction. Once the thickness of the disc is below the minimum permissible value, it is time to take the car to a workshop. It is impossible to determine how many kilometres a disc can last as there are many elements that affect its life: driving style, load and road surface roughness are the primary factors.

These are infrequent oscillations of the vehicle caused by braking.

Cold braking mechanism activation is indicated by steering wheel flicker, changes in brake force or a pulsating brake pedal. The cause is a difference in brake disc thickness, resulting from uneven wear, which becomes apparent when the brake is applied. During rotation, abrasion of the friction ring due to axial vibrations periodically brings the disc and brake pad into contact. Hot tearing occurs as a result of reversible deformation of the brake disc due to uneven heating of the brake disc. The friction ring of the brake disc can deform outwards or inwards in an unacceptable manner due to overheating. This phenomenon is intensified by the localised burning of the brake disc. Possible causes are an underinflated brake disc, worn brake pads and the use of brake agents that do not meet the manufacturer’s specifications

For this reason, we recommend that you contact our service centre where our professional mechanics will give you all the necessary assistance and, if necessary, perform brake disk resurfacing.

In our service we provide high quality diagnostics of the state of your car’s brake discs. We perform all the required operations in a quality and in time. We are working only with high-tech and modern equipment and tools. Our service technicians will perform grinding of the brake discs and all operations to restore the function of the brake discs. We grind discs with or without removing them. We have the capability of resurfacing the discs, even of different dimensions.

How is the grinding of the brake disc carried out?

Our technicians use different methods and equipment to perform this type of work. The most common is grinding on a lathe which requires the disc to be removed or on a special machine that does not require the disc to be removed from the vehicle. We do however recommend that the discs are removed to obtain a more efficient result.

The procedure itself is simply grinding away the damaged layer of metal and the disc will be as good as new. Due to this reason, we do not recommend grinding very thin discs, as the process involves grinding from 0.25 mm to 0.5 mm of the disc thickness. It depends on the wear of the disc. The technician will determine on site whether or not this work is necessary.

Advantages of disc grinding in out service

  • the braking distance is reduced
  • the brake pads’ service life is extended
  • the necessity of replacing a brake disc is prevented
  • function of anti-skid and anti-lock braking system of your vehicle is improved
  • it improves the wear characteristics of the brake disc and maintains its technical data.

Costs start at €25.

Tyre installation and tyre selling.

We also provide tyre service in our service point. Furthermore we also sell tyres.