Brake Disc |

Brake Disc

One of the most important components in a car for road safety is the braking system and one of its components, the brake discs. Only properly and efficiently functioning discs provide stability on the road and are responsible for slowing and stopping the car. Brake discs are the backbone of the entire braking system, where the brake pads are pressed into. Discs are constantly exposed to environmental factors and thermal effects and are therefore made of high-quality and durable materials: cast iron, ceramic, etc.

Brake disc function and working principle

The main function of brake discs is to shorten the braking distance and to reduce the speed of the vehicle during braking. There is a mechanism unit between the disc and the brake, and the principle of action of the brake is to generate friction. During braking of the vehicle, kinetic energy is converted into heat. The brake discs and pads are responsible for all this. The efficiency of the braking system as a whole depends on the rate of distribution of the heat generated. 

The discs are made with holes to prevent the 'gas cushion' effect and to remove the gases produced during dynamic braking. When the gas does not accumulate between the friction surface of the disc and the pad, greater friction and better braking are achieved. The carved discs and the grooves on the discs help to remove the brake dust generated by the wear on the pad surface.

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Types of brake discs

As well as varying by manufacturer and price, they are also available in different types, so they are designed for a specific car, according to its technical parameters. 

Brake discs can be made from the following materials: 

- Cast iron.

- Carbon.

- Ceramic.


- Ventilated discs. Consisting of two plates or spaces between them.

- Unvented discs. Consisting of a solid plate with or without perforations, cut-outs.

By type of perforation:

- With through-holes - for efficient cooling, exhaust and combustion product removal. Disadvantage - relatively short service life. 

- With enlarged holes. Unlike the slotted discs, these have a long service life.

How do I know when it's time to replace my brake discs?

Brake discs, like other parts of a car, are subject to various factors and mechanical stresses and eventually wear out and need to be replaced. The safety of the driver, passengers and all road users is only guaranteed by a proper and efficient braking system, so if any part of the system fails, it must be repaired. Brake discs are a continuously efficient component that is subject to high heat generation and often overheating, which leads to brake disc failure. There are a number of reasons why brake discs can fail, including prolonged exposure to moisture, sudden braking, the installation of faulty pads and other possible mechanical factors. 

Possible failures: 

- Discs have become wedge-shaped, flattened.

- Disc deformation.

- Bumps on the surface.

- Fracture of the part.

- Cleavage of the disc.

Indications of failure: 

- Clunking, squeaking and banging in the discs when the car is braking.

- The car deviates from its specified trajectory when braking.

- Whistling and squealing during braking.

- There is a vibration when the pedal is pressed.

- Increased braking distance.

- Steering wheel vibration during braking.

- Increased brake pedal play.

If you notice any possible signs of brake disc failure, have the vehicle parts inspected immediately. Brake discs should be replaced regularly as they become worn. Manufacturers indicate on the disc the minimum disc thickness that must be taken into account. Worn discs increase the risk of breakage and the risk of the caliper jamming. 

How often should brake discs be replaced?

As well as being replaced regularly, they should be checked at every general vehicle inspection and pad change. Brake disc manufacturers specify the minimum thickness allowed on the edge of the part. Discs must therefore be replaced when they reach this thickness. At the first sign of failure, the thickness of the disc should be measured with a caliper. A deviation of 1 to 3 mm from the initial reading is allowed. 

The front discs are usually replaced after 80 000 - 120 000 kilometres and the rear axle discs after 130 000 - 170 000 kilometres. Front discs tend to wear more than rear discs, due to the higher load they experience during braking. Sport or cut-out discs can also wear out early. Parts should be replaced as a set for each axle. It is recommended that new brake pads are fitted each time the brake discs are replaced. During the first 150-200 kilometres, once the components have been replaced, it is important to avoid continuous or sudden braking.

Which brake discs should I choose?

The choice of brake discs depends on the conditions of use, driving style and price. Choose quality, reliable brake discs because your safety depends on them. Disc prices range from the cheapest to the most expensive, so make sure you consider the conditions of use when choosing. For quiet, city-only driving, a set of low-cost brake discs can usually be sufficient. For dynamic driving on both urban and rural roads, off-road and heavy loads, it is recommended to choose discs in the mid-range and above, which will be made of robust materials, advanced technology and be able to withstand higher loads.