Brake disk

The brake disc consists of two main parts - the central part of the disc and the rotor.

The rotor is an annular surface with which the brake pads are in contact at the time of braking. This is the largest and heaviest part of a disc brake. Usually made of cast iron due to high friction and low material wear.

To improve cooling, the discs are ventilated. Ventilated discs between two surfaces of the rotor contain radial cavities through which air flows from the center to the edges.

The central part of the disk

The rotor is mounted on the central part of the disk, which, in turn, is mounted on the wheel hub. The central part of the rotor prevents heat transfer from the braking surface to the wheel bearings, so that the bearings do not heat up.

The central part of the disk is made of cast iron or lighter materials, such as aluminum.

There are two types: soldered with a rotor and in the form of separate parts. In cars of mass production, the central parts are usually made of cast iron and are integral with the rotor. In most racing cars, the center of the disc is a separate part and is made of aluminum and titanium alloys, composite materials or ceramics. ^[one]

The performance characteristics of brake discs include

• disk wear;
• temperature condition;
• geometric dimensions.

Wear

Drives work 100-150 thousand kilometers with quiet driving. With sharp and aggressive driving, the period is reduced to 30-40 thousand. The minimum thickness of the brake discs is indicated on the brake disc. Wear is checked with a caliper. Maximum wear is 2-3 mm from the initial disk thickness. The width of cracks and chips is not more than 0.01 mm. If the width of cracks and chips is greater, the discs should be replaced.

Temperature

During braking, kinetic energy is converted into heat through friction. Heat is generated on the contact surface between the brake pads and the disc. In theory, distinguish between ideal and imperfect contact of the disk and pads . Perfect contact implies that the temperature of the surfaces of the disc and the pads are the same. With imperfect contact, the temperature is different.

Braking is a short time and fast-paced process. Therefore, it is often impossible to achieve perfect contact. To simulate and study the processes of braking use an imperfect model. ^[2]

In this model, there are foreign particles between the disc and the pads. The friction material of the brake pad takes on the kinetic energy of the spinning brake disc and is abraded. Kinetic energy goes into heat and is transferred to the disk through foreign particles. This leads to a temperature difference between the surfaces of the disc and the pads. Therefore, a colder disk may receive heat generated in the pads.

The ultimate recipient of thermal energy is the caliper. It dissipates well the heat that it receives simultaneously from the brake pad and disc .

The amount of heat generated in the pads depends on the speed and weight of the car, and on the force pressing the pedal. A typical passenger car stop at 60 km / h heats the disc to 150 ºC. Sudden braking of a racing car raises the disc temperature to 800 ºC in a split second. ^[3] Silicon lava, which flows from the volcanoes of the Pacific Ring of Fire, has the same temperature.

Temperature regime of brake discs:

• for the city - 100-270 ºC;
• for the track - 177-900 ºC.

Geometry

The rotor diameter is measured by the outer diameter, and the width is measured by the total thickness between the contact surfaces. The size of the rotor surface in contact with the pads depends on the diameter of the disk. Manufacturers strive to make discs as light and small as possible, increasing braking power by improving braking performance. The ventilated rotor is always wider than solid.