Driving safety directly depends on the serviceability and effectiveness of the braking system. When a driver wonders what kind of brakes a car has, he often means only the visible parts of the wheels, but in fact we are talking about a complex engineering complex. A modern car is a combination of hydraulics, mechanics and electronics, designed to instantly extinguish the inertia of a multi-ton mass.
Understanding the operating principles of various components allows you not only to properly maintain a vehicle, but also to predict its behavior in an emergency situation. There are several main types of mechanisms, each of which has its own advantages, disadvantages and scope of application. From classic drum solutions to cutting-edge ceramic discs, the choice of technology is always a trade-off between cost, efficiency and durability.
In this article we will analyze in detail the design of the main systems, their interaction with electronic assistants and selection criteria for maintenance. Brake system is a critically important unit, so knowledge of its features is necessary for every car owner. We will look at the physical processes that occur during braking and find out why manufacturers still use different designs on different axles of the car.
Disc brakes: performance standard
The most common type in the modern automotive industry are disc mechanisms. Their operating principle is based on the friction of the pads against a rotating metal disc mounted on the wheel hub. When you press the pedal, hydraulic pressure forces the caliper pistons to compress the disc on both sides, converting the kinetic energy of movement into thermal energy.
The main advantage of this design is considered to be excellent heat dissipation. The open design allows air flow to effectively cool the work surface, which prevents so-called "brake fade" - loss of efficiency due to overheating. Ventilated discs, having internal channels for air circulation, are used on the front axles of most passenger cars, where the braking load is maximum.
There are several modifications of disk systems, differing in the design of the caliper:
- 🔧 Floating type caliper: the most common and cheapest design, where only the inner pad is movable, and the outer pad is pressed due to the reaction of the body.
- 🔧 Fixed type caliper: has pistons on both sides of the disc, provides more uniform and powerful braking, often used in sports cars.
- 🔧 Composite disks: The center section is made of aluminum and the brake ring is made of cast iron or ceramic, which reduces unsprung weight.
Despite their high efficiency, disk mechanisms require more frequent replacement of consumables compared to drum counterparts. The open design allows dirt and water to enter, which can accelerate wear, although modern pad materials minimize this effect. Ceramic brakes, representing the pinnacle of the evolution of disk systems, are practically devoid of drawbacks, but their cost makes them the domain of the premium segment.
⚠️ Attention: When replacing disc brakes, always check the condition of the caliper guides. Acidification of these elements leads to uneven wear of the pads and reduced braking efficiency.
When running in new brake discs, avoid sharp braking for the first 300-500 km to avoid local overheating and warping of the surface.
Drum systems: reliability and efficiency
For a long time, drum brakes were the only solution for all wheels of a car. Today their main niche is the rear axle of budget and commercial vehicles, as well as the parking system of many models. The principle of operation is to release two crescent-shaped shoes inside a hollow drum, which rotates along with the wheel.
The key advantage of the drum structure is its tightness. Dirt, water and road chemicals practically do not get inside the mechanism, which significantly increases the service life of the friction linings. In addition, drum mechanisms have a self-reinforcing effect: when braking, the shoes are pressed against the drum not only by the force of the hydraulic cylinder, but also by the inertia of rotation of the drum itself.
However, this system also has significant disadvantages that limit its use on the front axle:
- 🐌 Low heat dissipation: The closed housing does not dissipate heat well, which leads to overheating during heavy braking.
- 🐌 Inertia: The mechanism responds more slowly to pedal pressure and releases more slowly, which can increase the braking distance.
- 🐌 Difficulty of maintenance: Replacing pads requires more time and effort, often necessitating the clearance adjustment.
In modern conditions drum brakes often combined with disc wheels on the front axle. This scheme allows you to distribute the load: the front discs take on up to 70% of the work during active braking, and the rear drums work effectively in normal modes and are excellent for implementing the parking brake function.
Comparative characteristics of brake types
To better understand what brakes are on a car and how they differ in operation, it is necessary to conduct a direct comparison of their key parameters. The choice between a disc and drum system is always a balance between cost of ownership and vehicle performance.
Below is a table showing the main differences between the two main types of mechanical braking systems:
| Parameter | Disc brakes | Drum brakes |
|---|---|---|
| Braking efficiency | High, stable | Average, depends on temperature |
| Cooling | Excellent (especially ventilated) | Poor, prone to overheating |
| Pad life | Smaller (30-60 thousand km) | Larger (60-100+ thousand km) |
| Pedal response | Instant | Detained |
| Maintenance cost | Higher | Below |
The table shows that for active driving and difficult conditions, disc mechanisms are the only choice. However, for quiet city use or on the rear axle of a light car drum mechanisms remain an economically viable solution.
The combined scheme (discs at the front, drums at the rear) is optimal in terms of price/performance ratio for most civilian vehicles.
Parking brake system (Handbrake)
The parking brake, which is popularly called the “handbrake,” deserves special attention. Its main task is to hold the car in place when parking, preventing spontaneous rolling. Structurally, it can be implemented in different ways, depending on the type of main brakes.
In the classic version with drum brakes on the rear axle, the handbrake function is built directly into the mechanism. The cable moves the lever inside the drum, spreading the shoes. With disc brakes, there are more options: it can be a separate small drum on the inside of the disc (drum-disc system) or a helical mechanism inside the caliper that mechanically compresses the piston.
Modern cars are increasingly equipped electronic parking brake (EPB). This system eliminates cables and levers in the cabin, instead using electric motors built into the rear calipers. Activation occurs with a button, and control is taken over by the electronic unit.
- 🅿️ Mechanical cable: a classic that requires periodic adjustment of the cable tension.
- 🅿️ Hydraulic: uses pressure from the main brake system, often found on front-wheel drive cars with rear discs.
- 🅿️ Electronic (EPB): Automatically tightens when stopped, may have an Auto Hold function.
⚠️ Attention: On cars with an electronic handbrake, replacing the rear pads often requires connecting a diagnostic scanner to put the calipers into service mode. Attempting to press the piston without preparation will result in damage to the mechanism.
Truck brake system: pneumatic drive
When it comes to heavy equipment, hydraulic fluid gives way to compressed air. The question of what kind of brakes are there on a car weighing 40 tons has a clear answer: pneumatic. The physics of the process here is different: instead of liquid, air under high pressure, created by a compressor, circulates through the tubes.
The main feature of the pneumatic system is its fault tolerance. In hydraulics, a fluid leak leads to complete brake failure. In pneumatics, when the circuit depressurizes, the pressure drops, and special spring energy accumulators automatically brake the wheels. This ensures safety even in the event of a serious highway accident.
The main elements of the pneumatic system are:
- 💨 Compressor: pumps air into receivers (cylinders).
- 💨 Brake valves: control the air supply to the chambers.
- 💨 Brake chambers: convert air pressure into mechanical movement of the expansion fist levers.
Pneumatic drive has a high response inertia compared to hydraulics, so trucks and buses must be equipped with ABS and EBS (electronic braking system) systems, which optimize the pressure in each circuit. In addition, compressed air is used to operate other truck systems, such as seat suspension or door opening.
Why is there a whine sound when the truck brakes?
The whistling sound when releasing pressure is the work of the pressure regulator, which bleeds excess air from the system to prevent rupture of the lines. This is normal workflow.
Promising technologies: electromagnetic and regenerative brakes
The future of braking systems is already here in electric and hybrid vehicles. Here comes to the fore recovery - a process in which the electric motor switches to generator mode when braking. The kinetic energy of the machine does not turn into useless heat, but charges the traction battery.
In such systems, mechanical brakes (disc or drum) fade into the background, turning on only during emergency braking or a complete stop, when the efficiency of the electric motor drops. This significantly increases the service life of pads and discs, which can last hundreds of thousands of kilometers in the urban cycle.
There are also electromagnetic retarder brakes (retarders), often used on trucks and buses. They do not have rubbing pairs in the traditional sense. Braking occurs due to the creation of a magnetic field that prevents the rotation of the transmission shaft.
The advantages of new technologies are obvious:
- ⚡ Energy Saving: Returns up to 30% of expended energy back into the battery.
- ⚡ No wear: In recuperation mode, mechanical parts do not rub against each other.
- ⚡ Accuracy: Electronics control the braking of each wheel with millisecond precision.
Despite progress, it is still impossible to completely abandon classical friction mechanisms. They remain the only guarantor of safety in the event of battery discharge or electronic failure. Therefore hybrid braking system, combining recuperation and classical mechanics, is the de facto standard for modern transport.
How often should brake fluid be changed?
Brake fluid is hygroscopic, meaning it absorbs moisture from the air. Over time, the water content in it exceeds the permissible 3-4%, which leads to the liquid boiling when heated and the formation of vapor locks. It is recommended to change the fluid every 2 years or 40-60 thousand km, regardless of the mileage of the car.
Why do new brakes squeak?
Creaking often occurs due to vibration of the pads or the presence of metal shavings in the friction lining material. It could also be due to a lack of lubrication on the caliper guides or the back of the pads. If the squeak does not go away after grinding in (300-500 km), diagnostics are required.
Is it possible to install different types of brakes on one axle?
Strictly prohibited. The same brake mechanisms (left and right) must be installed on the same axle. Installing disc brakes on one side and drum brakes on the other on the same axle will lead to the car pulling away when braking and loss of control.
What is ABS and how is it related to brakes?
ABS (Anti-lock Braking System) is not a type of brake, it is an electronic add-on. It uses wheel speed sensors and valves in the valve body to prevent wheel locking during heavy braking. This allows you to maintain vehicle control even on slippery roads.