How does a brake caliper work. Rear brake caliper and its repair

Brakes are a design that cannot be skimped on. There are two types of brakes: disc and drum. A brake caliper is required to stop disc rotation. How brake calipers work should be considered in detail, as this essential element on which the safety of the driver and passengers depends.

Purpose

Even novice motorists need to know what a caliper is in a car. A caliper is a part necessary for evenly pressing the friction lining by means of pistons to the disc at the moment of squeezing. Since the caliper in the car should be considered in conjunction with the pads, we can conclude that more than 85% of front failures brake system associated with them.

Where is located

The assembly is mounted on the hub and fixed from below and above. It's held on by bolts. It does not rotate with the wheel.

Device

The node is a cylinder inside which the piston goes. The system also includes brackets - they hold the brake pads. On cars install products that are powered hydraulic system, on trucks install the pneumatic system.

Here's what the caliper consists of:

• frame;
• caliper guides - must be coated with grease;
• anthers of the fingers along which the caliper walks;
• inner and outer pads;
• brackets in which the braking elements are fixed;
• sealing and fixing rings;
• piston boot;
• hoses leading brake fluid.

The main element is a piston with a cylinder. The design includes a valve that removes air. Under the influence of pressure, the air temperature rises, which is why there is a risk that the liquid boils, and this negatively affects braking. The hole in the rear caliper is opened when bleeding the brakes. The rear brake caliper is connected to a cable, so the piston can be mechanically depressed by the parking brake.

How does it work

The principle of operation of the brake caliper is based on hydraulic pressure. The force causes the piston to move in the brake master cylinder. The property of a fluid is that it does not compress under pressure, so the pressure is transferred to the brake assembly. Since the caliper also has a piston, it is pushed out under the influence of pressure. The disk is on both sides, they rub against it, and the speed is extinguished by friction. The return of the piston to its place occurs as a result of the action of elastic rings.

Note! Since thermal energy is released during friction, the discs heat up to 500-600 degrees on any type of car. The design provides for constant airflow, so it does not heat up to more than 250 degrees.

Assembly body dimensions may vary depending on pad size. Both the rear and front caliper work the same way.

Types

The device is:

• fixed;
• floating;
• enlarged floating.

The fixed system is fixed on the steering knuckle, and the pistons are located on both sides of the disc, the pads compress the disc. In the inactive position, the pistons are held by springs. Brake fluid is supplied through branched pipes to the cylinders with different parties. Such a system works efficiently and is used for vehicles where the load is especially high - trucks.

Floating - has such a name because it can move along the guides. The pads are also located with inside and from the outside, but the piston (s) presses only the inner pad, the second rigidly fixed pad is pressed by the movement of the caliper in the direction opposite to the piston movement. This type of device is cheaper, less efficient, however, more popular.

The enlarged floating assembly works on the same principle as the standard floating assembly, but uses a piston. bigger size and pads increased in area, which increases braking efficiency.

Care

Competent care and monitoring of the state of the caliper will ensure it long term services:

1. It should be a rule to conduct every six months visual inspection both the caliper itself, and the hoses supplying the brake fluid, connecting assemblies. The hose must be replaced even if it is not completely damaged. Any damage sooner or later leads to fluid leakage, which means that the piston will work with insufficient pressure.
2. Rust on the piston impairs braking. It should be removed in a timely manner.
3. Pay attention to. When the thickness of the friction material reaches 2 mm, the brakes will start whistling, which indicates that friction linings worn out and the pads need to be replaced.

Service

The calipers get very hot and work in aggressive conditions, it is these factors that affect the parts in a destructive way. Chinese counterparts are generally destroyed by high temperatures. Professionals recommend installing on a car or spare parts from famous brands or originals. Don't skimp on brakes.

Symptoms of a malfunction:

• creaking brakes;
• brake lock;
• deviation of the course of the car when braking;
• change in the stiffness of the brake pedal.

An important detail on which the service life of parts depends is the anther. The boot protects structural elements, in particular the piston surface and the seal, from dust and dirt. If the anther is torn, dirt, sand are instantly clogged inside, the parts rust, the grease is washed out or dried out, the tightness of the stuffing box is broken and a leak forms. Running the piston dry leads to disastrous consequences: braking efficiency is significantly reduced, or it becomes impossible, the piston is blocked and.

Piston souring occurs when a worn brake pad is used for a long time. Insufficient thickness of the lining leads to the fact that the piston is strongly extended, and deposits form on its side surface, which prevent it from returning to its original position. If new pads are installed on such a caliper, the following problems will arise:

• fast pad wear;
• disk failure;
• uneven pad wear;
• creaking caused by overheating of rubbing parts;
• rudder beating due to constant pressure on a rotating disk. It is especially pronounced when braking at high speeds.

Noise in the assembly can be noticed some time after installing new parts. Causes:

• design features of the node;
• poor quality parts.

To eliminate this drawback, springs are additionally installed.

Corrosion of the inner surface of the piston occurs due to the neglect of the terms for replacing the brake fluid. It is able to absorb water even from the air. therefore, over time, even parts that only come into contact with brake fluid are exposed to water and.

Important! The brake fluid change interval is every 3 years.

In order for the caliper to serve for a long time, it is necessary to change the lubricant in a timely manner. This action will provide reliable performance piston and vehicle safety.

Cannot be used for calipers regular grease type of graphite lubricant or "Litol". It dries quickly even with a whole anther. The main requirement for lubrication is resistance to temperature changes. Specialized grease is sold in packs of 45 g. This is enough for a one-time service.

Repair kit replacement

A new assembly is expensive, but you can purchase a repair kit and replace all the “insides”. This will cost significantly less. It includes all the necessary parts, including anthers and cuffs.

Pistons with caverns of significant depth are not repaired, even if they are covered with rust. Grinding a part leads to a critical change in dimensions. However, it is necessary to clean rusty places with fine sandpaper. The guide pins may also wear out. They provide mobility to parts, so they should be inspected first and replaced if necessary.

Service order:

1. The car is jacked up from the side of the wheel where the service will be carried out.
2. Take off the wheel.
3. Dismantle the caliper by unscrewing the bottom bolt.
4. In preparation for servicing the rear assembly, the cotter pin holding the cable is also removed. parking brake.
5. Raise the top bracket.
6. Take out the pads.
7. Unscrew the top bolt.
8. Hang the caliper.
9. Unscrew the bolts holding the clamp. They take it off.
10. Remove the piston.
11. Take out the "fingers" and remove the grease.
12. Put on a new one lubricant.
13. Insert the guide into the bracket and check how freely the guide moves. The movement should be completely effortless when grasped with two fingers of the hand.
14. If necessary, replace worn-out elements with new ones.
15. Assemble the knot in reverse order.
16. Pumping the system.

Important! It is impossible to operate a car with unbled calipers, as the brakes will not work effectively.

The principle of operation of brake calipers is relatively simple - braking occurs due to friction. This system proved to be more advanced than drum brakes and is used in many domestic and foreign stamps cars. All elements of the node perform important features Therefore, their condition must be monitored and worn parts should be replaced with new ones in a timely manner.

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The brake caliper is the component of the brake system that develops most dynamically. This development is facilitated by competition. Several dozens are fighting for their place in the market. major manufacturers, offering car owners and workshops more and more modern "hydraulic vise" capable of working for a long time in the most different conditions. It is easy to get confused in the wide range of these spare parts. We will tell you about how brake calipers how to choose and use them correctly.

Excursion into history

Today it is believed that for the first time a braking mechanism equipped with a special disc appeared in 1890. Designed by Frederick Lanchester. The design included a caliper that compresses the brake pads. Such technical solution ahead of your time. Only decades later, the design began to be actively used in the aviation industry. Disc brakes installed for the first time in history on a car Chrysler models Crown Imperial, rolled off the assembly line in 1949 It was then that all automakers began to pay attention to the brake system.

Principal design

Disc brakes have evolved in two ways. Namely, the following "branches" of development of brake calipers are distinguished:

1. With floating bracket;
2. so-called. fixed design.

As for the fixed calipers, they included a metal case in which the working cylinders were located symmetrically with respect to the brake disc. The metal case was mounted on a knuckle (both front suspension and rear). When the driver applied the brake, the pads compress the disc at the same time on both sides. Non-working pads are held by special springs. Brake fluid moves through the tubes to all cylinders at once, which ensures the synchronous operation of the pistons. Unfortunately, fixed brakes cannot boast high reliability. They are installed on heavy vehicles, as well as on spotcars. This type brakes is the skate of large firms, somehow and.

Floating caliper designs differ significantly from fixed calipers: the pad is fixed on one side only, that is, it also does not budge. In this case, the caliper itself includes a cylinder body and a special bracket. The cylinder is located on the side of the inner surface of the wheel. The cylinder usually contains only one piston, but sometimes installed immediately two. At the moment of the beginning of braking, the piston must transfer force to the 2nd block located directly in front of it. As soon as the movable element is pressed against the disc, the aforementioned floating bracket begins its movement towards the piston. The outer block is activated. This mechanism is simple and cheap to manufacture. Distributed very widely. As a rule, calipers equipped with a floating bracket are installed on golf-class cars.

Features of work

The brake caliper must provide sufficient braking force to ensure effective deceleration and subsequent stop. vehicle. As soon as the driver wants to stop, he presses the pedal, thereby creating excess pressure in the brake line. Due to the pressure, the caliper pistons are triggered, fixing the pads, as you might guess, parallel to the disc. IN this case pads are compressed on both sides at once, allowing you to quickly reduce the speed of the car. However, friction generates heat. The disc heats up, as does the pads with the calipers installed. Hence the requirements for the latter:

• Calipers must have high heat dissipation;
• The part must have a high resistance to overheating;
• The part must be strong.

If the requirements are not met, the material begins to deform. Sooner or later it happens even if correct operation, so replacing calipers is not something extraordinary. However, you can delay the replacement time.

On old cars, somehow domestic UAZ, brake calipers were either only in front of the car, or they were not at all. The replacement was conventional brake drums.

Rear and front calipers

The brake system of the car has one feature: it is equipped with different calipers at the rear and front. Simply put, the front caliper cannot be put in the back.

The front caliper is an open, well-cooled unit. It works in tandem with a disc that is mounted on the wheel hub. Cylinders are placed in special nests, and inside the cylinders there are pistons with sealing materials. In addition, the caliper guides are protected from external irritants like dust and water with a high-strength boot. As soon as the reverse release process begins, the pistons in the braking system are returned to their normal position by elastic rings.

Unlike the front caliper, the technically more complex rear caliper is also adapted to work with the handbrake mechanism. Otherwise, the principle of its work is no different. However, the rear caliper is more expensive due to the greater complexity of the design. There can be two drive systems for the brake system of the rear wheels: hydraulic, mechanical.

Common Problems

If a car enthusiast knows about the device and the common "diseases" of brake calipers, he will be able to operate them for a long time. Regular maintenance will only benefit him - by identifying the problem in time, you can get rid of the headache associated with repairing not only the main unit of the car, but also adjacent units. Pay attention to the following:

• The brake pads began to wedge. The bottom line is that rust on the caliper elements creates an obstacle to the pads themselves. It is enough to dismantle the caliper to solve the problem with simple brushes for cleaning metal, available sandpaper or a small file. Immediately after removing rust from the metal, the surface is covered with grease. And if traces of wear are visible on the caliper, they are also pits from corrosion, there are two options left: carefully go through the metal with a file, if the wear is still small, or buy a new part;
• Stuck brake caliper guides. It should move freely along the guides. The pads are dismantled, the brake caliper is assembled and the freedom of movement is checked. In case of problems, check the guides for kinks, bends, and other things. Guides are cleaned and lubricated;
• Traces of corrosion are visible on the caliper piston. The problem is solved by disassembling the caliper, followed by grinding the piston using a special paste. seat additionally treated with WD-40. The assembly is assembled again, a fresh repair kit is installed (anther must be replaced with a new one in without fail). If the measures taken did not give anything, you will have to buy the piston separately or the entire caliper assembly;
• Piston started to stick. It is necessary to release the bleed valve immediately after the wedge of the car pads. This usually helps. If the caliper has already been removed, it will be difficult to push the piston back in. Preventive measure next: insert the piston into the caliper with a screw, then start pushing it out with the pedal so that the part does not completely fall out.

To avoid the above problems, monitor the condition of the protection of the brake calipers. In other words, change the anthers. It is they who protect the part from dirt, solid particles and dust getting inside, which over time will begin to act as an abrasive, as well as moisture getting inside, provoking metal corrosion. You can handle the replacement of anthers yourself.

Learn more about caliper repair

The brake caliper can be called a repairable element of the brake system. Some things are possible and simple car enthusiast. No special skills or technical education are needed.

Disassemble the caliper and remove old lubricant. Then a new lubricant is applied. Please note: in many stores you can find ceramic or even ceramic caliper lubricants under the name copper pastes, which, after drying, provoke jamming of parts. In fact, these are anti-creak pastes that are applied only to the contact points. individual elements brake system (stop pads in the caliper, pistons to the pads). Do you need silicone high temperature grease. For example, Slipkote 220-R DBC, sold in black tubes. Also determine the degree of wear, replace the sealing parts.

Examine the brake pads. If they are worn out, they can only be replaced. Perhaps it was in the pads that the reason lay incorrect operation braking system.

How to choose

The driver can choose new element braking system in two ways:

1. Search by VIN. It is very easy to find both the original and the analogues closest to it. Many experts advise looking for spare parts for your vehicle by its code, since in this way the chance of making a mistake is reduced to zero;
2. According to technical data. Or rather, by make, model and configuration of the car. Same a good option especially if you are looking for electronic catalogs, where these search criteria are specified without fail;
3. By part code. Find out the code of an existing caliper or consult motorists. You can also access the spare part code in one of the above ways.

But that's not all. You should get more information about manufacturers. It so happened that for the most important automotive system unscrupulous manufacturers produce the most disgusting fakes. They fail early, overheat, and sometimes they can only be installed with a hammer in their hands.

Brand Tour

Unlike, say, automotive sensors, it makes sense to take a non-original caliper. Spare parts for the brake system secondary market may not match the originals. It is only important to know the manufacturers. Here's who makes the best brake calipers:

• (Denmark);
• (Germany);
• (USA);
• (Netherlands);
• (Germany).

There are also cheaper alternatives. That's just cheap caliper the car enthusiast will not last long. It makes sense to take it only in case of limited funds at the time of purchase. Sooner or later the part will have to be changed. Possibly due to a breakdown. Take a look at the following companies:

For the first time, calipers were made at the end of the 19th century by the Englishman F. Lanchester, but they were not used. Later they began to be put on the chassis of combat aircraft and on sports cars. The caliper came to streaming car models only in the middle of the 20th century. The caliper is a key part of the brake system of the car. So, this is your confidence in the safety on the road. Remember to systematically diagnose calipers and fix problems immediately.

Types of brake calipers

At the moment of braking, a number of parts are involved: a brake disc, and a caliper. Key role in this process, the caliper is assigned, since it is he who presses the pads to the disc. Brake calipers come in fixed and floating calipers. Let's look at both types.

The principle of operation of the brake caliper

The fixed design brake caliper has a metal body and two working cylinders attached on both sides. The body of the structure itself is fixed on the steering knuckle. At rest, the calipers are held by springs. At the moment of braking, the pads are synchronously pressed against the disc from both sides.

In order for the brake calipers (pads) to operate synchronously, brake fluid is needed. It is fed through tubes to all cylinders (several cylinders increase the efficiency of the brakes). Such powerful pads stand on racing cars Oh and on heavy vehicles(e.g. Mercedes-Benz).

A floating caliper brake caliper has a bracket and cylinder body (with 1-2 pistons) attached to the inside of the wheel. This block is stable in one place. At the moment of braking, the piston presses on the front standing block. Then the pad is pressed against the disc, and the floating caliper bracket moves along the guide pins towards the calipers. As a result, the second (outer) pad is pressed against the brake disc.

The floating caliper is smaller in volume than the fixed caliper design. In addition, the mechanism itself is much simpler. There are floating calipers on economy class cars with regular disks small size.

Signs of a bad brake caliper

The driver must be observant in order to feel the malfunction of the caliper in time. What should alert you? The most common symptoms of a caliper failure are:

It takes a lot of effort to bring the car to a complete stop.

At the moment of braking, the car begins to pull to the side.

The brake pedal "fails" without effort.

The brake pedal vibrates.

There is some resistance in the brake pedal.

At great effort rear brakes are blocked.

There was a strange creaking, screeching when braking (so do not forget about regular lubrication of the calipers).

There is a brake fluid leak.

Methods for repairing a brake caliper

If the brakes are sticking, rust on the fixed caliper pads may be the cause. This happens when the car has been idle for a long time, or you have come across a poor-quality boot. To remove this corrosion, you will need sandpaper, a metal brush and a large file. After removing the rust, the metal is coated with a high-temperature type grease. If small pits from rust appeared on the pads, then you will have to grind them with a file(Otherwise, the pad will not press tightly against the brake disc). Change cuffs at the same time.

If the holes are of a decent size, then buy a new fixed part of the caliper, because grinding with a file is powerless here. If the caliper guides are sticking, you will have to remove the pads. Now we achieve free movement along the guides: we check the bend, clean and lubricate.

If the piston is stuck in the caliper. To check, release the bleeder plug after the pads are jammed. If there is a malfunction, then wedging will no longer be observed. If you dismantle the caliper, it will be very difficult to push the piston back in. In order to prevent it, you can periodically screw the piston all the way into the caliper with a screw, and then push it out with the pedal. But, again, not entirely (so that it does not fall out).

Part one is about what brake calipers are, how they differ and how they work, let's talk about the working brake cylinder and pads, arrange a little auto-guess and see a lot of photos. Let's start with brake disc.

Brake disk

Ferrari 430 floating rotor brake disc

The brake disc, made of cast iron, is rigidly fixed to the wheel hub, that is, it rotates at the speed of the wheel. Brake discs are what appears before us when the wheel is removed.

Front brake ford drive Focus ST

The brake disc absorbs almost all of the heat generated during braking. Therefore it main characteristic is the heat capacity and thermal conductivity. The latter, in turn, is also needed in order to quickly give off heat environment- heat up the air. The disc must be stiff enough to withstand pad pressure and must withstand frequent and severe temperature changes. IN civilian vehicles cast iron discs are used, which has a very low coefficient of friction, which increases wear resistance. It would seem that in the brakes the coefficient of friction should be large, but that everything ultimately rests on the coefficient of friction of tires with asphalt. And only where tires allow, it makes sense to use discs made of ceramic, carbon. But such disks will wear out noticeably faster.
By design, one-piece discs and ventilated (double) are distinguished. Solid ones are a flat solid disk - these are usually placed on rear wheels budget cars.

One piece rear brake disc

Ventilated discs are, in fact, two solid discs connected by partitions. Ventilated discs are much better cooled by the air that circulates between the discs. On expensive drives, baffles are specifically designed to improve air circulation.

BMW ventilated front brake disc

To lighten the weight hub part disk (bell) is made of lighter alloys (aluminum), and the rotor itself ( working surface) is bolted on. Moreover, the fastening may not be rigid and allow some axial displacement of the working part of the disk - disks with a floating rotor.

Composite brake mitsubishi drive Evolution X

Notched discs help to remove hot gases from the rubbing surfaces of the pad and disc, and on the one hand increase the surface area of ​​the disc (for better cooling), and on the other hand, reduce the contact area of ​​the pad with the disc, respectively, less heat is generated in the friction pair.

The ventilated disk with notches. The section shows the structure of the jumpers connecting the two parts of the disk

Perforated discs have through and blind holes and contribute to better cooling disk. Also, on the one hand, they reduce the rigidity of the entire structure, and on the other hand, they help the disk to more easily endure deformations associated with constant and rapid heating and cooling.

Brake disc with perforation Aston Martin in the form of a wall clock

Comparison different types disks

The brake disc, or rather its size, directly affects the minimum size rims and indirectly on the rubber profile. The larger the brake disc required, the larger the wheel will be, because the disc itself and the caliper must fit in rim and still have a gap for air access for cooling and not overheat the wheels themselves.

caliper

Brake caliper Brembo "Extrema" for Ferrari LaFerrari

The task of the caliper is to press the pads against the brake disc on both sides. On the front wheels, the caliper is attached to knuckle and stationary relative to the rotating brake disc. The pads are pressed against the disc by a working cylinder (from one to six to eight), driven by high pressure brake fluid. The working cylinders can be located on one side of the cylinder, or on both sides.

BMW Single Piston Floating Caliper

IN conventional machines in the caliper there is one working cylinder located on the inside. For racing cars, multi-cylinder (multi-piston) calipers work well, but in racing it is rare that braking comes to a complete stop, usually there you need to quickly and efficiently decelerate (well, say to 90 km / h and pass sharp turn). Several working cylinders press the pad more evenly against the disc, and heat is distributed more evenly. But such structures have less downforce, due to the small size of the pistons and cylinders themselves. One large working cylinder develops more force than, for example, two or three small ones.

Single piston floating caliper with brake pads

Two designs are common - with a floating and a fixed caliper. In civilian vehicles, the first is used. It consists of two parts - the caliper itself and the guide pads.

Pads in guide (no caliper)

The floating caliper is fixed only along the axis of rotation of the brake disc (wheel) and can freely move perpendicular to it along the guides (pins) fixed in the shoe guide. This allows you to place one or more brake cylinders on only one side of the caliper, but at the same time have uniform pressing of the pads to the disc on both sides. The piston of the working cylinder presses on the pad, pressing it against the brake disc, while pushing the caliper away from the piston, which leads to pressing the pad on the opposite side of the disc.
2-piston floating caliper with guides and pads

Fixed calipers are rigidly fixed relative to the disk and have from two to eight working cylinders located on different sides relative to the disk. The calipers themselves are split, or cast in one piece.

Sectional view of four-piston fixed monolithic caliper

The caliper is attached to the steering knuckle either directly or through special brackets.

caliper mount Honda Civic(fixed compound four-piston)

The caliper has two holes - for supplying brake fluid and for pumping (usually located on top so that air can escape more easily).

Floating single piston rear caliper Kia Sorento. The arrows mark the inlet port and the bleed valve (under the rubber cap)

Fixed calipers can be composite (the caliper has a longitudinal section and consists of two mirror halves) and monolithic. The former are easier to make. In general, they have approximately the same strength, and the steel bolts connecting the two parts of the aluminum caliper add rigidity to the composite. (Moreover, the modulus of elasticity of steel increases with increasing temperature, while for aluminum it falls, but for expensive monolithic calipers, special aluminum alloys are used that are not so susceptible to this).

Monolithic fixed caliper

The two halves of the fixed calipers are connected by a tube to supply brake fluid to the other half. Usually it is located outside, but it can pass through the channel and inside the caliper.

Composite six-piston fixed caliper. Bottom tube for connecting the two halves

On different machine the location of the brake calipers relative to the disc is seemingly completely random. There are no configurations (the most common - the front caliper is shifted back, the rear - forward, that is, the calipers “look” at each other). In general, the brake caliper should be kept away from dust, dirt and water flying off the road, but this results in a higher center of gravity (especially on race cars with huge and heavy calipers). The location of the front caliper is dictated by the location of the tie rod and suspension geometry. The location of the calipers can slightly affect the longitudinal weight distribution of the machine and the length of the brake line, which affects the speed of the brakes. Serviceability should also be taken into account. Where important, consideration should be given to the direction of air flow to cool the brakes - whether to cool the caliper or disc first.

Working brake cylinder

Section of the working cylinder with a piston Chevrolet Corvette ZR1

The slave cylinder is a piston that runs in a drilled hole in the caliper. The piston presses directly on the brake pad under the pressure of the brake fluid. For sealing, a rubber ring is used, inserted into a recess in the wall of the piston (caliper). The piston itself is hollow, usually cup-shaped, often chrome-plated to resist corrosion. To protect against dust and dirt entering the working cylinder, an anther is used, which is fixed on one side of the piston and the other on the caliper. The boot is made of heat-resistant rubber.

Piston of the working cylinder

In multi-piston calipers (6 and up), it is customary to use working cylinders of different diameters, which increase towards the back of the pad / caliper. That is rear end pads are pressed harder. This allows for more even pad wear, helping to distribute heat more efficiently. In addition, when braking, the pad grinds, forming dust that accumulates towards the back of the pad.

The piston of the working cylinder. This piston design allows less heat to be transferred to the brake fluid.

brake pads

The block is a metal plate with a friction layer applied to it, which must be resistant to high temperatures. The coefficient of friction of the friction layer for ordinary (civilian) pads does not exceed 0.4. It should be borne in mind that a high coefficient of friction in a pair of pad-disk leads to a squeal when braking due to vibrations that occur. For thermal insulation of the brake shoe from the piston of the working cylinder and, most importantly, from the brake fluid, rubber or copper compounds are used, applied between the shoe and the piston. It also helps to reduce the level of vibrations and squealing.

Due to the high hardness (and brittleness) of the friction layer, notches are used on the pads. Usually this is a vertical (one or more depending on the area of ​​the pad) cut in the center, which prevents cracking of the pad (due to constant thermal expansion and contraction), and also helps to clean the friction surfaces from rust from the brake disc, dust, dirt and promotes removal hot gases.

For timely notification of pad wear, a mechanical wear indicator is installed on them. It is a thin metal plate that, when the pads wear out, begins to touch the disc and emit a wigg when braking.

The upper pads have a clearly visible wear indicator.

In conclusion, let's look at a couple of photos and try to determine what's what.

Front brakes Ford Focus 2012

This is a photograph of the brakes of one of the cadabrovites. He likes to play checkers on the Moscow Ring Road and he has very cool brakes. Try to guess the car and the owner.

In the second part, we will talk about brake line, brake fluid, we will understand the principle of operation of the main brake cylinder, controller and vacuum booster brakes. In the third part, we consider the construction brake drums, parking brake, differences rear calipers and try to "open" the ABS unit.

Most often, when discussing the braking efficiency of a car, we are talking about discs and pads: comparison of compositions, manufacturing technologies, behavior in different road modes etc. And extremely rarely the subject of discussion are calipers. Maximum, in the context of replacing serial ones with red four-piston ones.

To start, a few words and types. Many people know that today two types of mechanisms are in operation: floating calipers and fixed ones: with one-sided piston placement and with two-sided, opposed.

First, most important question– which is more efficient? Is it worth it, at the first opportunity, to change the stock floating calipers to monoblocks of a reputable company? Don't be in a hurry to spend money.

Important principle: The efficiency of a caliper is determined not by the number of pistons, but by their total area. That is, the larger the piston area in the caliper, the higher the compression force brake pads. School geometry will help here. The area of ​​the circle is S \u003d πr ². Knowing the piston diameter, we can easily calculate the overall efficiency (in the case of calculating the total area for a floating caliper, the final value is multiplied by 2, by the brace). For example, legendary car The BMW 7 E 38 was equipped with both floating single-piston ATE calipers and fixed four-piston Brembo calipers. Let's calculate the effectiveness of the first and second.

ATE Single Piston Caliper (60mm Diameter). S=5652 mm²

· Four-piston Brembo (bore 40 and 44 mm). S =5552 mm²

The compression force is directly proportional to the total area of ​​the pistons. Therefore, the data

calculations clearly show that one piston will work more efficiently than four.

And a little about the practice of operation. Floating calipers are equipped with a very capricious part - guides. These things require not only timely and constant lubrication, but also the choice special composition. Even with a careful attitude - after 80.000-100.000 km. the guides wear out and begin to "please" the driver with a cacophony of ringing and metallic rattling. In addition, another bottleneck is the pad mounting kit: a set of metal plates that holds the pads in the bracket. These little things are recommended to be changed with each replacement of the pads. And given that the plates are not always sold separately, the driver is puzzled by another problem.

The practice of operating monoblocks differs from the floating counterpart in better side. Fixed calipers do not include guides in the design, and therefore are completely devoid of most of the problems described above. But there is something that unites both types of brakes - pistons. Moreover, in a multi-piston monoblock - there can be 8 or even 12 of them. How is this fraught for an inattentive motorist? Damage to rubber seals and corrosion of the pistons themselves. WITH mandatory replacement the latter. Well, one more positive factor that attracts motorsport enthusiasts: monoblocks are able to endure large quantity emergency braking than floating ones before they overheat.

To summarize: what are the pros and cons of floating brake calipers?

Considering frequent problems floating solutions with wedging, rubber wear and uneven wear pads and discs, this type of caliper has the main plus - the price. This type of mechanism is much cheaper. We will consider the weight of the caliper to be neither a plus nor a minus, because. it all depends on the comparison of specific samples.

What are the pros and cons of fixed multi-piston calipers? We will consider the price as disadvantages: even bush monoblocks will cost 400-800 dollars. Possible problems with pistons - this is unlikely (provided, of course, timely and high-quality brake service). Well, probably the installation. Well, pluses: uniform distribution of compression force, more organic wear of discs and pads. Appearance? Probably yes: it looks decent)