A front brake caliper is a device that stops a car's brake disc. Technical condition caliper should always be in excellent condition, since this is the only moving part of the brake system, and therefore more responsible. In this article, we will reveal the principle of operation and the device of the caliper, as well as tell you how to repair it.
The principle of operation of the front brake caliper
Structurally, the caliper consists of two pistons, at the ends of which brake pads are located. When you press the brake pedal, pressure appears in the system, under the influence of which the brake fluid begins to move towards the pistons. The pistons, in turn, having received the influence of hydraulics, begin to move towards each other and press the pads against the brake disc. Thus, the wheels of the car stop. The pressure on the brake pedal determines the downforce of the pistons, since this indicator directly depends on the pressure in the brake system.
The device and mounting of the caliper depends on the make and model of the car, this also applies to. The most common is the dual mount caliper to the wheel hub with two pistons. The number of pads is usually a pair, although sometimes more.
How to determine the malfunction of the caliper?
The caliper must have great mechanical stability, since it operates in the mode constant voltage. In addition, increased thermal requirements are imposed on it, since during the braking process, the pads heat up and, due to heat transfer, heat the caliper itself. If the caliper overheats, its shape can be seriously deformed, which will lead to jamming of the mechanism, and, accordingly, to a malfunction of the vehicle's brake system.
Signs that may indicate a malfunction of the caliper are different. Firstly, the braking efficiency is noticeably reduced, and secondly, various squeaks and vibrations appear in the front of the car. Squeaking can be caused by too much friction, which occurs when the brake pads are installed incorrectly or the caliper is clearly deformed. Usually, this is accompanied by the appearance of a beating in the steering wheel area when you press the brake pedal at high speeds.
The reason for the subsequent repair can also be defects in the piston boot, through which dust and moisture enter the cylinder. All these factors lead to the inevitable seizure of the piston and a decrease in the effectiveness of the brakes.
Video - Brake caliper - device and maintenance
Do-it-yourself front brake caliper repair
This operation does not require special skills from the driver, so many people do this work at home with minimal investment.
First of all, the car wheel is hung out and removed, then the caliper fasteners are unscrewed and it is disconnected from the brake system. After that, the assembly is disassembled and thoroughly cleaned of dirt and old grease. Then, the caliper is inspected for wear and deformation, if everything is in order, then you can continue to perform repairs.
All to be replaced rubber seals and other consumables. In addition, be sure to replace the brake pads and check their fit. Once all the work is completed, you can begin to assemble the part.
Install the caliper on the hub and secure. brake hose lower into a container with brake fluid and ask your partner to vigorously depress the brake pedal. As soon as bubbles stop coming from the hose, quickly install it on the brake caliper and add brake fluid to the reservoir. So you will pump brake system and save yourself from sudden brake failure.
This is everything you need to know about front brake calipers. As you can see, its repair and replacement does not cause any particular difficulties, so you can handle this task yourself.
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 the 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.
Compound brake disc Mitsubishi 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 the steering knuckle and is 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, placed with 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 with 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). Location front caliper 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 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 brake shoe 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 pad 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 the brake line, brake fluid, understand the principle of operation of the master brake cylinder, regulator 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.
The braking system of the car is different, there is. Now for this period of time, the most promising are precisely disk options they have a lot of advantages. However, what is the braking principle of this system? There is one more important device that works together is the brake caliper. It is he who stops the spinning disk. BUT how does it happen? Today I will try plain language Explain how this unit works. It will be interesting, so read on...
First, a little definition
Stopping support - this is the assembly that presses the brake pads against the disc during the braking of the car when you press the brake pedal. This is the only part that moves in the braking system. It is installed specifically on disc brake options, the drum system works differently.
This is very important node, to be honest, the caliper must be considered together with the brake pads, it is they who take on the main load when braking the system. So it is worth noting that 90% of the breakdowns of the front “brakes” are connected precisely with the calipers (but more on that later).
Principle of operation
This is enough simple system, there is nothing complicated in it. Used in almost all cars, that is, the design is similar, the changes are minimal. Based on hydraulic pressure.
After you have pressed the brake pedal, a special piston in the main brake cylinder begins to pressurize the brake fluid. She, in turn, through the tubes and later through the hoses begins to go to the brake caliper.
There is a piston in the caliper, from pressure, it begins to come forward. On one side of the piston, one brake pad is installed and presses on one side of the disc, on the other side, the other, it is simply attached to the caliper without moving. Thus, the disc is clamped by the pads, they rub against it and stop. The disk, in turn, is rigidly connected to the wheel of the car, thus, the speed of the entire car is “quenched”. It should be noted that with such contact a lot of heat is released, therefore, often, they simply cannot withstand the increased temperature.
Calipers come in both minimal designs and large enough to accommodate wide or long brake pads. As a rule, it is such a structure that is installed on the hub that is used in almost all modern cars.
Caliper malfunctions
As you understand, nothing lasts forever, and here is this knot with permanent job wears out moreover, it works in a constant aggressive environment, and even heats up a lot. In general, heating is another "enemy" of this design, often fake parts (from China) can simply collapse from overheating. So it's important to choose normal parts or originals. Remember - do not save on brakes.
Often, all caliper malfunctions are associated, oddly enough, with its anthers. How? - you ask. Yes, it's very simple, the boot protects the mirror surface of the piston, as well as (which seal the internal working cavity) from various aggressive environments. Simply, he does not let him rust, also does not let dust, dirt and other "charms" inside. It should be noted that the caliper with a good anther will work for a very long time. But as soon as this “elastic band” breaks, rust immediately begins to appear on the surface of the working piston, and particles of sand, dust and dirt penetrate into the caliper. They tritely break the seals, a leak appears. Thus, the brake fluid will simply come out of the brake system, and the pads will not compress effectively (perhaps not at all).
Yes, flow can be called malfunction number "1".
The second one is banal souring of the piston . It usually happens when the pad is already very worn out and the piston is constantly extended to maximum length. He seems to be pressing the block. But it doesn’t come back, because on its surface, from too much “promotion”, a sour edge is formed, which prevents it from returning back.
What does this mean for the driver:
- Increased brake pad wear.
- Increased disc wear.
- Uneven pad wear. You know this when one is still almost intact, and the second is completely worn out.
- Overheating of the disks, which means that they will stop cars worse, they will creak more often, especially in summer.
- Steering wheel beat. The piston can constantly press on the disc, which can cause vibrations in the steering wheel, especially if you press the brake pedal at high speeds.
The third problem is rattling of the calipers themselves . Some designs are made in such a way that after a certain period they begin to rattle, this indicates a malfunction of either the guides, or the unsuccessful design of the assembly itself. Need improvement. Often they put special springs that eliminate this rumble.
Also at this point I would like to note that often the piston can turn sour (or even rust) as if inside, that is, the part that comes into contact with the brake fluid. But how can this be? YES, everything is simple - the brake fluid is hygroscopic, it absorbs moisture over time, even from the surrounding air. After three years, you have a “compote” in the brake system, the pistons begin to rust or turn sour from the inside - THEREFORE, it is MANDATORY to change the brake fluid, at least once every three years.
Can it be repaired
I have a big and wonderful one, be sure to read it, everything is on the shelves. The calipers break down from this, there’s nowhere to go, maybe it’s just a corny anther “missed”, or the working piston soured. In general, if you buy a new assembly, then it is expensive. But this one can be repaired.
For this, it is purchased repair kit. In fact, these are all new internals that are worth replacing.
There is no point in repairing working pistons (cleaning them of rust or oxide), the surface is often already eaten, and even if you remove a part on a special machine, the dimensions will no longer fit.
Therefore, the sequence of actions should be as follows:
- We buy a repair kit.
- We remove the caliper from the car and disassemble it.
- We remove all the old rubber bands, if necessary, clean the case.
- Installing new parts.
- We install on the car, pump the brake system.
I would like to note separately the guides, in fact these are two long bolts along which the movable part of the structure walks. If they wear out or break sealing rubber, the operation of the caliper may also be disrupted, it is also desirable to replace them.
Main component safe movement on a car is, of course, the braking system. Its reliability allows the car to quickly slow down or stop in time. Accordingly, you need to constantly monitor the health of all parts of the brake system, in particular, pay attention to the calipers. After all, it is they who perform the main work of converting the applied force from the pedal
Caliper Definition
A caliper, by definition, is an assembly designed to hold a tool in a movable manner. This assembly includes a special mechanism and a tool holder. The design of the caliper ensures movement in the direction specified by the device. To understand what a caliper is in the brake system of a car, you need to understand the operation of the entire brake system of a car.
Here, the caliper is a piston that forms the braking force of the car, and a bracket that holds the brake pads. When the driver presses the brake pedal, the pressure of the brake fluid increases on the pistons located in the caliper housing, which, in turn, press the brake pad against the brake disc or drum. Thus, the vehicle slows down or comes to a complete stop. There are two types of brake calipers currently in use: fixed mount and floating caliper.
Fixed caliper design
Caliper in this case securely attached to knuckle. In this case, the working cylinders are located on both sides of the brake disc. When you press the brake pedal, the pistons press the pads simultaneously on both sides of the disc. Brake pads in this design are held in a divorced state with the help of special springs. It should be noted that such a braking system is very effective, therefore it is often used for sports cars or powerful cars with a large mass.
floating caliper
In this case, the working cylinder with the piston is located on one side, while one of the brake pads is fixed in a fixed position. When braking, the piston presses only one pad, while the second one is pressed against the disc gradually, moving along the guides. As a rule, the manufacture of parts of this type is cheaper, so this type of caliper is common on most cars.
Principle of operation
The rear caliper performs the function of pressing the brake pads to the disc. The resulting friction causes the car to slow down or stop. The front caliper performs the same function.
Both of these parts have a similar design. Since calipers in their work are constantly exposed to heavy loads(constant friction and, as a result, heating up to high temperatures), they must be strong enough and have a high heat transfer.
The main signs and causes of malfunctions
Many car owners only find out what a caliper is when the first signs of their malfunction appear. Therefore, it is necessary to know the symptoms of caliper malfunction, which are most common: the appearance of a creak, blocking of the brakes, the car moving to the side during braking, excessive smoothness or hardness of the brake pedal. As a rule, the pads and brake discs. This is due to the constant friction and heating of these parts. But do not forget that anthers, oil seals and a cuff inside the case also require due attention, because the tightness of the system depends on them. Due to the lack of proper care, some elements and parts may corrode and become rusty. This can lead to jamming of the moving parts of the mechanism.
Caliper repair
Most automakers instead of repair offer complete replacement caliper. However, this is a rather expensive procedure even for budget cars. It is possible to restore the caliper using a repair kit, which includes all the necessary elements for this, including anthers and cuffs. If the car owner clearly understands what a caliper is, he may well independently perform all the necessary manipulations to repair it.
First of all, the caliper must be disassembled and assess the degree of wear of each element. Special attention it is worth paying attention to guides, because they provide the necessary mobility of parts. In any case, traces of corrosion and rust, if any, must be removed from the caliper elements. To do this, it is enough to clean right places fine sandpaper. After that, you need to process the details special grease and set them in place. For modern auto repair shops, it is not difficult to replace the fittings and pistons of the caliper, which can significantly increase its service life.
So, if you are a careful and attentive driver, ensure safe work brake system, in particular calipers, is not difficult. The main thing is to know what a caliper is and to replace its consumables in time.
The brake caliper is one of the most important parts of the brake system. The safety of driving in a car depends on the serviceability of this part. The caliper is a relatively small device that presses the brake pads against the disc while the car is braking.
In fact, only this part is the moving part of the brake system of a car, so the performance of the system depends to a large extent on the serviceability of this element.
In the process of improvement disc brakes two separate development paths for brake calipers have been identified: with a fixed design and with a "floating caliper".
Fixed caliper
Calipers of this type chronologically appeared earlier than its modern alternative. It consists of a housing made of metal, and cylinders located symmetrically on 2 sides of the brake disc. His body is attached to rear suspension or on the front knuckle very hard.
While pressing the brake, the pads are pressed against the disc from both sides at the same time. When the pads are separated, they are held in place by specially shaped springs. In order to ensure the simultaneous operation of the pistons, the brake fluid is supplied simultaneously through an extensive system of pipes to all cylinders.
Since several cylinders are used in such a mechanism at once, fixed brakes are considered very effective. They are still put on cars with a lot of weight and / or sports cars to this day.
floating caliper
Such brake mechanisms differ from the fact that on one side the block is in one place all the time. Such a caliper consists of a bracket and a cylinder body directly attached to the inside of the wheel. One or two pistons are installed in the cylinder body.
During braking, the piston presses on the second pad, which is in front of it: first the pad moves, and then, when it is pressed against the disk plane, the floating bracket moves towards the piston along the guide pins.
The second outer pad is pressed against the brake disc. A caliper with such a mechanism is simpler and cheaper, and it is relatively small. Such a part is actively used on inexpensive cars.
Brake caliper: what is the principle of its operation?
The caliper circuit is not complicated and is the same in most representatives. model range. Pressing the brake causes pressure to build up in the area of the brake line. This pressure helps to move the caliper pistons, which push the pads to the brake disc mounted on the wheel, simultaneously pressing them from 2 sides.
The resulting friction is the braking effect of the car. The caliper device cannot be called complicated. In fact, it consists of pistons connected to hydraulic system, brake pads are attached to them.
The number of brake pads, the method of attachment to the hub may be different, depending on specific model car. The most common and familiar scheme is two pads per wheel, two-point attachment to the hub.
How to determine that the caliper is faulty?
A prerequisite for safety is the serviceability of the caliper, so it must be of high quality. It is important to remember that due to the friction that occurs during braking, the pads and caliper heat up. This is the reason for serious requirements for the quality of the part: it must be not only mechanically strong, but also heat-resistant, and also have enough high speed heat transfer.
In this way, piston jamming and/or deformation of parts of the braking system can be avoided. For example, the guide boot is a very inconspicuous and insignificant, at first glance, detail, but its defect can cause the caliper to jam.
In addition to those situations when the brake system of a car is no longer clearly working, other signs can “talk” that the brake caliper will soon stop working. Such signs can be a creak and a knock in the caliper area.
The appearance of a characteristic creak indicates a significant increase in friction processes in the mechanism, which gradually destroys it. The problems that can cause this are varied. This is the misalignment of the brake pads and / or their incorrect installation, this is excessively worn brake discs (even a beating in the steering wheel may appear).
Replacing the caliper may become necessary even if the piston boot is torn on it. The phenomenon is fraught with the fact that the inside of the caliper, namely its cylinder, becomes defenseless against the penetration of dirt, which can increase friction between the piston and cylinder, and provoke the formation of rust. Rust in the near future will lead to the inevitable jamming of the piston.
Subtleties of caliper repair
Based on the fact that calipers are rightfully considered conditionally accessible parts, motorists perform repairs at home. It will be true to note that the initial inspection and repair are simple activities.
For example: a standard caliper repair consists of a bulkhead, lubrication of the guides and replacement of the anthers of the guides.
At the very beginning, it is necessary to disassemble the part itself, clean it completely from the old lubricant and then apply a new one. After that, you need to check the degree of wear and aging of the rubber seals (replace if necessary) and assemble the entire structure back.
First of all, we put the car on the props and remove the wheel. If you need to replace a brake pad on a brake caliper, it is usually enough to unscrew just one screw, which is located at the bottom, the one that secures the caliper to the bracket. It is extremely important to install new pads in the same position as the old ones instead of already worn ones.
In the process of such repair of the caliper, the channel with the brake fluid should not be disconnected from the part in order to avoid leakage during further operation. If, when disassembling the part, a problem with the piston was found, others important details caliper, it is better to immediately go to a professional service station.
During the procedure self assembly You need to keep an eye on the brake fluid level. This is important as you will need to push out the remaining pistons. In addition, air must not enter the brake system.
The brake fluid level should be checked periodically and topped up if necessary. maximum level. After all the manipulations are completed, the caliper body and brackets should lie on a free, clean surface, which are subsequently disassembled to the last screw.
After a fairly thorough inspection, all elements must be cleaned to a shine, be sure to use cleaning fluids. Exceptionally in its pure form, you will be able to assess the condition of the brake caliper, and in particular you will need to carefully examine the surfaces of the cylinder, pistons.
Before starting the assembly process, you will need to prepare a brake caliper repair kit (rear and front) in advance. If a new repair kit was not at hand, it is worth putting the old parts in order. This can be done only under one most important condition: they must be intact!
