Good day, dear car owners! These small, inconspicuous parts of the brake system are brake pads. We so rarely think about them, much less check their technical condition. Level brake fluid We check the oil level regularly, or check the oil level daily, but we don’t think about the brake pads.
But in the end, they are the ones brake disk are the final stage, on the serviceability and efficiency of which the operation of the entire braking system depends. It is wear and tear brake pads affects the performance of the brakes and our safety. It's time to close this gap and learn how to determine brake pad wear.
First for information. A brake pad consists of two main parts: a housing and a friction lining. It is the friction lining, performing its main task - braking the brake disc, that is subject to natural wear.
In recent times, when the thickness of the brake pads became less than acceptable, the friction linings on the pads were changed. Today it has become easier to replace the brake pad itself. It is recommended to change the brake pads all at once on one axis.
Natural-unnatural wear of brake pads
Any part of the car that is constantly working becomes unusable. It’s good if for natural reasons, from a spent resource. The question especially concerns brake pads, which work in more than intensive mode.
For different models brake system, different manufacturers, depending on the material of the friction linings, there are calculated wear periods for brake pads and their own parameters. The minimum thickness of brake pads is usually indicated by the manufacturer on product models.
But, for normal, normal driving conditions, there are generally accepted average standards for wear or time for replacing brake pads. It is believed that brake pads should be replaced every 10-15 thousand km. mileage This is not true. For some it may be enough for 20,000, and for others even for five thousand km. will not be enough if the pads operate in constant emergency braking mode.
In addition to natural wear and tear, there are also malfunctions that accelerate this wear and tear. For example, uneven wear of brake pads occurs. Why and how is brake pad thickness controlled?
The main causes of premature brake pad wear
There aren't that many of them. Let's exclude natural wear of the brake pad from the reasons, and we are left with the following:
- high-quality composition of friction linings. This depends only on the manufacturer, and we are not able to influence this reason;
- driving style, and as a derivative – braking. The constant emergency braking mode, which reckless drivers are guilty of from traffic lights to traffic lights, leads to premature wear of the brake pads;
- malfunction of the brake system, in particular the brake system brake cylinders. Leads to uneven wear of the brake pads, and.
When to pay attention to brake pads
Without the use of measurements and various equipment, only by visual inspection you are able to understand that the service life of the brake pads is already approaching the extreme point or has already been exhausted. How? Simple enough.
- . A decrease in the level in the reservoir may indicate that the brake pads or brake discs are worn out;
- during sudden (extreme) braking average speed 60-80 km. you feel a beating. This occurs due to uneven wear of the brake pad or disc;
- brake pedal behavior. Braking too sharp or too slow, i.e. anything that goes beyond the standard (habitual) pressing should alert you;
- dust from friction linings (brake dust) on discs with clearly visible signs of metal shavings. And if the braking process is also accompanied by a grinding noise, then... it’s time to check the thickness of the brake pad or, in general, the presence of a friction lining (although you will hear about the absence of a lining right away);
- brake pad sensor, if equipped. The principle of operation of the sensor is simple. A soft metal core is mounted in the friction lining. When the brake pad wears down to a minimum, the circuit closes and an indicator in the control panel shows the driver that the pads need to be replaced.
In the case of the sensor, there is one significant “but”. The brake pad sensor may not always work. This is due to the fact that the wire is in constant contact with water (moisture), and due to corrosion, it may become unusable.
Those. You can apply the saying: “Rely on the sensor, but don’t make a mistake yourself.” Even if you have a brake pad sensor on board, visually determining brake pad wear won’t hurt you, and it won’t take much time. This is our safety - serviceable brakes, and in this case there is no waste of time.
Good luck with determining your brake pad wear and while driving.
Replacing pads in a car is a regular procedure, since their wear determines the quality of braking. We'll tell you how to independently determine the critical wear of your car's pads and the need to replace them.
Typically, for competent drivers who are used to driving without sudden stops, the pads will last 30-50 thousand kilometers or much more. It is worth mentioning that you should not always focus on the amount of distance traveled. Each driver has his own driving style. For fans of aggressive movement, they will require replacement twice as quickly. In addition, a lot depends on the quality of the pads themselves or the manufacturer. Condition also affects brake discs cars. If they have warping, “waves” or cracks, they will seriously reduce the service life of the brake linings.
What are the signs of wear?
To start looking for the causes of problems with your car's brakes, you first need to check the required tire pressure. If a tire is flat, that may be the reason. Hence the inadequate reactions when braking the car.
When braking hard, a pulsing sensation is felt.
At the very end of service, the linings wear off unevenly. During this period, chips or cracks may occur in the friction layer. A worn-out pad creates noise and vibration when braking. To do this, for example, when approaching a red traffic light, you need to pay attention to the presence of a beat on the brake pedal. If you release the brake pedal and the beating stops, then the pads are definitely to blame. If the level of wear is maximum, you should also hear a nasty squeak. This noise is created by the wear plates, which remind the driver to replace them.
It is worth noting that this effect can also occur due to wear of the brake disc. In this case, it needs to be grooved or replaced.
The brake system behaves inappropriately.
Too weak or, conversely, excessively sharp brakes may indicate worn out pads. In the first case, you may notice that the brake pedal, when pressed, drops lower than usual or the braking is not as intense (the pedal is sluggish when pressed). And if the wheels suddenly lock, then perhaps the friction lining has completely worn out and metal is rubbing against metal. This is very dangerous for brake discs, because... With such work they wear out instantly.
If the brake pedal falls completely, then the reason is in the brake fluid. Perhaps it is completely missing (leaked out) or its minimum level is in the master cylinder reservoir under the hood.
Brake dust on wheel rims mixed with metal shavings.
In some cases, wear on the brake linings is not noticeable when driving. It's worth looking under the wheel cover. If the coating is uniformly dark (charcoal), the pad still has a lining. If shiny metallic inclusions are visible in the plaque, the pad has worn off and is scratching the disc. With this picture, you need to change the pads immediately. This method control is practically inapplicable for light alloy rims and ventilated brakes.
All of the above verification methods are indirect. In the best way assessing the need to replace the pads is their visual inspection in a car service or on your own. To do this you will have to remove the wheels from the car. In a special hole through the caliper, estimate the thickness of the friction layer. It should be approximately more than 5-10 mm. It is impossible to check the linings in the rear drum brakes without disassembling them. During this procedure, also inspect the brake discs and drums and assess the condition of the brake system hoses.
Video - when should you change the pads?
The pads are selected based on the condition of the car, necessity, driving style, preferred brand and the amount the car enthusiast is willing to spend on them. It is important to remember that they need to be changed frequently, after approximately 30–50,000 km, without waiting for complete wear. If this time is missed, you can get more serious problems that will lead to significant costs or failure of the car.
If the budget is low, they most often choose products from ABE, JP Group, LPR, Delphi. Supporters sporty style When driving a car, they prefer manufacturers such as Ferodo, Brembo. For quiet trips in cities, products from Bosch, Remsa, TRW and ATE are best suited.
In most cars, during normal use, the inner pad wears out a little faster than the outer one, and this does not depend on the design of the brake mechanisms. However, under specific operating conditions or due to design features On some cars, the inner pads sometimes wear out noticeably more intensively than the outer ones. For example, on a second-generation Mazda 6, the inner pad on the front right wheel wears out one and a half times faster than the outer one.
In addition to design nuances, malfunctions may also occur. For example, increased pad wear due to a soured piston. Therefore, when inspecting the brakes for the first time on a car you have never driven before, it is important to remove the wheel to assess the condition of both the outer and inner pads. Unscrupulous servicemen often limit themselves to an approximate assessment of the wear of only the outer pads, looking at them through the spokes rim without removing the wheel itself. It is possible that soon a dissatisfied customer will return to this service station with worn out internal pads and complaints!
As an example, let's check the condition of the brakes on a car that has driven almost 63,000 km. In addition, we provide approximate indicators for critical wear of various elements of the brake system. For each specific model car, they can differ both up and down. This data can be found in repair and maintenance books or on the Internet.
On Kalina, it is not really possible to determine the wear of even the external brake pads if the wheel is not removed. The distance between the spokes of the alloy wheel is decent, but the bracket severely limits visibility. But, for example, on Mazda 3 of the first two generations, the wear of the external pads is clearly visible even with the wheel on. True, you still have to remove it to inspect the internal pads.But let's return to our Kalina. Only after removing the wheel is the real picture visible. The thickness of the friction lining is approximately equal to the thickness of the pad base: wear is about 60%. If the thickness of the friction lining decreases to 2 mm, this will mean 100% wear. Many cars have a metal tongue at the base of the block. When the lining wears critically, it begins to come into contact with the brake disc, producing a sound. Most often, the tongue is installed only on the inner pads.
Why might pad wear accelerate?
It is important to remember about difficult operating conditions, for example, driving along mountain serpentines or participating in amateur racing. In such modes, in a working brake system, the inner pad may begin to wear down many times faster than the outer one. Something similar once happened to my car. During everyday driving, pad wear is Volkswagen sedan Jetta latest generation was uniform. This lulled my vigilance, and I stopped monitoring the condition of the internal linings. After participating in two stages of sprints (far from the most difficult for equipment), it turned out that the internal ones were almost completely erased. This was especially noticeable on the left wheel. I was lucky that it didn’t come to the point of scuffing the brake discs!
Also, do not forget that if, for example, you drove 30,000 km and the wear of the front pads was about 50%, this does not mean that they will last up to 60,000 km. The smaller the thickness of the lining, the faster its further wear occurs. After all, the same portions of thermal energy from friction are absorbed by a less “fat” brake pad.
Brake disc wear
Brake disc wear is more stable and predictable. Most often, there are enough discs for two sets of pads. A reduction in disc thickness of approximately 2 mm means 100% wear. Over time, wear causes a chamfer to form on the edge of the brake disc.
The design of many wheel rims allows you to stick your hand between the spokes and feel the wear of the brake disc by touch. The main thing is not to do this while the brake disc is still hot, immediately after a trip with intense braking. This technique will be useful to those who are planning to purchase. Based on disk wear, one can draw conclusions about real mileage cars or about the conditions in which she had to drive. But it is best to remove the wheel and carefully inspect the brake mechanism, including the inside of the disc. It happens that it is there that grooves and a wavy surface are formed due to corrosion.
When to change brake discs and pads?
If the wear of the discs is already critical, but they are almost new, then do not rush to immediately change the entire set of consumables, especially if you operate the car in conditions that are not difficult for equipment. The work of replacing disks can be postponed for a while. But you shouldn’t completely turn a blind eye to the problem. Remember that as the thickness of the disks decreases, . After all, dissipate thermal energy the disk will be too thin, which will also overheat faster. In particularly advanced cases, due to excessive wear of the brake disc, the pad may even fall out of the mechanism!
With the wear of the rear disc mechanisms, the situation is similar, with only one amendment: they are less loaded, and therefore wear occurs more slowly. This has both its pros and cons. Rear brake discs and pads have a longer service life compared to the front ones (about one and a half to two times), but they also suffer more from corrosion. Therefore, it is on the rear brakes that it is important to check the internal surfaces! Our Kalina has drum-type rear brakes.
How to assess the wear of drum brakes?
Most machines have an inspection window on the side of the drum casing to assess the thickness of the linings. However, most often it can only be used if the car is hung on a lift or standing on a viewing hole. Otherwise, it is extremely difficult to see anything through this window.
Sometimes it’s also quite problematic. For example, for cars of French brands you will have to unscrew hub nut. In the case of Kalina, everything is simple; the drums can be removed without any problems.
Typically, drum wear is assessed by the internal diameter: its increase by 1 mm means a death sentence.
How are drum brakes different from disc brakes?
One of the disadvantages of drum mechanisms compared to disk ones is the lack of a self-cleaning effect. Wear products from the brake pads remain inside the drum and leave characteristic marks on the working surfaces of the friction elements.
Editorial Kalina is often used to participate in various competitions. That is, the conditions of its operation can be called difficult. However, to our surprise, the wear on the original pads turned out to be small - about 30%. Probably the reason is that the car has a relatively small mass, and its dynamic performance is not outstanding.
Unfortunately, wear products have significantly damaged the working surfaces of the linings and drums. This can't be fixed. The next time you replace the pads, you will also have to update the drums, otherwise they will immediately damage the new pads. However, there is nothing criminal in the further operation of the car in this form. Reduced efficiency rear brakes not noticeable even when driving on a race track. In general, drums, like discs, can survive two sets of friction linings.
The working condition of the brake pads is extremely important for safe driving. Therefore, when buying a used car, you need to know how to check the serviceability of these parts, as well as determine the need for timely replacement.
What affects the service life of brake pads
The brake pad has two components: a housing; friction lining. The latter bears the main load during braking, therefore this part details wear off over time. According to control rules technical condition brake pads, they should be changed after 10 thousand km. mileage But this is only an approximate indicator, since there are other factors that affect service life:
- quality of brake pads. The pressing technology and composition differ from different manufacturers, which affects the maximum possible service life;
- character of driving a car. City driving and constant hard braking lead to premature wear of the pads;
- Problems in the operation of the brake cylinders lead to uneven wear of the brake pads and problems with the brake disc.
Signs of Brake Pad Wear
When choosing a used car, you need to pay attention to signs of brake pad wear, which you can determine yourself:
- The handbrake is fixed in the far position. If the lever needs to be pulled back very far, or the car with the handbrake slides down inclined surface, this indicates wear and tear rear pads;
- too long braking distances;
- weak and ineffective braking with maximum pedal pressure;
- too sharp braking and the presence of the sound of metal friction may also indicate heavy wear. This means that the friction lining has worn out and the pad body is rubbing against the disc;
- A car squealing when stopped indicates wear on the friction lining. An indicator is specially mounted for this purpose. When the pad has worn down significantly, the indicator begins to cling to the brake disc, resulting in an unpleasant sound;
- clattering during hard braking. It occurs due to uneven wear of the brake pads;
- decrease in brake fluid level;
- a dark coating on the wheel means that the friction lining is still there, but metal inclusions indicate that the lining has been worn out, since the pad body is already scratching the disc;
- if there is a brake pad sensor, then when it reaches minimum thickness indicator on the control panel will light up.
Brake pads must be replaced when the friction lining becomes less than 5 mm. To be more confident that these parts are in satisfactory condition, it is recommended to show the car to a specialist at a service station.
Recommendations for operating and replacing brake pads
To protect brake pads from premature wear and ensure their serviceability, you should adhere to the following recommendations:
- a calm driving style and the absence of frequent sharp braking will significantly increase the service life of the pads;
- replacement must be carried out either on the axle or on the entire vehicle. Replacing only one side is unacceptable, as this will lead to serious problems with braking;
- Be careful when driving with new pads. The first couple of tens of kilometers the brakes will work worse because they need time to get used to;
- inspect the pads when changing tires from summer to winter and vice versa;
- when changing pads, you also need to assess the condition and need to replace discs and drums;
- Carry out regular diagnostics of the vehicle's condition at a service station.
Carefully check the brake pads before purchasing a used car, as well as their timely replacement will protect you from dangers while driving. Therefore, do not forget to periodically inspect the condition of the car, which guarantees you long term his service.
In order for the brake system to always be normal, it is necessary to constantly monitor its components. Since brake pads work exclusively on friction, they wear out faster than other parts. It is impossible to say exactly when wear will occur; their conventional service life is from 8 to 15 thousand kilometers during normal driving without “recklessness”. Checking the brake pads gives you an idea of when to replace them.
Brake system
Each vehicle is equipped with:
- braking mechanism;
- parking brake;
- spare brake. Applicable in in case of emergency, if the main brakes fail. IN passenger cars This is usually achieved by dividing the braking system into several circuits diagonally or front/rear.
The brake system consists of a drive and a braking mechanism with a drum or disc, as well as brake pads. Drum brakes are now used less frequently, although they last longer. Today in almost all cars are coming disk braking device, such a system is considered fixed and has a caliper and two pads that are stable in one position. When the brake pedal is pressed, they compress the disc. There are also systems with a floating block; they are more complex. During braking, the caliper piston touches one of them, it moves away, leans against the disc and moves it towards the other, after which clamping occurs.
A brake pad has two components: a frame and a friction lining. In short, it is the pad that performs the main task of braking, stopping the brake disc with its friction. Front brake pads wear out two to three times faster than the rear ones. This is because a large load during braking falls on the front wheel mechanism, and the weight of the car is redistributed to the front axle. The wear rate is directly affected by:
It is noteworthy that in winter time During the year, replacement is carried out less frequently, which means that in winter there are few maneuvers while driving.
Signs of wear
Sometimes, just to assess the condition of the linings, climb into braking system not at all necessary. Many people are interested in how to check brake pads without removing the wheel? Wear can be determined by the following signs:
Checking the pads without removing the wheel
Checking brake pad wear is easy, especially when vehicle are worth alloy wheels with large holes through which the brake assembly is visible. As a rule, only the outer block is visible. If you determine its thickness visually, then 1.5–2 millimeters is considered critical. When, even without removing the wheels, you notice that the thickness of the lining is less than 5 millimeters, this is a reason for replacement. If the holes on the wheel are too small and the brake mechanism is hard to see, you need to start dismantling the wheel. When nothing interferes with the view, it is easy to assess the condition of the second lining and, at the same time, the brake disc.
Proper Pad and Disc Inspection Process
Before checking, review the indicator table permissible sizes parts brake mechanism. When the data matches, start making replacements. The process is divided into the following stages:
Parts need to be replaced if:
- linings in oil;
- products thinner than 1.5 mm;
- the linings are not tightly connected to the base;
- Discs need to be replaced if there are scratches or deformation.
Replacing front brake pads
Replacing rear brake pads
The replacement process is almost the same:
- To immobilize the car, we put it in gear. You cannot turn on the handbrake, as it will press the pads against the disc, and replacement will not be possible. For safety, we place blocks under the wheels.
- We remove the wheel and remove the guide pins with a No. 12 wrench.
- We remove the drum.
- Disconnect the springs from the pads.
- We take out the front block, remove the drive lever from the cable and remove it. Do the same with the back.
- Now we install new parts exactly the opposite way.