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, examining them through the spokes of the wheel 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 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 impossible to really determine the wear even on the external brake pads if the wheel is not removed. Spoke spacing alloy wheel decent, but the bracket greatly limits the view. 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 on a sedan Volkswagen 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
Wear brake discs proceeds more stably and predictably. 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.
Design of many rims allows you to insert your hand between the spokes and determine by touch the wear of the brake disc. 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 the conditions in which she had to drive. But it’s best to remove the wheel and carefully inspect it. 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 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 the 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.
Alas, 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.
At the service station Volvo owner The 2001 S60 was caused by a vibration that appeared on the steering wheel when it was necessary to slow down the car while driving at speeds of 70 km/h and above. The owner suggested that the vibration could be caused by the runout of the brake discs, so in the repair request he asked the car service specialists to sharpen the front brake discs.
It is right to respond in a timely manner to the appearance of a problem in the brakes, because the slightest malfunction in the braking system of a car reduces its level of safety and endangers the lives of not only the driver and his passengers, but also other road users.
Why is brake disc runout dangerous? It indicates that somewhere on work surface the disc has formed a bulge, or, if you want for clarity, a “wave”, which periodically throws the pad away from the disc. Until the pad, having passed the top of the “wave”, presses against the disk again, the car slows down worse, which increases braking distances, necessary to reduce the speed to a safe value or stop the car.
However, is the correct method to resolve the problem chosen? We decided to take this opportunity to evaluate the effectiveness of grooving brake discs, and at the same time talk about what this procedure is, because a discussion of the article on the site forum showed that there is a need for this.
While the car is being driven onto a lift and being prepared for repairs, we ask specialist of the Libra-2000 auto center Evgeniy Slepyan why the brake disc may warp. It is believed that the discs “drive” after driving through a puddle, which causes them to suddenly cool, or when a car with overheated discs, without pausing to cool the brakes, drives into a car wash. Is it so?
“In my opinion, this is not the only reason,” Evgeniy answers. “All cars drive through puddles; in the city, most drivers use the brakes with approximately the same intensity, but in some cars the discs warp, while in others this does not happen - why? I think It's not a matter of puddles, but of the disk being exposed to too high temperatures. In other words, the disk was overheated - that's what caused it. And for this, sudden cooling is not necessary.
But when emergency braking With high speed the area where the pads press against the disc generates too much heat in a very short time. The heat does not have time to be transferred to the medium that surrounds the friction zone. As a result, overheating occurs.
Or take, for example, a case where the car has discs and pads of different brands. Manufacturers calculate pads for their brake discs so that they work perfectly together. When the discs are of one brand and the pads are of another, overheating is possible under certain braking conditions.
The second reason is the impact of large mechanical loads. It is difficult to imagine how much force the pads actually exert on the disc during emergency braking. Let's consider this situation: a car brakes sharply, until the wheels lock, in front of an unexpected pothole in the asphalt, crashes into it, but the driver does not release the brake pedal. Next, the wheel hits the sharp edge of the hole. The impact causes the wheel to spin sharply, but at this moment the pads hold the disc with enormous force. Why shouldn't it bend under such conditions? You don’t need much - a few tenths of a millimeter, but they will make themselves felt by vibration on the brake pedal, beating on the steering wheel or body when braking.
To eliminate runout and restore brake efficiency, we offer a service for grooving the working surface of the discs, however, not all discs are suitable for this procedure. First you need to assess the condition of the disk and then make a decision - to sharpen it or definitely replace it."
The left front wheel has already been removed - you can see what's wrong with the disc and pad. At first glance - nothing.
The disc appears evenly worn. The beads on the boundaries of the working surface of the disk have the same height along the entire circumference.
Measurements of the disk thickness in several sections also do not provide any clarity. The thickness is the same - 24.2 mm, so for now only one thing is clear - it is still possible to remove metal from the disk. However, the auto center workers assured us that as soon as the grooving begins, the cutter will show us what is not visible to the naked eye.
The discs will be sharpened using the Disk Aligner 8700 device from Mad (Netherlands).
The device consists of two parts. The first is an electric drive that connects to the hub and rotates it. The vehicle's gearbox is in neutral at this moment.
The second part is the machine itself.
It is installed in place brake caliper, which is previously dismantled without disconnecting the brake pipe.
The machine has two cutters. They can be fed over the surface being processed using an electric motor built into the machine or manually.
The machine is ready for work. Here we go?
Once the work started, we really began to see where the disk was bent. Moreover, we heard this from the tonality of the sound, which varied depending on the thickness of the metal that was cut in a specific place on the disk.
The matte spot left after the passage of the cutter is the same convexity that vibrated on steering wheel while the car is braking.
It was not possible to level the surface of the disk in one pass. According to repairmen, this happens most often. It happens that 5-6 passes are required to achieve a perfect plane. It is tempting, of course, to immediately give such an allowance for grooving so that the surface of the disk becomes smooth in one pass, but this will significantly increase the load on the cutters and worsen the quality of processing.
The second pass also did not lead to the desired result, but it allowed us to see how the surface of the disk was gradually leveled.
During the third pass, the area of the matte surface remaining after the cutter became even larger, but the ideal geometry of the outer side of the disk will be when the shiny stripes at the top and bottom disappear.
After the fourth pass, we finally didn't see them.
Grooving the disc from the inside followed a similar scenario, but required one more pass. The problem was caused by a deep circular depression in the upper part of the disk, which persisted until the last.
The disk is ready. We remove the machine. The thickness of the disc can be assessed again.
The result was 23.3 mm. This means that after processing the disc “lost” by 0.9 mm, but remained within tolerance.
The procedure for grooving the left disc has been completed front wheel replacing brake pads. Why do they need to be replaced after discs have been resurfaced?
“Opposite the place where there was a bulge on the disc, a wear appears on the pad,” says Evgeniy. “Therefore, the old pad will not adhere to the machined disc with the entire surface of the friction lining. And if the client, shortly after he left the service, suddenly has to urgently slow down? Again, the old pads will not only wear in, but will also work for the disc. In other words, they will “kill” the result of the work. Therefore, you should not save on replacing the pads.”
In addition to the unsuitability of the disc for grooving due to residual thickness, too deep scoring, severe corrosion and other serious damage, the cost of the issue also makes one think about the feasibility of the procedure. Grooving two front discs cost the owner of an S60 600 thousand rubles. Buying a couple of new discs from reputable brands would cost at least a million. However, it may turn out that regrowing is not much cheaper than buying new discs - with brake discs rear wheels This happens often. In such cases, the purchase seems to be a wiser use of money than grooving.
We would probably attribute its duration to the disadvantages of the procedure. It took about two hours to install, configure and machine the two brake discs.
Instead of a verdict
Five days after the tuning, we contacted the owner of the S60 to find out how things were going. It turned out that the car managed to travel about 1200 km. I had the opportunity to check how it brakes from a speed of 120 km/h - everything is fine, vibration on the steering wheel no longer bothers me.
Sergei BOYARSKIKH
Photo and video of Olga-Anna KANASHITS
website
We thank the Libra-2000 auto center for advice and assistance in organizing photography
Brake discs (BD) play a major role in the braking system, since they are the ones that come into contact with the pads, creating friction, as a result of which a car or any other vehicle slows down, until it comes to a complete stop.
The role of brake discs
From a scientific point of view, brake discs, in tandem with pads, perform deceleration by converting kinetic energy into thermal energy, as a result of which the speed of rotation of the disc, and thus the wheel, slows down. As a result, the car can stop safely, and the driver can effectively calculate the distance to objects that are on the way.
The first brake discs had a metal plate that had no cooling or heat dissipation other than forced airflow. Over time, engineers came to the conclusion that the implementation of a heat sink reduces the temperature during braking and at the same time increases its efficiency. Heat removal was realized using special ventilation ducts, as well as through holes located perpendicular to the working surface.
In addition to the vent. channels, contribute to cooling wheel disks a certain configuration (usually spoked), as well as special air intakes located in the front of the car (bumper, wings, diffusers). In addition to effective cooling, perforation of the brake discs allows the working surface to be cleaned from residual dust and dirt from the friction linings. The effectiveness of the brakes also depends on the correct “grinding in” of the working (rubbing) surfaces of the disc and pads. It takes about 500–1000 km for the discs and pads to break in; during this period it is strongly recommended to avoid sudden braking and prolonged pressing of the brake pedal.
In most cases, cast iron is used to produce brake discs, but recently more and more alternative solutions have begun to appear. So, for example, carbon and ceramics are used to make brake discs for high-speed cars.
Brake disc malfunctions and the reasons why this happens
The specific operation of brake discs involves heavy loads, as a result of which the working surface wears out due to high temperatures and friction. The thickness of the disc becomes smaller, grooves and irregularities appear, resulting in certain troubles. I note that, unlike brake discs, pads wear out much faster, and therefore are replaced much more often. A lot about the wear of brake discs and pads depends on the driver, or more precisely, his driving style. Too frequent accelerations, alternating with braking, lead to intense loads, which lead to premature wear and failure.
In general, there are quite a few reasons for brake disc wear. So, the speed of disc erasure is affected not only by the driver’s driving style, but also by the quality and composition. If with the first everything is more or less clear, then with the second everything is much more complicated. The fact is that the composition of the friction linings, as well as the brake discs themselves, is kept secret and each manufacturer has its own “recipe” for this product. However, it often happens that the disc and pads do not fit together, that is, they are incompatible. As a result, the problem will manifest itself in the following way: either braking will be ineffective, or unpleasant sounds will be heard during braking (creaking, grinding, etc.), or the brake disc will wear out faster than intended by the manufacturer.
Repair or complete replacement of brake discs is carried out if:
- Disc deformation occurs, which manifests itself in the form of vibration and ineffective braking;
- Deep edges and grooves form throughout the brake disc;
- The thickness of the disk reaches a critical point of 1-3 mm (the measurement is made with a caliper, it is measured exactly work zone, not the outer side);
- There are other damages that prevent effective braking.
- Brake disc crack.
- "Bead" formation.
- Uneven wear, the appearance of grooves, holes and depressions on the surface of the disc.
Reasons why APs fail
There are actually many reasons. Constant alternating heating and cooling, together with the friction and loads that the disk will experience when stopping the heavy mass of the car, one way or another affects its condition. By the way, during intense braking, the temperature of the disc can reach 400-450°C; if, with such heating, you encounter a puddle on your way, the result can be the most unpleasant. Microcracks form on the hot surface of the disk, and in more serious cases the disk becomes deformed. Deformation of the braking surface of the disc leads to vibration during braking, and microcracks, despite the prefix “micro,” increase over time, forming large grooves that, one way or another, impair braking efficiency and lead to inevitable destruction of the disc.
Uneven wear of the pads, and at the same time the discs, can also occur due to grains of sand and dirt getting on the working surfaces. As a result, furrows and grooves form on the disc, which lead to a decrease in the rubbing surface area, and as a result, braking becomes less effective. In addition, due to uneven wear of the pads, the TD itself will become unusable ahead of time. By the way, one of the signs of low-quality large solid elements manufactured in violation of technology is precisely the unpleasant creaking and grinding noise during braking. The presence of a constant squeak in the area of the wheels may indicate the formation of a shoulder, which was formed as a result of wear and now catches the edge of the block while driving.
Strong beating can be detected even without a device, but if the vibration is insignificant, a special device will be required that picks up the slightest vibration from 0.01 mm.
Is it possible to repair disks?
Until recently, repairing brake discs was impossible and no one talked about it; moreover, the TD manufacturer clearly indicates that brake discs cannot be repaired. However, today the restoration of brake discs is a real possibility. Special equipment allows you to eliminate disc defects by grinding the working surface. I will say more, sometimes this procedure does not even require dismantling the brake discs, although everything is individual depending on the degree of damage.
How to extend the service life of a TD?
- Driving style is the factor that most influences the service life of brake discs. If you like an aggressive driving style with sharp acceleration and the same braking, you should be prepared for the fact that the life of your wheels will be much shorter than usual.
- You should also consider the quality of the pads, which can also wear out the disc if incompatible.
- Driving through mud and puddles high speeds also does not bode well, do not overheat the brake pads if it is rainy outside or there are large puddles.
- Buy only high-quality brake discs and pads and follow the recommendations above, only then can you avoid premature or uneven wear of brake discs and pads.
That's all for me, if you have any questions you can ask using the comment form. I also remind you that the best gratitude to the author is a repost of this article on social media. networks. We will be grateful if you tell your friends about our site using the corresponding buttons located below.
The brake disc is one of the main components of the brakes and should, by default, always be in technically sound condition.
A large load, both mechanical and thermal, is constantly applied to the brake disc. So, when the brake pedal is pressed, the pads are pressed against the disc with great force, causing it to wear out as it is used.
At the point of contact between the pad and the disc, heating can reach over 350 degrees, which also negatively affects the working surface of the disc.
Let's look in this article why fast brake disc wear and what are the reasons for its wear and tear.
1.Brake pads
Sometimes, even on new cars, after a short period of use, car owners notice an edge appearing on the working surface of the brake disc.
The reason for rapid wear of the working surface of the disk is brake The fact is that filler is added to its linings as a filler to increase the service life of the pads.
Most pads from various self-respecting companies use a filler in the form of soft metal sawdust, such as copper. Since the hardness of copper is an order of magnitude lower than the hardness of the brake disc material, wear of the pad linings occurs, and the disc itself has minimal wear.
Unscrupulous manufacturers of “left-handed” pads use metal filings as a filler, not paying attention to their hardness. Copper is expensive, and steel filings from metalworking plants cost the pad manufacturer almost nothing.
In cases where the hardness of the sawdust is higher than the hardness of the brake disc material, intensive wear occurs.
Therefore, when purchasing brake pads, it is necessary to give preference to proven brands, without “saving” on the cost by buying a “left” product. The purchase and installation of new brake discs will more than cover such “savings”.
Plus, hard pads are not as effective when braking, which negatively affects traffic safety.
Intensive wear of the discs is also caused by brake pads worn to the limit, when iron begins to rub against iron.
2.Brake caliper
The next reason for rapid wear of the brake disc is a faulty . What happens is this: At the moment of braking, thanks to hydraulics, the caliper piston/pistons are squeezed out of the cylinder and push the pads in front of them towards the brake disc.
When the caliper is in good working order, after braking, the pistons return to the caliper cylinders, releasing the pads from the brake disc. If the caliper is faulty, this can be expressed in the jamming of the bracket in the guides, or the jamming of the piston in the cylinder, then the pads are not completely released from the disc. This causes increased heating and rapid wear both pads and brake discs.
The caliper must be removed and all its elements with increased wear replaced. In most cases, premature caliper failure is caused by rupture of the guide pin protective covers or piston/piston boots.
3.Brake disc
The original brake disc, as well as a replica from well-known manufacturers, has designations on the end of its main parameters: diameter, maximum and minimum thickness, etc. If there are no designations on the disc at all, then this is clearly a “left-handed” product produced with violation of technology. As a rule, such products are produced from any available metal and without any protective treatment.
Such discs wear out quickly, are prone to overheating and, as a result, deformation, which ultimately results in steering wheel beating. Operating a car with such brake discs is both costly and unsafe.
Therefore, it is always recommended to ask the seller for product quality certificates; if the product is of high quality, then all documents will be provided, but if they are not available, then it is better not to purchase such a product, so as not to buy a problem with your own money.
4.Wheel hub
A broken hub bearing can also contribute to disc wear when the brake disc starts to run out. In these cases, the brake pads cannot press their entire surface against the disc and act as if in steps, which also reduces the overall braking efficiency.
In order to be sure that all brake components are in good condition, it is recommended to periodically undergo diagnostics of the brake system.
The braking system always requires increased attention, because the safety of the driver and passengers directly depends on this. That is why a complete inspection should be carried out regularly to identify problems and malfunctions. Every motorist should know how to determine the wear of brake discs, since they, like pads, are the most important element the entire braking system as a whole.
Why is it important to pay attention to this component?
The fact is that during operation, discs and pads are subjected to quite high load. In this regard, they wear out and lose their original properties, which in turn significantly reduces reliability and safety. Every owner of any vehicle is obliged to correctly assess the condition of the brake system in general and the life of the discs in particular.
On average, the “lifespan” of discs and pads is about 100-150 thousand kilometers. But it’s still better to know how to determine the wear of brake discs yourself.
Features of work
Of course, any specialist will say that in this case it is best to send the car to a workshop and carefully check everything on the stand. But this pleasure is not cheap, and besides, there is simply not enough time for it.
During the braking process, the vehicle's kinetic energy is converted into thermal energy. This is why the discs get very hot, and heat, as is known, has a rather negative effect on metal and various mechanisms. For this case, developers use various methods cooling, usually based on ventilation with cold air through special perforations.
But in any case, it is better to know exactly how to determine the wear of brake discs, especially if it is excessive.
Several factors influence the longevity of the braking system:
The quality of the discs themselves;
Quality of brake pads;
Driving style.
“Left” spare parts have never been reliable and durable, so the desire to save sometimes turns into unnecessary expenses, or even a threat to life and health.
An aggressive driving style in urban conditions - with sudden acceleration and braking at traffic lights - also negatively affects the condition of discs and pads. The service life of 150 thousand kilometers may well be reduced to 30-40 thousand. So, whenever possible, it is better to be careful.
Diagnostics of the condition of brake discs
In some cases, the driver can independently and without the use of special tools determine the condition of the brake system, primarily based on his personal feelings.
What factors help determine brake system wear?
Vibrations, grinding, jerking, extraneous noise during braking;
The appearance of noticeable grooves and cracks directly on the disk itself.
If you notice something like this, it means that there is something wrong with the braking system of your car, therefore, it is necessary to take action.
The braking process of the vehicle should be calm and smooth. If at this moment noises are heard and the car begins to jerk or turn, then this indicates a malfunction.
If also with visual inspection If certain malfunctions and problems are discovered, then there is no need to shelve repairs at all.
To finally be sure of everything, special measurements should be carried out.
To do this, take a caliper and check the thickness of the brake disc. After that, compare with the original and recommended parameters. You can find them in the car's user manual, or even on the Internet on the manufacturer's website. As a rule, it is also indicated there approximate period service, so you can understand how effectively your braking system works.
The difference in thickness between new and worn disc should not exceed 2-3 mm.
The size of cracks and chips should not be more than 0.01 mm.
Otherwise, we can safely talk about significant wear of the brake discs. Accordingly, the braking system cannot be considered reliable.
Troubleshooting
If, however, the deviations from the norm are not too significant, then it is worth trying to restore the brake disc and extend its life.
Grooving using special equipment will help get rid of small beads and grooves. In principle, you can try to do this even with a regular file, but it is quite difficult and not very reliable. The essence of the groove is that a thin (of the same thickness) strip of metal is removed from both sides; in fact, it is simply ground off. After this, the disk receives a renewed, flat surface.
However, we should not forget that changing your driving style to a more relaxed one can extend the life of the braking system. But if there is excessive wear, you should still replace the discs and pads; you shouldn’t put yourself and your loved ones in danger because of the desire to save money!
Video
In the following video you will clearly see how to determine the wear of brake discs: