What system is the main load on ensuring the safety of a trip in the car? If you think that on the brake, then you are absolutely right: the ability to slow down in time never and nowhere is so appropriate as on the road. Today we have prepared a selection of answers to a variety of issues relating to the braking system of the car and its components.
What is the car brake system and what kind of varieties are most common?
The brake system is two main blocks: brake drive (usually hydraulic) and braking mechanism. The first converts the effort reported by the driver’s pedal driver to the pressure rendered on the braking mechanism. This pressure is created by compressing the brake fluid. The second, in turn, creates the strength of friction, which slows down or stop the rotation of the wheels, and the car resets the speed or stops.
In modern cars, a disk mechanism on all four wheels is becoming increasingly. However, on our roads, there are quite a few cars equipped with disk brakes on the front wheels and drums on the rear.
The disk mechanism consists of a brake disc on the wheel hub, the caliper and the brake pads located in its grooves — precisely they, pressing to the disk, create friction. In the drum brake on the wheel hub, there is a brake drum, inside which a pair of brake pads is located. When you press the brake pedal, the piston leads the column in motion, pressing them to the drum to create the friction necessary to slow down.
It is on the braking mechanism that accounts for the main load during braking — and on the state of its elements largely depends the effectiveness of the entire process. Therefore, at least twice a year — during the seasonal change of tires — it makes sense to check how it is about the brakes on your machine (since the wheels are still removed to replace tires).
In the case of a drum braking mechanism, without removing the wheel, in principle, it is not necessary — all its elements are inside the drum without visual access to them. Disc brakes allow a visual inspection (unless, of course, the review does not close the caps or wheel knitting). Normal is considered the thickness of the friction layer of at least 3.5 mm. However, even if you saw exactly such a picture, this is not a reason to calm down: it happens that the outer and the inner blocks wear it unevenly.
Therefore, you should pay attention to how the car behaves, which sounds make up when braking, how the brake pedal reacts to pressing. Unpleasant violets, the appearance of metal chips on the brake discs, the increase in the stroke of the brake pedal, vibration when braking or by the car in the direction — all these are signs of wear of the brake elements and the reason to immediately go to a hundred.
The fact that the brake pads are time to change can report special sensors — mechanical or electronic. The first are a metal plate of spring steel, which, when wearing the friction layer of the block, begins to rub about the brake disc and publish a nasty creak. When the electronic sensor is triggered, the corresponding indicator on the dashboard lights up.
The overall periodicity of the replacement of the pads of the disc braking mechanism is every 30-60 thousand km of run, depending on the axis drum — every 70-90 thousand km. But these figures are still very dependent on individual conditions and manners of the ride, so vigilance will never be excessive.
In this matter, much depends on the driving style. Calm urban style — the most sparing for the brake mechanism, in this mode, they are difficult to «heat up» above 400 ° C; A more aggressive driving manner with sharp accelerations and braking is capable of increasing this temperature to 500-650 ° C, and with the progenic racing loads, the braking mechanism is glowing in the literal sense of the Sausage — more than 800 ° C!
Resperating and respected by automakers brands — including Bosch, care that their components are not only safely withstanding extreme thermal and mechanical loads, but most importantly, the maintenance of braking.
Even if you are a lover of high speeds, outside the racing track of the need to use special pads. Moreover, such pads are created on a fundamentally different mode of operation and work most effectively at temperatures unattainable under normal conditions. So, on urban streets may not help out, but, on the contrary, let it down, increasing the braking path.
The brake disc can be solid or have in its design ventilation channels, notches or perforation. «Deaf» design is the simplest and affordable, but at the same time the most unreliable: quickly overheats as a result of friction and slowly removes heat. Therefore, it is used mainly on less loaded rear axle brakes and is suitable for low-power machines and the most relaxed ride manner.
Modern standard (at least on the front axle) are ventilated discs — consisting of two layers of metal, between which special channels for heat removal are located.
For the efficient operation of the braking system, the removal is not only heat, but also gases that are produced as a result of friction pads about the disk. To eliminate their disk, there may be perforation, notches or a combination thereof. The efficiency of braking They, of course, are increased, but at the same time not deprivable: due to the irregularities on the surface, the brake linings are wear out faster, and the wheels themselves (especially perforated) are characterized by less durability compared to their smooth «counterparts». Such discs come from motor racing — and, by and large, we need only experienced fans of sports style driving. And, most importantly, change the design and independently apply perforation or notches to a solid disk in no case is allowed.
Typically, brake discs are enough for 2-3 shoe replacements. However, it will not be possible to check the disk thickness of the disc in several places periodically to evaluate the need for replacement (maximum and minimum magnitude, the manufacturer indicates the disk itself).
The brake disc replacement must be carried out in a pair on one axis. This depends on the synchronization of the triggering of the brakes on both wheels — and therefore the behavior of the car during braking, that is, your own safety. Yes, and the load on other elements of the brake system in this case is distributed evenly.
By the way, simultaneously with the replacement of the discs you need to change and shods! Even if it seems to you that they are worn insignificantly and can still serve. The combination of old blocks and new disks can lead to the deferment of the latter. Do not become the meager that you have to pay twice.
Pads are also changed in a pair — for the same reasons that discs.
The general rule — you need to make sure that your chosen elements of the brake system correspond to each other and can work «pair». Accessories of different brands may be simply incompatible. Ideally, of course, it is better to use a set of one manufacturer. This ensures that the details are accurately suitable for each other.
This is just the case when the trigger occurs in the literal sense: new details just need to «introduce» with each other!
Immediately after replacing the disks or pads, it is necessary to pump the brake pedal — this is done literally a few presses. The first kilometers of the mileage after replacement do not forget that it is necessary to slow down smoothly, avoiding increased loads on the braking mechanism. Yes, and subsequently, for some time you can not dramatically drop the speed, «overtaking» the brake pedal to the floor with a sharp movement — pressing must be smooth and, possibly, intermittent. But when the surface of the new disk acquires a uniform color without strips and stains, it signals that the primary trigger was successful. Now, on the contrary, you need to perform several overclocking cycles and complete braking with an interval of 5-7 minutes. It «challenges» the surface of the pads, and they will not wear so quickly.
And you should not worry if the first time during the braking, extraneous sounds and screens are distributed: it is normal for new parts after replacement.
Another 20-30 years ago, when braking from 100 km / h to zero, the braking path of 50-60 meters was considered normal. Today — already 40-45 meters: technology does not stand still, and brake systems work more and more effectively. However, the magnitude of the brake path is directly associated with the state of the pad: the worn brake pads, discs or drums, as well as the late replacement of the brake fluid, can lead to an increase in the braking path!
It all depends on which one. For example, metal-containing lubricants (aluminum, copper, etc.) are not recommended: during operation between different metals, an electrochemical reaction occurs, as a result of which the parts can be oxidized, accelerated corrosion appears. There is traditional graphite lubricant, but it has a significant drawback — low efficiency. Therefore, many manufacturers offer special lubricants for brake system mechanisms (an example is Bosch Superfit, not containing metals and acids).
Each nuance relating to the efficiency of the brakes, deserves close attention and, if necessary, timely appeal to those skilled in the art. Pay attention to any change in the usual behavior of the machine during braking, perform all service manipulations in a timely manipulation, closely feel about the selection of spare parts for replacement — and then most unpleasant situations associated with brakes can be avoided.
And they helped us in this to deal with Bosch experts.