The situation where a car suddenly begins to vibrate when pressing the brake pedal is familiar to many drivers. Instead of a smooth and steady slowdown, you feel an unpleasant pulsation that is transmitted to the pedals or steering wheel. This is not just discomfort, but a signal that changes have occurred in the braking system that require immediate attention.
Ignoring symptoms can lead to a critical increase in the braking distance and road accident. The rudder beat or brake pedal often indicates deformation of the working surfaces or uneven wear of components.
In this article, we will discuss in detail the mechanics of vibrations, diagnostic methods and ways to solve the problem. You will know when you can limit your service and in which cases you will need to disk-replacement Or other expensive nodes.
Mechanics of vibrations in the brake system
To understand the cause of the problem, it is necessary to consider the principle of operation of the disc brake. When pressed on the pedal, the brake pads compress the rotating disc, creating friction that converts the kinetic energy of the movement into thermal energy. If the surface of the disc is perfectly flat, and the pads fit evenly, the process goes smoothly.
The problem arises when the geometry of the disk is broken. Disc curvature When it is turned, its thickness at different points becomes uneven. The pads, trying to cover the surface, begin to make reciprocal movements, pushing the pistons of the caliper.
These microscopic shocks are transmitted through the hydraulic system to the brake pedal and through the steering thrust to the steering wheel. The higher the speed, the more often these impulses occur, turning into a tangible one. vibration.
Often drivers confuse the beat of the brakes with the vibration of the engine or suspension. The key difference is the reaction to pressing the pedal. If the shaking appears only at the moment of braking, the source of the problem is localized in the brake circuit.
The main causes of brake discs
The most common cause of pulsation is thermal deformation of the metal. When a hot disk cools sharply, for example, when it enters a deep puddle, the internal stress of the metal leads to curvature. This phenomenon is known as “driving the disk”.
The second factor is the uneven wear of the friction material. If the pads of low quality or the caliper podklints, spots with different thickness of the friction layer are formed on the surface of the disk. It causes it. disk-thicknessIt feels like a beating.
The condition of the hub should also be considered. If the seat on the hub has production or corrosion, the disc is installed with a distortion. Even a new element of the brake system will not work correctly if the geometry of its installation is broken.
⚠️ Warning: Operating a vehicle with heavily deformed discs can cause the hub bearings to collapse and damage to the steering elements due to constant vibration.
Before buying new brake discs, be sure to check the condition of the hub. Installing new parts on the curved hub will lead to their rapid failure.
The table below shows the main symptoms and their probable causes:
| Symptoms. | Probable cause | Diagnostics |
|---|---|---|
| The rudder beat | Deformation of front discs | Visual examination, thickness measurement |
| Pedal pulsation | Wear of rear discs/drums | Measurement of beats with indicator |
| Scream and vibration | Calipor jamming | Checking pistons mobility |
| Vibration at speed | Wheel imbalance | Balancing on the stand |
Diagnosis: How to determine the source of the problem
The primary diagnosis can be carried out independently, paying attention to the nature of the vibration. If the steering wheel shakes when braking, the problem is most likely to lie in the front brake mechanisms. If the pedal itself or the body of the car pulses, attention should be paid to the rear axle.
A lift is needed to more accurately determine the fault. The wizard removes the wheels and visually assesses the state of the discs. The presence of deep furrows, color spots (traces of overheating) or chips indicates the need for replacement.
However, visual inspection is not always accurate. The minimum deviations are used to clock-type. The device is installed on a fixed part of the caliper, and its probe touches the working surface of the disk. When turning the disc with the hand, maximum deviations are recorded.
- 🔍 The permissible beating of the disc is usually no more than 0.05-0.1 mm (depending on the model of the car).
- 🔍 The minimum permissible thickness of the disk is stamped on its inner side.
- 🔍 Checking the backlash of the hub bearing is also mandatory during diagnosis.
It is also important to check the condition of the guide calipers. If they are rusted or lost lubrication, the caliper can not work normally, which leads to uneven pressing of the pads and, as a result, to local overheating and deformation of the disc.
Removal methods: flow or replacement
When the diagnosis is made, the question arises about the method of repair. There are two main ways: the flow (running) of the disks or their complete replacement. The choice depends on the residual thickness of the metal and the degree of deformation.
The flow is performed on a special machine without removing the disk from the car or with removal. The essence of the method is to remove a thin layer of metal from the working surface, which eliminates curvature and thickness differences. It is cheaper to buy new parts, but reduces the resource of the disk.
Replacement is required if the disc is already minimally thick or if deep cracks have formed on its surface. Operation of thinned disks dangerous: they can not withstand the temperature load and burst with sharp braking.
Do I need to change the pads when replacing the discs?
Yes, it's a mandatory rule. The old pads have already worn to the relief of the old (deformed) disk. Installing new discs with old pads will lead to accelerated wear and vibration preservation.
When replacing discs, always change the brake pads. It is also recommended to replace pairs on one axle to ensure symmetry of braking.
The role of pads and calipers in the occurrence of beating
Do not forget that the culprit of vibration can be not only discs. Low quality brake pads may have an uneven structure of the friction mixture. When heated, some areas wear out faster, creating “steps” on the surface of the disk.
A jammed caliper piston is another common cause. If the piston does not return to its original position, the pad is constantly rubbed against the disk. This causes constant heating and, sooner or later, leads to warping of the metal.
Checking calipers includes an assessment of the condition of the anthers and the presence of lubrication on the guides. The lack of lubrication leads to corrosion and loss of mobility of the mechanism. In this case, even the new disk will quickly fail.
- 🛠 Use only high-temperature lubricant for guide calipers.
- 🛠 Check the anthers for cracks through which moisture enters.
- 🛠 Make sure the brake hose is not squeezed and inflated inside.
⚠️ Warning: When replacing the caliper or repairing it, be sure to pump the brake system to remove air. The presence of air traffic jams will make braking ineffective and “cotton”.
☑️ Checklist for brake maintenance
Prevention and operation rules
To avoid expensive repairs, you should follow the rules of operation of the brake system. The main enemy of brakes is a sharp temperature drop. Try to avoid sharp braking followed by prolonged parking when the discs are still hot.
If you were moving on the track and actively braked, let the brakes cool down in motion before stopping. Do not put the car on the parking brake immediately after an intense drive, if it is possible to leave it in the transmission or on a flat surface without a “handle” (on the mechanics).
Regular washing of wheel arches also prolongs the life of brakes. Aggressive reagents and road mud accelerate the corrosion of the guide calipers and the discs themselves, especially if the car is rarely operated in winter.
Timely replacement of brake fluid (every 2 years) prevents corrosion inside the system and boiling of the liquid during braking, maintaining the efficiency of the work.
Keep an eye on the tyres. Uneven tread wear or a “hernia” on the sidewall can mimic the symptoms of brake failure, creating a beat at certain speeds.
Frequently Asked Questions (FAQ)
Why does the beating only appear at high speeds?
At high speeds, the wheel speed is high, and even a minimal disk beat (e.g., 0.1 mm) turns into a high-frequency vibration that is well felt on the steering wheel. At low speeds, these fluctuations may be smoothed or less noticeable.
Can I drive if the steering wheel shakes a little while braking?
You can drive, but it is highly undesirable. Vibration indicates uneven wear and tear that will progress. In addition, the effectiveness of braking is reduced, and the braking distance increases, which is dangerous in an emergency situation.
How long does the brake disc last?
The resource of the discs depends on the driving style and model of the car. On average, front wheels run 60-80 thousand. km, rear - up to 100-120 thousand. km. However, aggressive driving or frequent trips to the mountains can cut that time in half.
Do I need to go down after the brakes are replaced?
By itself, the replacement of discs and pads does not require adjustment of the angles of installation of the wheels. However, if work was carried out with suspension elements or uneven wear of the tires was noticeable, checking the collapse will not be superfluous.