Many modern cars are equipped with disc brakes both front and rear. But they also produce cars that use rear brake drums. This mechanism has been used in the automotive industry for over a hundred years. Like many other elements, such a braking system can wear out, and then it is necessary to dismantle and replace these parts.
Design
The rear brake drum is a few parts. This is a rotating drum and brake pads. During braking, the latter rub against the surface of the hollow inside the drum. In order for the pads to move, the design has special springs. They are compressed or unclenched depending on whether the driver presses the brake pedal or releases it.
The brake cylinder is responsible for the actuation of the pads - it presses the pad against the surface of the drum under the pressure of the working fluid. There may be several of these cylinders. The whole mechanism is mounted on a stamped brake shield.
The rear brake drum may have another design - tape. Here, braking is carried out due to a flexible metal tape, which is stretched and compresses the drum. This system has long been abandoned in the automotive industry.
Drum Brake: Solution Benefits
One of the main advantages of these mechanisms is that they are reliably closed from any environmental influences. Such a braking system is ideal for use in harsh or even extreme conditions.
Dust and moisture practically do not get into the pads, which significantly increases the resource of parts. Also, in the process of braking, such a system generates less heat, this makes it possible to use cheaper entry-level liquids with a low boiling point.
Another advantage is that the braking force can be increased not only due to the larger diameter of the brake drum, but also due to its width. So, the contact patch of the block with the surface of the element becomes larger, which can significantly improve the braking properties.
Rear brake drums due to their design can increase work efficiency. The drum rotates and in the process of braking constantly wants to take the pads behind itself, as if turning them. As a result, the effort on the pedals decreases.
Design cons
For all its merits, such a braking system has a low response speed, unlike disk counterparts. There are also some difficulties in setting up, the design has low stability. When the rear brake drum is heated, it happens that the pads "stick" and the braking performance deteriorates significantly.
If the air temperature is too low, it is not recommended to use the hand brake. There are many situations when the pads just freeze to the drum. Because of these troubles, in most modern expensive cars they prefer to leave this mechanism.
Rear brake drums can often be seen on budget models, in urban subcompacts, where they are installed at the rear. Also, this system is installed on trucks.
Malfunctions: signs and causes
Since the rear wheels participate in the braking process much less than the front ones, the car owner will not immediately be able to understand that their performance has decreased. In addition, a decrease in this very efficiency occurs gradually and slowly.
Problems with the drum brake can be felt with vigorous braking - the car stops much more slowly than usual. On most machines, a breakdown of this system is especially noticeable if you need to reverse. The front brake system, which has become the rear, does not want to work alone and stops the car inefficiently.
Leaks of
brake fluid can lead to shutdowns of one or two circuits of the brake system - this causes a decrease in braking efficiency by 30-60%. The air in the hydraulic drive leads to a feeling of softness when depressed on the pedal. And the brake only works at the end of the stroke.
If the pads distorted in the drum, the springs or racks break, the driver may hear scraping sounds. This can cause jamming and overheating of the drum. It can also lead to a decrease in the engine speed or high fuel consumption. Among the problems there is also an ovality of the drum.
Types of faults
Among the most common reasons why the rear brake drums lose their effectiveness, not a decrease in the life of the pads, but increased wear on the drum itself. Inside, on its working surface, the circumference of this same surface increases. When the pads and the working surface are developed at the same time, there is a risk that the pistons will squeeze out of the working cylinder, the wheels will jam or brake fluid will leak from the circuit.
On long-haul vehicles, corrosion can cause loosening, “sticking” or spring breakage. The pressure may decrease noticeably due to the weakening of the hand brake cable. Rarely, there is a detachment of the friction lining from the pads. In this case, it is recommended to replace the brake pads of the rear drums.
Troubleshooting
If there are traces of liquid on the surface of the working cylinder, this indicates that air has entered the system. For accurate diagnosis, you need to go to the service station, where there is a special stand that allows you to calculate the effectiveness of each mechanism.
In order for drum brakes to work properly, it is necessary to service them in time, check their operation. To do this, it is enough to stop abruptly at a speed of 60-80 km / h. These tests need to be done as many times as possible.
Removing the rear brake drum: when necessary
The drum is subject to replacement if it is deformed or its surface has through cracks and dents. In addition to the deformation of this mechanism, there may be a working out on its working surface (the inner diameter of the element increases). The rear brake drum (VAZ 2101-2107) has a diameter of 200 mm. If the size exceeds 201.5 mm, the part must be replaced.
Replacing the drum of the brake system VAZ 2101-07
The replacement process must be carried out on a hung machine, while the hand brake must be released. The first step is to remove the wheel from the side where the drum will be dismantled.
Then with the help of a wrench or a spanner, you should unscrew the guide pins that hold the drum and fasten to the wheel hub. When they are turned away, you should pull the drum housing - it should be removed.
If the rear brake drum (including the VAZ-2107) cannot be removed, which very often happens, then it is necessary to screw two M8 bolts into the holes that they screw into. You need to wrap them evenly. As a result, the part can be removed.
VAZ 2108-099
To remove the rear brake drums of VAZ models 2108-099, you need to turn on the first gear, and also set the thrust bars under the two front wheels of the machine. It is important that the hand brake lever is released . Then the wheels of the car are removed, and the brake mechanism is cleaned of dirt.
After cleaning, you need to unscrew the two mounting pins, apply a little WD-40 to the wheel hub and clean dirt and traces of corrosion. With the help of a rubber or polymer hammer, with light strokes, the drum is pulled from the hub. If the part does not want to give in, then with the help of pins or bolts M8 it is possible to compress the drum.
VAZ-2110
The VAZ-2110 rear brake drum may cause problems to the owner during the replacement or removal process. The part is dismantled quite simply, provided that the car is new. On older cars, the removal process entails problems. For work, you need a powerful hammer, a deep head of 7 mm, as well as a rattle. First of all, the bolts holding the rear wheel break down. After the car is lifted by a jack, they are finally turned away and the wheel is completely removed.
Now unscrew the studs on the drum. This is best done at a time when the car is still standing on its wheels. You can also
apply the hand brake. Then, on the reverse side, a drum is knocked down with a hammer from the wheel hub. If it doesn’t come out, then the studs help - they are screwed from the corresponding holes and when they are evenly twisted, the drum is dismantled.
The rear brake drum is removed in the same way on Korean cars (Nexia is no exception). In some cases, it is necessary to use force, but most often after processing the WD-40, the contact point of the drum is perfectly removed.
"Renault Logan"
If brute force was used with VAZ automobiles to dismantle the brake elements, then in the case of Logan, a different method is used. The first step in the gearbox is the first gear. Then the wheel chocks are placed under the two front wheels. Next, the decorative caps are dismantled if they are on wheels. When the caps are removed, gently knock out the protective cap from the hub and remove it.
After loosening the wheel bolts and the hub nut. In this case, the machine must be on the ground. Then raise the back of the machine and remove the wheel. Now you can unscrew the hub nut to the end - when installing a new drum, you should also purchase a new nut.
The rear brake drum is removed from the coupling pin (“Logan Dacia” is no exception), and with it the bearing. In these cars, the mechanism is a single unit with the hub.
The second part is removed in the same way. If an old drum will be installed, it is necessary to grind the bead on its working surface. It is also necessary to bring the gap adjuster mechanism into working position and reduce the brake pads with mounting blades.
During installation, the rear brake drums of Renault Logan must be twisted with a hub nut with a force of 175 Nm. After installation, it is necessary to adjust the clearances; for this, depress the brake pedal several times. In the process, clicks will be heard - when the gap is adjusted, they will stop.
Thus, the drum brake is dismantled for maintenance or replacement. As you can see, you can do this process with your own hands, saving money on service stations.