- What is silent block and its purpose
- Where are the silent blocks located?
- Types and types of silent blocks
- How to check silent blocks?
- Which silent blocks are better: polyurethane or rubber?
- Reasons for failure and what breaks down in the silent block
Silent blocks (hereinafter referred to as “s / b”) are a suspension part, which is two metal bushings with a rubber insert between them. The silentblock connects the suspension parts together, dampens vibrations between the nodes. The silent blocks contribute to a comfortable ride due to the elasticity of the rubber, which serves as a damper between the suspension parts.
What is silent block and its purpose
Silent blocks work to avoid deformation of suspension parts and bodywork. They are the first to take shocks and vibrations, after which they are damped by shock absorbers. Also silent blocks are divided into the following categories:
- construction (with one, two bushings or without metal elements);
- design load (solid elastic insert or with holes);
- type of attachment (bushings or housing with lugs);
- mobility (medium mobility and "floating");
- material (rubber or polyurethane).
Structurally, silent blocks differ in shape, depending on the version of the lever. Most often, two bushings are used on the triangular levers of the MacPherson-type front suspension - the rear silent blocks with two bushings, the front ones with an inner one for a bolt, there is no outer cage. By the way, the rear s / b front suspension can be hydraulically filled. This design allows you to better absorb the vibration energy, but as soon as the liquid begins to flow out, the efficiency of the silent blocks decreases sharply.
According to the design load, it is better to use solid s / b, their resource is much higher.
On the mobility of special attention are "floating" silent blocks. They are used in the rear multi-link suspension, they can be pressed into the steering knuckle or the transverse rod. The “floating” hub has a second task - to allow the wheel to turn freely at a certain angle, while remaining stationary in the vertical and horizontal plane. The product is generally closed with a boot on both sides, inside of which a hinge is installed. Due to the movement of the hinge, the rear suspension “steers” when necessary, the car on the road is therefore more stable on sharp turns .. The main disadvantage of the “floating” bushing is that the rubber boot is too vulnerable to an aggressive environment, after which it allows dust and moisture to pass through, drastically reducing the resource of the part.
Where are the silent blocks located?
Rubber-metal bushings are used in the following suspension parts:
- front and rear levers;
- longitudinal and transverse rods of the rear suspension;
- as stabilizer bushings;
- in the steering knuckles;
- in shock absorbers;
- as a mount for the power unit and transmission;
- on subframes.
The use of full-fledged silent blocks instead of rubber bushings has significantly improved the technical characteristics of the chassis due to the fact that the rubber in the rigid bushing works better for twisting, dampens vibrations more efficiently and does not wear out so quickly.
Types and types of silent blocks
There are two categories by which all silent blocks are classified:
- By the material from which they are made;
- By type (shape and design).
The bushings for the rear beam and front control arms are made of rubber or polyurethane.
By type they are distinguished:
- Standard non-collapsible. Such parts have a metal cage with a rubber insert inside. There are also modifications with one metal insert. In this case, it will be placed inside the rubber base.
- Perforated silent block or with cavities in the rubber part. Such silent blocks provide smooth twisting of the lever. The part must be pressed in evenly so that the load is distributed over the entire working part of the element.
- Silent block with asymmetric lugs. Such parts do not have a through mounting hole. Instead, lugs are used. This design allows you to fix parts that are in offset planes relative to each other.
- Floating design. Externally, floating silent blocks are similar to ball bearings. So that the rubber part does not wear out during operation, it is covered with a rubber boot. This modification provides a smooth movement of the part mounted on it. They can be used for levers, but more often they are installed in the steering knuckle of the hub.
How to check silent blocks?
The average resource of rubber-metal suspension parts is 100 km. S / w diagnostics are carried out every 000 km. To do this, you need to lift the car on a lift. Initial visual examination, it is required to identify the presence of cracks or ruptures in the rubber. If there are cracks, then this is a sign that the s / b will need to be replaced soon.
Further, the check is carried out using a mount. Leaning against the lever, we imitate its work, while the stroke of the lever should be tight. This also applies to engine mountings, shock absorber bushings.
On the go, a strong knock on irregularities, "laxity" of the suspension speaks about the wear of the silent blocks.
Replacement of silent blocks is made only with obvious wear, in other cases it makes no sense to touch them. It is strongly recommended to change the rubber-metal part on both sides, because on the go, the suspension begins to manifest itself inadequately due to the difference in the operation of the levers.
By the way, not every suspension starts to "sound" when the s / w is worn. For example: car Mercedes-Benz W210 и BMW The 7-series E38 maintains “silence” to the last, even when the silent blocks are completely torn. This suggests that running gear diagnostics should be based on mileage and the first signs of inadequate suspension behavior.
Typically, the resource of original components reaches 100 km or more, depending on where the car is operated. Speaking of analogues, the cheapest options may fail already at the second thousand kilometers. The normal mileage of a good analog is 000-50% of the resource of the original spare part.
Which silent blocks are better: polyurethane or rubber?
Unambiguously, if the silentblock fails, a reasonable solution would be to replace it with an identical one, which was provided by the manufacturer. If the driver is unfamiliar with the device of his car, then the selection of silent blocks can be carried out according to the catalog for a specific car.
Before replacing the silent blocks, the car owner should decide on the material from which the part is made.
In the modern auto parts market, the buyer is offered two options: rubber and polyurethane analogues. Here's the difference.
Rubber silent blocks
At the heart of such silent blocks, rubber is used. These parts are cheap and easier to find in stores. But this option has several significant disadvantages:
- Small working resource;
- Creak, even after replacement;
- They do not tolerate aggressive environmental influences, for example, rubber cracks under loads in severe frost.
Polyurethane silent blocks
The most significant drawback of polyurethane silent blocks in comparison with the previous version is the high cost. However, this factor is overridden by the presence of many advantages:
- Silent work;
- The car's behavior on the road becomes softer;
- The fulcrum is not excessively deformed;
- Increased working life (sometimes up to 5 times, when compared with a rubber analogue);
- It dampens vibrations better;
- Improves vehicle handling.
Reasons for failure and what breaks down in the silent block
Basically, the resource of any car part is affected not only by its quality, but also by the operating conditions. It so happens that a high-quality silent block does not deplete its resource in a car that constantly drives on a bumpy road.
In another case, the car is used mostly in the city, and the driver drives accurately and measuredly. In such situations, even a budget silent block can waste a decent resource.
The main breakdown of silent blocks is rupture or deformation of the rubber part, because it is a damper for the fulcrum. Twisting forces act on it at some nodes. The breakage of the metal clip is very rare. The main reason for this is a violation of the pressing procedure.
The rubber part wears out prematurely in the following cases:
- Violation of the technology for replacing silent blocks. When the mounting bolts are tightened, the vehicle should be firmly on its wheels and not jacked up. Otherwise, an incorrectly tightened part will twist after the machine is lowered to the ground. Subsequently, the rubber will break under additional load.
- Violation of the pressing process. If the part is installed with an offset, the load will not be evenly distributed during operation.
- Natural wear and tear. Some drivers pay attention to silent blocks only when there is a problem with them, often exceeding the recommended service life.
- Aggressive exposure to chemicals. This reason includes reagents with which the road is strewn. Ordinary engine oil also breaks down rubber with ease.
Here are the signs by which you can determine that the silent blocks need to be replaced:
- The car drove almost 100 kilometers (if the road conditions were of poor quality, then the replacement interval decreases - after about 000-50 thousand);
- Backlash appears, the car becomes unstable and less comfortable to drive;
- The tread pattern of the tires wears out unevenly (it should be borne in mind that this may be the result of other malfunctions, which are described in separate article);
- Lever mountings are damaged.
Carrying out timely and high-quality maintenance of the car, the owner of the car will avoid unnecessary waste on the repair of parts that have not yet arrived.