What is silent block,when to change

 ● design (with one, two bushings or without metal elements);

 ● design load (continuous elastic insert or with holes);

 ● type of fastening (bushings or case with eyes);

 ● mobility (medium mobility and “floating”);

 ● material (rubber or polyurethane).

Structurally, silent blocks differ in shape, depending on the design of the lever. Most often, two bushings are used on triangular levers of the MacPherson type front suspension - rear silent blocks with two bushings, front ones with an inner bolt, there is no outer clip. By the way, the rear s/b of the front suspension can be hydrofilled. This design allows you to better absorb the vibration energy, but as soon as the liquid begins to flow out, the efficiency of silent blocks decreases sharply.

According to the design load, it is better to use continuous s / b, their resource is much higher.

In terms of mobility, “floating” silent blocks are worth special attention. They are used in the rear multi-link suspension, they can be pressed into the steering knuckle or transverse rod. The “floating” hub has a second task - to allow the wheel to turn freely at a certain angle, while remaining motionless in the vertical and horizontal plane. The product is a cage, closed on both sides with anther, 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 more stable in sharp turns due to this .. The main disadvantage of the “floating” bushing is that that the rubber boot is too vulnerable to an aggressive environment, after which it passes dust and moisture, sharply reducing the life of the part. 

Rubber-metal bushings are used in the following suspension parts:

 ● front and rear levers;

 ● longitudinal and transverse traction of the rear suspension;

 ● as stabilizer bushings;

 ● in turning fists;

 ● in shock absorbers;

 ● as a fastening of the power unit and transmission;

 ● on stretchers.

The use of full-fledged silent blocks instead of rubber bushings significantly improved the technical characteristics of the chassis due to the fact that the rubber in the rigid sleeve 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 during operation the rubber part does not wear out, 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 knuckles of the hub.

When they change

Silent blocks are replaced only with obvious wear, in other cases it makes no sense to touch them. It is strongly recommended that you change the rubber-metal part from two sides, because on the move 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: the car Mercedes-Benz W210 and BMW 7-series E38 to the last remain “silence”, even when the silent blocks are completely torn. This suggests that running gear should be diagnosed based on mileage and the first signs of inadequate suspension behavior.