Bad Hydrobearings

Causes & Symptoms

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A defective tension strut with hydrobearings can have a rather unpleasant effect on the handling of your car. The most common cause of this is poor driving conditions such as bad roads and potholes. This leads to symptoms such as "jerking of the steering wheel" or banging noises from the wheel arch. You can find more causes and which symptoms indicate a defective hydromount in this article.

In our DIY guide, we show you how to make your Tension Strut incl. hydrobearings on BMW F models.

1) Where is the Tension Strut with Hydrobearings?

Oftentimes, there is confusion when it comes to the names of the individual components of the front axle suspension. In forums, everything located behind the front edges is often referred to as a “control arm.” However, each of these “rods” has its own name and specific function. This knowledge is especially important when searching for parts online. The following diagram will help you gain clarity:

Position of the tension strut incl. hydromount and the wheel suspension components
Components of the steering knuckle (position of tension strut with bearing)

The trailing arm forms a connection between the suspension springs and the wheel. On one side, the arm is connected to the assemblies via a hydraulic rubber mount. This is because the trailing arm needs to be movable to transfer the vertical movements from the suspension to the wheel. In summary, this means: The more the suspension springs are stressed, the more the hydrobearings and trailing arm are moved and subjected to wear.

2) Defective Hydrobearings: Symptoms & Causes

As with most mechanical components in a car, a defective hydrobearings has several symptoms and causes.

Hydromount defective and with fluid loss
Defective hydrobearings (hydraulic rubber bearing of the tension strut)

The most obvious symptoms that can occur when the hydrobearings is defective are:

Twitching in the steering wheel at a certain speed or steering direction.
Intense and brief jerking when braking.
Banging noises from the wheel arch, especially in stop & go traffic (city traffic).

The most common causes that can lead to a defective or torn hydrobearings are:

Driving into deep potholes or driving fast on bad roads.
Salt and cold shorten the service life of the hydraulic rubber bearing.
A sporty riding style also promotes wear on the hydromount, as the tension struts are subjected to more frequent and greater stress.
Incorrect installation can also lead to damage.
Example: If the tension struts are not in the normal position and have not been tightened to the required Newton meters.st item

INFO BOX:

You can find out how to change the tension struts including the hydrobearings on the front axle correctly in our instructions.

3) Why you should replace the whole Tension Strut?

Theoretically, it would also be possible to replace only the defective hydrobearings without renewing the entire trailing arm. However, the cost difference is minimal, and the repair is easier if you replace the entire trailing arm.

To remove the mount from the trailing arm and to insert the new mount, you will need a press. Since there is a high risk of damage and you won’t save much money by replacing just the mount, we recommend replacing the entire trailing arm. This makes the repair easier and, above all, faster.

Difference between old tension strut incl. hydromount and new tension strut incl. hydromount
Comparison of old tension strut with hydromount (left) and new tension strut incl. hydrobearings (right)

4) Tension Strut with Hydro Bearings Costs

Hydrobearings cost approximately €45 to €75 for a mid-range car. In most cases, the mount is not sold as an individual part but only together with the trailing arm.

The trailing arm, including the hydrobearings for the front axle, costs between €75 and €125 per piece, depending on the car model.
Since the repair becomes significantly easier when replacing the entire trailing arm, it is worth spending a bit more money. Especially when the cost difference is so minimal as in this case.

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