Rubber-to-metal components are subject to high dynamic stresses and frequently harmful environmental impacts, such as heat, de-icing salt, and ozone. Lemfoerder therefore recommends a regular check of these components within the context of the inspection or during work on the brakes or tires.
Tasks assumed by rubber-to-metal components
Rubber-to-metal components in a car chassis dampen undesired vibrations and noise. Depending on the model and manufacturer, up to twelve different rubber-to-metal components may be installed. They provide better comfort and driving safety as suspension strut mounts, subframe bearings, link mounts, stabilizer mounts, or axle beam mounts for instance. In addition to the standard mounts, hydraulic rubber-to-metal components are also used in the form of axle housing mounts or link mounts. In these cases, an additional liquid damping compensates for vibrations.
When and how a check makes sense
ZF Services recommends regular checks. Rubber-to-metal components are ideally tested during inspections and technical monitoring tests as well as during brake repairs or tire changes. A visual inspection for cracks, metal flaking, or fluid leakage on hydraulic mounts helps to diagnose whether any rubber-to-metal components are defective and, if so, which ones. In the case of suspension strut mounts, the workshop may also examine the "settling behavior" of the suspicious rubber-to-metal component after having removed it: The difference in height between an old and a new bearing should not exceed two to three millimeters. Furthermore, the rubber may not show any folds or cracks and may not have detached from the metal. In the case of hydraulic rubber-to-metal components, attention must also be given to liquid leakage.
The impact of defects
Although rubber-to-metal components do not belong to the classical wear parts, they are subject to high dynamic stresses and harmful environmental impacts, such as heat, de-icing salt, and ozone due to their complex tasks. This can lead to fatigue symptoms. If link mounts or axle bearings cease to work flawlessly, rattling, squeaking, and knocking may occur when driving over short road unevennesses. Further indicators: Wobbling of the steering wheel or "juddering" brakes. Damaged suspension strut mounts can increase the stopping distance, lead to spongy drivability, or make the steering heavy. Damaged rubber-to-metal components within the chassis not only affect safety and comfort; they can also have a negative impact on adjacent chassis components. If a defect has been detected, the bearings should always be immediately replaced in pairs where possible.
How to install and remove rubber-to-metal components
Installation and removal of these high-quality components require suitable tools and, in some cases, also special tools. Caution: In some cases, the installation position must be strictly adhered to. The installation position must be marked prior to removing the defective bearings. In some cases, the positioning marks are on the actual parts or are on the installation location in order to permit the exact mounting of the new bearing. Oil may not be used as an assembly aid when dealing with rubber-to-metal components as it attacks the rubber and damages the part as a result. Experts recommend using a soap solution. When dealing with link mounts and suspension strut mounts, only securely tighten the clamping screws with the required torque once the vehicle is in its assembly position once again. This prevents distortions in the bearing that could lead to premature wear of the new parts.
Identify and Remedy Damage to Chassis and Steering
Careless driving and dirt accumulation greatly increase the risk of wear on safety-relevant chassis and steering components. Workshops need to pay attention to typical damage patterns and remedy defects as required. If chassis or steering components are damaged, the person steering needs to expect handling of their vehicle to be critical. Experts at ZF Services therefore advise workshops to inform their customers of how important a regular inspection is. Many components can be affected.
Check rubber bellows, boots, and clamping rings
Mechanics should particularly check whether the rubber bellows on the joints are worn, damaged, or leaking. Because any splash water which gets in washes out the special grease and this then allows dirt particles to ingress the joint. These particles destroy the inner plastic spherical shell and damage both the ball stud and the joint housing. This means that the clearance in the joint no longer meets the standard. In the steering, the tie rod requires special attention: Apart from the rubber bellows, the steering boot needs to be checked for damage. The spring clamping rings should also be looked at so that any spots of rust are already identified as soon as they appear.
Curb contact with consequences
On the chassis, the supporting joint, control arms, and the stabilizer can show serious damage caused by corrosion, intruded foreign matter, or dirt accumulation. In addition, driving over curbs is often the cause of defects. The consequences of damage greatly impair the vehicle handling and thus, safety. Apart from that, they often lead to increased wear on other chassis components as well as tires wearing unevenly and worse riding comfort. This means higher risk of accidents and additional repair expenses.
Regular Vehicle Inspection
ZF Services recommends special tools for professional and smooth inspection or removal of supporting joints. This minimizes the risk of injury and reduces repair costs. ZF Services feels obliged to draw attention to the need for a regular vehicle inspection: After all, the idea is to improve safety on the roads.
Consequences of defective steering parts and chassis components
Parts for the steering system and the chassis – such as control arms, levers, struts, tie rods, supports, suspension joints, etc. – hold and guide the wheels of your vehicle. Possible damage to the steering system or the chassis can already be noticed when driving the vehicle and is therefore particularly dangerous. Moreover, they cause high costs – also as a result of consequential damage to other vehicle components. In case of doubt, a closer inspection is always advisable.