Pivot bushes allow for suspension movement and isolate road undulation from the truck or trailer and play a vital role in the vehicle’s driveability.
Deteriorated or damaged bushes can compromise safety, accelerate tyre wear, and lead to additional mechanical issues.
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Technicians may inadvertently damage pivot bushes or accelerate their deterioration through improper installation. Such practices may drastically reduce the lifespan of these otherwise durable components.
Here are some key factors that can significantly affect pivot bush performance and longevity.
Hendrickson provide pivot bush kits that include the correct lubricant for each application. Using unapproved lubricants can be detrimental to the rubber compounds, causing the bush to fail prematurely.
Unsuitable lubricants may also take too long to set, allowing the bush to shift within the trailing arm once the vehicle is in service. Bush movement will allow the trailing arms to contact the hanger and thus eventually resulting in hanger damage.
Even when the correct lubricant is used, it is important to allow enough time for it to dissipate before the vehicle is operated. Hendrickson recommends waiting at least four hours after installation before putting the vehicle back into service.
Proper bush orientation
Hendrickson TRI-FUNCTIONAL pivot bushes contain voids, which must be installed at the correct orientation.
If installed incorrectly, a void may be in a location where there should be supporting rubber. As a result, ride harshness will increase and the rubber will face unnecessary stresses that will cause it to fail prematurely.
Pivot bush voids must be vertically aligned when the suspension is at ride height. If the old bushes are only showing cracks, their orientation can be marked on the trailing arms to ensure that the new bushes are installed in the same position. In all cases, technicians should reference the suspension angle at ride height and ensure new bushes are installed within 10 degrees of this angle (refer to images).
Tightening at ride height
Although technicians generally do a great job installing pivot bushes, issues can arise when the pivot hardware is not fastened with the suspension at the correct ride height.
If the hardware is fastened when the suspension is hanging, the rubber bush will distort when the suspension is moved to ride height. If the lubricant has not set, this may cause the bush to move within the trailing arm. Otherwise, the bush will remain under stress and fail prematurely.
Pivot connections must only be tightened when the suspension is at the correct ride height to ensure proper bush operation and durability.
Pivot bushes are designed to be durable, however their service life does rely heavily on correct installation practices. Technicians should always refer to the recommended procedures, which are available on the Hendrickson website, to ensure optimal performance and avoid unnecessary component failure.
By paying close attention to lubricant use, bush orientation, and pivot hardware tightening procedures, technicians can help maintain suspension performance, improve ride quality, and maximise bush life.
