19th Annual Technical Forum: Shocks & Struts

19th Annual Technical Forum: Shocks & Struts

What are loaded strut assemblies, and why should I recommend them to my customers?

A. Loaded strut assemblies are completely assembled MacPherson struts with new springs and upper bearing plates. Reusing the old springs and upper bearing plates can be troublesome for a couple of reasons. All springs sag with age, and loss of ride height upsets wheel alignment. This, in turn, can have an adverse effect on steering stability and handling, and increase tire wear. Many springs also have fairly small cross sections and have a protective outer coating for corrosion resistance. If the soft plastic coating has been scratched or damaged, corrosion can concentrate at a single spot causing a spring to fail.

Reusing high-mileage upper strut bearing plates with worn or corroded bearings  also can affect steering effort, steering return and road noise. Installing a loaded strut assembly with a new spring and new upper bearing plate avoids the risks of reusing the old parts, while restoring the ride height and steering feel of the original system.

Loaded struts also are much faster and easier to install. No spring compressor is required because the original strut does not have to be disassembled and reassembled. This saves time and reduces the risk of personal injury, which is a risk if the spring compressor slips.

With a single part number, your customer gets everything he needs. There are no extra parts to order and no unnecessary trips back to your parts store for strut components that may have been forgotten or need to be replaced separately.

Struts should be replaced if the shock component is leaking or is not providing adequate ride control (rough bouncy ride, bottoming, excessive sway when cornering, etc.). Strut replacement also may be necessary if the upper bearing plate is stiff, making noise or rattling, or if the spring is sagging or broken. Most struts are gas-charged to reduce aeration and fluid foaming for more consistent ride control. As the miles add up, the sliding friction between the piston rod and seal in the top of the shock or strut wears the seal. Eventually, the seal begins to leak, allowing the gas charge inside the strut to slowly escape. The seal may also leak fluid, and once fluid is lost, the strut can no longer provide any suspension dampening or control.

Q. Do the wheels have to be realigned after replacing the shocks or struts on a vehicle?

A. Replacing front struts does require realigning the front wheels after the struts have been installed. Many struts have “camber bolts” at the lower end that allow the strut to be repositioned with respect to the steering knuckle. Even if the position of the camber bolt is marked prior to removing the old strut as a reference point, manufacturing tolerances in the new strut housing may change the alignment. For this reason, alignment should always be checked and adjusted as needed after the new struts have been installed to assure optimum handling and tire life.

On other struts, wheel alignment is adjusted by moving the top of the strut in or out to change camber, and/or moving the top of the strut forward or backward to change caster. Again, marking the location of the upper strut bolts prior to removing the old strut can serve as a reference point for realigning the suspension. As before, wheel alignment should always be checked and readjusted as needed after the new struts have been installed. With rear struts, there may be camber adjustments at the top or bottom of the strut that can affect rear wheel alignment.

But even if there are no factory adjustments, wheel alignment should be checked after the struts have been installed to make sure alignment is within specifications and that no other parts are damaged or bent. With shock absorbers, there is no need to realign the wheels after new shocks have been installed. The shocks play no direct role in wheel alignment other than to dampen the movements of the suspension.



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