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Shock & Strut Service Tips

Paying Attention to the Basics Pays Off

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Shock absorbers and struts control a vehicle’s suspension damping on both compression and rebound. Always view and service these components as a system, always replacing as a four-corner set or at the very least in axle pairs. (Courtesy KYB)

Shock absorber and strut service is certainly nothing new to your shop. However, for newly-hired technicians who may still be learning the ropes, this article is intended to help provide basic service tips regarding these essential elements of vehicle ride control.

Always replace both dampers on the same axle. For example, even if only the left front shock or strut has worn or failed, replace the right and left sides. If both e are the same age, the still-functioning unit is likely to fail soon anyway. In addition, by replacing only one side will disturb the handling characteristics, as the fresh side will provide proper damping, while the opposite side’s damping will differ (re weaker/softer). 

This can provide uneven damping affecting lateral handling and body control during braking. In the same of a coil-over unit such ads a MacPherson strut, not only will the damping cartridge characteristics differ, but the coil spring stiffness may differ, not only affecting ride control but potentially providing a difference in rise height.

A front-axle strut suspension unit features a top “hat” that features a bearing, which allows rotational movement of the strut at the strut tower during steering movements. Whenever replacing a strut, always replace the top hat as well to avoid any ongoing wear/stiffness issues due to a worn or rusted bearing assembly. 

Replacing a strut assembly poses a choice of two procedures… disassembly of the original strut (removing the top hat/bearing and coil spring and reassembly with the new strut damper); or replacing with a loaded/pre-assembled unit that already includes a new spring and bearing. The best approach is to use a loaded strut, which eliminates the potential of re-using a worn spring and/or bearing, and saves labor time. 

If you opt to only replace the damping unit, or if you purchase the damper, spring and top hat/bearing new in pieces, requiring assembly, keep in mind that the clock position of the top hat is critical. Before disassembly of the original unit, mark the clock position of the hat relative to the spring and lower strut mount as a reference when performing assembly of the new unit.

Whenever you prepare to assemble a strut unit, NEVER use pliers or a vice grip to hold the damper shaft from rotating while initially installing the top nut. This can easily create burrs, nicks or scratches on the polished shaft, which can then damage the seals during damping operation.

Strut

Shock and/or strut service may seem straightforward, but pay attention to details and always read the shock/strut maker’s installation instructions, as certain units may require specific installation steps. (Courtesy Gabriel)

When performing assembly of a strut unit, it’s imperative to compress the coil spring enough to fully expose the top stud threads prior to installing the nut. If you only have access to partial threads, you may be tempted to start the nut, and continue to full engagement by tightening the nut in order to gain full thread engagement, Don’t do this! Tightening the nut in order to draw the stud upwards can place excess loads on the stud threads, which could result in weakening the threads.

Always tighten the top stud nut of a strut to the OE or aftermarket torque specification. This goes for securing the top hat to the strut tower as well. Under-tightening can result in unwanted movement and over-tightening can easily lead to fastener failure. Use a properly calibrated torque wrench and follow the published torque specs! Avoid using an impact wrench, regardless of the desire to kick the job out quickly. Improper tightening of threaded fasteners can easily lead to a come-back.

Before installing a new strut or shock absorber, take the time to inspect the new unit to verify that you have the correct hardware (washers, bushings, fasteners, etc.). Whether the installer is a novice or even the most experienced technician, always read the new unit’s instructions. If any item differs in design from the OEM, any differences or design improvements may be explained in the instructions.

Strut3

Rather than taking the time to disassemble a strut assembly and replace only the damper, choosing to use an all-new, fully assembled unit is preferred, such as the Gabriel ready-mount shown here. This saves labor time, which is less expensive for the customer, and provides all new components, including coil spring, bumper, dust cover, upper bearing mount, etc.. This provides the customer with a worry-free assembly. (Courtesy Gabriel)

When installing shock absorbers, depending on the vehicle application and design, compressible rubber/silicone/elastomer bushings may be involved (for example, a shock absorber that features an upper stud mount). Follow the shock maker’s instructions for tightening relative to bushing compression. Under-tightening will allow the mount to move at its attachment point. Over-tightening and over-compressing the bushing will serve to promote early bushing failure. Generally speaking, tighten the nut until the bushing outer diameter matches the outer diameter of the washers that secure the bushing. Again, read the instructions, as nut tightness may differ from the OE spec based on bushing material.

Rather than simply replacing a pair (or all four) dampers with whatever brand/model of strut or shock you have on hand, talk to the customer first, as the aftermarket offer options in terms of ride control/ride quality. Does the customer want to maintain the factory-original ride/handling qualities? 

Does the customer feel that the original ride was too stiff, wherein they may want something that provides a slightly softer ride? Or perhaps the customer wants better handling/braking performance that would require an upgrade to a stiffer damper? By asking this simple question, you’re able to not only get the vehicle back on the road, but to improve customer satisfaction at the same time.

Strut5

Servicing rear shock absorbers often require accessing the upper mount by removing trim panels in the rear through the rear interior. It may seem obvious, but make sure that your hands are clean before handling any trim panels, especially if dealing with fabric-covered panels.

Whenever servicing a vehicle for suspension-related issues, check ride height and compare to factory specifications. If ride height has changed (typically lower), this will provide a clear indication of a potential issue with the springs (whether hydraulic or air). Naturally, if the vehicle was modified with a lowering kit for the purposes of customization, this is a different scenario).

Whenever a strut-equipped vehicle is serviced for strut replacement, it’s always recommended to check wheel alignment, since the act of replacing front struts can result in changes in camber and toe angles. 

Naturally, you should check tire wear at the offset (as part of the ride height check). Tire wear can help you to diagnose the need for shock/strut replacement, as well as indications for possible ball joint, tie rod and/or control arm bushing wear.

When replacing coil-over struts with new assemblies (including coil springs), don’t be surprised if a short break-in period is required. Until the coil springs “settle”, in some cases initial ride height may be a bit high. If this is the case, the springs should provide normal ride height after about 100-300 miles. Consider advising the customer to have the front toe angle checked and possibly adjusted to provide long-term optimum handling and tire wear.

Strut4

In the process of removing or installing a strut assembly, the front disc brake heat shield can often be bent, sometimes with the installer being unaware. Be sure to check the position of the heat shield before strut removal and after new strut installation to make sure the heat shield does not rub on the brake disc. Correcting a bent shield is easy. Just be sure to always inspect for distortion. (Courtesy Gabriel)

The following tips provided by Ted Wittman, Engineering Application Technician of Gabriel Ride Control:

TIRE INFLATION

Tire pressure should always be checked before doing any test drives, as it will affect assessment of the vehicle’s suspension. This is a simple task, yet the most frequently bypassed step of suspension diagnostics. Tire tread condition is a great indicator of suspension problems.

RIDE HEIGHT

Tire pressures affect ride height, so pressure needs to be set first and the vehicle must be parked on a level surface.

Measure from the ground up through the center line of the hub up to the fender lip (or follow the ride height measurement locations provided by the auto maker). Currently loaded strut assemblies are the most popular choice for replacement struts. Checking ride height before a replacement is the best way to confirm if there was a height change after parts have been replaced, as well as documenting an existing height issue before attempting repairs.

Strut7

Begin with the basics. Always measure ride height at all four corners. Compare LF to RF and LR to RR, and compare to OE specs. (Courtesy Gabriel)

REPLACE IN SETS

As already mentioned, loaded strut assemblies are the current popular choice due to speed and simplicity as well as value for the customer. Whenever you are making significant changes to one end of a vehicle (by replacing not only the damper but the spring as well), it’s important to understand how this will affect the opposite half of the vehicle. 

Replacement springs restore height as well as the handling improvement that comes with the new strut. If you don’t balance that improvement on the other end of the vehicle, you will not notice the ride quality improving to the level you would expect. 

Most ride complaints after new parts are installed can be attributed to a “partial replacement.” Installers can prepare customers for this result with a conversation prior to an installation where only one end of the vehicle is serviced. Knowing ahead of time that “the job is not complete” will make replacing the other half an easier sell.

Shock absorber tip: Leave the shipping straps on a gas-charged shock absorber when installing to the rear of a pickup truck to ease installation.

 ELIMINATE NOISE SOURCES

Whenever struts are replaced, there is a possibility of a noise issue and a customer return. Perform a test drive before the repair and listen for existing noises. Identify the source of these noises and inform the customer before making any repairs. Test drive after an installation and inform the customer if any noises remain. (Editor’s note: For instance, if worn anti-rill bar end links were causing a noise prior to the strut replacement and continue afterwards, the customer needs to understand that the strut job did not cause the noise. The same holds true for a worn rear suspension watts link, etc.)

Brake heat shields that have been bent when installing struts are the most common rub noise. Pay attention to this. It’s an easy fix, but if ignored the customer may immediately return with a complaint. Stabilizer bar end links (where they attach to the strut body) are the most common cause of noise when struts are installed, leading the customer to assume the noise is caused by the new strut. 

Be sure to inspect bar end links whenever inspecting/servicing struts, and advise the customer that end link replacement is needed where applicable. Any end link that is “floppy” when disconnected should be replaced. Compare the amount of resistance in the worn part vs a new part to the customer to convince them of the need.

 Note that the subject of electronic ride control requires a lengthy discussion involving the various OEM systems and related sensors and actuators. We’ve addressed this topic in previous issues and will continue to do so in the future. There simply is not space in this article to cover that market segment.

 MORE INSTALLATION TIPS

The following information was provided by Chris Gillund, Marketing manager, KYB Americas Corp.

 When it comes to the installation of shocks and struts, there are a few things that every technician should know. One of the most common issues handled by our technical support team is prematurely leaking shocks. The leakage is because of damage to the upper seal, which is usually caused by a scored or scratched shaft. Vice grips or pliers used on the shaft during installation make marks in the shaft. As the shock extends and compresses, these small marks slowly tear apart the upper seal causing the gas and oil to leak out of the shock. Additionally, using an impact gun to tighten to the top nut can cause the shaft to spin excessively and damage the upper seal, these can also cause a shock to leak prematurely.

Have you ever noticed a new shock being shorter than the old shock? This is usually because the new shock has a brand new internal rebound spring, while the old unit has a worn rebound spring, or may not even have one at all. The internal rebound spring stiffens the rebound rate towards the end of a shock’s extended length. This improves tire control and gives the driver more vehicle control when cornering.

Installing new shocks can often highlight other weak points in a suspension, such as worn suspension bushings, tie rod ends & sway bar links. A complete inspection of the vehicle and the vehicle’s control capabilities is always recommended.

We also know that recommended shocks and struts without evidence isn’t effective. The KYB Road Test App will help you rate the wear of shocks and struts and makes it easy to communicate with your customers. The app will generate a score based on the results of a short road test and that score, with an explanation can be sent directly to your customers. The KYB Road Testing app will give you more confidence in recommending shocks and struts and help keep your customer’s vehicles operating as designed.

New: KYB recently unveiled a Road Testing App and Updated Website

KYB has recently launched a new road testing app and have updated kyb.com. By utilizing technology, there are three goals KYB aims to accomplish. First, train parts and service professionals about shocks and struts. Second, provide better information to consumers on the condition of the vehicle. Finally, give a guide to consumers on how to select the correct replacement shock.

The KYB Road Testing App helps service providers start a conversation about shocks and struts with their customer. Shocks and struts are under sold category because technicians lack a good way to rate wear and service writers don’t have enough information or facts to recommend the sale with confidence. The app addresses those issues and can even send Vehicle Condition Reports directly to the customer’s phone or email address. The KYB Road Testing App can be downloaded at no charge and is available for Apple and Android devices. More consumers are researching auto parts before a purchase is made. To help consumers make better, more informed decisions KYB has updated kyb.com to be more consumer friendly. The site includes new videos, simple graphic icons which describe the purpose of each product, electronic catalogs by product category to reduce confusion, and 360-degree product images.

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