The strut of a suspension will only be as good as the mount attaching it. Strut mounts play a major role in dampening noise/shock transfer, and sometimes, they are even critical to front-end/wheel alignment.
Sadly, strut mounts do wear out and need to be replaced. We are going to review the symptoms of a bad strut mount, why it happens, and what to expect to pay for the mount replacement.
What is a Strut Mount?
When we talk about a worn strut mount, we are normally talking about the upper mount of a strut. Simply put, the upper strut mount is the point of attachment for the upper end of a strut to the vehicle’s chassis, to which it is attached.
The first purpose of the upper strut mount is to absorb the transfer of road noise and vibration to a vehicle’s chassis. This adds comfort to driving and reduces the harshness of taking a drive on less-than-roadworthy pavement.
In addition, most upper strut mounts come with a set of bearings. The bearings allow the strut to pivot when steering.
Therefore, a strut’s front struts (as in KYB or Monroe, or whatever) are essential for steering and alignment for a car’s front end and prevent irregular tire wear and issues with how the steering will function.
Signs of a Strut Mount
The failure of a vehicle’s upper strut mount is usually followed by one more symptom. While these symptoms do vary from vehicle to vehicle, a few of these symptoms are much more common.
Regardless, here are the most commonly seen symptoms of a damaged strut mount.
#1. Excessive Noise/Vibration.
One indicator of a damaged strut mount is excessive noise and/or vibration while driving. Strut mounts isolate the upper strut from any noise/vibration to the vehicle’s chassis and produce less strain on the vehicle.
When a strut mount is heavily worn, it can reduce the isolation of the structure from that noise or vibration. So subtle rattles and squeaks begin to emerge, many of which will worsen over time.
#2. Accelerated Wear of Additional Suspension Components.
Unfortunately, as strut mounts degrade, they often impart additional deterioration upon other suspension components. These suspension components usually consist of shock absorbers, but several front-end bushings as well.
Now, numerous additional issues may develop, many of which would be a nuisance, while also negatively affecting handling.
#3. Rapid Tire Wear.
As we mentioned above, the wear of a vehicle’s upper strut mounts affects how well the strut will align the front end of the vehicle in many cases.
A vehicle’s upper strut mounts can also throw a vehicle’s toe settings out of spec and could lead to rapid tire wear. This could even lead to majorly accelerated tire wear if the vehicle just had new tires.
#4. Wandering Steering/Poor Handling.
Similar to the toe setting issue mentioned above, the front end’s caster setting can also be negatively affected in the event of a failed strut mount, once again due to the changing of front-end geometry from the wear/failure of the upper shock mounts.
Mechanics can only resolve this issue by replacing it. All worn strut mounts must be replaced, and the vehicle’s front end should be aligned afterwards.
#5. “Clunking” in Front End.
In extreme cases, a severely worn strut mount can produce an audible “clunk”. This sound of “clunk” is different than the sound of sporadic rattles or squeaks that were previously mentioned. On occasion, occupants will be able to feel a “clunk” as well.
This audible clunk is the result of excessive strut play (or looseness) due to the failure of the mount in question.
This excessive strut play will disappear with the replacement of the strut mount in question, and once the front end is thoroughly inspected for any further damage or replacements, if any components are found.
What Causes Strut Mount Failure?
In most cases, strut mount failure is the result of everyday wear and tear. The struts of a vehicle and the strut mounts are always in motion, and some form of load is being placed on them while you are driving down the road.
In fact, even when a vehicle is at rest, the weight of the vehicle is loaded onto the struts and strut mounts, and they never get a break from the load.
In actuality, as soon as the strut mounts are installed on a vehicle, they become a wear item that is subject to unequivocal wear until the strut mounts are replaced. It is impossible for a strut mount on a vehicle not to have a repetitive load on it.
The rate of wear is also increased by exposure to external environmental conditions in most cases. Rainwater, ice, and road salt contribute to the breakdown of the strut mounts, which contributes to their failure.
What Happens if a Strut Mount Completely Fails?
You should never knowingly drive with a failed strut mount. That is never a good idea!
If you have a car in which the upper strut mount has failed, many things could happen.
From the mechanical standpoint, if the rubber mount of your upper strut mount completely fails, your strut will be able to “clunk” around and will not provide you with a good ride.
Additionally, any free-play created by a failed strut mount will only contribute to further premature wear of many other steering and suspension components.
There are several components located in the front and rear steering and suspension systems that are going to be significantly affected because they are going to see much greater loads during driving due to undamped shock loads.
Also, there is a safety concern. If the strut mount fails, it will change the suspension geometry and make it unsafe to drive. In some extreme situations, it can affect steering and handling.
Cost of Strut Mount Replacement
The cost for strut mount replacement varies from vehicle to vehicle. The costs may also vary depending on the make and model of the vehicle.
For the sake of discussion, we will provide a general guideline of the costs associated with strut mount replacements.
The average strut mount replacement will cost between $150-$300. The minimum figure represents costs associated with a standard sedan and economy mounts.
The higher figure usually reflects those costs associated with high-end performance vehicles or sports cars with dealer labor rates included.
Is an Alignment Required After Replacement?
In most cases, it is advisable to have the front end of a vehicle aligned after replacing the strut mounts. This is because struts are an important part of the alignment of numerous vehicles.
Therefore, the difference in length of a strut assembly after replacing the strut mounts could impact alignment.
Strut length pertains to the following alignment settings, on many vehicle models:
- Toe: The angle of the leading edge of the tires (inward vs. outward) is known as toe. Adjusting toe incorrectly can cause premature tire wear.
- Caster: The lean of a vehicle’s steering axis, forward or rearward, is known as caster. Adjusting caster incorrectly can result in steering wander.
There are some occasions when an alignment is not required after replacing strut mounts.
This can take place when the struts have no effect on the geometry of the front end, for example, on some wishbone suspension designs.
Can You Replace a Strut Mount Without Removing the Strut?
In some cases, it is “possible” to replace the upper strut mount on a vehicle without removing the strut assembly; however, doing so may be just as, if not more difficult, than removing the strut for replacement.
You are also likely to waste much more effort, and time, fidgeting with a shock you have previously installed than would be practical.
In any event, it is best to always refer to the manufacturer’s service literature for your specific vehicle for a safe and efficient strut mount replacement.
This helps to avoid unnecessary damage to any equipment, or worse, projects the possibility of injury to the person performing the work.