Strut Mounts: Should You Replace Them in Pairs?

When it comes to maintaining your vehicle's intricate suspension system, certain components often fly under the radar, yet their role is absolutely critical. Among these are the top strut mounts. Often overlooked until a distinct noise or handling issue arises, these mounts are fundamental to how your car rides, steers, and ultimately, your safety on the road. Understanding their function, recognising the signs of wear, and knowing the best practices for replacement can save you significant time and money in the long run.

Top strut mounts serve as the vital connection point between your vehicle's coil spring and damper strut assembly and its chassis. In essence, they are the pivot and insulator, allowing the strut to move with the suspension while isolating the cabin from road noise and vibrations. On vehicles equipped with all-round independent suspension, you'll find these mounts at both the front and rear, quietly working to ensure a smooth and controlled driving experience. Despite their paramount importance, they are frequently the last component considered when diagnosing perplexing suspension noises, primarily because many other parts can also be the culprits.

Deciphering the Clues: Identifying Strut Mount Failure

Diagnosing a worn or failed top strut mount often begins with an audible complaint from the driver. If you're hearing unusual noises, particularly at low speeds or when navigating uneven surfaces, your strut mounts could be signalling distress. Common symptoms include:

• Clunking or Knocking Noises: Especially noticeable when turning the steering wheel from lock to lock, driving over potholes, speed bumps, or rough terrain.
• Grinding or Creaking Sounds: These can indicate issues with the bearing within the mount, particularly during steering inputs.
• Loose or Wandering Steering: A less direct symptom, but worn mounts can contribute to a vague feeling in the steering, making it harder to keep the vehicle in a straight line.
• Uneven Tyre Wear: While many factors contribute to this, failing strut mounts can alter suspension geometry, leading to premature and uneven wear on your tyres.

Before jumping to conclusions about strut mounts, however, it's always best practice to first inspect other common suspension culprits. Checks should include suspension arms, link bars, ball joints, anti-roll bar bushes, and track rod ends. If these components are found to be in full working order, then a thorough assessment of the strut assembly, including the top strut mount, becomes the logical next step for any competent technician.

The Lifespan of Suspension Components: A Proactive Approach

Like all wearing parts on a vehicle, suspension components are subject to fatigue and eventual failure. To maintain your vehicle's suspension system in optimum working order, it is generally advised that serviceable items such as shock absorbers and dampers are replaced approximately every 50,000 miles. This proactive maintenance helps preserve ride comfort, handling, and safety.

Crucially, a golden rule in suspension maintenance is this: if a suspension strut is being replaced, the top strut mount should be replaced at the same time. To dismantle the entire system again at a later date, purely to replace an inexpensive mount, is simply uneconomical. The labour involved in accessing and replacing the strut assembly is considerable, making it highly cost-effective to replace both components simultaneously, even if the mount doesn't appear severely worn.

Why Do Strut Mounts Fail Prematurely?

While 50,000 miles is a general guideline, some strut mounts can fail prematurely, even at low mileages. This phenomenon has been observed in several instances, particularly with certain Fiat applications, including models like the Fiorino/Qubo (and their Citroën Nemo/Peugeot Bipper/Bipper Tepee counterparts), Doblo, Grande Punto, and Ducato. These early failures can often be attributed to several factors:

• Poor Design or Specification: In some cases, original equipment (OE) manufacturers have had to redesign and upgrade mounts due to inherent weaknesses in the initial design.
• Water and Grit Ingress: Road spray, dirt, and grit can penetrate the bearing within the strut mount, leading to rust, corrosion, and ultimately, seizure.
• Jet Washing: Ironically, trying to keep your car clean can sometimes contribute to failure. High-pressure jet washing under the wheel arches can force water into the delicate bearings of the strut mount, accelerating wear and corrosion.
• Freezing Conditions: If water has already penetrated the bearings, freezing temperatures can cause it to expand, leading to further damage and accelerated failure.

Understanding these common causes can help in preventative measures and in identifying why a mount might have failed sooner than expected.

The Domino Effect: Consequences of Neglecting Worn Mounts

Failing to address a worn top strut mount can have a detrimental knock-on effect on other crucial components within your vehicle's suspension and steering system. A deteriorating mount will quickly worsen, leading to:

• Accelerated Shock Absorber Wear: The shock absorber will be subjected to increased stress and movement it wasn't designed for, significantly shortening its lifespan.
• Uneven Tyre Wear: As mentioned, altered suspension geometry can cause tyres to wear unevenly, requiring premature replacement and potentially affecting grip and safety.
• Steering Pull: The vehicle may develop a tendency to pull to one side, requiring constant steering correction from the driver. If left unaddressed for too long, this effect can sometimes persist even after a new top strut mount has been installed, due to other components having already taken a permanent set or suffered damage.
• Compromised Handling and Stability: The overall handling of the vehicle will suffer, leading to a less predictable and potentially unsafe driving experience.

These consequences highlight the importance of timely replacement to prevent a cascade of further, more expensive repairs.

Should Strut Mounts Be Replaced Together? The Expert Recommendation

This brings us to the core question: is it necessary to replace both top strut mounts at the same time? While it's not strictly mandatory to replace both mounts together if only one is found to be faulty, the overwhelming advice from automotive experts is to change complete struts in pairs. Consequently, it is highly advisable to replace the top strut mounts simultaneously with the struts on both sides of an axle.

There are several compelling reasons for this recommendation:

1. Economic Efficiency: As previously noted, the labour involved in removing a strut assembly is significant. The top strut mount itself is a relatively low-cost part in what is a high-labour process. Replacing both at once ensures you only pay for the extensive labour charge once, rather than potentially paying it again in the near future for the other side.
2. Symmetrical Performance: Suspension components wear symmetrically. If one strut mount has failed or is showing significant wear, it's highly probable that the mount on the opposite side has experienced similar stresses and is also nearing the end of its service life. Replacing them in pairs ensures balanced performance and prevents uneven handling characteristics.
3. Preventative Maintenance: Even if the second mount isn't visibly failing, replacing it proactively helps avoid a return visit to the garage for the same job shortly after.

The job naturally involves removing the struts from the vehicle and compressing the coil spring using a specialised spring compressor to safely enable the removal and replacement of the top strut mount. This intricate process further underscores the value of performing the task once for both sides.

Here's a quick overview of symptoms and their implications:

Post-Replacement Best Practices: Alignment is Key

Following any work related to the steering or suspension system, including the replacement of struts and mounts, it is considered best practice to have the vehicle's wheel alignment, or 'tracking', checked and adjusted. This crucial step ensures that all components are correctly aligned to the manufacturer's specifications. Failure to do so can lead to several problems, including:

• Rapid and uneven tyre wear
• Poor handling and steering response
• Increased fuel consumption
• Premature wear on other suspension and steering components

Proper alignment not only prevents further issues but also restores the vehicle to its correct specification, ensuring optimum performance and safety.

Frequently Asked Questions About Strut Mounts

Q: Are the front strut mounts meant to have play when the car is jacked up?

A: Yes, it is quite common and often by design for front upper strut mounts to exhibit a certain amount of 'play' or movement when the suspension is in an unloaded state – i.e., when the vehicle is jacked up and the wheels are hanging loose. This is due to the way the rubber insulator and bearing components are designed to function under load. When the full weight of the car is bearing down on the suspension, the rubber cup at the very top of the strut is pushed up against the inner wing, taking up this free play. As long as there are no obvious signs of damage, excessive wear, or maladjustment, this movement when unloaded is usually perfectly normal. For instance, some Ford Fiesta models were known to have a significant amount of lateral play in their upper mounts, which was deemed a design characteristic rather than a fault. However, if there is any noticeable movement in the strut top mounts when the car is on the ground and fully loaded, this could indicate wear in the support bearing or other components and may constitute a 'reason for rejection' during an MOT inspection.

Q: Can a bad strut mount cause a knocking noise when going over bumps?

A: Absolutely. A knocking or clunking noise, especially when driving over bumps, potholes, or uneven surfaces, is one of the most common and definitive symptoms of a failing strut mount. The noise typically occurs when the worn rubber or bearing allows excessive metal-on-metal contact within the assembly, or when the strut shaft moves freely within the mount. This symptom warrants immediate investigation.

Q: How long do strut mounts typically last?

A: The lifespan of strut mounts can vary significantly depending on vehicle application, driving conditions, and quality of the part. Generally, they are designed to last as long as the shock absorbers, often around 50,000 to 100,000 miles. However, as discussed, factors like poor design, water ingress, or harsh driving conditions can lead to premature failure.

Q: Is it safe to drive with a bad strut mount?

A: While you might be able to drive with a worn strut mount for a period, it is not recommended and can be unsafe. A failing strut mount compromises the integrity of your suspension system, leading to poor handling, reduced steering control, increased stopping distances, and accelerated wear on other vital components like tyres and shock absorbers. The vehicle's stability and your ability to control it, especially in emergency manoeuvres, will be significantly impaired, making it a safety risk that should be addressed promptly.

In conclusion, while top strut mounts may not always be the first suspect in suspension diagnostics, their role is undeniable. Understanding their function, recognising the signs of failure, and adhering to best practices for replacement – particularly the economic and performance benefits of replacing them in pairs with new struts – are essential for maintaining your vehicle's safety, handling, and overall longevity. Don't underestimate these small but mighty components; they are integral to a comfortable and controlled journey.

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