Few car parts and systems do multi-tasking better than the suspension. This collection of struts, shocks, springs and linkages is pivotal in handling, comfort, control and safety. While configurations and parts differ across different vehicles, the suspension tackles road imperfections such as speed bumps and potholes, supports the weight of the vehicle and ensures correct ride height. Moreover, different suspension parts control body roll for effortless turning, aid braking performance for enhanced safety and ensure maximum control with the wheels and tires constantly gripping the ground.
Much of the confusion surrounding vehicle suspension is down to the multitude of parts and layouts. However, this also means different parts for different purposes. A performance car will have a surprisingly different setup than what’s found in heavier vehicles such as trucks. The same applies to common parts, with suspension struts and shocks often being confused, although performing discrete tasks.
Struts vs. Shocks – What’s the Difference?
While both struts and shocks are mentioned interchangeably, they’re two distinct parts with varied roles. Shock absorbers apply damping force to control rebound rates in suspension springs when vehicles encounter potholes and other road imperfections. Suspension struts, on the other hand, not only help with damping tasks like shocks, but are also structural components, supporting the vehicle’s weight, and having a bigger say in braking, handling and overall control.
Strut Assemblies
The obvious difference between struts and shock absorbers is the design and complexity. A strut assembly houses an internal shock to deal with bumps and road irregularities, and an integrated coil spring to add structural support.
Other parts include spring seats that cushion the spring and aid with spring fitment; the strut bearing which allows torsional movement in the shock and helps with steering control, bump stops that limit spring movement and prevent struts from smashing into the chassis and top mounting plates that affix the assembly to the rest of the car.
The bottom of the strut assembly attaches to the steering knuckle and provides a direct link between the vehicle’s suspension and steering systems. This means the handling and steering control of your vehicle is retained even when hitting deeper potholes or larger obstacles.
Types of Suspension Systems with a Strut Assembly
The MacPherson strut assembly is the most common type, and often the first choice for front axles in passenger cars. Though rare, some vehicles also have strut assemblies at the rear axles, minus the steering linkages. The simplified and compact all-in-one solution aptly balances performance and comfort, while providing more seating space in the front row. As a type of independent suspension, it also allows more control of the left and right wheels, meaning impact is constricted when hitting bumps. This produces a more comfortable ride.
What Are the Pros and Cons
The damping role of the strut means it’s also known as a strut absorber. Compared to conventional setups based around shocks, however, vehicles with suspension struts also benefit in a few other ways:
- Simple, low-cost design – integrated strut assemblies combine multiple parts in one simple, streamlined unit. This eases manufacturing costs and aids maintenance.
- More space – the compact design additionally saves space, meaning more room for passengers or other vehicle components. Strut assemblies take up considerably less space compared to conventional suspensions with separate springs and shocks.
- Improved handling – since the parts reduce unsprung weight (below the suspension parts), struts also help with more nimble handling. A few notable performance cars including the BMW M3, Porsche 911, Honda Civic Type R and the Toyota GR86 use MacPherson struts for their low weight and ability to increase traction and grip.
- Improved ride quality and comfort – the calibrated damping and vehicle control in varied driving conditions means struts are good alternatives to more complicated and expensive suspension without forgoing comfort and safety.
- Flexibility – different sizes to handle varied weight loadings allow struts to be used in multiple vehicle types, from everyday compact cars to larger SUVs.
- Durability – reduced maintenance stems from the durability of strut assemblies to contain common stresses cars experience in daily driving tasks.
There are, however, a few negatives to consider. If adjustability in ride height or compression rates, or improved control in heavier vehicles is more important, then look to coilovers or double wishbone setups. Strut assemblies offer little to no adjustability, meaning your car is stuck with the stock handling characteristics. For the models mentioned above, this is in no way a bad thing. Additionally, Machperon struts can affect camber, leading to advanced tire wear. And since the parts are directly attached to the chassis, there’s a slightly higher transmission of noise and vibrations creeping into the cabin.
Signs That You Need a Replacement
Regular inspections and maintenance extend the lifespan of strut assemblies well above the claimed 50000 miles in most vehicles. This though largely depends on how and where you drive. On poorly maintained roads, and when you’re more eager on the gas, that number plunges leading to advanced wear.
Common signs that the struts are nearing a replacement are increased tire wear (in the same and between left and right wheels), a bouncy ride even at lower speeds, excessive nose-dive when nudging the brakes, noticeable vibrations through the steering wheel accompanied with higher noise levels, and reduced stability in turns.
One or a combination of factors can significantly impact handling and safety. The vehicle becomes harder to control, braking distances increase, there’s more body roll and ride harshness and a higher risk of wear and damage to related parts and car systems, including the steering, brakes and chassis.
Buying Tips
Buy struts that are compatible with your vehicle. OE-spec assemblies usually include mounts and strut boots, are easy to install, take less time and labor than conventional suspension setups, and are also cheaper to buy. Replacements should restore your vehicle’s stock ride height, drivability and handling, but there are also variants meant for different driving scenarios, such as potholed roads or towing trailers with parts designed for higher stresses.
Performance types from established suspension brands promise better handling with reduced NVH levels. For vehicles with stock air suspension, conversion strut kits are an inexpensive way to restore drivability and ride comfort without spending thousands on repairs. Ensure the parts come with warranties and get a professional installation to get all the advertised benefits of new struts.