How a Typical Front Suspension Works
Your car's front suspension is made up of a variety of components that work together to provide proper driving comfort. Suspension also keeps your car's tires in contact with the road.
Because suspension repairs are so common, it helps to be able to understand how a typical front suspension works. This way, you have some knowledge that you can rely on the next time your car needs front work.
When the vehicle travels on the road, the springs support the vehicle and absorb the impacts of the bumps, while the shock absorbers control the oscillations of the springs.
How a front suspension works
The operation of the front suspension is quite simple. All suspension systems include springs and shock absorbers. When the vehicle travels on the road, the springs support the vehicle and absorb the impacts of the bumps, while the shock absorbers control the oscillations of the springs.
Some of the most common types of front suspensions
Today, many models of front suspension are used, from the MacPherson strut to the solid axle. The most common arrangements include:
The most common type of front suspension system these days is a MacPherson strut. Two sets of struts (one on each side of the vehicle) are the focal point of the design.
A typical MacPherson strut assembly contains a shock absorber, coil spring, and top bracket with an integrated bearing. Each strut assembly mounts between a steering knuckle and the car body. The struts act as a structural part of the suspension system and the upper brackets provide pivot points to steer the vehicle.
Modified double triangulation
The modified double wishbone (named for the triangle-shaped bottom of the strut) is another type of strut suspension. With this design, the upper ball joints, rather than the strut brackets, provide pivot points for the car's steering system.
There is also another less common type of strut suspension called a modified strut. Unlike other types of strut systems, the modified design does not incorporate the coil spring into the strut assembly. Instead, the coil spring is located on the lower control arm.
Today, many models of front suspension are used, from the MacPherson strut to the solid axle.
Short / Long Arm (SLA)
Many rear-wheel drive vehicles have a short / long link (SLA) front suspension. With this design, each side of the vehicle contains a coil spring (with a shock absorber in the middle) placed between two control arms. Since the upper suspension arms are longer than the lower arms, the configuration is known as a short-arm / long-arm front suspension.
Some four-wheel drive vehicles use a rigid axle front suspension. The design uses two leaf springs (one on each side of the vehicle) that serve as the mounting location for the front differential (axle) assembly. A pair of shock absorbers are connected between the differential case and the frame of the vehicle.
Instead of using leaf springs or coil springs, a torsion bar suspension relies on a pair of torsion bars (one on each side of the vehicle) to absorb road shock and support weight. Each torsion bar connects to a lower control arm at one end and to the vehicle frame at the other.
What are the parts of a front suspension (MacPherson strut design)?
Today, many types of front suspension designs are used. Each type of suspension contains a unique combination of different components.
Since the most common type of suspension is a MacPherson strut, we will focus on the front parts common to this design.
A typical MacPherson strut front suspension system consists of the following components:
There is a front strut assembly on each side of the vehicle. Each acts as a structural part of the suspension and provides an upper pivot point for steering the car.
A typical MacPherson strut assembly contains a damper mounted within a coil spring. The coil spring absorbs road shocks and supports the weight of the vehicle, while the shock absorber limits the oscillations of the coil spring.
The strut assembly also contains a top mount, which includes a bearing that allows the strut to rotate and a dust boot that protects the shock from dirt and debris.
Control arms and ball joints
Suspension arms allow the suspension to move up and down when riding over imperfections in the road. Each control arm has bushings that allow it to move with minimal friction.
A typical control arm includes a ball joint that connects the control arm to the steering knuckle. Ball joints also serve as lower pivot points for the steering knuckles when the driver turns the car's front wheels.
Suspension arms allow the suspension to move up and down when riding over imperfections in the road.
There is a steering knuckle behind each of the car's front wheels. Each steering knuckle connects to the bottom of a strut assembly at one end and a ball joint at the other end. On most vehicles, the outer tie rods are also attached to the sides of the hinges.
The steering knuckles also provide a mounting location for the wheel hubs, which hold the wheels and tires. When the driver turns the steering wheel, the tie rods pull or push the steering knuckles, causing the wheels to roll in or out.
Stabilizer bar and end links
Most vehicles have a type of torsion spring, called an anti-roll bar, that connects to the two lower control arms. As the vehicle turns, the stabilizer bar rotates to prevent roll and improve handling. The stabilizer bar also adds an extra level of stability when riding over rough spots in the road.
At each end of the stabilizer bar, there is an end link that connects to the control arm or strut assembly. Additionally, the stabilizer bar has bushings where it attaches to the frame of the vehicle.
How is a front suspension diagnosed?
Common symptoms associated with worn front suspension components include:
- Unusual landing gear noises
- Abnormal tire wear
- A tough race
- Shimmy before
- Reduced steering performance
Most professional technicians will begin their steering system diagnosis by duplicating the customer's concern through a test drive. From there, they will generally place the vehicle on a forklift for a visual inspection.
If there are no visible problems, the technician will typically use one or more diagnostic strategies to identify the problem.
For example, suppose the customer's complaint is a thud when driving over potholes. In this case, the technician can use a lever to check the various suspension components for excessive movement that could cause unusual noises.
Most professional technicians will begin their steering system diagnosis by replicating the customer's concern through a test drive and typically place the vehicle on a hoist for a visual inspection.
How much does it cost to repair a front suspension?
Front suspension repair costs will depend on the system components to be replaced. Other factors, such as the type of vehicle you drive, will also play a role in the cost.
If you need to rebuild your entire front suspension, you can expect to pay several thousand dollars to have a professional do the work for you. Of course, if you have the tools and know-how, you can save a lot of money by doing the work yourself.