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What is Suspension System: Types, Parts, Working and More

In this article, you learn about the suspension system and types in automobile vehicle and working of each suspension system.

Suspension System and Types

The automobile vehicles frame and body are mounted on the front and rear axle not directly but through some form of springs and shock absorbers. This is done to damp to road shocks transmitted parts which perform this function are collectively called a suspension system.

Suspension system in a car

Thus, the suspension system includes springs, shock absorbers and their mountings. The suspension system of a motor vehicle is divided into the rear end suspension and front end suspension.

Types of Suspension System

Following are the 15 different types of the suspension system:

  1. Front End Suspension System
  2. Rigid axle front suspension.
  3. Independent front suspension
  4. Twin I-Beam Suspension System
  5. Single I-Beam Front Suspension System
  6. Independent Front End Suspension Using Torsion Bar
  7. Parallelogram Type Independent Front Suspension
  8. Struck and Link Type Suspension System
  9. Trailing Arm Independent Front Suspension
  10. Sliding Types Suspension System
  11. Vertical Guide Suspension System
  12. Rear End Suspension System
  13. Longitudinal leaf spring rear end suspension
  14. Transverse leaf spring rear end suspension
  15. Coil spring rear end suspension

Read also: Rear Axles, Front Axle and Stub Axle

Functions of Suspension System

  1. To prevent the stability of the vehicle in pitching or rolling while in motion.
  2. To safeguard the occupants from road shocks.
  3. Suspension system prevents the road shocks from being transferred to the vehicle frame.
  4. To provide good road holding while driving, cornering and braking.
  5. To maintain proper steering geometry.

Requirements of a Suspension System

  1. Minimum deflection is consistent with required stability.
  2. Comparability with other vehicle components-type, frame wheelbase, steering linkage.
  3. Minimum wheel hop.
  4. Low maintenance and operating costs.
  5. Low initial cost.
  6. Minimum weight
  7. Minimum wear.

Read also: What is a steering system? and how it works? [The complete guide]

1. Front End Suspension System

The front end suspension is more complicated than the rear end suspension because the front wheels not only move up and down with respect to the car frame but also swing at various angles to the car frame for steering.

In order to permit the front wheels to swing to one side or the other for steering, each wheel is ported on a spindle which is part of the steering knuckle. The steering knuckle is then supported through ball joints, by upper and lower control arms which are attached to the car frame.

Types of Front End Suspensions System

The Front End Suspensions May Be of Two Types

  1. Rigid axle front suspension.
  2. Independent front suspension

1. Rigid Axle Front Suspension

This type of suspension was universally used before the introduction of independent front wheel suspension. It may use either two longitudinal leaf spring, as shown in the figure, or on transverse spring, usually in conjunction with shock absorbers. These assemblies are mounted similar to rear leaf spring suspensions.

Rigid Axle Front Suspension

In this type of suspension, the front wheel hubs rotate on antifriction bearings on steering spindle which are attached to the steering knuckles. To permit the wheels to be turned by the steering gear, the steering spindle and steering knuckle assemblies are hinged on the axle ends.

The pin that forms the pivot of this hinge is usually referred to as the kingpin or steering knuckle pin. Where the forked portion is integral with the steering knuckle and fits over the end of the axle, the construction is known as Reverse Elliot. In Elliot type construction, the ends of the axle are forked to hold the steering knuckle extension between the ends.

2. Independent Front Suspension

In this type of suspension, each front wheel is independently supported by a coil, torsion bar, or leaf spring. Most of the passenger cars now use the independent front suspension in which the coil spring system is the most common.

Read also: Four Wheel Steering System

Types of Independent Front Suspension

1. Twin I-Beam Suspension System

Different types of front suspension, besides coil spring type, are also in use. The twin I-beam construction is another type, used on some models of Ford trucks. Each front wheel is supported at the end by a separate I beam.

Twin I-Beam Suspension System

The ends of the I-beams are attached to the frame by pivots. The wheel ends of the two I-beams are attached to the frame by radius arms, which prevent backward or forward movement of the wheels. This type of suspension provides more flexibility.

2. Single I-Beam Front Suspension System

Single I-beam front suspension is employed in larger vehicles. The I-beam has a hole in each end through which a kingpin is assembled to hold the steering knuckle in place. Each end of the I-beam is supported by a leaf spring.

3. Independent Front End Suspension Using Torsion Bar

This type of suspension system, a steel rod, known as a torsion bar, act as a spring to hold the upper and lower control arms parallel under load. The front end of the rod is of hexagonal shape to fit tightly into an opening in the lower control arm.

Its rear reaction is also the hexagonal shape to fit tightly into an opening in an anchor attached to the frame cross member. A seal hides the hexagonally shaped end of the torsion bar.

The torsion bar gets twisted due to the forces on the wheel assembly outer end of the lower control arm. The torsion bar is designed to balance these forces so that the lower arm is kept at a designated height.

Front End Suspension Using Torsion Bar

The height can be adjusted by a tightening mechanism at the anchor end which twists the rod by means of an adjusting bolt and swivel. A strut rod is used to keep the suspension in alignment.

This suspension is able to protect road shock causing the lower arm to twist the torsion bar. When the wheels are no longer under stress, the arm returns to normal.

4. Parallelogram Type Independent Front Suspension

The figure shows the simplified diagrams of the independent front suspensions using a coil, torsion bar and leaf spring. Basically, the system is known as parallelogram type independent front suspension. It consists of an upper and lower link connected by stub axle carrier.

In general, the lower link is larger than the upper and they may not be parallel. This arrangement maintains the track width as the wheels rise and fall and so minimize tyre wear caused by the wheel scrubbing sideways.

5. Struck and Link Type Suspension System

This type of suspension system is unusually for integral body construction because the loading points are widely spaced. The normal top link is replaced by a flexible, mounting and the telescopic damper acts as the kingpin. This suspension system known as the Mac Pherson System has slight rolling action and absorbs shocks easily.

6. Trailing Arm Independent Front Suspension

Trailing arm independent front suspension maintains constant track and wheel attitude with a slight change in wheelbase and caster angle. A coil spring is attached to the trailing arm which itself is attached to the shaft carrying the wheel hub. When the wheel moves up and down, it winds and unwinds the spring. A torsion bar has also been used in certain designs in place of the coil springs.

7. Sliding Types Suspension System

In this type suspension system, the stub axle can move up and down as well as rotate in the frame members. Track, wheel attitude and wheelbase remain unchanged throughout the rise and fail of the wheel.

8. Vertical Guide Suspension System

In the vertical guide suspension system, the kingpin is attached directly to the cross member of the frame. It can slide up and down, thus compressing and expanding springs.

Coil Spring Front Suspension.

There are 3 types of coil spring front suspension.

1. In the first type, the coil spring is located between the upper and lower control arms. The lower control arm has one point of attachment to the car frame.

Coil Spring Front Suspension type 1

2. In the second type, the coil spring is located between the upper and lower control arms. The lower control arms have two points to the attachment to the car frame.

Coil Spring Front Suspension type 2

3. In the third type, the coil spring is between the upper control arm and spring tower or housing that is part of front end sheet metal work.

Coil Spring Front Suspension type 3

2. Rear End Suspension System

Following are three types of rear-end suspensions generally found in vehicles.

  1. Longitudinal leaf spring rear end suspension
  2. Transverse leaf spring rear end suspension
  3. Coil spring rear end suspension

Longitudinal and Transverse Leaf Spring Rear End Suspension

Longitudinal leaf spring and coil spring rear end suspensions are widely used in modern vehicles. Transverse leaf spring rear end suspension is used in conjunction with the Hotchkiss drive, the leaf springs must be made strong and resilient enough to transmit the driving thrust and torque to resist sideways, in addition, to hold the spring weight of the body.

Longitudinal Leaf Spring Rear End Suspension

The spring weight is kept as less as possible, in order to improve the side of the vehicle. Because the springs do not generally support the wheels, rims, tyres, brakes and rear axles, the weight of these parts is called the spring weight. The spring is clamped the rear-axle housing by U-bolts, its every end is pivoted to the frame, by means of eyes formed in the ends of the longest leaf.

Leaf Spring Rear End Suspension

One end of the long leaf is secured to the front hanger by a bolt and the other end to the rear hanger by spring shackles. Both the hangers are bolted to the frame. The spring elongates in compression and shortens in expansion. This change in length of the spring is compensated by a shackle.

At the middle position of the spring length, the rebound clips are placed. They are loose enough to permit the leaves to slide on the other, and yet tight enough to permit the leaves together when the spring rebounds. The spring eyes are usually provided with bushings or some anti-friction material, such as bronze or rubber.

rear end suspension with leaf type auxiliary springs and torque rods

The figure shows a heavy-duty truck rear end suspension with leaf type auxiliary springs and torque rods. This type of suspension is used in truck intended for more severe operations and with rear axle loading exceeding 10000 kg. The figure shows rear-end suspension of a car with Hotchkiss drive.

Coil Spring Rear End Suspension

The figure shows coil spring rear end suspension. This type of suspension is always used in conjunction with torque tube, torque reaction link, or torque rod drive. Therefore the coil springs are not subjected to driving thrust or twist.

Coil Spring Rear End Suspension

Stabilizers and radius rods are also used which relieve the coil springs of all stresses except those acting in a vertical direction. The stabilizer prevents excessive roll or sideways when the car is concerning.

The radius rod keeps the rear axle and frame in lateral alignment. The coil springs are seated in pan-shaped brackets spring seats attached to the rear axle.

De-Dion and Independent Type Coil Spring Rear End Suspensions

The figure shows De-Dion and independent type coil spring rear end suspensions. At (A), the rigid De-Dion tube is located longitudinally by two parallel links and laterally by a watt linkage. The tube maintains the track at a constant width.

It is to be noted that De-Dion suspension is not an independent suspension because a tubular axle connects and supports both the wheels. At (B) is shown a rear-end suspension using the radius arm. This is an independent rear end suspension.

In traverse leaf spring rear end suspension, a single transverse spring is used. Such springs are mounted in an inverted position parallel to and above the rear axle. Each end is shaken to the axle.

The transverse rear springs are always used in combination with torque-tube drive, and hence they do not carry the driving thrust and torque.

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Saif M
Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at theengineerspost.com