1. A
PRESENTATION on
“ SUSPENSION SYSTEM ”

2. Suspension Systems Topics covered in this presentation:
Basic Suspension System
Spring Types
Suspension System Construction

3. Basic Suspension System
The primary purpose of a suspension system is to support the weight of the vehicle and give a smooth ride.
It is desirable that it should also:
allow rapid cornering without body roll when the car leans to one side.
keep tyres in firm contact with the road at all times and conditions.
prevent body squat (tilting down at rear) when accelerating.
prevent body dive (tilting down at front) when braking.
allow front wheels to turn for steering.
keep the wheels vertical and in correct alignment at all times.

4. Elementary Suspension System
In a modern vehicle, the typical suspension components are:
Coil spring
A control arm that pivots on the vehicle frame.
Shock absorber
The steering knuckle is ball-jointed to the control arm to allow for vertical and horizontal movements.
Steering knuckle
Control arm
This simple example has a coil spring and built-in shock absorber.
Frame
All of the components are attached to the frame.

5. Independent suspension
A solid axle tilts with road bumps.
Solid axle
This causes both wheels to be tilted.
Independent suspension allows one wheel to move up or down without appreciably affecting the other.
Independent suspension
The design of the control arm keeps the wheel upright.
This is the preferred system for most modern vehicles.

6. Coil Spring There are four main types of springs in common use:
Leaf Spring
Torsion Bar
Air Spring
Coil spring
Coil Spring
This consists of a spring-steel rod wound into a coil.
It is ideally suited to independent suspension.
This is the most common type of spring used by modern vehicles.

7. Leaf Spring Flat plates of spring steel are bolted together.
The front end of the spring is bolted directly to the frame.
A swinging shackle at the rear permits the length of the spring to change when it is flexed.
U-bolts and plates clamp spring to axle housing.
This type used to be common but is now only used on a few rear suspension systems.
Swinging shackle

8. Steering knuckle connects onto control arm
Torsion Bar
One end of the torsion bar is fixed to the vehicle frame.
The other end of the torsion bar is attached to the control arm so that it twists as the control arm moves up or down.
A strut rod prevents front or rear movements of the control arm.
When the control arm is moved by the suspension, the twisting motion of the torsion bar resists the movement.
Torsion bar
Vehicle frame
Control arm
Steering knuckle connects onto control arm
Strut rod

9. Air Spring
This is normally a two-ply rubber cylinder filled with compressed air.
It has similar rebound reaction to a coil spring.
The air spring is much lighter in weight, compared with its steel sprung equivalent, resulting in increased economy and an adjustable controllable ride.
Rebound (expansion) allows the control arm to move down when there are hollows in the road surface.
This is especially adaptable to automatic levelling systems.

10. Control Arm
A control arm holds the steering knuckle, bearing support or axle housing.
Bushes
The control arm is connected to the steering knuckle by a ball joint.
Ball joint
Control arm bushes act as bearings.
The control arm is free to move up and down with the suspension.
Control arm
Steering knuckle
Rear suspension control arms may have bushes at both ends.

11. Ball Joints Ball joint is short for ball-and-socket joint.
Upper pivot ball joint
Steering knuckle
Ball joints allow limited movement in all directions.
Two pivots, one above and one below, keep the wheel vertical.
Drive shaft
A front wheel system is shown, including a steering knuckle.
Hub
The drive shaft must allow universal movement.
Lower pivot ball joint

12. Pressurized gas chamber
Shock Absorber
Top mount
The function of a shock absorber is to reduce spring oscillations (up and down movements) following a road shock.
The upper end (top mount) is attached to the frame and the lower end (bottom mount) to the suspension unit.
Dust cover
A piston and valve assembly moves in an oil-filled cylinder. Movement is controlled by the valve, rate-of-flow, restriction.
Oil cylinder
Piston and valve assembly
A pressurized gas chamber is sometimes added to prevent air bubbles in the oil causing foaming.
Pressurized gas chamber
Bottom mount
The cylinder is enclosed in a dust cover.

13. Stabilizer (Sway) Bar
The purpose of the stabilizer bar is to prevent excessive body leaning when turning.
Links both the lower control arms together.
When one end of the bar is deflected in either direction (up or down), the bar tries to pull the other side in the same direction, this has the effect of stabilizing and controlling the suspension.
Stabilizer bar
When cornering, the outside of the body tends to drop, which twists the bar and limits the amount of the sway.