1. The Suspension System
Dampers
Strut Assembly

2. The Suspension system
A vehicle needs a suspension system to cushion and damp out road shocks, so providing comfort to the passengers and preventing damage to the load and vehicle components. A spring is fitted between the wheel and body of the vehicle, this allows the wheel to follow the road surface. The tyre plays an important role in absorbing small road shocks, they are often described as the primary form of suspension.
The vehicle body is supported by the suspension springs, which are located between the body and wheel axles. Together with the damper, these components are referred to as the suspension system. The weight of the vehicle including its load acts on the springs. The springs and other components compress and expand as the wheel hits bumps or holes in the road, this allows the wheel to move up and down without moving the vehicle body.
When the road wheel hits a bump, it moves upwards with some considerable force, this energy is absorbed and stored the suspension spring, this energy is then transferred to the suspension damper and changed into heat energy, this prevents the suspension spring from continually bouncing/oscillating and affecting the ride of the vehicle.

3. Terminology
Spring – The part of the suspension system that takes up the movement or shock from the road or vehicle movement. The energy of the movement is stored in the spring. There are many different forms of spring, ranging from steel coil to a pressurised chamber of nitrogen.
Damper – The energy stored in the spring after the bump has to be got ride of, otherwise the spring would oscillate ( bounce up and down). The damper reduces these oscillations by converting the energy from the spring into heat. If working correctly, the spring should stop moving after just one bounce and rebound.
Shock absorber – This term describes the action of the spring. It is often used to incorrectly describe a damper.
Strut – Often the combination of a coil spring with a damper inside it, between the wheel and stub axle and inner wing. This is a very popular type of suspension.
Wishbone – A triangular shaped component with two corners hinged in a straight line on the vehicle body and the third corner is hinged to the moving part of the suspension,
Sprung mass (weight) – The weight that is supported by the road springs.
Unsprung mass – The weight of the components fitted between the road wheels and springs e.g. wheels, tyres, brakes and parts of the steering and suspension. This weight should be kept to a minimum

4. Terminology
Bump stop – When the vehicle hits a particularly large bump, or is carrying a heavy load, the suspension may bottom out ( reach the end of its travel). The bump stop, usually made of rubber, prevents metal to metal contact that would cause damage.
IFS – Independent front suspension.
IRS - Independent rear suspension
Independent suspension – This allows a wheel of the vehicle to move without affecting the one at the other side.
Link - A very general term to describe a bar or similar component that holds or controls the position of another component. Other terms may be used such as tie bar.
Beam axle - A solid axle from one wheel to the other. Not now used on the majority of light vehicles, but still come on heavy vehicles as it makes a very strong construction.
Axle – Part of the suspension the wheel rotates on. A live axle also has engine power transmitted through it to the wheel. A Dead Axle only supports the vehicle.
Gas/fluid suspension – Some vehicles use pressurised gas/fluid as the spring, on some vehicles, these units are interconnected

5. Non – Independent Beam Axle Suspension
Advantages – strong, could support very heavy loads.
Disadvantages – Non independent, engine and vehicle body would have to be mounted high up to allow for the movement of the beam. High level of un-sprung mass. Stiff springs where used due to the limited amount of beam movement that could be aloud.

6. Independent Suspension
Solid axle - tilts with road bumps.
Both wheels tilted.
Independent suspension - one wheel moves without affecting other.
Control arm pivots, this helps to keep the wheel upright.
Preferred system for modern vehicles.
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7. Leaf Spring Flat spring steel plates. Front end pivot fixed to frame.
Swinging shackle at rear permits change of length.
U-bolts and plates clamp spring to axle housing.
Now only used on few rear suspension systems.
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8. Coil Spring Four main types of spring: Coil Spring Leaf Spring
Torsion Bar
Air Spring
Coil Spring
Spring-steel rod wound into coil.
Suited to independent suspension.
Most common.
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9. Torsion Bar Torsion bar attached to vehicle frame.
Control arm attached to torsion bar.
Torsion bar
Strut rod keeps control arm stable.
When control arm moved, torsion bar resists movement.
Track control arm ball joint
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10. Elementary Suspension System
Suspension system supports the weight of vehicle and gives a smooth ride.
Track Control arm pivots on frame.
Steering knuckle ball-jointed to control arm.
Coil spring and damper shown.
Components attached to frame.
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11. Track Control Arm/ Wishbone
Stub Axle Carrier
Holds the stub axle carrier, bearing support or axle housing in correct alignment
Connected by ball joint.
Bushes
Bushes act as bearings.
Free to move up and down with suspension.
Ball joint
Rear suspension - may have bushes both ends.
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12. Ball Joints Ball Joints allow for the movement
Drive shaft
Stub Axle carrier
Lower ball joint
Upper ball joint
Hub
Ball Joints allow for the movement
of the steering and suspension.
Front wheel Drive -
Allows the Stub Axle Carrier to be turned by the steering system
Drive shaft must allow for suspension and steering movement.
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13. The Suspension Damper Reduce spring oscillations.
Upper end attached to frame, lower end to suspension unit.
Piston and valve assembly moves in oil-filled cylinder.
Movement is controlled by valve restriction.
Some have pressurized gas chamber that reduces air bubbles.
Enclosed in dust cover.
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14. MacPherson Strut Damper
Combined spring and Damper.
Upper pivot is strut mount.
Bearing to allow steering.
Bump stops or rebound bumpers prevent metal/metal contact.
Damper inside strut.
Lower spring seat on shock absorber body.
Metal strut tube houses shock absorber reservoir, valve, pressure tube etc.
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15. Stabilizer bar (Anti – Roll)
Stabilizer (Anti - Roll) Bar
Prevents excessive body lean when turning.
Links both the lower control arms together.
When cornering, outside of body drops and twists the bar to limit sway.
Stabilizer bar (Anti – Roll)
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16. Wheel Alignment Topics covered in this presentation: Caster Camber
Steering Axle Inclination

17. Suspension/Steering Wheel Geometry (Alignment)
Introduction – Most manufactures provide adjustment methods for both front and rear wheel alignment.
Correct wheel alignment is essential for vehicle stability, lighten steering, prolong tyre life and steering recovery (self centring)
Only when all the suspension/steering angles are correctly set can the above be achieved.

18. Caster The stub axle carrier tilts to the rear for positive caster.
This causes the wheels to resist turning and tend to return to “straight ahead” position.
The stub axle carrier tilts to the front for negative caster. The wheels turn more easily (less steering force required) but tend to follow road imperfections.
Caster is measured in degrees from the vertical.
Positive caster is more often found on vehicles with power steering, (harder to turn).
Front
Negative caster is more common for manual steering, (easier to turn).

19. Camber
Camber is a vertical inward or outward tilt of the wheel and tyre assemblies.
Prevents uneven tyre wear on outer or inner tread.
Loads the larger inner wheel bearing.
Aids steering by putting the weight on the inner end of the spindle.
Positive camber - top of wheels tilt outward.
Negative camber - top of wheels tilt inward.

20. Swivel Axis / Kingpin Inclination
The swivel axis inclination is the vertical axis of the ball joints, king pins or MacPherson strut tube.
This is normally an inward tilt.
In a similar way to caster, it aids directional stability, helping the steering wheel to return to the straight-ahead position. This angle can also change the steering radius and camber.
Small adjustments can be made on some vehicles, but normally components must be replaced if there is an error.