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Suspension Fundamentals

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Presentation on theme: "Suspension Fundamentals"— Presentation transcript:

1 Suspension Fundamentals
Chapter 63

2 Objectives Identify parts of typical suspension systems
Describe the function of each suspension system component Compare the various types of suspension systems

3 Introduction Vehicle chassis includes:
Frame Shocks and springs Steering parts Tires Brakes Wheels Suspension system part of the chassis

4 Suspension Supports the vehicle, cushions the ride
Holds tire and wheel in correct position Sprung weight is weight supported by car springs Reducing unsprung weight increases control

5 Suspension Sprung weight includes
Powertrain Body and frame Anything carried by the weight of springs Sprung components insulated from road surface

6 Frame and Suspension Designs
Cars designed to be lightweight Improves fuel economy Newer cars have front-wheel drive Older cars had rear-wheel drive Front-wheel-drive cars made with sub-frame and uni-body construction

7 Frame and Suspension Designs
Most FWD cars and some RWD made with sub-frame Sub-frame supports the engine, transaxle, steering/suspension system

8 Frame and Suspension Designs
Uni-body - sheet metal floor pan with small sections of frame at front and rear

9 Frame and Suspension Designs
Rear-wheel-drive cars made with a ladder or perimeter frame

10 Springs Support the load of the car
Absorb the up-and-down motion of wheels Coil spring most common spring used in front and rear of passenger cars

11 Springs Support the load of the car
Torsion bar – straight rod that twists when working as a spring Mounted in the chassis

12 Springs (continued) Leaf spring – long, flat strip of spring steel rolled at both ends to accept rubber insulated bushing As leaf spring is deflected it becomes stiffer

13 Springs (continued) Air spring – rubber air chamber attached by tubing to an air compressor

14 Suspension Construction
When wheel attached to rigid axle goes over a bump, other wheel also affected When wheel with independent suspension goes over a bump, only that wheel affected

15 Suspension Construction
Control arms – used on independent suspensions, allow springs to deflect

16 Suspension Construction
Rubber bushings keep suspension parts separate

17 Suspension Construction
Ball joints attach control arm to spindle

18 Suspension Types Double Wishbone
Two equal length control arms which are parallel Double wishbone suspensions have improved directional stability

19 Suspension Types Short and long arm suspension (SLA)
Two unequal control arms which are not parallel Shorter control arm slants down toward outer end

20 Suspension Types Macpherson Strut Suspensions
Coil spring and shock absorber incorporated into front suspension Single control arm on bottom Spindle attached to strut housing Strut bearing at top allows entire unit to rotate

21 High-Performance Suspensions
Multilink suspension – independent suspension with more than two control arms Extra links keep wheel in more precise position during cornering and on bumps

22 Shock Absorbers Four shock absorbers
One at each vehicle corner Shock absorbers dampen spring oscillations Convert spring energy into heat energy Poor shock absorbers aggravate SUV rollovers

23 Hydraulic Shock Absorber Operation
In hydraulic shock absorbers one end attached to suspension, other to car body or frame

24 Hydraulic Shock Absorber Operation
Force oil through valves Generates hydraulic friction Converts motion energy into heat energy Two chambers with piston that forces fluid through valve from one chamber to the other

25 Hydraulic Shock Absorber Operation
Front and rear shocks usually different Double-acting – control both up and down motion


27 Compression and Rebound Resistance
Hydraulic shocks sensitive to velocity Faster piston moves in shock, higher resistance Series of orifices and valves manages flow

28 Compression and Rebound Resistance
Compression damping controls unsprung tire weight Works with spring to keep tire in contact with road Rebound damping controls excess chassis motion as shock extends

29 Bump Stops and Limiters
Shock absorber movement follows travel of vehicle suspension If shocks or struts reach extreme travel limit, damage results

30 Bump Stops and Limiters
Shock must be installed in nearly vertical position

31 Bump Stops and Limiters
Aeration – hydraulic fluid mixes with air Shock operation suffers when fluid aerated

32 Gas Shocks Invented to control cavitation or foaming of oil
Pressurizing oil column in shock absorber keeps the bubbles in the solution Some gas shocks have pressurized gas-filled cell Takes place of free air in normal shock Rear shock absorbers on RWD vehicles mounted in two ways: Slanted inward toward rear at top On shock mounted in front of axle, other behind

33 Air Shocks/Leveling Devices
Shocks not designed to carry vehicle weight Aftermarket products use shock to correct vehicle height Air shocks Coil springs mounted on outside of shock body Disadvantages of leveling vehicle using shocks Shocks and shock mounts prone to breakage Coil spring shock prevents body roll

34 Air Shocks

35 Coil spring shock (coil-over)

36 Other Front End Parts Other front end parts attached to suspension to control the ride Stabilizers and strut rods insulated from front suspension parts with rubber bushings

37 Stabilizer Bar Connects lower control arms on both sides of vehicle
Reduces sway Functions as a spring when car leans to one side If one wheel moves up, bar twists as it tries to move the other wheel along with it

38 Stabilizer Bar Links Attach the sway bar to the control arm …

39 Stabilizer Bar Links … or the strut

40 Ball joints attach the control arm to spindle
On suspensions with two control arms, ball joints function as load carrier or follower ball joint

41 Suspension Leveling Systems
Passive systems have firm or soft ride With electronically controlled systems, computer reacts to signals from sensors at wheels Changes amount of air in air springs Electronically controlled shock absorbers have variable valving Magneto-rheological (MR) uses fluid that rapidly changes viscosity in response to computer Active suspensions have double-acting hydraulic cylinder at each wheel to keep vehicle level


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