1. CCAS 3381 AUTOMOTIVE SKILL I
SUSPENSION &
STEERING SYSTEM

2. OBJECTIVES
To understand the operational principles and basic mechanisms of suspension & steering systems
Double-wishbone suspension on Honda Accord 2005 Coupe
Lecture – 1 hour
Workshop – 1 hour

3. SUSPENSION SYSTEM (1)
Power of a car is useless if car cannot be controlled
Car suspension:
maximizes friction between tires and road surface
provide steering stability with good handling
ensure the comfort of the passengers

4. SUSPENSION SYSTEM (2) Vehicle dynamics
Ride - car's ability to smooth out bumpy road
Handling - car's ability to safely accelerate, brake & corner
Road isolation - allow vehicle body to ride undisturbed while traveling over rough roads
Road holding - keep tires in contact with ground (friction between tires and road affects a vehicle's ability to steer, brake & accelerate)
Cornering - minimize body roll

5. SUSPENSION SYSTEM (3)
Frame - structural, load-carrying component supporting car's engine & body (supported by suspension )
Suspension system - setup supporting weight, absorbing & dampening shock & helps maintaining tire contact
Steering system - mechanism enabling driver to guide & direct vehicle
Tires & wheels - components making vehicle motion possible by way of grip &/or friction with road

6. SUSPENSION SYSTEM (4) Springs: Coil springs Leaf spring Torsion bars
Air springs
Sprung mass & unsprung mass

7. SUSPENSION SYSTEM (5)
Sprung mass - mass of the vehicle supported on the springs
Unsprung mass - mass between the road and the suspension springs
Stiffness of springs affects how sprung mass responds while the car is being driven
Loosely sprung cars versus tightly sprung cars - balance passenger comfort with handling is a complex task

8. SUSPENSION SYSTEM (6)
Shock absorbers - controls unwanted spring motion through dampening
compression cycle
extension cycle

9. SUSPENSION SYSTEM (7) Struts and Anti-sway Bars
Strut: shock absorber inside a coil spring
provide dampening function
provide structural support for the vehicle suspension
critical safety feature - worn shocks & struts allow excessive sway reducing tire grip, handling & braking performance
Anti-sway or anti-roll bars
give moving stability
creates a more level ride & reduces vehicle sway
Common strut design
Anti-sway bars

10. Double-wishbone suspension on
SUSPENSION SYSTEM (8)
Dependent front suspension - rigid front axle connecting the front wheels
Independent system - front wheels are allowed to move independently (MacPherson strut, double wishbone)
Double-wishbone suspension on
Honda Accord 2005 Coupe
Double-wishbone allows for more control over camber angle of the wheel (degree to which the wheels tilt in and out) & they also help minimize roll or sway and provide for a more consistent steering feel.

11. SUSPENSION SYSTEM (9)
Dependent rear suspension - solid axle connects the rear wheels
Independent rear suspension system – both rear wheels are mounted & sprung individually
Bose® Suspension Front Module

12. SUSPENSION SYSTEM (10)

13. SUSPENSION SYSTEM (11)

14. STEERING SYSTEM (1)
During turning your front wheels are not pointing in the same direction
Geometry of steering linkage makes the inside wheel turn more than the outside wheel

15. STEERING SYSTEM (2) Rack-and-pinion steering most common
converts steering wheel rotation to linear
provides gear reduction to turn wheels
A steering wheel rotates 360o causing wheels turning 20o has steering ratio of 360/ 20 = 18:1
Variable-ratio steering
Power Rack-and-pinion

16. STEERING SYSTEM (3) Recirculating-ball steering
Used on many trucks and SUVs today
contains a worm gear
Power steering in a recirculating-ball system works similarly to a rack-and-pinion system

17. STEERING SYSTEM (4) Power Steering
Rotary-vane pump driven by car's engine via a belt and pulley - amount of flow provided by the pump depends on the car's engine speed (pressure-relief valve)
Rotary valve senses steering wheel force – assist driver only when necessary like during parking

18. STEERING SYSTEM (5)
Today’s steering system runs constantly, pumping fluid all the time (wastes)
"drive-by-wire" system (like joysticks)
General Motors concept car (Hy-wire)

19. STEERING SYSTEM (6)

20. WHAT COULD GO WRONG (1)
Worn & loose ball joints causing suspension noise (typically a "clunking" sound when hitting a bump)
Bent wheel (shimmy on steering wheel & sideway movement of wheel)
Leaked shock absorbers (realignment after strut change)
Shocks too soft
Worn shocks (sway, dip, bounce)
Loose steering wheel (> 0.25”) – tie rod ends, rack, wheel bearing)
Power steering ‘morning sickness’ – worn steering rack

21. WHAT COULD GO WRONG (2)
Steering wheel jerks to one side upon hitting bump – misalignment in chassis & bent steering arm
Car pulled to one side – wheel misalignment (camber, toe-in), tire pressure, mismatched tires, sagging spring, dragging brake, unreleased parking brake, uneven load)
Unbalanced tires – static & dynamic
Most problems affecting the suspension and steering system develop gradually as a result of wear. Watch for the following warning signs.

22. WHAT COULD GO WRONG (3)
There’s too much play (free movement) in the steering wheel. With power steering, there should be virtually no play in the wheel. In a manual system, there should be no more than 2 inches of play.
The steering wheel vibrates or is difficult to turn.
The front end of the car wobbles or shimmies.
The car bumps as you turn the wheel while driving on a smooth road.

23. WHAT COULD GO WRONG (4) The car pulls to one side as you drive.
The car bounces too much after hitting a bump.
Tread wear on the front tires is uneven.

24. THE END
IQ + EQ + SQ = TQ*