CCAS 3381 AUTOMOTIVE SKILL I

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. SUSPENSION SYSTEM (8) Double-wishbone suspension on Honda Accord 2005 Coupe • 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 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 valvesenses 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*