CCAS 3381 AUTOMOTIVE SKILL I SUSPENSION & STEERING SYSTEM

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

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

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

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

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

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

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

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

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.

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

SUSPENSION SYSTEM (10)

SUSPENSION SYSTEM (11)

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

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

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

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

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)

STEERING SYSTEM (6)

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

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.

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.

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.

THE END IQ + EQ + SQ = TQ*