suspension system

Alignment

The main purpose of wheel alignment is to make the tires roll without
Scuffing, slipping, or dragging under all operating conditions.

•Caster
•Camber

•Toe
•Steering axis inclination

•Toe-out on turns (turning radius)

•Tracking (thrust line)

Alignment

Caster is basically the forward or rearward tilt of the steering knuckle
when viewed from the side of the vehicle.

Basic purpose:

•To aid directional control of the vehicle.
•To cause the wheels to return to the straight ahead position.
•To offset road crown pull (steering wheel pull caused by hump in center
of the road).

Alignment

Positive Caster

•Tilts the top of the steering knuckle towards the rear of the vehicle.
•Helps wheel traveling in straight line.
•When turning, the vehicle lifts up,
the resistance to the extra weight
returns the wheel to straight ahead
position.

Negative Caster

•Tilts the top of the steering knuckle
towards the front of the vehicle.

•Wheel is easier to turn.

•Wheel will tend to swivel and follow the imperfections in the road.

Caster is measured in degrees.

Alignment

Caster-Road Crown Effect

•Road crown is normal slope towards the
outer edge of the road surface.

•Caster is different on both wheels, this
prevents the vehicle from pulling toward
the outside (lower) edge of the road.

•Right front wheel may be set with slightly positive caster than the left.

Alignment

Camber is the inward or outward tilt of the wheel and tire assembly
when viewed from the front of the vehicle.

•To prevent tire wear on the outer or inner tread.
•To load the larger inner wheel bearing.
•To aid steering by placing vehicle weight on the inner end of the spindle.

Alignment

Positive Camber

•Top of the wheels tilt outwards when
viewed from the front of the vehicle.

Negative Camber

•Top of the wheels tilt inwards when
viewed from the front of the vehicle.

Most manufacturers recommend a slight positive camber setting of about
¼° to ½ ° (compensate the weight).

Alignment

Toe is determined by the difference in the distance between the
front and rear of the left and right-hand wheels.

•Toe controls whether the wheels roll in the direction of travel.

Toe-out wheels are farther apart at the front than the rear.
Toe-in wheels are closer at the front than at the rear.

Alignment

Rear-Wheel-Drive Toe Setting

•Front wheels tend to toe-out while driving.
•As the tires roll over the road, they are pushed rearward, causing the
tires to turn outward (toe-out).
•To compensate this the front wheels are set to have toe-in at the front wheels
(1/16’’ – ¼’’).

Front-Wheel-Drive Toe Setting

•Front wheels propel the vehicle, they push forward by engine torque.

•This push causes the wheels to point inward (toe-in).

•To compensate this the front wheels are set to have toe-out at the front wheels
(approximately 1/16’’).

Alignment

Steering Axis Inclination (SAI)

•Angle away form the vertical, formed by the
inward tilt of ball joints, king pin, or
MacPherson strut tube.

•Always an inward tilt.

•Not a tire wearing angle.

•Not adjustable.

•Must replace part if not correct.

Alignment

Toe-Out on Turns (Turning Radius) is the amount the front wheels
toe-out when turning.

•Around the turns the inside tire must
travel in a smaller radius circle than
the outside tire.

•Prevents tire scrubbing and squealing.

•Is not adjustable (built in angle of steering arm).

•If incorrect, check for bent or damaged
steering parts.

Alignment

Pre-Alignment Inspection

•Loose wheel bearings
•Wheel or tire run-out.
•Worn tires.

•Tires of different size and types.

•Incorrect tire inflation.
•Worn steering components.

•Worn suspension components.incorrect curb height and weight.

Alignment

Caster is adjusted by moving the control arm so that the ball joint moves toward the
front or rear of the vehicle.

Control arm can be moved by :

•Adding/removing shims
•Adjusting strut rod
•Turning eccentric bolt
•Shifting control arm shaft bolts.

Alignment

Camber is changed by moving the control arm in or out without moving the ball joint.

Adjusted by shims, slots, or eccentric bolts.

Alignment

Toe is adjusted by lengthening or shortening the tie-rods.

Alignment

After installing tie-rod ends, check toe-in.

Alignment

Jeff Crawford
Crawford’s Auto Repair

Slows and/or stops the vehicle for safety
Converts kinetic energy into heat energy

by applying a friction material against a
rotating surface.

When going downhill, don’t ride your
brakes, this wears them out.

Brake quickly to reduce speed, then shift
to a lower gear.

When possible and if you can anticipate it,
shift to lower gears before approaching a
descending hill.

Master Cylinder
Anti-lock brake system (ABS)

• Series of electrical and hydraulic components,
HCM and others

The parking brake is independent
of the other brakes

DISC BRAKES DRUM BRAKES

 Discs or Rotors  Drums
 Pads (Friction Material)  Shoes (Friction Material)
 Calipers  Wheel Cylinders

For credit you need to know how to check
the brake system. Download our ebook
and sign up for the intermediate classes.

Anyone is invited to do this (even if you’re
not a boy scout or taking a formal class).

http://crawfordsautoservice.com/crawfords-auto-repair-guide-free-ebook/

 Start under the hood.
 Check the brake master cylinder for leaks.
 Check the level and condition of the brake fluid.
 Inspect all lines and the anti-lock brake module for leaks or loose,

damaged connectors.
 Raise the vehicle and support it securely on a lift or jack stands

(review Chapter 1 in the ebook if needed)
 Remove all four wheels
 If the vehicle has drum brakes, then remove the drums.
 Inspect all brake lines and hoses for signs of leaking or cracking
 Inspect the caliper hardware and dust boots for damage
 Inspect the caliper (or wheel cylinders) for brake fluid leaking.
 Inspect the rotors for smoothness. If a rotor has any pits or grooves

then it will have to be reconditioned or replaced.
 Check the thickness of all the brake pads.

 If the friction material (pads or shoes) are 20% of original thickness
or less, then they should be replaced.

If the pads are 20% of original thickness or
less, then they should be replaced.

BRAKE PAD REPLACEMENT + ROTOR REPLACEMENT

 $200  $260

Replace friction material before they wear down and the brakes are metal to
metal. It’s also safer.

This is a general rule for auto repair: maintain the vehicle and make timely
repairs to avoid additional costs later.

It helps to know a mechanic you can trust so that you know you’re saving
money and not spending more in repairs than you have to.

(Prices may vary per vehicle. Ads and coupons for cheaper brake jobs are
probably to get vehicles into the shop for additional repairs)



VEHICLE TIRE MANUFACTURER’S
MANUFACTURER’S SPECIFICATIONS
SPECIFICATIONS
 On the tire itself
 Driver’s side door jamb and
owner’s manual

Use the level indicated in the door jamb
(Vehicle Manufacturer’s Specifications)

Camber, Caster and Toe

Generally with every oil change.
(Free at Crawford’s Auto)

Wear Bar

This tire still has good tread. When the height of the tread is the same as the
wear bar, it’s time to change the tire.
Also, in hot environments like Arizona, generally change tires within every 4
years. (may vary by tire, some are made to last longer)

Students and Boy Scouts, download the
ebook and sign up for intermediate
classes.

Our live classes include a tire change
demo in the shop or parking lot.

 Make sure the vehicle is on level ground (see Chapter 1 of ebook, Safety, proper lifting
points)

 Apply the parking brake
 Remove the spare tire and tools from the vehicle
 Use wheel chocks to block the wheels opposite of the wheel you’re changing (i.e. if you’re

changing a rear tire, then put the chocks in front of the front wheels).

• Wheel chocks are similar to triangle-shaped door stoppers. When chocks are included with the tire
changing kit, then they should be used. However, they are not present with every vehicle. Cases
where they’re not present may include vehicles with a rear parking brake and front wheel drive.
When changing a rear wheel in these vehicles the front wheel drive keeps the vehicle stable, and
when changing a front wheel in these vehicles the rear parking brake keeps the vehicle stable.

 Loosen the lug nuts before lifting the vehicle, but do not remove
 Pump or crank the jack to lift the vehicle using the proper lift points (see Chapter 1 of

ebook, Safety, proper lifting points)
 Remove the lug nuts
 Remove the flat tire
 Place the spare tire
 Replace the lug nuts snug
 Lower the vehicle
 Torque the lug nuts (tighten them as much as possible after the vehicle has been lowered)
 Replace the tools in the appropriate location for future use.
 Carry the flat full-size tire to the tire shop with you.

 Spare tires are not meant to be a replacement, only there to get you to a repair shop, must drive at slower
speeds.

Any time you purchase a tire, the tire shop
is responsible for charging a disposal fee
and disposing the old tire properly.

 Dealership-trained technicians
 Over 35 years of combined

experience
 We treat each vehicle as if it

belonged to our own mother
 High customer satisfaction (read

our reviews online)
 2014 Angie’s List Super Service

Award.
 No service writers! We never try to

sell unnecessary repairs.
 Free Quotes and a Price Match

Guarantee

www.CrawfordsAutoService.com

Chapter no 3
Automobile Suspension System

By Er D S Phapale

B.E. Automobile, M.E. Cad/Cam(Appear)

Function Suspension System

•Supports the weight.
•Provides a smooth ride.
•Allows rapid cornering without extreme
body roll.
•Keeps tires in firm contact with the road.
•Prevents excessive body squat.

•Prevents excessive body dive.
•Allows front wheels to turn side-to-side for steering.
•Works with the steering system to keep the wheels in correct alignment.



Types of Suspension System

1.Non-independent/Rigid suspension has both right and left wheel attached to the

same solid axle. When one wheel hits a bump in the road, its upward movement
causes a slight tilt of the other wheel.

2.Independent suspension allows one wheel to move up and down with minimal

effect to the other.

Suspensions

Independent
Nonindependent

Suspension System

Coil spring is the most common type of spring found on modern vehicles.
Leaf springs are now limited to the rear of some cars.

Types of Springs

A. Coil spring
B. Leaf spring
C. Air spring
D. Torsion bar

Suspension System

Basic Parts

Control arm – movable lever that fastens
the steering knuckle to the vehicle’s
body or frame.

Steering Knuckle – provides a spindle or
bearing support for the wheel hub, bearings
and wheel assembly.



1 Wishbone Suspension Upper wishbone

The suspension must be Lower wishbone
designed in such a way as to
keep the wheel upright for 10 of 12
maximum tyre contact
(vehicle control) and to
minimize tyre wear.

The upper wishbone is
short and the lower
wishbone is longer.

Both wishbones pivot points
and lengths are calculated to
provide the best operating
angle for a given suspension
movement.

Advantages & Disadvantages of
Wishbone type independent suspension

Advantages Disadvantages

•Ride quality is good. •Initial cost is more
•Maintenance cost is more.
•Improve the steering •Required frequent wheel
preciseness since the
wheel movement are not alignment otherwise increase
link
tyre wear.
•Ground clearance
increase

Applications:-SUV,CARS

2 MacPherson Strut Strut
assembly
This is a very popular and efficient form of
suspension. It has one control arm and a strut Shock
assembly. A coil spring and shock absorber absorber
will normally form parts of the strut assembly.
Knuckle
Coil springs may be mounted on Frame Control
the control arm instead of being
around the strut. On this type, arm
the shock absorber connects
the knuckle to the frame. 12 of 12

This type of suspension strut is
often also used on rear
suspension systems.

Coil spring

Front Suspension

(MacPherson Strut)

MacPherson Strut Suspension

The top of the strut is bolted to Steering knuckle
a reinforced section of the
frame structure.

The lower end of the strut is Strut
attached to a steering knuckle.
Frame
The control arm is also attached Control
to the steering knuckle. arm

The control arms are mounted on Cradle
a cradle section of the frame.
14 of 12
An anti-roll bar links the two Anti-roll bar
control arms together to reduce
sway (body roll).

Advantages & Disadvantages of
Macpherson strut suspension

Advantages Disadvantages

•Light in weight. •Not suitable for Heavy motor

•Camber does not change due vehicle.
to up & movement of wheels •Load caring capacity is less.

•Maximum Engine compartment

available.

•Maintenance cost is less.

•Initial cost is less.

•Ride comfort is more.

•Improve road safety.

Applications:-CARS