Steering Geometry

Question 1

What are the 2 aims of steering ?

Answer 1

Centre point steering

When cornering all steered wheels must turn about a common centre

Question 2

What is the scrub radius?

Answer 2

Centre of the king pin to the centre of the tyre

Question 3

What does a large scrub effect cause?

Answer 3

Large splaying out effect

Heavy steering

Large bending forces on the stub axle and kingpin

Question 4

How do you overcome the problem of a large scrub radius?

Answer 4

Arrange the wheel and king pin so the centre line of the wheel meets the centre line of the king pin at the road surface

Question 5

How do you achieve centre point steering

Answer 5

Wheel camber

Kingpin inclination

Dished wheels

Question 6

What is positive offset?

Answer 6

Wheel centre line and KPI/SIA centre line is below the road surface

Question 7

What is negative offset?

Answer 7

Wheel centre line meets KPI/SAI above the road surface

Question 8

What is camber angle?

Answer 8

Angle formed between the vertical and wheel centre line

Question 9

What is positive camber?

Answer 9

Wheel tilts outwards at the top

Question 10

What are the disadvantages of positive camber?

Answer 10

Cone effect - roll in circle

Wear on outer edge of tyre

Question 11

What are the advantages of positive camber?

Answer 11

Lighter steering

Offset is reduced

Question 12

What is negative camber?

Answer 12

Wheel tilts inwards at the top

Question 13

What are the disadvantages of negative camber?

Answer 13

Offset increases

Heavier steering

Increased tyre wear

Question 14

What are the advantages of negative camber

Answer 14

Improved handling

Camber angle reduced

More tyre contact with road surface

When travelling over rough surfaces, small movements are absorbed instead of through steering linkages

Helps keep vehicle in a straight line

Question 15

How can a dished wheel reduce KPI

Answer 15

Slightly dishing the wheel

Question 16

What is castor action

Answer 16

Gives driver the feel of the straight ahead position , wheels follow the general direction of the weight

Question 17

What must be exerted to overcome the self centering or castoring action?

Answer 17

Torque

Question 18

Too much and too little castor causes what?

Answer 18

Too much- heavy steering

Too little- wandering

Question 19

What is positive castor?

Answer 19

When the centre line- road contact is ahead of the wheel

Question 20

What is negative castor?

Answer 20

When the centre line road contact is behind the wheel

Question 21

What type of castor is required for front or 4 wheeled drive vehicles?

Answer 21

Negative

Question 22

What type of castor is required for rear wheel drive?

Answer 22

Positive

Question 23

What forces can cause slip angle?

Answer 23

Cornering, camber, wind and weight

Question 24

What is the slip angle?

Answer 24

Difference between intended direction of travel and actual direction of travel

Question 25

What are the 2 ways slip angles can affect a vehicle?

Answer 25

Oversteer - vehicle turns more than intended Under steer- vehicle turns less than intended

Question 26

How does oversteer occur?

Answer 26

When the slip angle on the rear tyres are greater than the slip angle on the front

Question 27

What will occur if the slip angle are equal on the front and back?

Answer 27

Turn the corner uniformly

Question 28

How can oversteer be caused?

Answer 28

Increase load on the rear of the vehicle Lower pressure in rear tyres Large load transfer from inner rear wheel to the outer rear wheel when Cornering

Question 29

What causes under steer?

Answer 29

The slip angles are greater on the front than the rear

Question 30

What happens during understeering?

Answer 30

The front wheels are turning a lesser amount than the driver intended

Question 31

What can be another cause of understeer apart from slip angle?

Answer 31

Increase load on the front Lower pressure on front tyres Large load transfer from inner front wheel to outer front wheel when Cornering

Question 32

What is front wheel alignment (tracking)

Answer 32

Wheels on each axle should be parallel when travelling in a straight line

Question 33

What is the allowance known as in tracking?

Answer 33

Tow in , toe out

Question 34

On RWD, forces exerted cause wheels to?

Answer 34

Splay out

Question 35

On FWD, forces exerted cause wheels to?

Answer 35

Splay in

Question 36

What is toe in?

Answer 36

Distance on the front of the wheel is shorter than the measurement at the rear

Question 37

What is toe out ?

Answer 37

When the distance between the front of the wheel is greater than the measurement between the rear of the wheel

Question 38

Toe setting is determined by what?

Answer 38

Manufacture

Question 39

How is the setting adjusted?

Answer 39

By altering the length of track rod, activated by LH/RH thread

Question 40

Toe setting is checked by?

Answer 40

Alignment gauges Optical tracking gauges

Question 41

What should you check before tracking alignment?

Answer 41

Tyre size, pressure and uneven wear Wheel bearing play Check front suspension for damage Check run out of the wheels

Question 42

What must you do before checking alignment?

Answer 42

Rolled backwards and forward to settle the steering and suspension Allows all play to be taken up

Question 43

What will occur if the wishbones are the same size?

Answer 43

Road deflections lift the wheel , the track will vary but the camber will stay the same Make it unstable and increase tyre wear

Question 44

What occurs if the wishbones are different lengths?

Answer 44

Road deflections lift the wheel but the track stays the same but camber angle alters More stable will only cause slight tyre wear

Question 45

What prevents scrubbing when turning?

Answer 45

Wheels must turn about a common centre A true rolling action must be achieved

Question 46

What can almost true rolling action be achieved by?

Answer 46

Inclining steering arms towards each other Line projected from each king pin meet on the centre line of the vehicles ahead of the rear axle

Question 47

What will distortion of the track arm cause?

Answer 47

Misalignment Incorrect wheel angles

Question 48

How is the alignment checked?

Answer 48

Turntable measuring angles Carrying out a toe out on turns test

Question 49

What are the possible causes of wander?

Answer 49

Excessive negative castor Excessive play in steering joints Tight ball joints, kingpins or steering joints Incorrect steering box adjustment

Question 50

What are the possible causes of shimy?

Answer 50

Excessive play in steering box Excessive play in ball joints or kingpin/swivel pins

Question 51

What causes the vehicle to pull to one side?

Answer 51

Incorrect front wheel alignment Unequal track rod adjustment Incorrect steering angles