SsangYong Rodius (2013 year). Manual — part 176

12-8

When the vehicle is driven on a road surface covered with water at high speed, tires do not contact

with the road surface but rotate floating on a thin film of water.

It causes brake failure, lower traction force and losing the steering performance.

To prevent this, increase the tire inflation pressure, use tires with leaf shape tread which is not worn.

However, it is a best measure to drive slowly.

2) Hydroplaning

12-9

4170-01

If weight is not equally distributed around the wheel, unbalance centrifugal force by the wheel rotation

produces vibration. As the centrifugal force is produced proportional to the square of the rotating

speed, the wheel weight should be balanced even at high speed. There are two types of the tire and

wheel balancing: static and dynamic. Abnormal vibration may also occur due to unbalanced rigidity or

size of tires.

1) Static Balance

When the free rotation of the wheel is

allowed, the heavier part is stopped on the

bottom if the wheel weight is unbalanced

and this is called "Static Unbalance". Also,

the state at which tire's stop position is not

same is called "Static Balance" when the

wheel is rotated again. If the part A is heavier

as shown in the figure 1, add the balance

weight of a weight corresponding to

unbalanced weight from B to A to maintain

the static balance. If the static balance is not

maintained, tramping, up and down vibration

of the wheels, occurs.

2) Dynamic Balance

The static unbalance of the wheel creates

the vibration in the vertical direction, but

the dynamic unbalance creates the

vibration in the lateral direction. As shown

in the figure 2 (a), if two parts, (2) and (3),

are heavier when the wheels are under the

static balance condition, dynamic

unbalance is created, resulting in shimmy,

left and right vibration of the wheels, and

the torque Fxa is applied in the axial

direction. To correct the dynamic

unbalance, add the balance weight of a

same weight for two points of the

circumference of the rim, A and B, as

shown in the figure 2 (b), and apply the

torque in the opposite direction to the

torque Fxa to offset in order to ensure

smooth rotation of the wheel.

Center

a

a

Fxa

Fxa

F

F

A

B

(a)

(b)

[Figure 1]

[Figure 2]

3. WHEEL BALANCE

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4. WHEEL ALIGNMENT

▶Toe-in

▶Camber

In automotive engineering, toe, also known as

tracking, is the symmetric angle that each wheel

makes with the longitudinal axis of the vehicle, as

a function of static geometry, and kinematic and

compliant effects. This can be contrasted with

steer, which is the anti-symmetric angle, i.e. both

wheels point to the left or right, in parallel

(roughly). Positive toe, or toe in, is the front of the

wheel pointing in towards the center line of the

vehicle. Negative toe, or toe out, is the front of the

wheel pointing away from the center line of the

vehicle. Toe can be measured in linear units, at

the front of the tire, or as an angular deflection.

Camber is the angle made by the wheels of a

vehicle; specifically, it is the angle between the

vertical axis of the wheels used for steering and

the vertical axis of the vehicle when viewed from

the front or rear. It is used in the design of

steering and suspension. If the top of the wheel

is farther out than the bottom (that is, away from

the axle), it is called positive camber; if the

bottom of the wheel is farther out than the top, it

is called negative camber.

Wheel alignment consists of adjusting the angles of the wheels so that they are parallel to each other

and perpendicular to the ground, thus maximizing tire life and ensures straight and true tracking along

a straight and level road.

Camber angle alters the handling qualities of a particular suspension design; in particular, negative

camber improves grip when cornering. This is because it places the tire at a better angle to the road,

transmitting the forces through the vertical plane of the tire rather than through a shear force across it.

Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. Negative

camber can also be caused by excessive weight on the front wheels. This is commonly seen on

modified cars with larger engines than standard; the weight of the modified engine can make the

wheels negatively camber. The inside edge of the contact patch would begin to lift off of the ground if

the tire had zero camber, reducing the area of the contact patch. This effect is compensated for by

applying negative camber, maximizing the contact patch area. Note that this is only true for the outside

tire during the turn; the inside tire would benefit most from positive camber.

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4170-01

▶Caster

Caster is the angle to which the steering pivot

axis is tilted forward or rearward from vertical, as

viewed from the side. If the pivot axis is tilted

backward (that is, the top pivot is positioned

farther rearward than the bottom pivot), then the

caster is positive; if it's tilted forward, then the

caster is negative.

Positive caster tends to straighten the wheel

when the vehicle is traveling forward, and thus

is used to enhance straight-line stability. The

mechanism that causes this tendency is clearly

illustrated by the castering front wheels of a

vehicle. The steering axis of a vehicle wheel is

set forward of where the wheel contacts the

ground. As the vehicle is driving forward, the

steering axis pulls the wheel along, and since

the wheel drags along the ground, it falls directly

in line behind the steering axis. The force that

causes the wheel to follow the steering axis is

proportional to the distance between the

steering axis and the wheel-to-ground contact

patch-the greater the distance, the greater the

force. This distance is referred to as "trail."