Suzuki XL7 2007 Service Manual page 999

Front Suspension
General Description
The front suspension has 2 primary purposes:
• Isolate the driver from irregularities in the road
surface.
• Define the ride and handling characteristics of the
vehicle.
The front suspension absorbs the impact of the tires
travelling over irregular road surfaces and dissipates this
energy throughout the suspension system. This process
isolates the vehicle occupants from the road surface.
The rate at which the suspension dissipates the energy
and the amount of energy that is absorbed is how the
suspension defines the vehicles ride characteristics.
Ride characteristics are designed into the suspension
system and are not adjustable. The ride characteristics
are mentioned in this description in order to aid in the
understanding of the functions of the suspension
system. The suspension system must allow for the
vertical movement of the tire and wheel assembly as the
vehicle travels over irregular road surfaces while
maintaining the tire's horizontal relationship to the road.
This requires that the steering knuckle be suspended
between a lower control arm and a strut assembly. The
lower control arm attaches from the steering knuckle at
the outermost point of the control arm. The attachment is
through a ball and socket type joint. The innermost end
of the control arm attached at 2 points to the vehicle
frame through semi-rigid bushings. The upper portion of
the steering knuckle is attached to a strut assembly. The
strut assembly then connects to the vehicle body by way
of an upper bearing. The steering knuckle is allowed to
travel up and down independent of the vehicle body
structure and frame.
This up and down motion of the steering knuckle as the
vehicle travels over bumps is absorbed predominantly
by the coil spring. This spring is retained under tension
over the strut assembly. A strut is used in conjunction
with this system in order to dampen out the oscillations
of the coil spring. A strut is a basic hydraulic cylinder.
The strut is filled with oil and has a moveable shaft that
connects to a piston inside the strut. Valves inside the
shock absorber offer resistance to oil flow and
consequently inhibit rapid movement of the piston and
shaft. Each end of the shock absorber is connected in
such a fashion to utilize this recoil action of a spring
alone. Each end of the strut is designed as the
connection point of the suspension system to the vehicle
and acts as the coil spring seat. This allows the strut to
utilize the dampening action to reduce the recoil of a
spring alone. The lower control arm is allowed to pivot at
the vehicle frame in a vertical fashion. The ball joint
allows the steering knuckle to maintain the perpendicular
relationship to the road surface.
General Description
Front suspensions systems utilize a stabilizer shaft. The
stabilizer bar connects between the left and right lower
control arm assemblies through the stabilizer link and
stabilizer shaft insulators. This bar controls the amount
of independent movement of the suspension when the
vehicle turns. Limiting the independent movement
defines the vehicles handling characteristics on turns.
Caster Description
Caster is the tilting of the uppermost point of the steering
axis either forward or backward, when viewed from the
side of the vehicle. A backward tilt is positive (+) and a
forward tilt is negative (−). Caster influences directional
control of the steering but does not affect the tire wear.
Caster is affected by the vehicle height, therefore it is
important to keep the body at its designed height.
Overloading the vehicle or a weak or sagging rear spring
will affect caster. When the rear of the vehicle is lower
than its designated trim height, the front suspension
moves to a more positive caster. If the rear of the vehicle
is higher than its designated trim height, the front
suspension moves to a less positive caster.
With too little positive caster, steering may be touchy at
high speed and wheel return ability may be diminished
when coming out of a turn. If one wheel has more
positive caster than the other, that wheel will pull toward
the center of the vehicle. This condition will cause the
vehicle to pull or lead to the side with the least amount of
positive caster.
Front Suspension: 2B-1