WHAT ARE
SHOCK ABSORBERS ?
Basically,
all shock absorbers perform 2 functions They
dampen the oscillations of the springs ( both
coil and leaf type ) or the twisting action of
torsion bars. That is they control the movements
of the above forms of suspension springs found
in all 4WD vehicles and they keep your tyres in
contact with the road surface.
They do not help to support the weight of the
vehicle or effect the ride height of the vehicle
(apart from the high pressure Bilstein shocks
which can raise a light vehicle by up to 5mm).
Shock absorbers are basically an oil pump with a
restrictor valve. They control the springs rate
of travel through both it’s compression and
rebound stages of each suspension stroke. The
compression and rebound valves inside the
hydraulic fluid filled shock body slow down the
spring’s movement and in this way they ‘control’
the springs on your 4WD.
The amount of resistance a shock offers depends
on the speed of the spring and the size and
number of orifices in the valves of the shock.
Shock absorbers are velocity sensitive damping
devices and the faster the suspension moves the
more resistance the shock absorbers provide. It
is this feature that allows shocks to adjust to
the given road conditions.
A vehicle
with good shock absorbers fitted will have less:
BOUNCE &
PITCH, BODY ROLL & SWAY, NOSE DIVING UNDER
BRAKES, POWER SQUAT UNDER ACCELERATION and
GREATER TYRE CONTACT WITH THE ROAD!
When the springs and shock absorbers are in good
condition, the vehicle’s suspension will allow
the vehicle’s body to ride over rough surfaces
with a minimum of disturbance to the occupants
of the vehicle. It also allows the vehicle to
corner with a minimum amount of roll or sway, be
able to stop with a minimum amount of brake dive
and control acceleration squat. Therefore, the
control that good shocks offer will help to keep
the tyres in contact with the road surface and
give you the best possible level of grip as long
as your tyres are in good order and condition.
A vehicle with worn or poor quality shock
absorbers will be unsafe and can bounce and
pitch excessively, roll and sway excessively,
nose dive steeply under brakes loosing rear tyre
contact and allowing the wheels to bounce as
well as excessively squatting under
acceleration. All of which leave you and your
passengers in a very vulnerable, unsafe
position.
There are 2 basic designs of shock absorbers in
the market today – the TWIN TUBE or the MONO
TUBE designs. Both do a similar job in different
ways. All mono tube shocks are Gas Pressurised
at a high gas pressure . Twin tube shocks can be
of 3 variations - the straight Hydraulic shock,
the Low Pressure Gas Charged shock and the Foam
Cell or Cellular Gas shock. Both of the last 2
do a similar job in different ways. The 3
various Shock absorber types are: TELESCOPIC,
MACPHERSON STRUT (STRUT) & COIL-OVER SHOCKS.
Good shock absorbers along with good tyres
and good brakes form what is known as the Safety
Triangle as these are the 3 most important
safety items fitted to every 4WD vehicle!
