Many
motorists don’t appreciate the importance of ride control and how it
affects driving, handling and braking safety. Not replacing a worn set
of shocks or struts may seriously compromise the ability of the vehicle
to handle bumps, dips, crosswinds or extra weight. Worn shocks and
struts also will increase wear and tear on other steering and
suspension components, too.
On
rough roads, worn dampers that fail to keep the wheels in firm contact
with the road may increase stopping distances. Tests have shown that
stopping distances increase significantly when the tires bounce and
lose grip on the road. This also hurts traction when accelerating and
cornering.
Shocks
and struts should be replaced when they no longer provide adequate ride
control or fail to meet the driver’s expectations. Replacement is also
required if a shock or strut is leaking, broken or damaged.
The
best way to evaluate the condition of a vehicle’s dampers is a test
drive on a variety of road surfaces (smooth and rough) and under
various driving conditions (stopping quickly, cornering and changing
lanes). Excessive body roll, sway or rocking would tell you the dampers
are not up to the task and need to be replaced. For parts stores, of
course, this method is not really practical. However, the old “bounce
test,” can be easily done right in the store’s parking lot. To do the
bounce test, rock the suspension up and down several times, then
release it to see how many times it rebounds. As a rule, good dampers
should stop the chassis from rocking almost immediately. Worn ones may
allow it to rebound several times.
A
visual inspection can also identify shocks or struts that are failing
or have failed. Oil on the outside of the housing means the piston rod
seal is leaking. The shock may still be doing its job, but for how much
longer is anybody’s guess.
Ride Control Upgrades
A
more compelling reason to replace shocks and struts these days is to
upgrade handling and ride control performance. This approach seems to
work best with motorists who want to improve the way their vehicles
rides or handles.
If
a vehicle is used to pull a trailer, a ride-control upgrade may provide
a more sure-footed track without wagging or whipping, better stability
in cross winds and better handling on curvy roads.
Popular
upgrades include high-pressure gas shocks and struts with firmer
valving or adjustable valving, shorter, stiffer springs to lower the
center of gravity, stiffer sway bars to keep the body flat, and firmer suspension bushings to reduce suspension compliance.
Though
most late-model vehicles come factory equipped with gas-pressurized
shocks or struts, many OEM dampers are valved more for ride comfort
than ride control. Soft valving provides a nice boulevard ride, but the
trade-off is reduced body control and more roll — exactly what you
don’t want on a vehicle with a high center of gravity like your typical
SUV.
GAS SHOCKS
Gas
shocks come in one of two basic varieties: single tube (monotube) and
double (twin tube). The single tube variety has all its major
components contained within a single large tube (thus the name) and
typically uses a very high-pressure charge (280 to 360 psi). The gas
charge is separated from the hydraulic fluid by means of a floating
piston in the top or bottom of the tube. This type of shock must be
manufactured with a heavier gauge cylinder and a highly polished
internal surface (some are Teflon-lined).
A
less-expensive alternative for upgrading ride control performance is
the double- or twin-tube gas shock. Available from many suppliers of
single-tube shocks, the double-tube design is essentially a
gas-pressurized conventional shock with lower pressure. Some are in the
70-130 psi range while others are 112 to 130 psi or higher.