Dampers,
usually incorrectly called shock absorbers, wear out
slowly, which is why changes in handling often pass
unnoticed, until there is a sudden failure. It follows
that, while you use your car in the normal manner,
the roadholding, braking and comfort are gradually
deteriorating.
The
only sure way to test these items is to remove them
from the car and plot the movement on a damper dynamometer,
but this is not practicable, so a good alternative
is to get an experienced technician to drive the car
and examine the tyres. He will drive the car uphill
on a bumpy road under power to feel for signs of wheel
hop, and will also examine the tyres for uneven tread
wear. He will take a close look at the units for signs
of fluid leaks, rust, and damage to the piston rod,
or mounting body.
Many
service centres have so-called "shock absorber test
machines", but they often give results that, taken
on their own and interpreted by an unskilled operator,
are far off the mark.
The
familiar bounce test depressing the suspension
at each wheel in turn, and taking note of how the
car bounces needs interpretation. If the car
dips and then recovers immediately without any further
bounce, the damper may be fine, but could still be
below par when it has to damp small movements.
However,
if the car responds by bouncing past the normal level
and then settling, it is a positive indication of
worn our dampers. In other words, the test will tell
you if the dampers are very bad, but not if they are
good. Damper
manufacturers recommend regular checks every 15 000
km. At every service, the vehicle should be visually
inspected for damper leaks, damaged or broken mountings,
and irregular tyre wear, and assessed for deterioration
in ride stability.
Of
course, the latter three conditions may not be due
to the dampers, but could result from faulty suspension
settings or broken/damaged components. Modern
struts last a lot longer than they did 20 years ago,
but they should be checked every 15 000 km.
