Shock
Absorber
A
shock absorber is a suspension component that dampens the
up-and-down motion of a vehicle. In the UK, shock absorbers
are called dampers, which is a more appropriate name as it
is really the task of the springs to absorb the jolts that
result when the wheels pass over bumps or dips.
Inside each shock absorber is a piston that slides through
a cylinder. Hydraulic fluid on either side of the piston head
supplies the resistance against which the up-and-down movements
of the wheels must work as it compresses and expands the shock
absorber. A valve in the piston head, and typically another
at the base of the cylinder, allow the fluid to flow through
as the unit expands and compresses. When the compression is
faster or greater, however, the fluid can’t squeeze through
the valve fast enough, and it becomes pressurized. The more
the fluid is pressurized, the more it resists the piston’s
motion.
The size of the valve aperture helps determine the degree
of firmness of the shock absorber. Firmer shock absorbers
make for a harder ride but may improve handling and help to
minimize body roll. There are also variable-rate shock absorbers
- both manual and electronically controlled. Manual ones have
a setting that the owner or a mechanic can adjust. Electronically
controlled types are the key to adaptive suspensions, the
most sophisticated of which are computerized to vary individual
shock firmness numerous times a second in response to conditions.
The simplest way to test a shock absorber is to push down
on the vehicle’s bumper; a healthy shock absorber will allow
the body to rebound but quickly come to rest. If the vehicle
goes into a prolonged bounce cycle, the shock needs to be
replaced. Bad shocks are unsafe because they fail to maximize
tire contact with the road, which degrades handling and braking.
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