Smoothing Out Rough Roads
(35-4)
Good
Shock Absorbers Improve Safety and Comfort while Reducing
Road Damage and Vibrations
As we
drive on today’s roads, we often find that our
tires encounter bumps, potholes, and expansion joints
that transmit vibration from our tires directly to the
seat of our pants, and that affects our comfort, steering
and braking.
 The
spring suspension of our RV is designed to allow the
body to ride up and down as we travel over undulations
in the road. Unfortunately, the body can rebound after
the springs compress, giving us a porpoise-type ride
over the ocean. Years ago, we used to test the shock
absorbers on a car by pushing down and quickly releasing
the front or rear of the vehicle, then watch the vehicle
to notice how it rebounds back to its original position.
If the vehicle continued to bounce, the shocks were
considered to be worn out, and not doing their job.
This is almost impossible to do with a motorhome or
a heavy duty truck used to tow a large trailer.
Well, what is the shock absorber’s job? Primarily,
its job is to keep the tires in contact with the road
as we drive over bumps, expansion joints, and potholes.
When a tire bounces off the road surface, it loses speed
during the short time it’s in the air, then, when
it comes back in contact with the road surface, small
amounts of rubber tread are scrubbed off each time the
tire hits the road. This causes scalloping of the tread
that will result in a very bumpy ride. Simply changing
a scalloped tire with a new one will not cure the bad
tire wear.
The shocks on a vehicle dampen the unwanted effect of
the front diving during stops, help prevent the body
from swaying side to side during lane changes, and prevent
the front from leaning into the corners. They also prevent
the front of the vehicle from constantly bouncing up
and down (porpoising) as we drive over a sharp rise
and go down the other side. Not only do the shocks help
prevent the vehicle from suddenly diving down, but also
from jumping up. The pistons inside the oil-filled tubes
have to push against the fluid to absorb the compression
and rebound forces. Valves inside the pistons control
how fast the movement occurs. Many shocks are pressurized
with nitrogen gas to prevent the oil inside from foaming,
as well as cavitation. When the oil foams, it loses
its ability to resist the movement of the piston inside
the shock. Nitrogen is used since it will not chemically
affect the oil or the metal casings of the shock. Gas
charged shocks are better as they fade less after extensive
driving.
Shock absorbers maximize safety, minimize road damage,
improve driver ride comfort and reduce vehicle body
vibrations. Over the years, the wear of some moving
parts can cause shock absorbers to leak oil, and the
shocks lose their effectiveness to prevent rebound.
Shock absorbers have a built-in hydraulic rebound valve
with spring. This rebound valve substantially increases
the damping forces during the last 40 or 20 mm of the
rebound stroke to prevent metal-to-metal contact.
Many trailers are sold without shock absorbers included
in their suspension. They come standard with normal
leaf springs, or torsion axles. We often hear from owners
about clothes that jump off the hangers in the rear
closet, or dishes that leap out of the cabinets over
a rear kitchen when travelling over certain roads. Shocks
reduce the bounce and wander of your trailer for improved
towing capacity, and also reduce the surge caused by
trailer motion feedback to the tow vehicle, for a smoother,
more comfortable ride. Aftermarket shock kits are available
from Monroe and Mor/Ryde for travel trailer and Fifth
Wheel units. Many new Fifth Wheel trailers have an air
bag suspension in their hitch to smooth out movements
of the trailer that can be transferred to the tow vehicle
through the normal hitch. A good shock absorber will
dampen the action of the air bag as it compresses and
rebounds.
...
(Read the full article in the magazine.) |
