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Shock Absorbers
The purpose of shock absorbers is to slow down
or
dampen the oscillation (bounce) rate of the
spring.
It does this by restricting up and down motion
through
the use of hydraulic valves that restrict
fluid flow
within the shock absorber.
Gas-filled shocks are often used on today's vehicles.
In
a gas-filled shock, pressurized nitrogen gas is located in
the chamber above the hydraulic fluid. This results in a
slight pressure on the fluid which helps to keep the shock
extended against its mountings, resulting in control of small
deflections in the suspension and also prevents air from
mixing with the fluid.
Wheel Bearings
There are two types of bearings used at the
front
and rear wheels of most of today's vehicles.
Tapered Roller Bearing
The wheel hub is used in conjunction with at tapered
spindle and a smaller outer, and larger inner, tapered
roller bearing set. This system is used at the front
wheels of rear wheel drive vehicles, and at the rear
of most front wheel drive vehicles. These bearings
should be cleaned, repacked with fresh grease, and
readjusted at least every 20,000 km.
Sealed Ball Bearing
The sealed double-row ball bearing is used at the
front wheel hubs of most front wheel drive cars,
and is sometimes used at the rear of front wheel
drive cars as well. It is not servicable, and if it
is worn it must be replaced as a unit. Some vehicles
will require replacement of the bearing and hub
assembly as a single part.