Shock Absorber

~Function~

Shock absorbers are an important component of any vehicle suspension system. The majority of vehicles have once shock absorber for every vehicle tire. Each shock absorber provides significant strength and functionality to a vehicle's suspension system.

The main purpose of shock absorbers is to limit overall vehicle body movement, or sway. As a vehicle is driven, the body will move up and down or side to side to various degrees in response to driving and road conditions. These type of vehicle movements are held in check by shock absorbers.
◎Stabilize Vehicle Ride
Depending on road conditions or driving style, a vehicle can go from smooth and controlled to bumpy and erratic in a short time period. Shock absorbers stabilize the overall vehicle ride, preventing an excess of vehicle body lean or roll in any one direction, especially when cornering or navigating sharp turns. This stabilization allows for greater vehicle control and stability.

◎Stabilize Vehicle Tires
Most vehicles have one shock absorber per vehicle tire. Each individual shock absorber, in addition to controlling ve
hicle body movement and ride, exerts a tremendous stabilizing force on each vehicle tire. A shock absorber prevents a vehicle's tire from hopping or bouncing in uneven or choppy terrain and helps to a vehicle tire planted firmly on the ground or road surface.

◎Minimize Tire Wear
By helping to stabilize and control the movements of a vehicle tire, a shock absorber helps to minimize tire tread wear. Tires that are held firmly against the ground and held in position by a firm shock absorber last longer and experience much less tread wear.

◎Reduce Overall Suspension Wear
Shock absorbers are only part of a vehicle's overall suspension system. Most vehicles utilize a combination of various leaf springs, coil springs and struts to stabilize and control a vehicle's movement. Shock absorbers basically absorb and deflect a great deal of initial road impacts and/or body movements. What shock absorbers can't contain gets passed on to other parts of a vehicle's suspension system.

Types
◎Basic twin-tube
Also known as a "two-tube" shock absorber, this device consists of two nested cylindrical tubes, an inner tube that is called the "working tube" or the "pressure tube", and an outer tube called the "reserve tube". At the bottom of the device on the inside is a compression valve or base valve. When the piston is forced up or down by bumps in the road, hydraulic fluid moves between different chambers via small holes or "orifices" in the piston and via the valve, converting the "shock" energy into heat which must then be dissipated.

◎Twin-tube gas charged
Variously known as a "gas cell two-tube" or similarly-named design, this variation represented a significant advancement over the basic twin-tube form. Its overall structure is very similar to the twin-tube, but a low-pressure charge of nitrogen gas is added to the reserve tube. The result of this alteration is a dramatic reduction in "foaming" or "aeration", the undesirable outcome of a twin-tube overheating and failing which presents as foaming hydraulic fluid dripping out of the assembly. Twin-tube gas charged shock absorbers represent the vast majority of original modern vehicle suspensions installations.
◎Position sensitive damping
Often abbreviated simply as "PSD", this design is another evolution of the twin-tube shock. In a PSD shock absorber, which still consists of two nested tubes and still contains nitrogen gas, a set of grooves has been added to the pressure tube. These grooves allow the piston to move relatively freely in the middle range of travel and to move with significantly less freedom in response to shifts to more irregular surfaces when upward and downward movement of the piston starts to occur with greater intensity. This advance allowed car designers to make a shock absorber tailored to specific makes and models of vehicles and to take into account a given vehicle's size and weight, its maneuverability, its horsepower, etc. in creating a correspondingly effective shock.

◎Acceleration sensitive damping
The next phase in shock absorber evolution was the development of a shock absorber that could sense and respond to not just situational changes from "bumpy" to "smooth" but to individual bumps in the road in a near instantaneous reaction. This was achieved through a change in the design of the compression valve, and has been termed "acceleration sensitive damping" or "ASD". Not only does this result in a complete disappearance of the "comfort vs. control" tradeoff, it also reduced pitch during vehicle braking and roll during turns. However, ASD shocks are usually only available as aftermarket changes to a vehicle and are only available from a limited number of manufacturers.

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