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DieselTruckResource.Com FAQ Listing : High Performance and Aftermarket Accessories : Shocks explained |
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| Question: | Shocks explained | | Answer: | I have read a lot of posts asking what shocks are best. I do not plan on answering that question but I will give a general background into shock absorbers. First let me explain where my knowledge comes from. I am a ride development engineer for an OEM shock and strut supplier. In more general terms I am the guy who goes to the proving grounds and works with development engineers from the OEM to determine/develop the ride and handling characteristics of the vehicles. I do not work for the company who manufactures the shocks on our trucks. I want to keep this information unbiased so I will not be referring to any manufacturers.
A shock absorber is a type of suspension damper. The purpose of the damper is to absorb the kinetic energy of the suspension system and transfer it into thermal energy and then dissipate the thermal energy. The shock absorber does this by forcing oil through/past internal passages in the damper. Most non-specialty shocks have two valve assemblies that develop the control or Damping Forces of the shock, one assembly for compression/jounce and one assembly for rebound/tension/traction. The damping forces for a shock are different at different stroke speeds.
Advertising hype has led to some misconceptions about shocks as well. Nearly all shocks manufactured now are gas charged.
1) Twintube shocks are charged to a lower pressure roughly 50psi to 150psi, while Monotube shocks are generally in the 250psi to 300psi range. The gas used is Nitrogen. 2) All shocks are speed or velocity sensing, the number of speeds that they “sense” may vary from design to design and manufacturer to manufacturer and how they chose to test their product.
3) The size of the OEM shocks is determined by strength and performance requirements and must pass strict testing before being used in production. Bigger in shocks is not always better. More oil volume means more heat dissipation capability but larger internal components means a reduction in fine-tuning capabilities for comfort.
4) You do not always get what you pay for, some times you are buying the name that is carried over from another product the company makes.
In general there are two types of shock absorbers, Monotubes and Twintubes. Each type has its advantages and disadvantages.
Twintubes can generally develop a plusher ride due to the lower nitrogen gas charge and monotubes generally have a sportier ride.
Monotubes are lighter but more sensitive to damage. The piston slides inside the tube passing oil through it, if the tube becomes dented the piston is no longer able to slide rendering the shock useless, potentially causing more damage. On a twintube the piston slides in the inner tube so a dent to the outer body not critical. The tube on a monotube is generally made thicker to offset this weakness as well as the higher internal pressures.
Monotubes can be mounted with the body up because the gas and oil are in separate cavities and held in place not free to move to the bottom of the body. The separate cavities can also lead to better performance because the gas and oil can not mix.
Monotubes are more expensive to manufacture because they require thicker tubes and a higher degree of precision.
Article written by Ryan | | last updated 3.09.2002 | user rating:  | |
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