RE: Coilovers vs. Shocks/Springs/Struts

["Belt, Stephen D" <stephen.d.belt@intel.com>]

Kevin sez>
> > also, I'm not sure what struts are. Are 
> > they simply a different term for shocks?
> > 
> Yup. "Shocks" is not really the proper terminology, since they're not
really
> doing any of the shock absorbing (that's what the springs are for). Call
'em
> dampers or struts.

I believe there is a definition difference between shocks and struts:  

Yes, they are both do on thing in common, dampen the spring so that it 
doesn't oscillate forever.  However, struts do one thing that a shock does 
not do:  struts help control the direction of movement of the wheel, most
notably straight up and down.

Put another way, a strut defines clearly the direction that the wheel can
travel up and down, and is attached to the vehicle in a way that controls 
the direction of travel.  

A shock only dampens.  It does not control the direction of travel of the 
wheel.  

Struts are typically mounted so that they allow the movement in a vertical 
direction on vehicles with independent suspensions.  Shocks can be mounted 
vertically (for example on the front end of a Ford or Dodge truck), but can 
also be mounted at an angle to the direction of travel of the wheel (for 
example on the rear end of any full size pickup truck).  The reason they are

mounted at an angle is to help with spring-wrap or axle-hop.  The shock is 
able to help keep a leaf spring from forming into an "S" shape if it is 
mounted at an angle (though it should be noted that shocks offer only very
limited help in solving this problem).  Vehicles with a lot of low end
torque, 
tall tires, and leaf spring suspensions are able to best utilize the
advantage 
of mounting a shock at an angle to the direction of travel of the wheel,
which 
is why you see them so prominantly on full size trucks.

Last, because struts affect the location of the wheel in which they dampen, 
they are a key element of the alignment geometry of those wheels, and
changing
them will require a new alignment be done.  Changing a pair of shocks,
however,
will not require a new alignment be done.

Steve Belt - Scotts, AZ
1998 VW Jetta GLX