please explain shocks, struts, & coilovers

[starquestbd]

i'm not positive on all of my suspension knowledge.  are shocks and struts basically the same thing?  if so, then you don't need shocks AND struts on any vehicle, right?  also, are coilovers just adjustable shocks/struts?  am i correct that the starquests have struts with coil springs on all four corners?  please forgive my stupidity....i'm trying to learn.

 

thanks,

Brandon

[mikec]

Okay, my understanding of the various types...  but I'm not 100% positive on everything.

 

Shocks: pure dampers - they keep the car from bouncing up/down on springs.  Shocks provide some resistance to motion; the faster the motion the more the resistance.  Performance shocks allow different force vs. velocity curves for rebound compared to compression.  This way, you can let the wheel "ride over" bumps in the road easily (i.e. low damping in the compression direction) with more damping in rebound.  Airplanes work this way too - keeps the aircraft from bouncing on landing.  It just "settles" lower and lower on the suspension; the high rebound damping keeps the aircraft (or NASCAR cars) sucked down to the ground... it takes a while to rise back to normal heights.

 

Coil-overs: basically, shocks with a "helper" coil added that supplements the springs already present in a vehicle.  Typically these are used as a cheap way to increase load capacity of trucks, RVs, etc.  Side effect: that extra spring stiffness causes a rougher ride.  Also, extra spring rate acts like a stiffer roll bar too - the car won't roll as much in corners which is why some people add coil-overs onto sports cars.  Now, some coil-over designs do include an adjustable collar that you can screw up/down to change the ride height of the car.

 

Both shocks and their coil-over cousins mount to the car via bolts/studs at both ends... and all they do is damping - they do NOT do wheel "locating" like the A-arms, axles, or whatever.  In other words, if you took them off, the car would still be able to stand on its wheels and drive.  Struts, on the other hand, are a major component of the suspension - they are the vertical load path.  Without them, the car would have its floor sitting on the ground and the tires would be all the way up inside the fenders.  Typical struts, including the StarQuest design, incorporate the damper (shock) function and a spring that looks just like a coil-over shock.  Most strut suspension designs have 3 links: the strut itself to locate the wheel vertically (relative to the car body), a lateral link to locate the wheel in/out from the body, and some sort of longitudinal link to locate the wheel front/aft along the car.  The lateral links are typically beefy parts - also called "control arms" and are the big beams on the front suspension, part of the lower "A" shape on the rear.  Longitudinal links in the front are just metal rods; part of the "A" in the rear.

 

So yes, the StarQuest design is 4 struts.  Advantages of a strut: the layout is basically an "L" shape - so the engine and trunk "fit" between the suspension.  Disadvantages: the wheel motion isn't purely up-n-down, the tilt (camber) varies a bit especially near the extremes of wheel travel.  The lower "A" arm on the rear of StarQuests mvoes along a diagonal line (crawl under the car and look at the bushings) so the wheel tilts in/out and left/right as the wheel moves... nasty for handling... so the springs are pretty stiff in the back to limit total travel.

 

Adjustable shocks work by varying the diameter of the oil passage inside the shock.  88-later StarQuests with the handling package had adjustable shocks.  There are aftermarket strut assemblies for StarQuests that include adjustable spring perches/collars to allow the ride height to be adjusted.

 

mike c.

[xero]

Very well explained except for one thing.  When replacing a suspension on a starion what would be the needed replacements if you wanted to replace every part of the suspension on the starion.  Shocks, Struts and any other known notoriously bad high mileage parts.

 

Joe C.

[cooltsi]

I have not seen too many "coil-overs" that are used as a supplement here.  Most are a replacement for the stock spring.  The term 'coil-over' was coined many years ago when the springs(often leaf) and shocks were disassociated.  

 

If you see "coil-over" here it is in reference to the Ground Control or a custom built spring and perch that replaces the stock spring and perch.  Gramatically, any McPherson strut is a Coil-over.  

 

Now if your on the Camaro boards of old then a coil-over would be a helper in addition to the Leaf springs or hopefully part of a 4 link conversion.

 

Sorry for the grammatics but Coil-over is not an accurate depiction of the Ground Control or any other setup for the Starion/Conquest.

 

If your looking to replace suspension components look to the steering also.  Check the end links and balljoints on the frontend.  Realistically the stock springs and shocks on the Starquests are fairly decent.  Tokikos and KYB's or a mix of the two depending on your year and model.  I've torn a few Starion Suspension down now and the bushing the front arm pivots on is pretty worn on most.  The radius rod ends are a bit cracked usually but they are easy to change.  Sway bar bushings and end links are usually shot, especially the front.  The front upper strut caps.  The rubber portion that sticks into the engine compartment is almost always shot, look to the rears also.  Rear lowers are usually fairly healthy with some wear on the outer two pivot bushings.  Realistically they are pretty durable with the exception of the front upper strut bearing plates.