RE: Coilovers vs. Shocks/Springs/Struts

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

Khan-

The coil isn't fixed in place.  It isn't attached in any way.
Compression and weight are all that holds it in place.  On my
Dodge Ram, there isn't even compression, just the weight of the
vehicle.  On the spring perch is a rubber gasket that's about
1/2" thick that provides some adhesion and noise reduction.

I know this probably makes it sound like the spring should be
moving all over the place, but with several hundred pounds 
pressing on it all the time, and with the way that the upper
mount point is fixed and the lower point is allowed to move
only vertically (never side to side, unless ball joints are
extremely worn), the spring doesn't need anything further to
keep it in place.

On many vehicles, catching air is a problem, as the suspension
system is not really designed with this in mind (jumping, that's
is, not hoisting).  When jumping, the suspension uncoils very, 
very quickly.  Whatever suspension element limits maximum droop 
will undergo an extreme stress.  Often that element is the shocks 
as they expand to their maximum point.  

You may notice that some 4x4 trucks that want to jump will have 
limiter straps added to the system, to address this problem.
The strap keeps the spring from fulling releasing, and perhaps
moving from its intended location on the spring perch, and from
the shocks being the droop limiter and inadvertantly breaking a
shock.

Steve Belt - Scotts, AZ
1998 VW Jetta GLX

-----Original Message-----
From: Khan Klatt [mailto:khan@mediaaccess.com]
Sent: Thursday, April 06, 2000 8:34 PM
To: jettaglx@igtc.com
Subject: Re: Coilovers vs. Shocks/Springs/Struts



Beautiful. I got it now. So the first coil and the last coil actually 
sit inside the "trays" of the strut. So, where the strut comes in 
contact with the first and last coil of the spring, what holds the 
spring in place is simply that the spring is compressed, and can not 
expand beyond what the strut can expand to...

Maybe you said it below, but I'm not exactly sure how the first coil 
and the last coil are "fixed" (if they even are) to the strut 
"trays", or what you called the perch. Perhaps they turn a little 
into a slot in the perch on the bottom and the top, effectively 
locking it in place?

-Khan


At 6:55 PM -0700 04/06/2000, Chuck Van Pelt wrote:
>I guess it's a hard concept to explain without a visual aid. The strut is
>made up of a shock mounted inside a spring. The shock is basically a piston
>moving inside a cylinder, dampened with some fluid.
>
>There are two "perches" on the strut that hold the spring in place. The
>lower perch is mounted to the strut body (the cylinder) and the upper perch
>to the top of the shock (the piston). The piston can only come out of the
>cylinder so far...that's what holds the spring in place. To install the
>spring, you have to compress it (with spring compressors), slid it onto the
>lower perch, put on the upper perch and put a nut on the shaft to hold the
>upper perch in place. Then you release the compressed spring and you have a
>strut.
>
>Check out this illustration...I did it in Paint so I apologize for the
>crappy quality.
>
>http://www.aracnet.com/~cvanpelt/strut.jpg
>
>Chuck
>
>Khan Klatt wrote:
>
>  > Thanks to Chuck and Steve for the responses...
>  >
>  > I still have a question about how the components attach still. If
>  > these things car vary, take the Jetta as an example.
>  >
>  > You bolt the strut to the body of the car, and to the axle or some
>  > other fixture on the drivetrain, that I understand.
>  >
>  > The question still remains in my mind... Chuck used the words "spring
>  > perch". How do you attach a spring to a spring perch? Or does it just
>  > stay in place due to the weight of the car (not likely, what happens
>  > if you try to tow the car, or catch some air...?)
>  >
>  > Does the spring "thread through" an eye in the strut? Does it have a
>  > threaded hole through which to pass a bolt to affix it to the
>  > drivetrain and to the body of the car? Do you simply "coil" it
>  > through an opening?
>  >
>  > I just can't picture how, mechanically, the spring is kept in place.
>  > I guess the simplest thing to do is to crawl under my car or
>  > something...