More..Upper stress bar questions

[Larry" <rocco16v@netzero.com (Larry)]

After reading recent posts about rear stress bars, I started thinking
(uh-oh...).
Does that item actually perform a useful function?  Oh, I know many of you
report impressive handling improvements resulting from the installation of
one, and I was seriously considering putting one in my own roc.  But, after
looking carefully at the rear suspension design, I don't believe they can be
of much benefit.
  Yes, they certainly minimize the movement of the rear damper/spring unit's
upper mounting points, but only in one plane, that plane being directly
towards and away from each other (>< or <> aka the x-axis).  The big
question is:  what stresses would make these two mounting points move
together/apart?
   Lateral forces from cornering are completely absorbed by the rear axle
mounts (axle-to-floorpan). No lateral stresses (x-axis) can be present at
the top of the damper/spring units because these units are attached to the
body and the rear axle with flexible attachments.  When the rear axle moves
slightly sideways during cornering, the damper/spring units just pivot
slightly in their upper and lower rubber bushings and absorb this movement.
The bottom of the d/s unit moves in the x-axis with the axle, but it pivots
on the mount, therefore it cannot transfer x-axis forces to the top of the
d/s unit. (Okay, it does transfer very small amounts, because the mounts
have some stiffness, some resistance to that flex, being made of rubber or
polyurethane.  If the mounts were Heim joints, there would be zero transfer
of force).

The only significant stress on the upper mount (at any time) is in the
z-axis; a VERTICAL direction (^), which the stress bar cannot control.
I realize that this may unleash a flood of responses telling me how wrong I
am, but before any of you do that, be sure you can back up your postion with
more than "Hey, all the racers use 'em and they can't all be wrong!" or "I
put one on my car and could really tell the difference."  Those are not
valid, defensible engineering positions.

Any thoughts?
Larry  sandiego16V

----- Original Message -----
From: <Cmr446@cs.com>
To: <scirocco-l@scirocco.org>
Sent: Saturday, June 15, 2002 12:28 AM
Subject: Upper stress bar questions


>   I need opinoins or reasons on which is the better design for an upper
> stress bar;
> the solid type like the Eurosport, Neuspeed or ABD model, or an adjustable
> one like the Autotech bar.
> Carl
> 77rocco
> 89fox