[200q20v] Strut braces, here we go again!

Bernie Benz b.m.benz at prodigy.net
Thu Feb 1 00:06:40 EST 2001

The ultimate goal any strut brace device is to minimize strut rod latteral
movement relative to the ball joint, i.e. to minimize camber change caused
by latteral cornering forces.  To understand the effectiveness of any such
device, one must differentiate between a strut to strut brace and a tower to
tower brace, and analyize how each differently affects strut rod latteral
movement in a MacPherson strut suspension design.  The Benz Brace is a strut
to strut brace, most others (all others, to my knowlege) are tower to tower

The latteral cornering force exerted by the strut rod is first exerted on
the compliant rubber bushing between the rod and the tower, causing
deflection therein, and is then passed on from the bushing to the tower,
causing tower deflection.  In the ultimate corner, this maximum latteral
cornering force is transmitted only from the outside strut rod (inside wheel
off the ground) to its rubber bushing, causing a maximum deflection of this
bushing, and thereon to the outside tower, causing a maximum deflection of
this outside tower.  Thus the total outer strut rod movement causing camber
change is the sum of bushing and tower deflections.  Further, realize that
stiffness of the welded steel tower is orders of magnitude greater than is
the compliant rubber bushing, i.e. bushing deflection is much greater than
tower deflection

A tower to tower braced system divides the tower deflection between both
towers but retains in full the larger deflection of the outside bushing, and
thus results in only a small camber change improvement over the unbraced
condition.  Further, because of the high stiffness and resultant small
deflections of the towers, to be effective in dividing tower deflection
forces between the two towers a tower to tower brace must be extreemly
stiff.  None are, most having bolts, brackets, and bends.  IMO, they serve
only as cosmetic window dressing and a lighter wallet.

Contrast this with a strut to strut braced system, in which the brace
divides the latteral cornering force equally between the two strut tower
systems, bushings plus towers.  The resultant movement of the outside strut
rod is half of the same unbraced system, and considerably better than the
tower to tower braced system because, by design, the t to t has excluded
bushing deflection, whereas the s to s has included bushing deflection in
the dividing process.

Think about it!



> From: C1J1Miller at aol.com
> Date: Wed, 31 Jan 2001 14:39:44 EST
> To: <b.m.benz at prodigy.net>
> Cc: <200q20v at audifans.com>
> Subject: Re: [200q20v] Re: Strut Brace
> In a message dated Wed, 31 Jan 2001  2:15:46 PM Eastern Standard Time, Bernie
> Benz <b.m.benz at prodigy.net> writes:
> << Chris, from a strength of materials perspective a bent tube is useless as a
> load bearing column, including all of the S4 stock and aftermarket tower to
> tower braces.  Further, the brake fluid reservoir is not in the way of a
> straight strut to strut brace.
> Bernie
> Nah, just make the walls of the tubing thick enough.  Again, deflection is
> very small; forces are fairly small.  Without the brace, the car is _almost_
> stiff enough.  You're not trying to withstand _all_ the forces, just add
> strength to the existing structure.  Point taken, though; if the bar is bent,
> you're using a spring to keep the struts apart...
> Again, simplest (for a strut tower brace, not Bernie's style, but the S4/6 or
> V8 style) would be to use Audi's parts, including the brake fluid reservoir.
> Haven't tried to swap it, but expect it would be a swap...  Anyone have both
> cars?
> Chris
> _______________________________________________
> 200q20v mailing list
> 200q20v at audifans.com
> http://www.audifans.com/mailman/listinfo/200q20v

More information about the 200q20v mailing list