Chucks' Strut Tower Bar

[Bernie Benz]

Chuck, 

Different solution philosophies are involved in Strut vs. Tower braces.
The Strut brace design intent is to reduce the maximum applied lateral
deflecting force applied to the tower thus likewise reducing tower
deflection. The Tower brace intent is to stiffen the tower(s) to better
withstand the full maximum lateral force. They accomplish the same result
relative to strut top deflection caused by lateral cornering forces, if one
ignores the considerable upper strut elastomeric isolator deflection in the
comparisome. 

LetŒs do so at this point. Thus, this limited design comparisome is one of
applying elementary strength of materials considerations within the physical
constraints, as well as cost and weight considerations. Either brace, to be
effective, must be an order of magnitude stiffer than is the structure being
stiffened. This implies that the column member must be straight and without
couple (rotational) forces applied by the end attachments, and that this
stiffness requirement include these attachment devices and associated
fasteners. Inasmuch as you (Chuck) neglected to supply attached photos of
your brace design, I leave this subjective comparisome to your interested
parties.

Now, letŒs consider the upper strut elastomeric isolator deflection
differences in the two brace concepts. The Strut brace, by combining in
parallel the isolators of both struts, reduces this isolator deflection by a
factor of 2. It further allows static preloading of the isolators for
additional stiffness and camber correction. The isolator loading remains
stock, out of the picture, in the Tower brace configuration.

Chuck, if you have suffered permanent displacement of your strut towers (I
have not, maybe because of the installed Strut brace for the past 8 or 10
years), IMO you need to jack them back within the chassis spec before adding
any brace.

Happy New Year!

Bernie

> From: Chuck Pierce <cpcycle at earthlink.net>
> Date: Sat, 30 Dec 2006 21:39:35 -0800
> Cc: 200q20V mailing list <200q20v at audifans.com>
> Subject: Re: Chucks' Strut Tower Bar
> 
> Bernie
> 
> One of the reasons I chose to not use your design was the application of
> a more than normal preload to the upper strut mount bushing.  I
> preferred to try to get the strut towers back to the original position
> and adjust to spec. from there. I was originally going to build the bar
> and then have a body shop use their laser frame table to get the front
> of the car straight. The cost of that procedure was more than I wanted
> to spend. Since we have had some success in spreading the towers on a
> car and the fact that this lowered car is now within factory specs. I
> believe we have accomplished the goals I set. These cars are known for
> being a little soft in the front end when it comes to torsional
> rigidity. So this bar addresses some of that problem. (Remember when the
> Type 44 V8 was built it was given a strut tower bar) When speaking to
> the folks that I know that build race cars and modify performance
> vehicles, their opinion was that the way we spec'd the bar and built it
> was a good solution.
> 
> Both of our solutions get the cars to be able to be aligned within spec.
> 
> Just different ways of accomplishing it.
> 
> <> 
> Chuck Pierce
> 
> 91 200 20V Avant
> 
> 
> 
> Bernie Benz wrote:
> 
>> Pat,
>> 
>> Maybe ³ineffective³ was an overly strong word. Better might have been: Less
>> than maximum, optimum functional effectiveness at a severe cost premium.
>> 
>> A well designed strut brace doubles apparent chassis lateral stiffness as
>> reflected at the upper strut mounting point by equally dividing the strut
>> top latteral cornering force between the two towers. The best possible
>> outcome within the chassis design limitations. A tower brace accomplishes a
>> small portion of this objective.
>> 
>> Bernie  
>> 
>> 
>> 
>>> From: "Patrick Anderson" <patrick.anderson1 at comcast.net>
>>> 
>>> My car benefitted from installing a tower bar. Noticed the difference
>>> primarly when pushing the car really hard but I could also tell the
>>> difference in front end rigidity on my normal commute if I paid close
>>> attention. Why do you think it is functionally ineffective? Many car
>>> manufacturers put them on cars right from the factory and they seem to think
>>> they work. My personal experience and factory know how seem to suggest they
>>> are good for something.
>>> 
>>> Patrick
>>> 
>>> 
>>> 
>> 
>> 
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