Answers to Strut brace and body roll

[sincatx@airmail.net]

Hey, Lewis if you want to see how well the strut brace works I have one left
over. Your questions can all be answered for $165.00 and alittel time to bolt
it on correct.   Rick
P.S. Huw got his from me.





>Huw Powell <human@nh.ultranet.com> wrote:
>
>> OK, let me first point out that I don't know what the heck I'm talking
>> about here...
>> 
>> My observation is mostly based on what changed about my car when I
>> bolted that sucker on.  It stayed level while turning, radically so. 
>> On little turns, low speed stuff, it was like a lawnmower or something
>> - it just stayed level.  On harder turns, it dips a whole lot less
>> than it used to.  Is this body roll that has been lessened?
>
>Did you change anything else when you installed the strut brace, Huw?
>By stiffening the front end the car is likely to respond quicker to steering
>inputs and subjectively it may "feel" like flatter cornerring, but I bet the
>actual roll for a given lateral acceleration is virtually the same (unless you
>changed springs/swaybars at the same time).
>
>> How does it do it?  I think the sway bar is doing as much as it can
>> from below, to apply opposing force to the control arms, trying to
>> keep them level.  (deep water warning - I can't swim!)  Since the
>> suspension seems to me to be essentially a parallelogram (or
>> trapezoid?) in the lateral cross section of the car pair of
>> dimensions, stiffening the other long side of the figure (the top)
>> aids in the process.  Of course what this "stiffening" amounts to
>> dynamically is that as the parallelogram (trapezoid!) is being pushed
>> out of shape at one corner, the sway and stress bars are transferring
>> the force across to the opposite side, even the opposite corner, to
>> attempt to correct this distortion.
>
>I'm not sure I follow what you are saying, but yes, there is some distortion of
>the uni-body sheet metal - even though it's very small relative to how much a
>sring compresses on the outside and extends on the inside.
>
>> This all depends on the tendency of the strut towers to be able
>> (undesirably) to move relative to each other without something taking
>> corrective action.  The stress bar does this.  This relative motion I
>> would presume to be in all three dimensions, affecting caster, camber
>> and toe in.  Lessening this makes the car behave better while
>> cornering, by keeping the alignment of the tires where it is supposed
>> to be, relative to each other and the body.
>> 
>> Have I rented a clue yet?
>
>Yes, you have a clue :)  The small movement of the strut towers translates in
>small changes in the suspension geometry.  The towers may move in at the
top, or
>they may move out, or one may want to go up and the other may want to go down. 
>Minimizing these deflections gives you a stiffer, more responsive, perhaps less
>understeering chassis.  But let's  be realistic.  How much can these strut
>towers really move? 0.1"? (educated guess) That translates into about 0.1
>degrees of body roll.  Compared to the 5-7 degrees (or more) or body roll
due to
>how much the suspension compresses on one side and extends in the other, that's
>negligible.  Even the best track suspensions will roll 2-3 degrees.
>
>> Love to hear how close I am from someone who actually knows about this
>> stuff.
>
>I would also like to hear from someone who really know this tuff, as I am not a
>chassis expert either ;)
>
>Luis Marques
>
>