Re: [tech] suspension - Front upper stress bar Q's

[16v Jason <jason@scirocco.org>]

Hi Andy,
         The upper stress bars won't help the strut towers themselves from 
cracking or disforming -- but they will help the torsional rigidy of the 
car as a whole.  Imagine for a minute what the front of the car looks like 
without any body pieces up front.  You have two crossmembers running 
longitudinally, connected at the bottom by the front crossmember, 
stressbar, and engine.  But you have no support higher up, because the hood 
can't be welded to the fenders...

Thus, on bumps and high-force curves, the whole front end of the car can 
easily bend.  Adding an upper-level support member greatly reduces body 
flex down below.

If you drive a car with an upper brace right after one without, you can 
feel the difference immediately.  Turn-in is considerably quicker with the 
tie-bar.  The steering is more precise over surface irregularities, and the 
car tracks much better.  The biggest difference is on long sweepers with 
undulating or slightly bumpy (i.e. not enough to bottom the 
suspension).  Take the turn really fast (like at 90%) and keep the steering 
wheel in the same spot.  You'll notice the car squirm around a whole lot 
less with the upper tie bar.  The reason is because the front isn't flexing 
as much, which keeps the steering geometry more consistent.

Mind you, you'll _never_ eliminate body flex on an A1 by doing anything 
short of welding in a 500-point roll cage, but if you're a sensitive enough 
driver to be able to feel the frame flexing, you'll feel a tremendous 
difference with the upper tie bar.

And, as an aside, if it didn't work, stiff-framed cars like the E36 BMW 
3-series wouldn't use them on the M3s. :)

Jason



At 08:14 PM 1/15/01 , andkat wrote:
>I don't think anybody would notice the car handling any different with or
>without a upper stress bar.  The only time I've seen the paint on the strut
>towers cracking is after somebody hit a curb.  There is just know way those
>things are going to flex enough to make a difference. The lower is a
>completely different story.
>
>Andy 1.9 '79
>-----Original Message-----
>From: Randy Block <RandyB@E-Risk.com>
>To: scirocco-l@scirocco.org <scirocco-l@scirocco.org>
>Date: 15 January, 2001 12:29 PM
>Subject: [tech] suspension - Front upper stress bar Q's
>
>
> >Ok,
> >Since were on the subject of suspension components.
> >I am currently running a Neuspeed upper strut tie bar, always have on my
> >A1's
> >What are others running that they believe to be better and why?
> >I have always had my doubts about the Neuspeed unit due to small tubing
>dia.
> >and possible flex at the bends.
> >I have had to BOW the bar to get it to fit before, this seems to discredit
> >the functionality of the bar, right?
> >Should the bar have SOME flex in it?
> >I have seen other designs that seem to provide more stiffness, Dick W's
> >square tube bar, Craig's stainless bar, bars with much larger tubing dia,
> >etc... etc...
> >My guess is the reason the Neuspeed bar is so common is simply due to the
> >#'s made and the low price.
> >
> >I guess my question is:
> >Is STIFFER better, or should there be a little flex in the upper strut tie
> >bar.
> >
> >Thanks,
> >
> >Randy B
> >81 (Mars) Scirocco S - Techtonics Tuning 1847cc 8V
> >81 (Cosmos) Scirocco S - future Oettinger 16V project
> >87 Jetta GLI 16V - daily driver
> >
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> >
>
>
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----------
1987 Scirocco 16v
1988 Mercedes 190E Sport Euro


http://www.scirocco16v.org


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