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[tech] swaybar question
Let me restate my original point.
If you put stiffer sway bars on both ends of the car the car will roll
less. This assumes the bars are stiffer in the correct proportion and
that the front/rear roll stiffness distribution remains unchanged. The
car will handle substantially the same, will have slightly higher grip
due to the more upright tires and will be more responsive.
You are correct in that getting the roll stiffness distribution correct
will have a much bigger influence on handling in a street driven car
than reducing body roll and adverse tire camber by a couple of degrees.
You are incorrect in you description of the Scirocco rear axle's
behavior. The Scirocco rear axle with its twist beam essentially at the
trailing arm pivot has NO camber gain. In other words the tire's camber
will change the same amount the body rolls. Later VW's have the twist
beam moved back from the pivot. These have camber gain that is some
consistent percentage of body roll. Cars with a beam axle where the
cross beam is placed longitudinally at the axle center line have camber
gain that matches body roll.
For all intents Sciroccos have essentially no camber gain front and
rear. Limiting body roll is the key to getting maximum grip with this
kind of suspension particularly in racing applications with wide low
profile tires.
Dan
Neal Tovsen wrote:
>
> > Changing both makes the car roll less. So, the tires are more upright
> > for a given cornering speed. This should give higher grip.
>
> This is true. However, if this were the whole truth, a large rear swaybar
> would make the rear end stick MORE, making it understeer MORE. Right? It
> isn't the whole story, and actually isn't even the most important part.
>
> A swaybar transfers load from one wheel to the other. Specifically, it
> transfers load from the outside wheel to the inside, thus REDUCING traction
> on that end of the car, moving the traction balance of the car toward the
> opposite end. This is how a larger rear swaybar promotes oversteer - a rear
> swaybar actualy reduces rear traction, allowing the car to turn better. The
> weight transfer properties are (almost always) much greater than the grip
> gained by keeping the body/tires flatter. This is especially true for the
> torsion beam rear tire, which doesn't have tire contact issues because it
> gains camber fairly consistently with the amount of body roll.
>
> Neal
>
> > -----Original Message-----
> > From: scirocco-l-admin@scirocco.org
> > [mailto:scirocco-l-admin@scirocco.org]On Behalf Of Dan Bubb
> > Sent: Friday, January 18, 2002 9:04 AM
> > To: ATS - Patrick Bureau
> > Cc: Jeffrey Lowe; scirocco-l@scirocco.org
> > Subject: Re: [tech] swaybar question
> >
> >
> > Changing both makes the car roll less. So, the tires are more upright
> > for a given cornering speed. This should give higher grip.
> > Also, the car will respond better in transient manuevers. If
> > it doesn't
> > roll as much it takes less time to get to it's maximum roll angle, so
> > the car would feel much better if you were doing a slalom.
> > The downside? The suspension is slightly less independant
> > side-to-side.
> > Dan
> >
> > ATS - Patrick Bureau wrote:
> > >
> > > No this I can UNderstand, Thank you for the answer, now one
> > more question,
> > > why would someone with an 8v wnt to jump up the swaybar
> > from 17/20mm to
> > > 25/28mm race swaybars? what does changing BOTH to tighter
> > provide? If
> > > changing only the rear to a 16v swaybar is bad for my 8v,
> > how about changing
> > > BOTH to higher specs? would that provide "stiffness"
> > without understeer?
> > >
> > > Patrick
> > >
> > > -----Original Message-----
> > > From: scirocco-l-admin@scirocco.org
> > > [mailto:scirocco-l-admin@scirocco.org]On Behalf Of Dan Bubb
> > > Sent: Friday, January 18, 2002 6:36 AM
> > > To: Jeffrey Lowe
> > > Cc: scirocco-l@scirocco.org
> > > Subject: Re: [tech] swaybar question
> > >
> > > The 16V is heavier than the 8V. Specifically, the front of
> > the 16V is
> > > heavier. So, the front springs have a higher spring rate than the 8V
> > > front springs. (The rear factory springs are different
> > also, but their
> > > spring rate isn't much different.) Higher front spring rate
> > increases
> > > the front roll stiffness. So, with a cornering load more of
> > the weight
> > > transfer will happen at the front causing the car to understeer. VW
> > > compensated for the stiffer front springs by increasing the
> > rear roll
> > > stiffness with a larger rear sway bar.
> > > For a street driven car where ride is important, the ratio of
> > > front-to-rear spring rates is calculated based on front/rear weight
> > > distribution, wheelbase and average speed (speed you want the ride
> > > optimized for). so, if you change the front/rear weight distribution
> > > that should change the ratio of front/rear spring rates which will
> > > change front/rear roll stiffness distribution. This roll stiffness
> > > distribution may not be optimum for handling. This is corrected by
> > > adjusting the roll stiffness distribution with sway bars.
> > > Putting a stiffer rear bar on will cause the car to
> > oversteer more. If
> > > the car is reasonalby balanced in it's handling from the
> > factory, then
> > > the stiffer rear bar could cause pretty drastic oversteer just like
> > > removing the front bar. I still remember the pictures of
> > the guy that
> > > removed his front bar and then, without approaching the limits with
> > > caution, went out and backed his car off the road causing
> > considerable
> > > damage.
> > > (Yes! I know Shine racing says to remove the front bar, but
> > that is with
> > > their springs which have a different ratio of front/rear stiffness!)
> > > The suspension on a car is a system. Springs, shocks, swaybars,
> > > bushings, geometry. It all has to work together. Just
> > because 16V parts
> > > will fit on an 8V doesn't mean they're appropriate for that
> > application.
> > > Dan
> > >
> > > Jeffrey Lowe wrote:
> > > >
> > > > What? I'm a little confused, if the front sway bars
> > > > are the same then how would upgrading the 8v to 16v
> > > > configuration make the handling something to be
> > > > concerned with? Wouldn't it just make the 8v the same
> > > > as the 16v?
> > > >
> > > > --- Dan Bubb <jdbubb@ix.netcom.com> wrote:
> > > > > The front swaybar is the same between the 8V and the
> > > > > 16V.
> > > > > If you install the 16V rear bar your car will
> > > > > oversteer more or understeer less depending on how
> > > > > you look at it. In particular the back end will come
> > > >
> > > > > around alot more dramatically if you let off the
> > > > > throttle in the middle of a corner.
> > > >
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