Sway bars tranfer weight from the inside wheel in a corner to the outside
wheel-think about that for a minute.

At a given cornering speed a car will transfer X amount of weight from the
inside to the outside. Some of the weight will be transfered at the front,
some at the rear, depending on suspension design, ride height, weight
distribution etc...  Sway bars allow you to vary the percentage transferred
at either end of the car, generally the more weight you transfer at an end,
the less grip it has.  A VW has 65% of the weight over its front wheels,
therefore in stock configuration most of the weight is transfered at the
front - onto the outside wheel which quickly becomes overloaded and starts to
slide. Factor in trying to get the power down and the understeer increases
even more.  Increasing the size of the front bar just makes this problem
worse.  The only mitigating factor is the bar does reduce suspension
compression, therefore keeping the camber in a more favorable area of the
curve.  This is why people autocrossing in stock class, where the rules
prohibit any spring/rear bar change find that a big bar actually improves
times. The front bar has another bad effect- it unloads the inside front
tire often resulting in wheelspin (especially in VR6 cars).

On a street car a big front bar just makes the car feel worse than stock. A
rear swaybar increases weight tranfer at the back of the car (and reduces it
at the front) onto the outside wheel.  This is desirable since the rear tire
is not doing much work (compared to the front).  By reducing the load on the
front tire you increase available grip, and the car feels much more
balanced.  For people who don't want to change springs the best setup for
street driving is a large rearbar in conjunction with the stock front bar.
This gives improved overall grip, and a much better "balance".

By improving the grip you are able to corner at a higher rate of speed,
which means more weight will tranfer, which means the outside front tire
will overload, which means it will slide = understeer again.  To counteract
this weight transfer and compression of the suspension we supply stiffer
springs which control the roll.  With less weight transfer you can corner
faster = more weight transfer = overloaded outside tires = need stiffer
springs = less weight tranfer = can corner faster = more weight
transfer = overloaded tire  etc..  This continues until the springs are so
stiff that you you lose adhesion over bumps or you are lifting both inside
wheels.

We choose our street springs to offer a good compromise between ride and
handling.  This is not to say that stiffer springs will always handle
better, especially on the street where there are many bumps and tires offer
comparatively low adhesion. We try for a rate that allows good compliance
while limiting bodyroll to a minimum.