der Bayerische March/April 2020 - 34

more to the understeer side of the spectrum. If you've already done a competition alignment (as previously described), and your car still understeers (as is
typical with front-wheel-drive or all-wheel-drive cars), then replacing the rear
sway bar with a bigger, stiffer bar will help the car rotate and make the car's
handling more neutral. If your car tends to oversteer (as is typical with rearwheel-drive cars, especially higher-horsepower cars), then replacing the front
sway bar with a bigger, stiffer bar will reduce body roll during cornering and
will adjust the car's handling more towards understeer. DO NOT add a bigger
front sway bar to a car that already understeers, even if you're trying to reduce
the car's body roll; that'll only make the understeer even worse (unless you're
David E, who somehow manages to make a bigger front bar work for him, in
conjunction with his Koni shocks & struts and bigger tires. However, us
normal human beings swear that David [and Tommy, and Mark S, and Mark
C, among others] must be aliens from another planet to make a car do what
they do.) In that scenario (a rear-wheel-drive car that understeers), try an
alignment with a little bit of front toe-out, or wider front tires (same width
as in the rear), or stiffer
springs (in any class
except street/stock) or
stiffer dampers instead.
If you're trying to correct
an understeer or oversteer
issue and you're shopping
for an aftermarket anti-roll
bar, pick one that's hollow,
adjustable, and bigger in
diameter than your stock
bar. An adjustable bar
makes more than one stiffness setting available to
you. A hollow bar is lighter
than a solid bar. A bigger
(Above) Exit close to the cone.
diameter bar is stiffer than

a smaller diameter bar. Note that an anti-roll bar's torsional rigidity is proportional to the cube of its radius, so even small increases in the diameter of an
anti-sway bar make big differences in its stiffness. The outer 20% of the
diameter of the bar contributes most of the torsional rigidity to the bar. For a
given diameter, a hollow bar is almost as stiff as a solid bar, but weighs a lot
less. Think of a solid anti-roll bar as having a weak inner core and a stiff outer
shell; discarding the weak inner core leaves you with the stiff outer shell:
a hollow anti-roll bar.
It is possible to reach the point at which an anti-sway bar is so stiff that it
causes the inside wheel to lift off the ground during tight, hard cornering,
especially if you replace just one bar (front or rear, but not both, to be compliant with stock/street rules). If a wheel lifts clear off the ground, this means that
only one tire on that end of the car is firmly planted, so the overall grip at that
end of the car is greatly reduced. This is not necessarily a bad thing in
autocross, if that's the effect you're trying to achieve, but I'd be careful
about employing such a setup on the track unless you're an experienced
competition driver.
For a great write-up on
how sway bars work, see
http://speed.academy/howswaybars-work/.
With regards to a catback exhaust: that $1000+
exhaust may add a few
horsepower, but autocross
is more about technique
than power. Better to spend
that money on training the
driver, training the driver,
and training the driver.

(Below) Now that's a stiff sway bar.

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http://speed.academy/how-swaybars-work/

der Bayerische March/April 2020

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