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Bars & Toes
There are two significant departures that have emerged since
I posted setups for version 1.0 in "Steve Smith's Advanced
Setup Guide" on Alison Hine's "Eagle Woman" Web
site (www.simracing.com/alison/gpl/).
To me, the changes in the new physics model are most apparent
in improved front end grip. So much so that the basic balance
of the car has been altered in such a way that "tail happy"
doesn't begin to describe it. Taking a page from the real-world
Indy-car chassis engineers, I've reduced the rear anti-sway (aka
anti-roll) bar value to zero in some of these new setups. Real-world
Indy-car engineers often disconnect the rear bar (and sometimes
the front, too), particularly on the street circuits like Long
Beach, to gain the maximum mechanical grip, at the expense of
driveability (the car will tend to wallow unless you build stiffness
back into the suspension with harder springs, shocks, or the
bar at the other end of the car). This trick doesn't work for
all cars nor at all tracks. Indeed, the most successful no-rear-bar
setups are at the pure handling tracks: the Ring, Mosport, and
Monte Carlo; and the most successful car without a rear bar is
the Brabham, although I expect to take a lot of heat on this
issue.
The other setup change is in the amount of toe (-out in front,
-in at the back). The new physics have ameliorated the traditional
Papy front-end "washout" (mid-corner understeer, or
push), but not eliminated it. Michael Hausknecht, my frequent
partner in this venture, was the first guy I know who experimented
with unrealistically high front toe-out, to get the car to turn-in
more crisply, and to keep the front-end glued to the apex through
the middle of the turn. Normal values are -.025 to -.075 in.,
but Michael started with -.125 and often went as high as -.225.
The effect, once again, was to dramatically increase the front-end
grip, so I started increasing the rear toe-in (you never, ever
want toe *out* at the rear unless you're designing an amusement
park ride) from the nominal +.025 in. or so (I'd gone as low
as .000 to minimize rolling resistance at tracks like Spa) to
+.075, and eventually went as high as +.225, which has the additional
benefit if making it easier to catch a rear-end slide.
At first, cranking in a lot of toe seems as magical as Wolf Woeger's
original "lo-rider" setups (now thankfully absent from
version 1.1 and following). Indeed, it seems like a kind of faux
aero...but like real aero, there is a penalty in drag. Tire drag
is modeled in GPL, and for every click of negative front toe,
for example, you scrub about one mph off the cars' top speed
at the end of a long straight like Kyalami's. Thus, this trick
works best on tracks where top speed isn't much of an issue:
the Ring, Mosport, Monaco, Zandvoort, and the converted NASCAR
version of Watkins Glen. You probably won't want to try it at
Spa, Mexico, Monza, or Rouen. |