As to question 1, RR+LF=LR+RF holds for a car where RF+LF=RR+LR. It is a
pretty good approximation usually. What you really want is that the RF
holds the same relative portion of the right side weight that the LF holds
of the left side weight.
Unless you sit exactly at the cg of the car, which you don't, the corner
weights will change when you get in the car. It's possible to calculate the
moments, similar to aircraft cg calculations, and figure out how the corner
weights change. I did a little spread sheet for my BP car to recalculate
cornerweights based on adding or removing weight at any location.
As to question 2, unless your car races without you in it the only setup
that matters is when you're in the driver's seat. Also, tire pressure and
fuel load effects corner weights so have that as-raced also. Similarly,
sway bars should be set for zero preload as-raced.
This all assumes that you are looking for the same handling balance left to
right. On ovals you obviously don't, but even on road courses and autocross
courses you don't have exactly the number and type of left hand and right
hand turns so by jacking weight and adding stagger using springs and sway
bar preloads you can change the balance to favor one direction or the other
which can improve times on particular tracks and courses.
Hope that helps.
Rick Brown
BP Corvette
-----Original Message-----
From: owner-ba-autox@autox.team.net
[mailto:owner-ba-autox@autox.team.net]On Behalf Of Joseph Weinstein
Sent: Monday, May 10, 2004 8:25 PM
To: ba-autox@autox.team.net
Subject: some corner weight and sway bar questions.
Hi all.
I'm getting my corner weights checked and diagnosed. Let's assume I
have my sway bars
detached and the scales show the RR+LF = LR+RF, so my corner weights are
perfect, and I
take this to mean that my chassis is straight and all my springs are OK and
have the same
preload side to side etc. *IF and only if* that is true, I believe that if
I were to add a load to the
car, such as adding my weight to the driver seat, then the RR+LF will still
equal the LR+RF.
the number will be different, of course, by half my weight, but if the
chassis, springs and
tire pressures etc are all even, then the equation will hold for the new
numbers.
*But* if the corner weights were off, say, initially, and the problem
was not fixed, but
simply compensated for, at the initial chassis load, eg, one weak spring
got more preload,
then even if the RR+LF was tweaked to equal LR+RF as it stood, if I changed
the load, then
the equation would not hold for the new load. The weaker spring would still
travel farther for it's
new load, and the problem would return.
Thus I believe that the true test of a well-set up chassis (for neutral
handling) is that
the cross weights stay equal *under a range of static loads*.
What do you think?
Second part: Once everything is set, should I tighten the sway bars with
the car unloaded,
or with the car loaded as it will be raced? When I sit in it, one side is
going down more than
the other, and should this dial in some preload in the sway bars (if I
tightened them up unloaded),
or should the sway bars be stressless except while cornering, such as if I
fastened their end
mounts with my weight's worth in the seat? Setting them with the car
unloaded seems like
the equivalent of having stiffer springs on the heavy side...
thanks in advance,
Joe Weinstein
|