In a message dated 1/22/02 10:17:26 AM Central Standard Time,
StolzK@mso.umt.edu writes:
<< Gary,
I'm completely in the dark about cornering weighting and how it's done with
coilovers.
Can you share some info or point me to a good reference?
TNX!
~ Ken Stolz
#12 STS Scooby-Roo >>
I have several books about suspension setup.
I recomend Fred Puhn's "How to Make Your Car Handle"
ISBN# 0-912656-46-8
I paid $10 for it a long time ago. Physics never changes, 90% of the book is
still very current. The other 10% is getting a bit old due to better
technology allowing things they couldn't do. Tires have gotten far better
since this book was written.
So for the newer perspective, read Don Alexander's book,
"Performance Handling" techniques for the 90's
ISBN# 0-87938-418-2
This book has alot of information about corner weighting, tire temps, setting
toe, choosing spring and sway bars, etc. They even do a couple project cars
with the complete progress laid out.
The idea behind corner weighting is to make the tires all work the same while
turning in either direction. No car is perfect, especially production street
cars that are sold by the thousands. If the car had no springs at all, the
static weight of the car would rest where it is located, and any twist in the
car body would virtually unload a tire right off of the ground. With springs
at each wheel, they will compress until all of the weight is help by the
springs, but the distribution might not be the same as the static weight
distribution of the car. This is called weight jacking. If you are only
turning in one direction, you can use this to greatly effect the way a car
turns. Oval track racers use this all the time, even during a race. But to
make the car turn equally in both direction, you want to make the
distribution is equal as possible.
For example, lets say you have a front drive car with the engine offset to
the drivers side. You put it on a set of four scales and get
LF 750 pounds RF 700 pounds
LR 500 pounds RR 350 pounds
This does not look very good, and it can use some adjustment. This is a total
weight of 2300 pounds, about a Neon or Celica. With 850 rear and 1450 front,
that is 63% front heavy which is about right. The car is also 54% left heavy
at 1250 left 1050 right. This is not out of line with real cars either. The
diagonal weights are a bit off though.
The LF + RR = 1050 and RF + LR = 1200 this is about 48% 52%
By adjusting the spring preload on each corner, you could get something like
this.
LF 775 pounds RF 675 pounds
LR 475 pounds RR 375 pounds
This still looks very bad, but is not as bad as you might think. The weight
spread on the two front tires is actually worse. This might make one front
tire spin a little easier at launch. This is a small trade off you might have
to make. The total weight of 2350 pounds, is still the same. With 900 rear
and 1450 front, the 62% front bias is still the same.
What we want to get equal are the diagonal totals.
LF + RR = 1150
RF + LR = 1150
This is perfect 50% 50% I doubt very many cars on the road will be even
close to that without work. Even with adjusting it is hard to get perfect,
but I have mine to within .50% with just a driver, and within .20% when I
have a passenger in the car. Of course the car is still 1250 pounds left and
only 1050 pounds right, or still 54% left. Unfortunately there is nothing you
can do about static weight distribution with just springs. You have to move
weight in the car to correct static weight distribution. My battery went from
the extreme left front corner to the right rear corner. This is 40 pounds off
of the left front and onto the right rear. No change in the diagonals, but
look what that can do.
LF 735 pounds RF 675 pounds
LR 475 pounds RR 415 pounds
The diagonals are still right on 1150 each, but now the L/R split is
1210/1090 or just 52.6% left. Moving just a 40 pound battery made about a
1.4% improvement in weight distribution.
Gary M.
Street Mod 1983 Turbo Celica
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Partial archives at http://www.team.net/archive
|