If you are speaking of the later (swing-spring) models, that might be pretty
much accurate. However, earlier fixed spring models don't suffer from the
effects of that pitiful rear suspension (excessive body roll), so the normal
cause and effect issues are in effect.
As a rule:
1. Increasing front stiffness increases tendencies toward understeer.
2. Decreasing front stiffness increases tendencies toward oversteer.
Obviously, you can't state the above without adding:
1. Increasing rear stiffness increases tendencies toward oversteer
2. Decreasing rear stiffness increases tendencies toward understeer.
Of course, these all have to be taken with both ends into consideration.
The later Spits can take a lot more front swaybar without displaying adverse
understeer problems because the rear is so loose to begin with.
As an example of what I am talking about, when I first started monkeying
with the original suspension on tiny Tim, I installed a large additional
main leaf to the already heavy GT6+ rear spring stack and knew that I had to
stiffen the front. I had some custom 350 pound coils made for me and
installed a 1 inch front bar. The first autocross I entered in showed me
that the front end was much too stiff because it was all I could do to keep
the car from plowing in turns. I went to the 7/8" bar until I installed the
dual A-Frame suspension and Koni Coil-over shocks to the rear and was able
to put the 1 inch bar back on.
After I converted the car to street use, I went back to the 7/8" bar for
comfort reasons.
Joe
-----Original Message-----
Increasing front roll stiffness primarily creates two different events. The
end result is the
combined effect of these two events.
The first is to reduce body roll. This is a good thing. When the body
rolls over, this rolls the
wheels over, which is never good for handling as the sidewalls of a tire
aren't noted for doing
good things on the pavement. So reducing body roll is good as it keeps the
tires more upright, and
this promotes better handling, typically reducing understeer.
The second thing is to increase the load on the front tires. This is not a
good thing. This
increased of loading more rapidly overloads the tires, causing them to
slide, or understeer. This
is not a good thing.
In the case of the Spitfire, particularly with the swing spring, the net
effect of a stiffer front
rollbar is better handling. The car stays flatter, maximizing the first
point above. As there is
virtually no roll resistance in the rear, you are not particularly
increasing it in the front, the
front is already taking it. So you net out with better handling. That's
why this setup is
virtually universal on all racing Spitfires, it works.
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