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- Tuning
the Balance
In balancing the car, we have several factors at our disposal.
As we've seen, we can adjust tire pressures, compounds, and camber.
But we want to find the optimum for each of these, and not degrade
a tire's performance just to reach balance.
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- Fortunately,
we have several chassis adjustments that will allow us to tune
the balance. These adjustments impact the weight transferred
to a tire during cornering.
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- The
first is the spring stiffness. ICR2 and N2 [for example]
lump the spring stiffness together with shock stiffness into
one factor. This isn't quite realistic, but fortunately in Papyrus'
driving model it works well. It also simplifies our task.
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- Basically,
if we stiffen the springs at one end of the car, that end will
give up grip in relation to the other end. So if we make the
rear shocks stiffer, the car will tend to oversteer more. If
we soften that end, the opposite will happen.
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- If we
stiffen the spring on only one corner, we will get a different
effect when we are turning one way as opposed to the other. For
example, if we have two slow hairpins on a given track, and they
both go to the right, we might want to stiffen the right rear
so the car will turn right better. This will also make it tend
to understeer in medium-speed turns, so if we have some left-hand
sweepers, the car will be more stable.
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- Be warned,
however, that it can be very easy to get lost in the effects
from asymmetrical changes to the chassis. Make sure you make
only once change at a time, and keep copious notes!
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- In the
cockpit, we have two more adjustments which affect the car's
balance: the front and rear anti-roll bars. These affect the
roll stiffness - i.e., how much weight is transferred to the
outside wheel during cornering - at each end of the car. If we
stiffen the front bar, the the car will tend to understeer more;
if we soften it, the car will tend more towards oversteer. Stiffen
the rear, and the car will tend towards oversteer.
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- We want
to arrive at a basic setup that gives us some adjustment range
in these bars, because as we race and burn off fuel load, the
car will tend to go from understeering to oversteering. We want
to be able to set the rear a little stiffer on full tanks, and
soften the rear or stiffen the front to maintain the balance
as we burn off fuel.
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- In the
cockpit, we can also adjust brake balance. This will adjust the
amount of work each end of the car does under braking. Too much
braking by the rear wheels, and the car will have a tendency
to spin under braking, because if the rear wheels lock they no
longer have any directional stability. Too much the front, and
the car will tend to go straight under braking, and will be less
efficient as well.
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- Transient
States
Transient states refers to the moments when the car is changing
from one condition to another - acceleration to braking, cornering
to straight, etc. The most important of these is the transition
from straightline to cornering. At this time, the car transfers
weight from all four wheels to the outside wheel. How it does
this - how quickly, and the impact of this on the car’s
responsiveness and feel, as well as stability - is critical to
the drivability of the car.
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- Transient
behavior is mostly impacted by the shock absorbers, or dampers.
Since [for example] ICR2 and N2 both combine
the damping adjustment with spring adjustment, we can't do any
independent tweaking of the shocks. Since I don't understand
this area really well anyway, I'll move on to the much sexier
topic, aerodynamics.
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