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| GTR Guide - Page 5 - Suspension settings:
Warning: My suggestions here are based on limited
experience and should not be taken as the ultimate settings for
performance or top lap times. Using settings from another player can help but
ultimately it us you that has to configure your handling to suit your
driving style and abilities.
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First lets look at the default
settings for the Porsche 996 as this is the car I am using at the moment.
All examples
are in US (Imperial) measurements.
|
| Default Setting |
Explanation |
 |
Makes
your adjustments to both sides of the car if set to yes or individually if
set to no. |
| Yes
/ No |
Yes
until you need to fine tune
|
Note:
Range is under the default setting on
left and my suggestions are on right |
 |
Packers
space the bumpstop (Suspension travel limiter) closer to the shock body,
limiting travel. Too little travel will result in greatly increased tire
loading and increased wear. |
| 0
- 1.5 in |
0 |
 |
Springs
are one of the personal settings and their strength depends on the way you
drive.
Lowering the strength results in a "smoother" transition from
traction to slide but can decrease the overall cornering traction by
allowing for more weight transfer or body roll.
Remember, if you lower the spring strength the ride height drops so you
might have to increase this setting. |
| 286-1142
lbs/in |
400 |
 |
This is a "gray" area
for me, Doug Arnao
has a much greater understanding so I will quote his Guide
to the Physics & Car Dynamics Model
Fast damping is what the tires see and feel i.e.: reactions over bumps or
kerbs. Its job is to keep the rubber on the ground over the various
surface undulations. Traveling over a bump at speed causes a relatively
large and “fast” movement of the damper shaft, and hence it's name. If
the front of your car is “overdamped” in the fast bump direction, then
you will experience UNDERSTEER on the bumpy sections of turns. If the rear
is overdamped you will experience OVERSTEER. |
| 4
- 9.7 lbs/in/s |
6.9 |
 |
| 6.9
- 24 lbs/in/s |
13.7 |
|
For fast speed adjustments, pick a bumpy
turn at the particular track you're working on. Start with bump at 0 and
rebound at 2 and work your way up until the front UNDERSTEERS over the
bumps, then back off 1 or 2 clicks. Then do the same for the rear until it
OVERSTEERS over bumps, again back off 1 or 2 clicks. Always keep the fast
rebound higher than the bump - 1.5 to 3 times so. The stiffer the spring
the stiffer the rebound setting. It is the fast rebound's job to resist
spring pressure and unsprung weight (wheel, tire, hubs, brakes etc) when
the suspension oscillates. Usually a setting of 2 times the fast bump
works well in GP2. Make sure the car likes "usable" kerbs, too.
This may require softer settings than done in your bumpy turn test -
everything is a compromise. |
 |
Slow damping is what the driver feels ie:
turn-in throttle-out, and mid-corner transitions (chicanes). It controls
the dynamic weight transfer and overall motion of the main chassis
relative to the track surface as the car is turned, slowed, and
accelerated. These motions cause “slow” and small movements of the
damper shaft, again the name. The slow rebound usually ends up being
higher than the bump, but can be at times 1:1. |
| 5.7
- 14.3 lbs/in/s |
10.3 |
 |
| 9.1
- 26.3 lbs/in/s |
19.4 |
|
Most fiddling will be done with the slow
speed settings. First settle on a spring and roll bar setting using a
constant radius neutral throttle corner. Next do the “fast” bump
adjustments as described previously, then fine tune with slow speed
adjustments. |
 |
Camber is the
tilt of the tire as viewed from the front of the car. If the top of the
tires lean toward the center of the car then you have negative camber. If
the top of the tire tilts out away from the center of the car then you
have positive camber. |
| -6
to +2 degrees |
-3
front -2 rear |
|
Negative camber is when the top of the tire
tips inward, and positive is when it tips outward. Negative camber is
necessary for good cornering performance. The main question is how much.
When turning a corner the body rolls and the outside tire is forced to tip
outward in relation to the road. This causes the tire to ride on it's
outside edge and lose grip rather than being flat on the road. |
 |
Set
to adjust center tire temperatures. As you increase tire pressure the
center of the tire stands higher or "crowns". The higher
it stands the higher the center temperatures go.
|
| 13.1
- 28.3 psi |
19.5 |
 
|
Tire Temperatures should be in the 203 - 239
° F range. The readouts show the temperatures on the
outside/center/inside on the left side and inside/center/outside on the
right.
While center temps are controlled by tire pressure the outside and inside
are |
|
governed by a number of settings. Spring
rates, brake bias, anti sway bars, shock settings, camber, toe in, and
ride height all combine to modify the running temperatures. |
 |
Ride height is how far the lowest part of
the car is from the ground. Due to weight transfer increasing ride height
in the front increases understeer while increasing rear ride height
increases oversteer. |
| 1.97
- 3.35 |
To
suit track |
 |
The front splitter (wing) and rear wing
work together. The settings should be determined by the track as higher
settings will reduce to end speed. Quoting again from Doug's guide:
Front:
1 – Le Mans or the Old Hockenheim
2 – Monza
3 – Most medium speed tracks. You will use this the most.
4 – Short tracks like Hungary and Monaco. |
| 1
to 4 |
To
suit track |
 |
| 1
to 20 |
To
suit track |
|
Rear Wing settings
Basically 5 degrees of rear wing for every splitter setting is the
baseline you use. So for a 3 front splitter you’d use a 15 rear wing.
The rear wing has a much finer adjustment that the splitter so that’s
what you’ll be doing your “at the track” aero balancing with. So
splitter x 5 will get you a basic rear wing setting. Choose the splitter
first for the speed of the track. |
Front
 |
|
Anti-roll Bar Changes |
| Increase front rate |
| Front roll resistance increases,
increasing understeer or decreasing oversteer. May also reduce camber
change, allowing better tire contact patch compliance with the road
surface, reducing understeer. |
| Increase rear rate |
| Rear roll resistance increases,
increasing oversteer or decreasing understeer. On independent rear
suspensions, may also reduce camber change, allowing better contact
patch compliance with road surface, reducing oversteer. |
| Decrease front rate |
| Front roll resistance decreases,
decreasing understeer or increasing oversteer. More body roll could
reduce tire contact patch area, causing understeer. |
| Decrease rear rate |
| Rear roll resistance decreases,
decreasing oversteer or increasing understeer. On independent rear
suspensions, more body roll could reduce tire contact patch area,
causing oversteer. |
|
Varies
with car make
Porsche 996
171 - 971 lbs/in |
500
- 700 |
| Rear
|
Varies
with car make
Porsche 996
57 - 457 lbs/in |
2
above lowest setting |
 |
When a pair of wheels is set so that their leading edges are pointed slightly towards each other, the wheel pair is said to have toe-in. If the leading edges point away from each other, the pair is said to have toe-out. The amount of toe can be expressed in degrees as the angle to which the wheels are out of parallel, or more commonly, as the |
| -2
to 2 degrees |
-.5
front -.3 rear |
|
difference between the track widths as measured at the leading and trailing edges of the tires or wheels. Toe settings affect three major areas of performance: tire wear, straight-line stability and corner entry handling characteristics.
If the car is set up with toe-out the front wheels are aligned so that slight disturbances cause the wheel pair to assume rolling directions that do describe a turn. Any minute steering angle beyond the perfectly centered position will cause the inner wheel to steer in a tighter turn radius than the outer wheel. Thus, the car will always be trying to enter a turn, rather than maintaining a straight line of travel. So it's clear that toe-out encourages the initiation of a turn, while toe-in discourages it.
With four-wheel independent suspension, the toe must also be set at the rear of the car. Toe settings at the rear have essentially the same effect on wear, directional stability and turn-in as they do on the front. However, it is rare to set up a rear-drive race car toed out in the rear, since doing so causes excessive oversteer, particularly when power is applied.
Source: Pointed the Right Way
by John Hagerman |
Effect of
Suspension Changes
Before making changes to
suspension components and settings, it is good to know how the changes will
effect performance and ride. The following chart will help give you a general
idea of the effect a specific change will make to handling and ride.
|
Spring Rate Changes |
| Modification |
Effect on Suspension |
| Increase front and rear rate |
Ride harshness increases; tires may not
follow bumps causing reduced traction. Roll resistance increases. |
| Increase front rate only |
Front ride rate increases. Front roll
resistance increases, increasing understeer or reducing oversteer. |
| Increase rear rate only |
Rear ride rate increases. Rear roll
resistance increases, increasing oversteer or reducing understeer. |
| Decrease front and rear rate |
Ride harshness decreases; tires follow
bumps more effectively, possibly improving traction. Roll resistance
decreases. |
| Decrease front rate only |
Front ride rate decreases. Front roll
resistance decreases, decreasing understeer or increasing oversteer. |
| Decrease rear rate only |
Rear ride rate decreases. Rear roll
resistance decreases, decreasing oversteer or increasing understeer. |
|
| |
|
| Increase front rate |
Front roll resistance increases,
increasing understeer or decreasing oversteer. May also reduce camber
change, allowing better tire contact patch compliance with the road
surface, reducing understeer. |
| Increase rear rate |
Rear roll resistance increases,
increasing oversteer or decreasing understeer. On independent rear
suspensions, may also reduce camber change, allowing better contact
patch compliance with road surface, reducing oversteer. |
| Decrease front rate |
Front roll resistance decreases,
decreasing understeer or increasing oversteer. More body roll could
reduce tire contact patch area, causing understeer. |
| Decrease rear rate |
Rear roll resistance decreases,
decreasing oversteer or increasing understeer. On independent rear
suspensions, more body roll could reduce tire contact patch area,
causing oversteer. |
Shock Absorber Changes |
| Modification |
Effect on Suspension |
| Increase rebound and bump rates |
Ride harshness increases. |
| Increase rebound rates only |
On bumps, tires may leave track surface. |
| Increase bump rates only |
Body roll resisted; outside tire loaded
too quickly; car won't stabilize into a turn. |
| Decrease rebound and bump rates |
Ride harshness decreases; car may float
over bumps. |
| Decrease rebound rates only |
On bumps, tires follow track surface
more effectively; car may continue to oscillate after bumps. |
| Decrease bump rates only |
Body rolls quickly; car is slower to
respond to turn-in. |
The Importance of
Tire Temperatures
In the course of testing the
handling of a car, use tire temperatures and driver feel to make adjustments.
It is critical to monitor tire temperatures often. They offer valuable clues
to the setup of the car. The areas of adjustment that tire temperatures are
used for include: tire pressure, camber, body roll, shock settings, wheel
width and transient handling response.
|
Troubleshooting Tire Temperatures |
| Reading |
Handling problem |
Reason |
| All tires too hot |
|
Compound too soft for track and ambient
temperature conditions. |
| Front tires too hot |
Understeer |
Front tire pressures too low. |
| Rear tires too hot |
Oversteer |
Rear tire pressures too low. |
| Inside edges too hot |
Too much body roll |
Too much negative camber or too much
toe-out. |
| Outside edges too hot |
Too much body roll |
Too little negative camber, too little
toe-out or too much toe-in or wheel width too narrow for tire width. |
| Center of tread too hot |
|
Tire pressure too high. |
| Edges on too hot |
|
Tire pressure too low. |
| All tires too cold |
|
Compound too hard for track and ambient
temperature conditions or car not being driven to limit. |
| Front tires too cold |
|
Inadequate load on front tires. |
| Rear tires too cold |
|
Inadequate load on rear tires. |
Solving Handling
Problems
The key to setting up your
suspension is in diagnosing what the handling problems are and resolving how
to fix them. While car enthusiasts often baulk at the "black art" of
suspension tuning, there's no reason to. As with working on the mechanical
aspects of an engine, the trick to suspension tuning is in the
troubleshooting; there is always a cause and an effect.
|
Solving Handling Problems |
| Problem |
Manifestation |
Solutions |
| Steady state understeer |
All turns or low-speed turns only |
If front tire temps are optimum and
rears are low, stiffen rear antiroll bar; if front temps are too hot,
soften front (most likely).
If front tire pressures are optimum, decrease rear tire pressure.
Increase if chunking occurs.
Improper front camber.
Too much body roll at front, causing excessive camber change. |
| Steady state understeer |
High-speed turns only |
If front tire temps are OK, increase
front downforce.
If front tire temps are too hot, reduce rear downforce. |
| Steady state oversteer |
All turns or low-speed turns only |
If rear tire temps are optimum, with
fronts too low, stiffen front antiroll bar; if rear temps are too hot,
soften rear antiroll bar (most likely).
If rear tire pressures are optimum, decrease front tire pressure.
Increase if chunking occurs.
Improper rear camber. |
| Steady state oversteer |
High-speed turns only |
If rear tire temps are OK, increase rear
downforce.
If rear tire temps are too hot, reduce front downforce. |
| Corner entry understeer |
|
Front shocks are too soft in bump
resistance.
Too much front toe-in; use a small amount of front toe-out. |
| Corner exit understeer |
|
Rear shocks are too soft in bump.
Front shocks are too stiff in rebound. |
| Corner entry oversteer |
|
Rear shocks are too soft in rebound.
Rear ride height is too high (too much rake) compared to front. |
| Corner exit oversteer |
|
Rear shocks are too soft in rebound.
Too much rear toe-in or any rear toe-out. |
| Straightline instability |
|
Tire pressure is too low in one or more
tires.
Too little positive front caster.
Too much front toe-in or any toe-out in rear. |
| Straightline speed too slow |
|
Too much overall downforce.
Too much toe-in or toe-out.
Ride height is too hight. |
| Excessive steering effort |
All turns |
Too much positive caster.
Front tire pressures are too low. |
| Chassis or suspension bottoms |
|
Spring rates are too soft.
Shock absorber bump rates are too soft.
Inadequate suspension travel.
Inadequate ride height. |
| Source:
Miata Racing net |
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