Tuning FAQ by BChmilnitzky

Updated: 06/15/98 | Printable Version

Subject: GT Tuning FAQ (long)
From: chmilnirtooth@worldtoothnet.att.toothnet (Jet Jaguar)
Date: Mon, 15 Jun 1998 06:15:36 GMT
Newsgroups: rec.games.video.sony, alt.games.video.sony-playstation

Gran Turismo Tuning FAQ

By:  Bob Chmilnitzky  a.k.a. "Jet Jaguar"


	The reason I'm writing this FAQ is to help others make
intelligent, informed decisions concerning car setup.  I've found this
area of the otherwise excellent Gran Turismo manual is sorely
deficient.  This FAQ is based on real-life car physics.  This may or
may not apply to the game, depending on how accurately the game
depicts car physics.  Any areas that I feel I have found to be
different are noted in brackets, though the real-world effect is still
listed for the sake of completeness, since I haven't sat down and
tried everything out to see if it works (or in case I'm wrong :-) ).
It should also be noted that my real-world experience is limited to
rear-wheel drive cars, so any special considerations that need to be
made for front- and four-wheel drive vehicles is not mentioned, but,
from what I understand, the basic principles of setup are the same.

	Feel free to use this FAQ on a web page, as long as you let me
know first.  Also, I don't feel it is quite finished yet.  I would
have liked to have talked about dynamic camber changes caused by
suspension movements (a.k.a. double wishbone suspensions:  why you
need them, and why everything else is junk :-) ), expanded the section
on gearing, and added a troubleshooting section (i.e.  if your car
understeers while exiting corners then do this... type of thing), but
that's not gonna happen any time soon, as I'm just too busy at the
moment.  In fact, I've been sitting on what I've got here for the
better part of a week already.  *sigh*    :-(

[Tip:  Make one adjustment at a time and test it.  If you make several
adjustments at once, it can be difficult to isolate the effects of
each adjustment, as one adjustment can cancel out another.]


	The purpose of the springs is to control wheel movement and
keep the tyre in contact with the road over bumps and undulations.
Stiffening the springs front and rear will reduce body roll and make
handling more responsive, but cause a loss of traction over bumpy
surfaces.  Likewise, softening all of the springs will give more grip
on bumpy tracks, but increase roll and reduce responsiveness.  You can
also use the springs to affect the car balance.  You can reduce
oversteer by stiffening the front springs or softening the rear.
Likewise, you can reduce understeer by softening the front springs or
stiffening the rear.  However, be advised that changing just one end
also affects fore/aft weight transfer.  By softening the front
springs, you'll also get more dive under braking.  Softening the rear
will give you more rear weight transfer under acceleration, which can
give you more traction on the rear wheels in straight-line
acceleration.  [Tip:  I generally do not use the springs to adjust
balance, because of its effects on fore/aft weight transfer.  I
reserve the stabilizers for this purpose.]

Ride Height:

	A lower ride height lowers the center of gravity, which
reduces weight transfer during cornering, acceleration, and braking.
The reduced weight transfer improves cornering.  A lower ride height
also lowers drag at high speed because you are presenting a smaller
frontal profile to the airstream.  Also, by lowering the front end and
raising the rear, you can improve high speed stability and increase
downforce by preventing high-pressure air from building up underneath
the nose of the car.  [Note:  I have not noticed ride height affecting
aerodynamics at all in the game]  If the car is too low, it can bottom
out, though this can be eliminated by stiffening the springs.  For
rear-wheel drive cars, you can improve rear traction under
acceleration by increasing ride height, since maximum traction can be
obtained with the maximum amount of weight on the rear tyres.
Generally, you'll only want to do this in the acceleration tests,
since it will hurt cornering performance, and never with front-wheel
drive cars, since the driving wheels will be losing grip.


	The purpose of the dampers (also called shock absorbers) is to
dampen the oscillation of the springs.  The shocks not only dampen
spring oscillations, but they also affect handling during transient
conditions (such as the entry and exit of turns), but not steady-state
conditions.  Softening the dampers reduces responsiveness, and
likewise stiffening the dampers will increase responsiveness.
However, if they are too stiff, they can lead to a loss of suspension
sensitivity and increase the harshness and bumpiness of the ride.  If
they are too soft, it will cause the handling to feel mushy.  You can
reduce understeer during corner entry and exit by softening the front
dampers or stiffening the rear.  Conversely, you can reduce oversteer
in the entries and exits by stiffening the fronts and softening the
rear dampers.


	Camber is the angle the tyres make with the road and is
measured in degrees.  Tyre grip varies with the camber angle, and
ideally is maximum when the angle is zero.  However, the maximum grip
is found with a small amount of negative camber because of tyre
sidewall deflection (when the top of the tyre is tilted inward it is
called negative camber.  The game does not allow positive camber, and
in real life it is never used).  Also, as the body rolls in a turn,
the suspension movements themselves causes some adverse camber change.
These combined effects mean that for maximum cornering power you need
to have some amount of negative camber.  [Note:  Unfortunately, I have
not found a reliable way in the game to determine the optimum camber
settings.  In real life, camber is generally determined by measuring
tyre temperatures at different points across the tread surface, or by
monitoring tyre wear.  Generally, I just play around with the settings
until I come across a setting I think feels best.]


	The purpose of the stabilizer (also known as the anti-roll
bar, or anti-sway bar, although I prefer anti-roll bar because it can
very well destabilize a car and has nothing to do with sway) is to
resist body roll in a turn, much like a spring.  However, unlike the
springs, they do not come into play on two-wheel bumps or on fore/aft
weight transfer.  Stiffening the stabilizers front and back gives more
responsive handling and less body roll, but can upset stability on a
bumpy track by transmitting loads from one-wheel bumps to the opposite
wheel.  Likewise, softening the bars all around can increase body roll
and reduce responsiveness, but make the car more stable on bumpy
tracks.  Because the anti-roll bars are fairly independent of other
chassis settings, they are ideal for fine-tuning car balance.  You can
reduce understeer by softening the front bar, or stiffening the rear.
You can reduce oversteer by stiffening the front bar or by softening
the rear.


	The brake balance allows you to adjust the proportion of
braking power distributed between the front and rear brakes, which
affects the balance under the car under braking.  Oversteer under
braking (i.e. the back wants to jump out while braking) can be reduced
by increasing front brake balance, or reducing rear balance.
Understeer under braking (the car doesn't turn in) can be reduced by
decreasing front brakes, or increasing rear.  [Tip:  generally, you
always want higher front brakes than rear.  This is because of forward
weight transfer under braking.  As the weight is transferred forward
off of the rear tyres, they are unloaded and lose grip, which causes
them to lock up before the front tyres.]

Gear Ratio:

	The purpose of the gearbox is to keep the engine within it's
optimum rpm range over a range of road speeds.  Shorter gear ratios
(bigger ratio numbers) give you more acceleration and rpms.  Taller
ratios (smaller ratio numbers) give you higher speed before the engine
redlines, but less acceleration.  The final drive ratio can be thought
of a sort of "multiplier" that affects all of the gear ratios
simultaneously, which makes it convenient to fine tune your
transmission to different tracks.  

	[Tip:  The way I generally set up the gears is to first set
1st gear so the engine rpm is in the meaty part of the torque curve
for the exits of the slowest turns on the track.  I then set top gear
for top speed and space out the rest of the gears evenly between the
two, except for the top couple gears, which I space a little closer
together than the lower gears since acceleration is slower at high
speed due to increased air resistance.  I don't normally change gear
ratios from one track to the next, I just set a good compromise and
stick with it.  The only exception is I'll sometimes adjust the final
drive ratio at certain tracks.  For example, at the Autumn Ring I'll
bump the final drive to a shorter ratio to get more acceleration since
you won't be hitting top speed anywhere on the track anyway, and on
the oval track I'll change to a taller ratio to get more top end


	Downforce is the aerodynamic force pressing the car down on
the track and improves cornering grip.  This downforce is dependent on
forward speed, and increases as you go faster.  Increasing the
downforce all around increases cornering speed, but also increases
drag, which gives you slower straightaway speed, and you may also need
to increase ride height and/or spring stiffness to prevent bottoming.
Likewise, decreasing downforce gives you lower cornering speeds but
higher straigtaway speeds, and allows you to run softer springs and/or
a lower ride height.  [Note:  I find downforce has only a small effect
on drag.  For example, in the Viper GTS on the top speed test, the
difference between maximum and minimum downforce top speeds is only
about 5 mph (8 km/h).]  Also, you can also use downforce to fine-tune
balance at high speeds.  To reduce understeer, increase front
downforce or reduce rear.  To reduce oversteer, decrease front
downforce or increase rear.  Keep in mind that these adjustments are
dependent on forward speeds and has less effect as speeds drop, so you
can use this to give the car different handling characteristics for
different speed ranges.

Bob Chmilnitzky, a.k.a. Jet Jaguar
To reply, do dental work on my address and pull all of the teeth.
MSTie #54297

The Face on Mars issue is dead.  Deal with it, and move on.