Forza 3 - Reduce understeer?

[wy906]

More newbie question. What is the first thing to adjust to reduce understeer?

FYI the car in question is the 997 GT3 RS, lightly tuned to PI 599; then settings have been adjusted as according to Forzatrader calculator. Before the upgrade the handling is very adjustable with the throttle, but now I find it too ‘tight’ and not ‘pointy’ enough.

I don’t want to randomly adjust the settings to make it even worse, so I thought I’d ask the experts before I waste hours of my time.

Thanks very much.

[S3_Graham]

what have you done upgrade wise??

my first stop would be full tyres upgrade and full width upgrade. if not head over to the forza tuners wesite for a flash version of their app to tune cars... worked well on my Gallardo... got me 7th in the PH Time Trial

[vdubbin]

The tuning calc at www.croisened.com allows you to select the rebound to dial in more or less understeer.

[sidaorb]

Right basics off the top of my head. Haven't got machine infront of me.

Front Camber -0.5

Front Toe OUT +0.3

Front Springs roughly 1/3 of 'default'
Rear Springs as default.

Anti Dive F&R 9.0
Rebound F&R 3.5
(can never rememebr which is which but 9 on the top set 3.5 on bottom set)

Diff 40/15

Once that lot is dialled in then start tweaking.

Edited by sidaorb on Wednesday 9th December 16:47

[wy906]

S3_Graham said:

what have you done upgrade wise??

I can’t remember on top of my head (I’m at work at the mo). It’s only a light upgrade cos the standard PI for GT3 RS is 562 or something.

The car handles beautifully standard without upgrade, but now it understeers quite a bit and really requires the slow-in-fast-out approach.

I tried to keep the spec as near to ‘road car’ as possible, so no ‘racing’ upgrade, only ‘sports’ (apart from racing tyres). It’s running at @450 bhp with racing tyres, rear tyres with width increase, no weight reduction and some suspension / damping upgrade (can’t remember what and as mentioned, only ‘sports’ upgrade)

I think it must be the Forzatrader calculator’s default settings. It tends to make the car more ‘neutral/understeer’. I’ve used it for the Focus RS and it’s great, but for the GT3 RS, not so good.

[wy906]

vdubbin & sidaorb

Cheers, will try it later.

[satans worm]

Try stiffening the rear antiroll bar and soften the front a little?

[PhillT]

Scandinavian flick.

HTH.

[S3_Graham]

wy906 said:

S3_Graham said:

what have you done upgrade wise??

I can’t remember on top of my head (I’m at work at the mo). It’s only a light upgrade cos the standard PI for GT3 RS is 562 or something.

The car handles beautifully standard without upgrade, but now it understeers quite a bit and really requires the slow-in-fast-out approach.

I tried to keep the spec as near to ‘road car’ as possible, so no ‘racing’ upgrade, only ‘sports’ (apart from racing tyres). It’s running at @450 bhp with racing tyres, rear tyres with width increase, no weight reduction and some suspension / damping upgrade (can’t remember what and as mentioned, only ‘sports’ upgrade)

I think it must be the Forzatrader calculator’s default settings. It tends to make the car more ‘neutral/understeer’. I’ve used it for the Focus RS and it’s great, but for the GT3 RS, not so good.

Ditch all the engine mods... concentrate on handling!!

Tyres first (both upgrades), Then suspension and brakes, Then weight...

[ih8thisname]

satans worm said:

Try stiffening the rear antiroll bar and soften the front a little?

As a general rule of thumb just make sure the rear is stiffer than the front. (Oo-err)

[Curry Burns]

You sure you don't add in camber...

I tend to completely soften the ARB's, and put up the front tyre pressure by around 1 PSI...

[WildCards]

Reduce weight, add adjustable ARB's and suspension, then soften both and apply tyres as needed. Tyre widths make a big difference sometimes too.

[wy906]

I'm off work on Friday, so I'll try you guys' suggestions.

THANKS!

[GravelBen]

sidaorb said:

Right basics off the top of my head. Haven't got machine infront of me.

Front Camber -0.5

Front Toe OUT +0.3

Front Springs roughly 1/3 of 'default'
Rear Springs as default.

Anti Dive F&R 9.0
Rebound F&R 3.5
(can never rememebr which is which but 9 on the top set 3.5 on bottom set)

Diff 40/15

Once that lot is dialled in then start tweaking.

That sounds a bit of an odd camber/toe setup IMO if F3 has much relation to the real world - I'd be starting from more like 5° castor, -1.5° front camber with minimal toe, a bit more camber on the rear (try -2.0° and see how it feels) and slight rear toe-in.

As said above, ARB's are the simplest way to adjust front/rear balance once the basics are sorted.

Edited by GravelBen on Thursday 10th December 04:57

[deviant]

Undo whatever it was that started the understeer...sounds simple but I wouldnt get mired in tweaking settings and trying to patch it up.

Start by removing mods one at a time until you find the one that messed it up, you can then concentrate on that one area.

[y2blade]

also the tyres should be 32psi when WARM (ie after a couple of laps, use the temp indicator and telemetry)

[S3_Graham]

y2blade said:

also the tyres should be 32psi when WARM (ie after a couple of laps, use the temp indicator and telemetry)

all of the tuner programs drop the tyre pressures by 1.
They then say on every car that you should have the camber at -1.

They soften everything up by a considerable margin also... as when you mod the car it makes them mega stiff....

[Chr1sch]

Defo little bit of negative camber and toe out will sort turn in a treat, if you get bored, start racing B500 in an NSXR GT, its just sublime

[S3_Graham]

Chr1sch said:

Defo little bit of negative camber and toe out will sort turn in a treat, if you get bored, start racing B500 in an NSXR GT, its just sublime

not sure on the NSX... but race B/A class racing is the closest online!

[Matt_N]

GravelBen said:

sidaorb said:

Right basics off the top of my head. Haven't got machine infront of me.

Front Camber -0.5

Front Toe OUT +0.3

Front Springs roughly 1/3 of 'default'
Rear Springs as default.

Anti Dive F&R 9.0
Rebound F&R 3.5
(can never rememebr which is which but 9 on the top set 3.5 on bottom set)

Diff 40/15

Once that lot is dialled in then start tweaking.

That sounds a bit of an odd camber/toe setup IMO if F3 has much relation to the real world - I'd be starting from more like 5° castor, -1.5° front camber with minimal toe, a bit more camber on the rear (try -2.0° and see how it feels) and slight rear toe-in.

As said above, ARB's are the simplest way to adjust front/rear balance once the basics are sorted.

Edited by GravelBen on Thursday 10th December 04:57

That goes against what all the tuning calculators say, the one I use recommends -0.7 front and rear.

They also recommend to reduce rear rebound stiffness.

Here is a cut and paste of one of the calculators, they are available as spreadsheets online though:

Tuning said:

1. BEFORE YOU BEGIN -
1.1 - You need....
- to have....
a. A basic calculator, a pencil, and something to write on.
b. A car with a Race suspension, Race brakes, Race Springs and Dampers, and a Sport or Race Differential.
- to know....
a. The weight of the car, and what the weight distribution values are for front and rear. These are found in the game.
b. These abbreviations:

AWD = All wheel drive
FWD = Front wheel drive
RWD = Rear wheel drive

FF = Front engine, Front wheel drive
FR = Front engine, Rear wheel drive
FA = Front engine, All wheel drive
MR = Mid engine, Rear wheel drive
MA = Mid engine, All wheel drive
RR = Rear engine, Rear wheel drive
RA = Rear engine, All wheel drive

Understeer - the car doesn't turn easily
Oversteer - the car turns too easily

2. SPRINGS, ANTIROLL BARS, and DAMPERS -
2.1. Find the weight multiplier -
a. Get the weight of the car from the garage screen.
b. Multiply the weight of the car by .3
c. This is your weight multiplier - write this number down.
Example FF car: 2600 lbs x .3 = 780

Advanced Tuning - To stiffen the suspension multiply by .32, to soften the suspension multiply by .28

2.2. Find the modified weight distribution -
a. Get the weight distribution values for the car.
Example FF car: 57% front/43% rear

b. Calculate the cars modified weight distribution values with the following table:
FF = subtract 8% from the front, and add 8% to the rear.
FR = add 8% to the front, and subtract 8% from the rear.
FA = subtract 4% from the front, and add 4% to the rear.
MR = add 2% to the front, and subtract 2% from the rear.
MA = no change.
RR = add 2% to the front, and subtract 2% from the rear.
RA = add 1% to the front, and subtract 1% from the rear.
Example FF car: 57% front (-8%)/43% rear (+8%) = 49% front/51% rear

c. These modified percentages are your modified weight distribution - write this number down.

2.3. Find the Spring settings -
a. Weight multiplier x modified weight distribution = Spring value - enter these settings.
Example FF car:
- 780(weight modifier) x .49(49% modified front weight distribution) = 382 Front Springs
- 780(weight modifier) x .51(51% modified rear weight distribution) = 397 Rear Springs

Advanced Tuning - You may need to adjust your ride height. Lower is better, but too low may cause excessive bottoming out. Adjust as needed.

2.4. Find the Antiroll Bar settings -
a. Weight distribution x 25 = AntiRoll Bar settings - enter these settings.
Example FF car:
- .57(front weight distribution) x 25 = 14.2 front AntiRoll bar
- .43(rear weight distribution) x 25 = 10.7 rear Antiroll bar

Advanced Tuning - For stiffer Antiroll Bars multiply by 35, for softer Antiroll Bars multiply by 15

2.5. - Find the damper Bump Stiffness -
a. (Spring value + 200) x .011 = Bump Stiffness - enter these settings.
Example FF car:
- (382 front springs + 200) x .011 = 6.4 front Bump Stiffness
- (397 rear springs + 200) x .011 = 6.5 rear Bump Stiffness

Advanced Tuning - For stiffer dampers multiply by .012, for softer dampers multiply by .010

2.6 - Find the damper Rebound Stiffness -
a. Get the Bump Stiffness values for the car.
Example FF car:
- 6.4 front Bump Stiffness
- 6.5 rear Bump Stiffness

b. Calculate the cars Rebound Stiffness values with the following table:
FF - Front Bump stiffness x 1.5 = Front Rebound Stiffness
FF - Rear Bump stiffness x 1.1 = Rear Rebound Stiffness

FR - Front Bump stiffness x 1.1 = Front Rebound Stiffness
FR - Rear Bump stiffness x 1.5 = Rear Rebound Stiffness

FA - Front Bump stiffness x 1.5 = Front Rebound Stiffness
FA - Rear Bump stiffness x 1.1 = Rear Rebound Stiffness

MR - Front Bump stiffness x 1.2 = Front Rebound Stiffness
MR - Rear Bump stiffness x 1.3 = Rear Rebound Stiffness

MA - Front Bump stiffness x 1.3 = Front Rebound Stiffness
MA - Rear Bump stiffness x 1.2 = Rear Rebound Stiffness

RR - Front Bump stiffness x 1.3 = Front Rebound Stiffness
RR - Rear Bump stiffness x 1.4 = Rear Rebound Stiffness

RA - Front Bump stiffness x 1.4 = Front Rebound Stiffness
RA - Rear Bump stiffness x 1.3 = Rear Rebound Stiffness
Example FF car:
- 6.4(front bump stiffness) x 1.5 = 9.6 front Rebound Stiffness
- 6.5(rear bump stiffness) x 1.1 = 7.1 rear Rebound Stiffness

Advanced Tuning -
- Increase corner entry oversteer OR Decrease corner entry understeer = Subtract .1 from the rear Rebound Stiffness multiplier, and recalculate.
- Increase corner exit oversteer OR Decrease corner exit understeer = Add .1 to the front Rebound Stiffness multiplier, and recalculate.

- Increase corner entry understeer OR Decrease corner entry oversteer = Add .1 to the rear Rebound Stiffness multiplier, and recalculate.
- Increase corner exit understeer OR Decrease corner exit oversteer = Subtract .1 from the front Rebound Stiffness multiplier, and recalculate.

- For faster weight transitions lower both of the multipliers by .1
- For slower weight transitions increase both of the multipliers by .1

3. ALIGNMENTS -
3.1. Set Camber -
a. Set camber to -.8 Front/-.8 Rear

b. Adjust camber based on aerodynamic downforce.
- +.1 camber per 200lbs downforce

Example R4 car with 150lbs front/300lbs rear
- 150lbs front downforce = -.8(front camber) + .0 = -.8 front camber
- 300lbs rear downforce = -.8(rear camber) + .1 = -.7 rear camber

3.2. Set Toe -
FF = .1 front/.1 rear
FR = .0 front/-.2 rear
FA = .1 front/.1 rear
MR = .1 front/-.1 rear
MA = .1 front/0 rear
RR = 0 front/-.2 rear
RA = 0 front/-.1 rear

Advanced Tuning - Increase front positive toe to improve turn-in response, decrease to improve stability. Increase rear negative toe to improve rear stability, decrease to reduce understeer.

3.3. Set Caster -
Set caster to 5.5
Notes: I don't want to get into the details of caster tuning, but it is very closely related to front camber settings, and it shouldn't be adjusted out of the 5.6~6.0 range while used with the other settings. 5.5 caster adds approx. 3 degrees of dynamic camber to the front wheels at full steering lock.


4. TIRES -
4.1. Set Tire pressures
Set all tires to 32psi when hot - after 4 or 5 laps

5. BRAKES -
5.1. Set Brake Force
a. Set brake force to 110% with ABS, or 90% without ABS.

5.2. Set Brake Balance
a. Set brake balance to 47% front

Advanced Tuning -
- Adjust force in +/-5% increments for best feel or benchmark performance.
- Adjust balance in +/-2% increments for best feel, stability, or benchmark performance.

6. DIFFERENTIALS -
- FWD = 40% Accel./0% Decel.

- RWD = 65% Accel./55% Decel.

- AWD Front = 30% Accel./0% Decel.
- AWD Rear = 80% Accel./70% Decel.
- AWD Split = 25% Front/75% Rear

Note: Gearing, power, and torque won't directly how the diff. work but they will changes the feel of it's effects. Keep this in mind while tuning.

Advanced Tuning -
Accelerating oversteer?
- Adjust rear diff. = -5% Accel.
Accelerating understeer?
- Adjust front diff. = -5% Accel.

Braking oversteer?
- Adjust diff. = +5% front Decel. OR -5% rear Decel.
Braking understeer?
- Adjust front diff. = -5% Decel. OR +5% rear Decel

Ive used this on a few cars and it does work.