Forza Motorsports 2
Suspension Setup Calculator
Version 3
by Feuerdog

INTRO - The new physics modeling of FM2 has changed the realism and overall feel from FM1. In order to take advantages of the new physics, a new guide with new calculations needed to be written. Improvements have been made in the guide, just as in the sim. Hopefully these new suspension setup calculations will provide you with a car that handles better, is easier to drive, and faster too. Enjoy!

PURPOSE - Why use this calculator?
- What it might do you for you....
- help drivers and tuners by giving them a way to tune or retune their own cars without having to understand all the definitions and relationships within a suspension setup.
- To possibly improve the performance of a car that is troublesome to drive and/or tune.
- To provide an easy way to establish a baseline tune from which more advanced tuning can be done.

- What it won't do for you...
- It is not intended to explain why or how everything works, independently or as a whole, but it might provide some useful information.
- No two cars, drivers, tracks, or setups will act exactly the same. Your results will be subjective and will vary.
- These calculations will not achieve a perfect tune, but they may be an improvement, or at least an alternative.
- This is NOT an ultimate setup guide. You can improve these tunes further. I do.

MY DRIVING STYLE - Do we drive the same way?
The same tune that works for one driver doesn't always work well for other drivers. In order for you to understand why the tune from this guide will handle the way it does, it helps to understand the way that I drive and what characteristics I look for.

- I use a standard controller(sometimes the wheel and pedals), with trigger brake, trigger throttle, and stick for steering.
- No assists usually except for ABS. In car view. Auto transmission.
- I memorize physical objects like signs, walls, barriers, and curbs to mark where my braking and turn-in points are.
- I like my tunes to be stable, balanced, and easy to drive.
- I like moderate spring, stiff damper setups.
- I tend to brake hard and straight at first, and then transition into a trail-braking turn-in. I then transition into full acceleration from apex to exit.
- I prefer on-throttle, and throttle lift oversteer characteristics.
- I usually use the same tune for every track, but there are always exceptions.
- I am not the greatest driver, but I manage to have fun.

REALISM - Keeping it real.
I have tried to tune my cars based, for the most part, on reality. If the physics of Forza are realistic, then realistic values should work in the sim, and they do, which is a good thing. The Turn 10 team did very well. Tuning and testing in a realistic way adds to the enjoyment of the whole simulation for me. Therefore, I have gone to some lengths to keep my tuning based on "real world" values and ratios. I have actually spent a lot of time, and some money, to learn more about suspension dynamics and racing car tuning in general. In the end it's all about fun. If this calculator can provide you with a car that is more fun and easier to drive then my work here is done.

SUSPENSION SETUP CALCULATOR
1. Before you begin.
2. Tires
- Pressure
3. Alignments
- Camber
- Toe
- Caster
4. Springs, Dampers, and Antiroll Bars
- Springs
- Dampers
- Antiroll Bars
5. Brakes
- Force
- Bias
6. Differentials
- FWD
- RWD
- AWD
7. Aerodynamics
- Camber
- Springs
- Brake bias

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.

1.2 - You need to know....
a. The weight of the car, and what the weight distribution values are for front and rear. This vehicle information is found in the game itself.
b. Any changes to the weight of the vehicle will mean you have to recalculate the settings!
c. These settings assume the use of ABS, but with NO TCS, and NO STM! There is a good chance your car won't handle very well with these assists enabled when using these calculations.
d. A few 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. TIRES -
2.1. Set Tire pressures -
a. Set all tires to 29psi

b. Adjust tire pressure for best operating pressures -
1. Free Run five or more laps of Tsukuba.
2. Watch the telemetry screen for tire pressures.
3. Note the pressure increase of the left side tires from lap one to lap five.
4. Adjust the tire pressures so that the tire heats "up" into its best operating pressure and/or temperature.

Advanced Tire Size tuning -
a. For cars with larger rear tires than front tires, add -1% brake bias and add .1 to front toe.

Advanced Tire Temperature tuning -
a. If single tire temperature differences exceed 10 degrees, then increase antiroll bar settings and retest.

Note: There is a relationship between the vehicles weight, aerodynamic downforce, and the tires ability to warm and cool to optimal operating pressures. Lighter cars may benefit from lower pressures, and high downforce or heavyweight cars may require higher than normal pressures.

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

Advanced Tuning - Add or remove camber to prevent uneven heating.

3.2. Set Toe -

FF = .1 front/.1 rear
FR = .0 front/-.2 rear
FA = .1 front/.1 rear
MR = 0 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. SPRINGS, DAMPERS, and ANTIROLL BARS -
4.1. Find the weight multiplier -
a. Get the weight of the car from the garage screen.
b. Subtract 300 from vehicle weight and multiply by .34
c. This is your weight multiplier - write this number down.
Example FF car: (2600 lbs - 300) x .34 = 782

Advanced Tuning -
- For slightly stiffer suspension add 50 to this result.
- For very stiff suspension add 100 to this result.
- For slightly softer suspension subtract 50 from this result.
- For very soft suspension subtract 100 from this result.

4.2. 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 by altering the stock weight distribution using 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 5% from the front, and add 5% to the rear.
MR = add 2% to the front, and subtract 2% from the rear.
MA = add 2% to the front, and subtract 2% from the rear.
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.

4.3. Find the Spring value -
a. Weight multiplier x modified weight distribution = Spring value - enter these settings.
Example FF car:
- 782(weight modifier) x .49(49% modified front weight distribution) = 383 Front Springs
- 782(weight modifier) x .51(51% modified rear weight distribution) = 398 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.

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

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

4.5 - 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 1.4 = 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 1.4 = Rear Rebound Stiffness

FA - Front Bump stiffness x 1.3 = Front Rebound Stiffness
FA - Rear Bump stiffness x 1.1 = Rear Rebound Stiffness

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

MA - Front Bump stiffness x 1.4 = Front Rebound Stiffness
MA - Rear Bump stiffness x 1.1 = Rear Rebound Stiffness

RR - Front Bump stiffness x 1.1 = Front Rebound Stiffness
RR - Rear Bump stiffness x 1.3 = Rear Rebound Stiffness

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

Example FF car:
- 6.4(front bump stiffness) x 1.4 = 8.9 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.

4.6. Find the Antiroll Bar settings -
a. Weight distribution x 24 = AntiRoll Bar settings - enter these settings.
Example FF car:
- .57(front weight distribution) x 24 = 13.6 front AntiRoll bar
- .43(rear weight distribution) x 24 = 10.3 rear Antiroll bar

Advanced Tuning -
- For slightly stiffer antiroll bars change multiplier to 33
- For very stiff antiroll bars change multiplier to 44, and decrease caster to 5.4
- For slightly softer antiroll bars change multiplier to 17
- For very soft antiroll bars change multiplier to 12, and increase caster to 5.6

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

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

Advanced Tuning -
- If rear tires are at least 30mm wider than front tires subtract 1% from brake balance.
- Adjust force in +/-5% increments for best feel, or benchmark performance.
- Adjust balance in +/-2% increments for best feel, or benchmark performance.
- Use friction telemetry screen to determine which wheels are losing traction first and adjust balance accordingly.

6. DIFFERENTIALS -
- FWD = 35% Accel./0% Decel.

- RWD = 60% Accel./50% Decel.

- AWD Front = 35% 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 change the feel of it's effects. Keep this in mind while tuning.
Sport differentials are adjustable in accel. only.

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.

7. AERODYNAMICS(Optional adjustments)-
7.1. Adjust camber based on aerodynamic downforce -
- Add +.1 camber per 100lbs downforce
Example R4 car: 150lbs front/300lbs rear
(150lbs front = +.1) = (+1) + (-.8 camber) = -.7 front camber
(320lbs rear = +.3) = (+.3) + (-.8 camber) = -.5 rear camber

7.2 . Adjust spring value for aerodynamic downforce -
- (Downforce x .15) + Spring value = Adjusted Spring value
Example FF car: 110lbs front/25lbs rear
(110lbs front x .15) = 16 + 383 = 399 front springs
(25lbs rear x .15) = 3 + 398 = 401 rear springs
Note: Do NOT recalculate damper settings after this spring adjustment is made.

Advanced Tuning - For lower compensation multiply by .1, for higher compensation multiply by .2

7.3. Adjust brake bias based on aerodynamic downforce -
a. Subtract front downforce from rear downforce.
Example FR car: 80lbs front/190lbs rear
190lbs rear - 80lbs front = 110lbs positive(rear bias) DF difference

b. Adjust brake bias using the following:
- For every full 100lbs of negative(front bias) adjust brake bias by +1%
- For every full 100lbs of positive(rear bias) adjust brake bias by -1%
Example FR car with 110lbs positive(rear bias) DF difference:
110lbs(positive) = Brake bias 47% - 1% = 46% front brake bias