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Re: Tips for a new player on Tuning
08-19-2008, 1:43 PM

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Re: Tips for a new player on Tuning
It's a little late, but I found this in the general forums written by Detrick. I don't think he'll mind me pasting it here:

my67gto:
ALIGNMENT

Handling characteristics are usually defined by oversteering and understeering.

Oversteering is fish tailing, when the *** comes out. good for drift bad for race pace.
Understeering is when the car experiences little or no steering when your trying to to turn left or right.

Camber, Toe and Caster

The three major alignment parameters on a car are toe, camber, and caster. Most enthusiasts have a good understanding of what these settings are and what they involve, but many may not know why a particular setting is called for, or how it affects performance. Let's take a quick look at this basic aspect of suspension tuning.

Once you understand the terminology you can move into the adjustment stage.

What is Toe?

My simplest analogy is made to pigeons and ducks. Most people's feet point straight ahead. Compared that to a pigeon or duck there is a significant difference. In some people, however, the feet point inward. This is called intoeing (say "in-toe-ing"), or "pigeon feet." If your Charlie Chaplin then I'm sure you've seen his duck walk with his toes pointing outward.

Top down view of a tire in pairs

Toe - Straight (0 degrees)

/ \ **** ****
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Toe - In (Positive Degrees)

/ **** ****
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Toe - Out (Negative Degrees]

\ **** ****
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The amount of toe can be expressed in degrees as the angle to which the wheels are out of parallel

Toe settings affect three major areas of performance:

Tire Wear
For minimum tire wear and power loss, the wheels on a given axle of a car should point directly ahead when the car is running in a straight line. Excessive toe-in or toe-out causes the tires to scrub, since they are always rotating relative to the direction of travel.
Too much toe-in causes accelerated wear at the outboard edges of the tires
Too much toe-out causes wear at the inboard edges.

Straight-line Stability
So if minimum tire wear and power loss are achieved with zero toe, why have any toe angles at all?
The answer is that toe settings have a major impact on directional stability. With the steering wheel centered, toe-in causes the wheels to tend to roll along paths that intersect each other. Under this condition, the wheels are at odds with each other, and no turn results. Even with slight steering input the rolling paths of the wheels still don't make a turn. In this way, toe-in enhances straight-line stability.

Corner Entry Only
If the car is set up with toe-out on the front tires 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

What is Camber?
Have you seen the stance of a skier, usually their knees are closer than the feet. This stance is said to be a camber effect. Imagine running on a 200m oval track. When on the corner, you feel to get better track traction you need to make your outer feet is touch the inner side of your feet. Camber is the inward or outward tilt of the wheel when viewing from the front or rear of the car. Camber is probably the most useful and popular alignment adjustment that can be made to a street car.
Maximum cornering force is achieved when the camber of the outside wheels relative to the ground is about -0.5 degrees. A slight negative camber in a turn maximizes the tire contact patch due to the way the tire deforms under lateral load. Hence, it is good to have some negative camber to increase cornering force.

View from the front of a car

Camber - Straight (0 degrees)

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Camber - (Negative Degrees)

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Camber - Out (Positive Degrees]

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The best way to determine the proper camber for competition is to measure the temperature profile across the tire tread immediately after completing some hot laps. In general, it's desirable to have the inboard edge of the tire slightly hotter than the outboard edge.

What is Caster?
This is probably the hardest to explain. The technical description is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. Lost? Don't worry I bring it back with some diagrams. Picture a harley with a long nose or fork. This a positive caster setting that is very high. Makes it good to go straight mostly, but the mini will beat it at turning radius.lol

In a car you have ball joints connected to your wheels. These keep the wheels attached to the car. Also you have a steering column attached to the ball joint. The angle between the joint and the steering is the caster angle.
Say you driving down the straight on the hwy and you need to get your hands of the wheel. Notice how easily the car continues to go straight when you let your hands off. This is because of caster in the wheel. Anything attached to a wheel has caster. With caster you have a positve and negative setting. In Forza its represented by low and high. Forza doesnt have a negative caster because cars are not designed the same way the casters are in shopping carts.

Positive Caster which provides good directional control but harder top speed cornering.
Negative Caster does not provide good directional control stability but easier low speed cornering.

Top Down View of a car

******
****** () <- Lower Ball Joint
******
****** () <- Upper Ball Joint
******

Side View of a car

********
*******(*)* () <- Lower Ball Joint
***********
****(*)**** () <- Upper Ball Joint
********

Low Caster (Positive) of a Car

********
*******(*)* () <- Lower Ball Joint
***********
******(*)* () <- Upper Ball Joint
*******


High Caster (Positive) of a Car

********
*******(*)* () <- Lower Ball Joint
***********
*(*)******* () <- Upper Ball Joint
********



Low Caster (Negative) of a shopping cart

********
**(*)****** () <- Upper Ball Joint
***********
*****(*)** () <- Upper Ball Joint
********


Notice the shopping cart. see how easy it becomes to turn at a low speed. Imagine 60 mph with that caster setup turning left of right would be dangerous.

So high caster is good but makes it hard to turn, low caster is bad make it hard to keep straight.

Tuning

Questions? What are you experiencing when you drive the car through turns. Oversteer or Understeer?

Camber
Patience is the key because alignment tuning is the hardest in Forza.
Again you will need a telemetry for this. Stop the car completely on a flat track with no elevation. Launch Telemetry and goto Tires. Note the camber angle the car makes with the road. If it matches the setting you have tuned then you are on flat surface.

Restart tuning and race for a couple of hot laps. Usually 3 is good enough. Dont worry about red penality. Stop after 3 and watch the replay. During the replay launch the telemetry and jump to the "Tires Misc".

you need to watch the replay at least 2 times to get this down.

Start by looking at the camber angle on the front wheels.
Note how many times you see a positive number.
Repeat for the rear tires on the 2nd replay.

Now go back to tuning and change the following if applicable

Positive camber on straights - Decrease camber by .1
Positive camber on turns - Decrease camber by .1

No Positive camber on straights - Increase camber by .1
No Positive camber on turns - Increase camber by .1

Whats the point? Positive camber is the enemy and reduces traction and stability.

Tuning for Cornering.

For Left Turn
The Left Tire must be less than or equal to 0.0 degrees.

For Right Turn
The Right Tire must be less than or equal to 0.0 degrees.

Closer to 0 better the handling. Anything above 0 means that the tire is not helping you.

Toe

General Rule of Thumb Is to Improve the car for corner entry.

Combinations include:


Front Toe + Rear Toe 0 <- Better Corner Entry Any Car
Front Toe - Rear Toe 0 <- Reduce Steer Sensitivity Bad Corner Entry

Front Toe 0 Rear Toe + <- Understeer tendencies but Better Corner Exit in any Car and stability under braking.
Front Toe 0 Rear Toe - <- Slow Corner Exit

Front Toe + Rear Toe + <- Provides stability under braking and creates oversteer tendencies in cornering.
Front Toe + Rear Toe - <- Amazing Handling on any car but can cause undertsteer

Front Toe - Rear Toe + <- Amazing Handling on any car but can cause oversteer
Front Toe - Rear Toe - <- Oval track

Examples
Any Car for Better Turn In Response
Front Toe Out : - .1 (duck feet ready for turning left or right)

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Cars with massive power and no handling.
Front: 0
Rear Toe In: -.1 (pigeon feet, ready to face the direction of turn on acceleration)


/ \ **** ****
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/ **** ****
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BRAKES

What is Brake Bias?

Brake bias is the balance of braking power between the front and rear brakes. It is usually represented as a percentage. For example, a brake bias of 65/35 means that the front brakes get 65% of the braking power, and the rear brakes get 35% of the braking power.

Why do I need to know?
Brake bias controls the way that the car handles when the brakes are applied. Therefore, it is useful in changing the corner entry handling characteristics of a car if braking is necessary going into a corner.

What happens on adjustment?
Moving the brake bias toward the front brakes makes the car tighter and more stable while braking and entering a turn. Moving the brake bias toward the rear makes the car looser while braking and entering a turn. Excessive front braking power can lock up the front tires and decrease the overall effectiveness of your brakes since you are not using the rear tires to slow down the car.

Rule of Thumb
The front brakes should always have more braking power than the rear because the weight transfer during braking loads the front tires and unloads the rear tires. If you have too much rear brake, the rear tires will lock as weight transfers forward and makes the rear of the car lighter. However, make sure you do not have too much front brake either.

How To Tune Brakes?
As a starting point "TURN ABS OFF", try setting your brake bias between 70/30 and 80/20. Fine-tune the car from there. I found that the Optimal Setting is 47% Front. I will get into the pressure later.

As Usual Replay Your Runs and Bring Up Telemetry and go to Friction.
Reading the Telemetry for Friction is as follows.

Red Circles is a visual of the grip available at each tire, and the blue lines inside them are the amount of grip you are actually asking the tire to produce. This displays a more detailed brakedown of the "Friction Circle" type telemetry from the "Body Acceleration" telemetry screen. If you watch the red circles off the start line, the front ones will get slightly smaller and the back ones will grow. That is because a tire's grip is related to the amount of weight on that tire... more weight = more grip, to an extent. So as you jump on the gas, weight shifts backward, and the rear circles grow because your rear tires have more grip. When you go into a corner, you will also see the circles change size as weight shifts side-to-side. jump over a curb, and the circles disappear if the tire leaves the ground! The blue line shows how much you are asking of the tire - if it is outside the red circle, it means you are pushing that tire too hard and it has lost grip, so it is sliding. If you look at the telemetry during a spin, the blue lines will be well outside the red circles. If the blue line is inside the circle, it means that there is more grip available, since the circle is the limit. You are using your tires most effectively when the blue line is touching the red circle.

Notice while Braking which circles are getting bigger, usually the front will get bigger than the rear with the bias > that 50% Front. Keep moving 1% Front till you have lost grip completely skidded out as a result of understeer when braking. Move back 1% to be in the safe zone.

Tuning Brake Pressure
Also look at the brake indicator (vertical red line on the left of the telemetry) notice if you are completely at 100% or just 70%. This will imply your braking input sensitivity on the controller. Once you have found the optimal setting for your brake bias. Brake pressure will improve your stopping.

Based On Braking Style You Maybe Doing 1 of the following:

1. On Demand (Pull the trigger all the way back)

2. On Power (Pull the trigger all the way back with acceleration)

3. Off Throttle Down Shift Half Brake (Pull the trigger half way)


With ABS OFF (ABS ON counters your braking, meaning more the light is on the more your travelling forward)
1. On Demand: Try going for a less brake pressure, you want all the tires to skid only when the trigger is completely back. Try tunning so that you have a little play to create a skid and a good brake. Start at 100% and keep going down 5% till you have that perfect brake. Using the Telemetry make sure you have 4 big red circles when skidding to indicate good brake bias.

2. On Power: Same as above but make sure you dont get into a race-brake situation where your locking the front and burning the rears tires..looks cool but can be costly.

3. Off Throttle: Brake sensitivity is the key. You use only 10~40% on sensitivity (i.e depressing the brake 1/2 to 1/4, you never completely hold the entire brake down during a race (unless you want to show off your ABS skills lol). You know how to lock brakes to your advantage. You use the gear down to your advantage ONLY AFTER you started braking. Typically you keep going up in pressure settings because feel you can stop at a dime.

TIRES

You can't transmit your car's power and handling potential to the road without the right tire setup, because tire pressure affects a tire's peak grip, responsiveness and wear. Adjust the front tire pressure when the tires are cold so they reach peak grip after they heat up to race temperatures.

Note from Time: Peak Grip Temperature is between 180 and 210 degrees

This is a Master's Class Tuning and you need to use the telemetry for this.

Start by picking any track and test run 3 laps in test drive mode, now bring up the heat and tires misc. telemetry and observe the temperature & pressure.

Tires reach peak friction at 32 psi; however as long as you're running a race psi of 30-34 degrees, you're still in good grip range. Race psi and race temperature is measured after a few laps when your tires have heated up and reached their performance levels.

Tire Temp - Cause - Recommended Adjustment

Center hotter than edges - Tire pressure too high - Reduce 1 psi for each 5 deg F difference

*****
* ** *
* ** *
* ** *
*****



Edges hotter than center - Tire pressure too low - Add 1 psi for each 5 deg F difference

*****
* ** *
* ** *
* ** *
*****


Inner edge hotter than outer edge - Too much negative camber - Decrease negative camber

*****
* ** *
* ** *
* ** *
*****


Outer edge hotter than inner edge - Not enough negative camber or too much toe-in - Increase negative camber or decrease toe-in

*****
* ** *
* ** *
* ** *
*****


Tire below peak temperature range - Tire pressure too high, tire too wide or springs/sway bars too soft at that axle - Decrease tire pressure. reduce tire width or stiffen up springs and sway bars on that axle

Tires above peak temperature range - Tire pressure too low, tire too narrow, or springs/sway bars too stiff at that axle - Increase tire pressure, increase tire width or soften up springs and sway bars on that axle

Front tires hotter than rear - Car is understeering. Too much front spring/sway bar, not enough rear spring/sway bar, front pressure too high, front tires too narrow, rear tires too wide - Soften up front spring and sway bar, stiffen up rear spring and sway bar, increase front pressure or decrease rear pressure

Rear tires hotter than front - Car is oversteering. Too much rear spring/sway bar, not enough front spring/sway bar, front pressure too high, rear pressure too low, rear tires too narrow, front tires too wide - Soften up rear spring and sway bar, stiffen up front spring and sway bar, increase rear pressure or decrease front pressure
I hope you use the telemetry to adjust this setting based on your driving. This is the correct way to set it, so the next time some dude tell you 28/28 or 29/28 ask him how he came to that conclusion ...just make that you did the 3 laps to see if the pressure reached its peak which is 32....

Gearing

Tuning Gear Ratios
Gearing is the key to better acceleration, braking, cornering and top speed.

There are endless debates on torque and horsepower and we wont get into that here.You know this because most American/German cars make torque and Japanese make horsepower. But its important to understand the terminology.

The Formula

Torque X RPM
Horsepower = -----------------------
5252


Case for Torque
Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that same torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

Case for Horsepower
OK. If torque is so all-fired important, why do we care about horsepower? Because, "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.


-Grizzld
"Expect nothing and you'll never be disappointed"
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Great find genocide.

i have found that brake balance and pressure makes a bigger difference to how the car handles than most of the other settings, i tend to spend alot of time getting it right and to react how i want the car to behave under breaking.

i tend to run alot lower pressure than most people but i seem to be able to brake deeper into corners because i know the car wont lockup on me when i do.

typically i run 54% to the front and pressure is about 82%.