Tuning Guide

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Tuning Guide

Post by o MANIC o on Tue Jan 17, 2012 1:59 pm

I found this tuning guide on the net. None of this is my writing.

Tire Pressure

Tire pressure affects a tire’s grip, responsiveness and wear so adjusting front and rear tire pressures under different circumstances is important to keep that grip. You need to adjust the front tire pressure when the tires are cold so that they can reach their grip potential after they heat up to race temperatures.
Maximum grip potential of a tire ranges from 180 to 200 degrees. You can use the telemetry to get an idea about the grip potential of your tires and what setup you would need in race.
Peak friction of the tires is generally 32 psi but, you are doing even if you are somewhere between 30-34 degrees. You will still have necessary grip. You will know the tire temperatures and PSI once you have raced through few laps and tires have heated up.
When your tires heat up, you may need to do some adjustments to keep them in good grip range. The general rule is if the tire center is hotter than edges, tire pressure is too high and you need to reduce 1 psi for each 5 degree temperature difference.
If tire edge are hotter than center, tire pressure is too and you need to add 1 psi for each 5 degrees of temperature difference. If inner edge of the tire is hotter than outer edge, your tires have too much camber so you need to decrease negative camber.
If outer edge is hotter than inner edge, there is too much toe or not enough negative camber so you need to increase negative camber or decrease toe-in. If the tire is below peak temperature range, tire pressure is too high or tire is too wide or springs are too soft at the axle. In this case, you need to decrease tire pressure or reduce the tire width or stiffen up the springs and sway bars on the axle.
If the tires are above peak temperature range, tire pressure is too low or tire is too narrow or springs and sway bars are too stiff at the axle. In this case, you need to increase tire pressure, increase tire width or soften up springs and sway bars on the axle.
If front tires are hotter than rear tires, your car will under steer. This is because, too much front spring/sway bar, not enough rear spring/sway bar, or front pressure is too high or front tires are too narrow or rear tires are too wide. In this case, soften up front spring and sway bar, stiffen up rear spring and sway bar, decrease front pressure or increase rear pressure.
If rear tires are hotter than front tires, your car will over steer. This is because, too much rear spring/sway bar, not enough front spring/sway bar, rear pressure is too high, front pressure is too low, rear tires are too narrow or front tires are too wide. In this case, soften up rear springs and sway bar, stiffen up front spring and sway bar, decrease rear pressure or increase front pressure.
Your best shot to help you adjust these settings appropriately is Telemetry. Instead of following your guts when adjusting the tire pressure, do a quick 3 lap session in quick race and find out your tire pressures and other variables that will help you adjust your tires’ pressure for that track.


Camber, Toe, and Caster are the three major alignment parameters. Let’s first see why these alignment parameters are important to adjust.
Camber is the inward or outward tilt of the wheel, which makes it the most important alignment adjustment for a street car. If you want maximum cornering force, set camber of the outside wheels on the ground to about -0.5 degrees.
It is good to have some negative camber as it increase cornering force but the important question is, how you would know how much negative camber you need for a particular track ?
You will find this out in a quick session before the race by measuring the temperature profile across the tire immediately after completing few laps. You want the inboard edge of the tire slightly hotter than the outboard edge.
Toe affects three major aspects of car performance. Tire Wear – excessive toe-in or toe-out can cause the tires to scrub, since they are always rotating relative to the direction of the travel.
If you set too much toe-in, it will cause accelerated wear a the outboard edges of the tires and if you set too much toe-out, it causes wear at the inboard edges of the tires.
Straight-line Speed – When the steering wheel is centered, toe-in causes the wheels to tend to roll along the paths that intersect each other. Under this condition, even with slight steering input, the rolling paths of the wheels don’t make any turn so toe enhances the straight-line stability and helps you keep the speed.
Corners Entry – If the car is set up with toe-out on the front tires, any small steering angle will cause the inner wheel to steer in a tighter turn radius than the outer wheel. Under this condition, the car will always be trying to enter a turn, rather than maintaining a straight line speed.
Now we are left with Caster. It’s tricky, and difficult to grasp but let’s try. Caster is your angle to which the steering pivot axis is tilted forward or backward from vertical, as viewed from the side. In a car, ball joints connect your wheels and steering column. The angle between the joint and the steering is called the caster angle.
You have positive and negative settings for the caster. It’s your low and high settings in Forza Motorsport 4. High caster setting is good for straights but makes it harder to turn, low caster is good for turns but makes it harder to keep the straights.
Tuning these settings depends on your style of driving. Do you understeer or oversteer through turns ? This will decide how you should go about tuning the alignment in Forza Motorsport 4. Remember, it will need great deal of trial and testing before you will finally fine tune the alignment of your car.

Tuning Camber

To adjust Camber, stop the car on a straight road with no elevation and go to telemetry to note the camber angle the car makes with the road. If it matches the setting you have tuned then you are on a flat surface.
Do a quick race and after three laps, watch the replay. Launch Telemetry and go to ‘Tires Misc’ to get what you need. You need to note the several times you see a positive camber for your front and rear tires by looking at the camber angle.
Once you have noted down these values, go back to tuning adjust these settings as follows:
• 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
We can conclude that positive camber reduces traction and stability. Now, let’s tune for cornering:
For Left Turn
• The right Tire must be less than or equal to 0.0 degrees.
For Right Turn
• The left Tire must be less than or equal to 0.0 degrees.
We can conclude that close to 0 better the handling and anything that’s above 0 means that the tire is not helping you. You must have negative camber and if you are tuning for drag racing, set camber and toe at 0.


Toe improves the handling of the car for corner entry.
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 +
• Under steer 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 over steer tendencies in cornering.

Front Toe + Rear Toe -
• Amazing Handling on any car but can cause under steer.

Front Toe – Rear Toe +
• Amazing Handling on any car but can cause over steer.

Front Toe – Rear Toe -
• Oval track.

Brake Bias

Brake Bias maintains the balance between the front and rear brakes. It is represented by a percentage such as, 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. It’s an important setting that you would need to adjust subjected to how you go into the corner and get out of it.
Now to the tuning part – When you move brake bias toward the front brakes, the car is tight and more stable while braking and entering a turn. When you move the brake bias toward the rear, the car is loose while braking and entering a turn.
Be careful though, excessive front braking can lock up the tires and decrease overall effectiveness of your brakes since you are not slowing down the car by using the rear brakes.
It is recommended that your car always have more front braking power than the rear because the weight transfer during braking loads the front tires only. If you set brake bias toward rear, the rear tires will lock as weight transfers forward and makes the rear of the car lighter.
Set the brake bias between 70/30 and move from there to fine tune your car. Don’t forget to ‘Turn ABS OFF’. How would you fine tune the brake bias ? Replay and Telemetry combo… read the telemetry for friction.
How Should You Read Telemetry For Friction ?
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 brake down 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

Once you have found the ideal setting for brake bias, the brake pressure will increase your stopping power. To fine tune brake pressure, look at the brake indicator and notice if you are at 100% or 70%.
Subjected to your braking style, you may do one of these:
• On Demand (Pull the trigger all the way back)
• On Power (Pull the trigger all the way back with acceleration)
• Off Throttle Down Shift Half Brake (Pull the trigger half way)
On Demand
Go for less brake pressure as you want the tires to skid only when the trigger is pulled all the way back. Start at 100% and keep going down 5% till you have the perfect brake. Using the Telemetry, make sure you have 4 big red circles when skidding to show good brake bias.
On Power
Similar to On Demand but make sure you get into a race-brake situation you are locking the front tires and burning the rear tires.
Off Throttle
Squeezing the brakes coming out of the corner is similar to squeezing the throttle, you will learn it over time and it comes natural afterwards.
Differential controls how your car transfers its power and torque to the road. Differential sends the power to the wheels with least grip and because of the way your car transfers power to the wheels, it is prone to wasting it and losing traction.
Similarly, when the differential sends the uneven amount of torque to the wheels, the limited slip kicks in, and locks the wheel together. Though, it evenly locks both wheels still one wheel is receiving more torque.
Differential has two settings, Acceleration and Deceleration. Acceleration controls at what point the differential locks while on gas. Having a higher percentage of acceleration will prevent each wheel from slipping, which will allow you to harness more power when exiting a corner but if you are driving an RWD car, it is easier to spin out a drift.
Having a lower percentage will make it easier for each wheel to slip, resulting in power loss when exiting a corner but if you are driving a RWD car, it is hard to spin out and drift.
Use the high-slip rate, even in front wheels because it usually creates a less sloppy feeling when you exit a corner and it allows you to leave the corner with higher speeds but if back-end of your car slides out more than you should stick to lower rate.
Deceleration controls at what point the differential locks when you let off the gas, usually when entering the corner. The high the rate, the more stable your car will be.
It will make your car less agile, and can cause under steer. Having the higher rate while accelerating, makes it harder to stop the skid, so be careful with whatever setting you choose. Use the low-slip rate here, because it will make your car more agile. If your car tends to over steer, increase the slip-rate a bit.
The central differential of AWD cars control how the torque is divided between the front and back wheels. It sends more power to wherever there is least amount of grip, just like any other differential. Rear biased central differential gets the most performance out of AWD, so give it a try.


It controls the suspension’s stiffness and compression between wheel and wheel-well. Rebound and Bump work in ‘reverse-way’ like having the Front Rebound higher than rear increases grip on rear, because more weight is concentrated in the front tires under spring compression, so rear wheel con work more freely.
Rebound Stiffness
Increasing Front Rebound
• More grip in the rear.
Decreasing Front Rebound
• Reduces transitional under steer.
Increasing Rear Rebound
• More grip in the front.
Decreasing Rear Rebound
• Reduces transitional over steer.
Front biased Rebound
• Increases under steer & increases grip in RWD cars, sacrificing turn-in slightly.
Rear biased Rebound
• Increases over steer & highly recommended for FWD & AWD cars.
How high rebound setups you can have depends on the Bump stiffness that you have set. If you are using high Rebound with low Bump, your car may get upset by curbs etc. This is modified by ride height and suspension stiffness.
Higher Rebound than Bump is must but the Bump Stiffness should be 75% of the Rebound’s stiffness at maximum. Low Bump Stiffness goes great so don’t limit yourself with officially given tip that 50% of the Rebound’s stiffness should be a minimum.
Bump Stiffness
It fine tunes damping and suspension.
Increasing Front Bump
• Increases under steer and slightly increases rear grip + modifies the effectiveness of Damping and Spring setups.
Increasing Rear Bump
• Increases over steer and slightly increases front grip + modifies the effectiveness of Damping and Spring setups.
Decreasing Front Bump
• Improves bump absorption + modifies the effectiveness of Damping & Springs.
Decreasing Rear Bump
• Improves bump absorption + modifies the effectiveness of Damping & Springs.
Front biased Bump
• Increases under steer + slightly increases grip in RWD cars.
Rear biased Bump
• Increases over steer & highly recommended for FWD & AWD cars.
To test the excessive Bump Stiffness, let your car take a mild curb aggressively and then see if your car rolls. If it rolls, your setup is too stiff.

Last edited by o MANIC o on Sat Jan 21, 2012 8:49 pm; edited 1 time in total

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Re: Tuning Guide

Post by TEEROY 34 on Wed Jan 18, 2012 2:53 am


Good find buddy
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Re: Tuning Guide

Post by Magz on Wed Jan 18, 2012 3:15 pm

Sweet as thank you
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Re: Tuning Guide

Post by o MANIC o on Sat Jan 21, 2012 8:54 pm

OP Updated. It is now finished

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Re: Tuning Guide

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