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Forza Tuning Guide

Before using this Forza Motorsport tuning guide, it is assumed you have installed the following upgrades:
Race suspension, Race front & rear anti-roll bars, Race brakes & Race Aero.

In each section of this tuning guide, there is a written explanation, followed by a video version, showing detailed yet simple visuals to help you maximise your understanding of tuning!

TYRE PRESSURE
We'll begin with tyre pressure, as this is the only part of the car that can be tuned without making any upgrades!
​As you drive, friction between your tyres and the track will cause your tyres to heat up.

As the tyre compound heats up, it becomes softer and more pliable, helping it to mould into small cracks in the track's surface, therefore increasing potential grip.  This could lead us to believe that hotter is better, but it isn't!

As the tyre gets hot (which is something we want), the air inside begins to expand.  This causes the pressure inside the tyre to rise.  If the pressure rises excessively, the tyre may 'balloon' (which is something we don't want).  Ballooning is when the edges of the tyre lift off the ground, significantly reducing the contact patch, and available grip is drastically reduced!

Tyres need pressures that suit a maximum contact patch, along with tempertaures that suit the compound.

In most cases, 'road' compound tyres reach their optimum grip with temperatures ranging somewhere between 140-170 degrees Farenheit (F).  Sport compound tyres will perform best between 160 - 200 degrees F, while race compound tyres can run much hotter, often performing best between 170 - 220 degrees F.

Remember: Tyres will not be at these optimum temperatures straight from the pits!  Run a few corners (or maybe even an entire lap) to bring the tyres up to race temperature before  you start making any adjustments.  Once race temperatures are achieved, re-check tyre pressures to ensure they have not climbed too high!  Race temperature tyres should ideally have pressures between 32-33 PSI or 2.20-2.27 BAR.  This will result in a good shape, and largest contact patch.

You can check tyre information by using the in-game telemetry.  While on the track, press 'up' on the d-pad on your xbox controller, and then, using the 'right' d-pad button, scroll across to the 'Heat' page.  Here you can see the temperature of the tyres.  They are divided into 3 areas for each tyre: Inside, Middle, and Outer.   If the centre of the tyre is hotter than the edges, then the pressure is set too high - The tyre is ballooning!  If the edges are hotter than the centre, the pressure is set too low.

Adjusting tyre pressures can also effect the response of the car.  Increasing tyre pressure increases response, while decresing pressure reduces response. Personally however, I recommend you focus on contact patch and temperatures when adjusting tyre pressures, and use suspension adjustments to tune response. This is covered later in the guide.

Should the inside edges of the tyre remain hotter than the outside edges (or vice-versa), this is not a pressure issue.  This is a camber problem and is discussed in the section covering tuning  camber.

​​CAMBER

Positive Camber:
Increased load on the outside edge of the tyre.

Negative Camber:
Increased load on the inside edge of the tyre.

During cornering, the more centralised you can make the tyre's contact patch (or the more neutral you can make the camber), the larger the contact patch will be. This maximises cornering grip.

Negative camber increases load on the inside edge of the tyre. While cornering, weight is transfered to the outside edge of the tyre. With this in mind, we can adjust camber to help centralise the contact patch through corners, increasing it's overall size and maximizing grip!

In a straight line, the tyre is not being squashed into the road like it is in a corner.  Large camber angles can limit the size of the contact patch, as the inside edge is the only part of the tyre making contact!  This reduces grip both in acceleration (increased wheel spin) and braking (increased stopping distances), and will almost certainly reduce turn-in responce.

You can check if the camber angle is appropriate for cornering by using the in-game telemetry to monitor tire temperatures.  You should aim for even temperatures across the whole width of the tyre (inside, centre, and outside edges) at the point of corner exit.

If the inside edge is hotter than the outside, reduce camber (less negative).  If the outside edge is hotter than the inside edge, increase camber (more negative).  If the temperatures are not exactly even, then aim for the outside edges to be slightly warmer than the inside edges on corner exit,  On the straights, the inside edges will be warmer. This is normal and to be expected.

As is always the case when tuning cars, there is a compramise to be made.  Here you need to find an 'ideal' angle, allowing for maximum cornering grip, without impairing handling too much whilst driving in a straight line.
 
It's up to you to find the balance!​​

TOE

Positive Toe or Toe-Out

Negative Toe or Toe-In

When a vehicle is cornering, the inside tyre traces a tighter radius than the outside tyre and therefore needs to turn at a greater angle.  
 
With the front wheels toed out, the inside tyre turns at the required tighter radius, increasing grip and making it easier to turn the wheels.
With the front wheels toed-in, the inside tyre actually turns at a larger radius, fighting against the outside tyre, and making it far harder to turn the wheels.  
 
As the turn develops, weight transfers to the outside tyre, significantly reducing the effects of toe.  It is because of this weight transfer, toe adjustments tend to only affect the vehicle during corner entry.
 
At the rear of the car, the extra stability and resistance to turn caused by toe-in, reduces power-on and lift-off oversteer, enabling far more control under both conditions,  This is especially useful with high-powered rear-wheel-drive vehicles resulting in more grip and less slide.


To summarise:
 
Increase turn-in grip by increasing front toe-out.

Reduce unwanted power-on / lift-off oversteer by increasing rear toe-in.​​​
CAUTION!

Using toe in ANY amount or ANY direction causes tyres to scrub.  This reduces top speed and could increase lap times!  Where possible, tune oversteer and understeer using anti-roll bars, springs, and dampers.  Leave toe settings at 0.0 for both front and back unless other areas have been exhausted.

Tuning toe cannot always be avoided, so if adjustments are required, only tune using very small increments.

CASTER

Caster refers to the angle between 'true' vertical and the suspension strut assembly.

Caster angle should never be negative, and in fact, this is not even an available option within Forza. 
 
Positive caster encourages the wheels to return to 'centre' if you were to remove your hands from the steering wheel.  The more positive the angle, the more stable the car will be on the straights.  Even so, set the caster angle as low as possible without the car wanting to weave all over the track.  Most cars will have a setting around 5 degrees (plus or minus 0.5 degrees).
If during long straights you feel instability, and you find yourself constantly having to correct it, simply increase the  angle. 
 
* Increasing caster angle also increase the effort required to turn the wheels.  This may be reflected in your wheel setup, but will have clearly no effect for those using a controller.  
 
 
  • If the car feels too responsive to steering input, increase the angle.
 
  • If the car isn’t responsding enough to steering input, decrease the angle.
​ANTI-ROLL BARS
An anti-roll bar (sway bar) connects opposite (left/right) wheels together through short lever arms linked by a torsion spring (bar).

This bar increases the spring stiffness in turns, independently of the spring stiffness on the straights. 
Due to weight transfer during cornering, vehicles roll.

The rolling of the car compresses the spring on the outside wheel, while the spring on the inside wheel extends.  The anti-roll bar connects the inside and outside wheels together, forcing the inside wheel to mimic the movements of the outside wheel.  As the two wheels are forced to mimic each other during cornering, body roll is restricted in relation to the ARB stiffness, and the car stays flatter in the turn.

The stiffer the bar, the closer the inside and outside wheels are forced to mimic each other, which means less roll.  Likewise, the softer the bar, the less the wheels are forced to mimic each other's movements, and therefore more body roll is experienced.  

n.b.  On rough surfaces, inside and outside wheels would need the ability to move more independently from one another, and soft ARB's would be used.

ARB's effects are only noticed in mid-corner and corner exit, and have no effects on drving in a straight line.  Think of ARB's as a way of adding spring stiffness only while cornering.
 
Although body roll causes the laden (outside) tyre to 'squash' into the track more - increasing the grip the tyre is able to produce, soft ARBs and low ride-heights do not mix well, as the outside spring may bottom out as the turn develops,
 
Find the balance!
 
Anti-roll bars should be your first stop for tuning oversteer and understeer. 
Conclusion:
Reduce understeer by reducing front ARB stiffness

Reduce oversteer by reducing rear ARB stiffness

REMEMBER

Understeer is controlled with front ARB adjustments

Oversteer is controlled with rear ARB adjustments



When tuning, make sure to focus on the area with the problem.  i.e. Do not try to reduce oversteer (rear) by increasing understeer (front)!​

Spend some time adjusting ARB’s.  They are quite complex but once adjusted correctly, increase predictability and control!
SPRING RATES

The 'spring rate' defines the load required on the spring in order to compress the spring.  ​eg. lbs/Inch or Kg/cm
Tyre compliance is crucial, and correct spring setup ensures tyres are kept in contact with the track surface for as much time as possible.  Incorrect spring setup will significantly reduce tyre compliance.

Springs have 'spring rates'.  

The softer the spring rate, the less force is required to compress the spring.  This means that when you go over a bump or onto a steep curb, the spring compresses and keep the tyres in contact with the road.  Go too soft however, and bottoming-out is much more likely!
Bottoming out is when the spring is fully compressed.  A fully compressed spring would be no different to removing the spring all together! We go from a soft spring rate, to an infinate one!  Sudden, unpredictable changes in handling like this will cause serious handling issues!

The higher the spring rate, the more force is required to compress the spring. A car with a high spring rate, although far less likely to bottom-out, is now  more likely to skip over the bumps.  This causes a loss of control as the tyre loses contact with the road...
And you can't steer while your off the ground!

You want to ride with the softest springs possible that a track's surface will allow, without the car bottoming out.
​​So we want springs to be as soft as the track will allow, but we also have to take into account some other factors. Vehicle weight, weight distribution, and ride height.

The heavier the car, the stiffer the springs needs to be, and likewise, if the car's weight is distributed unevenly, ie. more weight at the front, then the springs at the front need to be stiffer than those at the rear.

Lowering ride height, lowers a vehicles centre of gravity, which is the key area to providing more grip in corners!  Think of an F1 car.  They are incredibly low to the ground, and corner like they're on rails!  When setting the ride height, go as low as you can for the track you're racing.  Smooth tracks may allow the car to be lowered all the way, however you need to allow for suspension travel on the bumpier tracks using softer spring rates, so raise the ride height to accomodate this.
 
 
Oversteer and Understeer.
 
  • Setting front springs softer than the rear reduces understeer.  This is because when cornering, the front will roll more, transfering more weight to the outside wheel, increasing grip at the front.
 
  • Setting rear springs softer than the front reduces oversteer.  This is because when cornering, the rear will roll more, transfering more weight to the outside wheel, increasing grip at the rear.


HOWEVER:

Using springs to control oversteer and understeer is not necessarily a good idea.  This is because softening spring rates may very well lead to excessive squating and diving.  Squating is when the rear springs are too soft and the car rolls back onto the rear wheels while accelerating, and diving is when the front springs are set too soft and the car rolls forward onto the front wheels when braking.


Conclusion: 
Run soft spring rates to help absorb bumps in the surface,
but not so soft that the car bottoms-out,

AND

Run stiff enough springs to prevent too much squatting and diving,
but not so stiff that the car skips over any bumps



Then use the ARB’s to balance the spring stiffness’s for the corners.
DAMPERS

Koni performance dampers

As discussed in the section above, springs control how far the suspension moves.  Dampers however, control how quickly the suspension moves.  They also help the suspension settle quicker.
 
They do this by simply resisting suspension displacement in both compression and extension.
 
Bump refers to the state of the suspension as it is being compressed.  The damper controls the speed of this compression.  

Rebound refers to the state of the suspension as it extends, and again, the damper controls the speed of extension.
 
The stiffer the damper, the more resistance it has, and the quicker the suspension will reach a steady state.  This makes the vehicle more predictable.
As we know, while cornering, the suspension compresses (bump) on the outside as this is where the weight transfers to. Suspension on the inside of the car extends (rebound) as this is where the weight tranfers from.  Stiffer bump settings will resist the weight transfer gained on the outside wheels, while stiffer rebound settings resist weight transfer by stopping the suspension extending on the inside, effectively holding the weight back.  The dampers are preventing weight transfer! Very useful in maintaing a 'flat' car through the corners, controling understeer to oversteer transitions, and making the vehilce more predictable.
 
On smooth surfaces, such as race tracks, this stiff resistance to weight transfer is desirable, however these setting will certainly not be suitable for bumpy, irregular surfaces.  If the overall stiffness of the dampers is set too high, the suspension cannot react quickly enough, and the vehicle will bounce over the bumps. If the rebound is set too high, tyres will  not return to the track surface fast enough after the bump , and will momentarily leave the ground.  Tyres off the ground are obviously not much use!
 
It’s up to you to find the correct settings for your car as there is no golden rule.  Dampers will certainly need adjusting when moving from a flat race track to a bumpy street based circuit!
 
Dampers are a good way to fine-tune handling without major changes elsewhere.  Remember they control the speed the suspension moves and not the potential length of suspension travel - That's the spring rates.
 
Generally;
 
  
Soften the front to reduce understeer.

Soften the rear to reduce oversteer.


And also note,
 
The front is often softer than the rear.
 
The rebound is usually stiffer than the bump.
 
​AERO

Front Race Spoiler

Rear Race Spoiler

When travelling at high speeds,  air flowing over the top of the car can be utilised to increase cornering grip.  

Increased wing angles, combined with high speeds, increases grip by using  the air flow to push down on the vehicle, essentially adding "weight" to the tires.  The steeper the angle of the wing, the more effective the downforce.

This increase in downforce does however increase the aerodynamic drag of the vehicle and reduces top speed.  For this reason, handling improvements created by wings is not noticeable in slow speed corners.
 
A suitbale setting will certainly be track dependent.  

Short winding tracks will be more suited to increased grip, but if you can't get the car fast enough to benefit from the wing's effects, is the wing beneficial?  Probably not.  Tracks with long straights benefit from less downforce to help maximise top speed.


Aero should therefore be used on tracks with high speed, sweeping corners.  Should those corners lead onto long straights, the increased grip throughout the corner will help to build a high exit speed and leave you flying off down the straight!
 
Anylise the track and decide what you want to achieve from your car before installing and tuning aerodynamic wings! 

Tuning front and rear downforce independently, can be useful in creating balance through the turn.  While at high speeds, should the front be lacking grip, increase the front dowforce, and likewsie if the rear is losing grip, increase the rear downforce.
​BRAKES

Brembo Race Brake Discs

Balance
 
Adjusting brake balance will depend on your style of braking. 
 

Trail-braking
 
If you tend to trail-brake, (braking late and turning into corners whilst trailing off the brakes) and suffer from turn-in understeer, send brake balance towards to rear.

Likewise, if you turn-in and the rear begins to slide, send brake balance towards the front. 
 

Straight-line Braking
 
If braking in a straight line the front wheels lock, causing you to miss your turn, send brake balance rearwards.  If the rear locks up, send the balance forwards.

Ideally, if the brakes are going to lock up at all,  the front and rear brakes should lock together!
Pressure
 
This is not really a case of what is 'best'.  Pressure adjustments are all about how far you squeeze the brake on your pedal or controller.  

If you prefer to squeeze the trigger through the full range, and find that your brakes are consistantly locking up, simply reduce the pressure setting. 

Likewise, if you only tend to apply brake perssure to around half-way and the brakes are not effective enough, increase the pressure setting.
 
n.b. Over the period of a race, you my notice that one set of tires has worn more than the others.  You can reduce this difference by moving the brake balance towards the least worn tires.

To ensure the braking pressure you choose provides you with the full range of braking force, aim for a pressure setting where the wheels lock in the final 10-15% of you trihher or pedal movement.  This will give you a higer "resolution" in brake application. ie. more accuracy with finer movements.

DIFFERENTIALS

Inside a limited-slip differential

While driving round corners, the outside wheel travels further than the inside wheel but must complete the turn in the same time.

The outside wheel must therefore travel faster than the inside wheel.  

A differential allows this difference in rotaional speeds, which is vital in order to maintain traction during cornering.

Differentials are only found at sets of wheels that are being "driven".  So a front wheel drive car has a differential at the front, and a rear wheel drive car has a differential at the rear.  All wheel drive cars have differentials at the front and the rear. plus an additional differential in the middle to control torque split.

As mentioned before, wheels need to rotate at different speeds.  Lower differential settings allow this and help the car to maintain traction.

An open differential allows the wheels to rotate at independent speeds, helping to retain traction through the corners.
Acceleration
 
When tuning the acceleration setting, the effects are only present while the throttle is being applied.

With the acceleration set to 0%, the differential is open and therefore has no lock!  Set here you will have less acceleration through the turn.  This is because instead of power being sent to both driven wheels, the differential sends more torque to the wheel with less grip.  

In a turn, less grip will be the on the inside wheel due to weight transferring to the outside.  The power ends up at the wheel with less grip and the car can't efficiently accelerate. This setting does however increase stability by reducing oversteer in rear wheel drive cars.

With the acceleration set to 100%, the differential is 100% locked, forcing inside and outside wheels to rotate at exaxtly the same speed. Oversteer will be typically inevitable, particularly in high-powered cars, and gentle throttle control is essential to tame the oversteer.


The trick is to find a balance.  (The less traciton you have available, the lower you need the setting!)

  • High acceleration settings INCREASE oversteer!
  • Low acceleration settings REDUCE oversteer!

 

Deceleration
 
When tuning the deceleration setting, the effects are only present while off the throttle.


With the deceleration set to 0%, just as with the acceleration setting, this means the differential is 100% open and has no lock.  This allows the wheels to rotate independently, getting the car around the corner earlier for sooner throttle application.  Note:  A setting of 0% will cause one wheel to lock during abrupt downshifting and result in instability!


With the deceleration set to 100%, the differential is 100% locked, forcing inside and outside wheels to rotate at exactly the same speed.  As you lift off the throttle, both wheels grip the track equally, and the car refuses to rotate.  Note: A setting of 100% will cause both wheels to lock during abrupt downshifting creating an effect similar to applying the handbrake!


Again, you need to find a balance.

  • High deceleration setting INCREASES understeer!
  • Low deceleration setting REDUCES understeer!

To finish this tuning guide, below are two troubleshooting flowcharts.  You can follow these to quickly help you identify the  most likely cause for common problems experienced in both oversteer and understeer.  
Both troubleshooters were sourced online, and I take no credit for them.

UNDERSTEER TROUBLESHOOTING

​​​Corner Entry

​Mid Corner

​​​Corner Exit

​​​Does The Front
Bottom out?

​​​Reduce Front
​Rebound Damping

​​​High Speed

​​​Mid-Low Speed​

​​​Yes

​​​No

​​​Increase Front
​Toe-Out

​​​Increase Front
​Downforce

​​​Stiffen Front
Anti-Roll Bar

Soften Front
Anti-Roll Bar

​​​Reduce Front
Ride Height

​​​Increase Front
Bump Damping

​​​Reduce Front
Spring Rate

​​​Increase Front
Spring Rate

​​​Increase Front
Caster Angle

​​​Increase Front
Bump Damping

​​Reduce Front
Shocks (Overall)

​​​Reduce Front
Ride Height

​​​Increase Negative Front Camber

​​​Reduce Front
Ride Height

OVERSTEER TROUBLESHOOTING

​​​Corner Exit

​Mid Corner​

​​​Increase Rear
Toe-In

​​​High Speed

​​​Mid-Low Speed

​​​Increase Rear
Downforce

​​​Reduce Rear
Bump Damping

​​​Does The Rear
​Bottom Out?

​​​Yes

​​​No

​​​Increase Rear
​Rebound Damping

​​​Increase Rear
​Spring Rate

​​Soften Rear
​Anti-Roll Bar

​​​Reduce Rear
Ride Height
If Higher Than The Front

​​​Reduce Rear
Ride Height
If Higher Than The Front

​​​Reduce Rear
Spring Rate

​​​Soften Rear
Shocks (Overall)

​​​Increase Negative Rear ​Wheel Camber

​​​Reduce Rear
Ride Height
If Higher Than The Front

Hopefully you have found this tuning guide both informative and helpful?  Maybe you haven't?  Either way, your feedback is incredibly important, so please spend just 2 minutes commenting via the link provided here.  

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