Forza 7 Tuning Guide

Part 5 - Balance and Stiffness Tuning

This part explains build related balance and stiffness issues and how they can be fixed.

Understanding General Balance and Stiffness Issues

As you may have noticed already not every build configuration works well in Forza. Moreover a build configuration that works well on some cars doesn't work on others and vice versa. This is because Forza has a set of built-in rules which upgrades work well together depending on the type of car and certain car properties such as power and weight and which don't.

There are two type of issues that arise when using upgrades that don't work well together:

  • handling issues

  • balance and stiffness issues

Handling issues are caused by certain upgrade combinations and will result in an inherently inferior handling of the car that to my knowledge cannot be tuned out.

Balance and stiffness issues however can be tuned out so it is important to understand under which circumstances they are created and how they can be tuned out.

The following table depicts which upgrade area can cause general balance or stiffness issues. For details please refer to the related section below.

|                                                   Engine         Platform & Handling        Drivetrain       Aero & Appearance     Tires & Rims

General Balance Issues                ✓                                                                        ✓                               ✓                              ✓ 

General Stiffness Issues                                                ✓                                                                                                          ✓ 

General Balance Issues

General balance issues can be caused by engine, drivetrain, aero and tire upgrades and are created on the front of the car, on the rear of the car or on both front and rear of the car depending on the upgrades causing the issues. 

 

Balance issues are given in +/- numbers for front and rear and simply add up across engine, drivetrain and tires. 

Engine

General balance issues on the engine occur when using Fuel System, CarburetorIgnition and Displacement upgrades. These engine upgrades are considered speed upgrades that offer power increases without any weight reduction. 

Using fuel system, carburetor, ignition or displacement upgrade creates an understeer (-1) on the front of the car.

General balance issues on the engine also occur when the Flywheel doesn’t match installed engine upgrades.

 

Using a flywheel that is lower than any other installed engine upgrade except exhaust, camshaft and aspiration and cooling upgrades creates an understeer (-1) on the front of the car. 

Using a flywheel that is higher than any other installed engine upgrade except exhaust, camshaft and aspiration and cooling upgrades creates an oversteer (+1) on the front of the car.
 

Example: stock flywheel + race air filter creates an understeer (-1) on the front of the car.

Note: this applies also to stock engine parts, e.g. the stock flywheel might be a street flywheel (only sport and race flywheel upgrades are available) and a stock airfilter might be a sport airfilter (only race airfilter upgrade is available).

 

Drivetrain

 

General balance issues on the drivetrain occur when the Transmission does not match with the cars power requirements except when using Full Speed or Full Grip builds, see below.

Street transmission is required for cars with a power >= 200 hp.

Sport transmission is required for cars with a power that exceeds car stock power by 100 hp.

Race transmission is required for cars with a power that exceeds car stock power by 200 hp.

Using a transmission that is higher than the cars power requirements creates an understeer (-1) on the front and the rear of the car.

Using  a transmission that is lower than the cars power requirements creates an oversteer (+1) on the front and the rear of the car.

General balance issues on the drivetrain also occur when Clutch and Driveline don‘t match the installed transmission.

Using a clutch that is lower than the installed transmission creates an understeer (-1) on the front and the rear of the car.

Using a clutch that is higher than the installed transmission creates an oversteer (+1) on the front and the rear of the car. 

Using a driveline that is lower than the installed transmission creates an understeer (-1) on the rear of the car.

Using a driveline that is higher than the installed transmission creates an oversteer (+1) on the rear of the car.

 

Example: car with 219hp, 180 hp stock power, stock clutch + race driveline + sport transmission creates an understeer (-2) on the front of the car and an understeer (-2) and oversteer (+1) on the rear of the car. 

Note: this applies also to stock drivetrain parts, e.g. the stock clutch might be a street clutch (only sport and race clutch upgrades are available) and a stock transmission might be a sport transmission (only race transmission upgrade is available).

Aero and Appearance

General balance issues in aero and appearance occur when using the Sideskirts upgrade. The Sideskirts upgrade is considered  a speed upgrade that offers improved aerodynamics but comes with a weight increase.

Using the sideskirts upgrade creates an understeer (-1) on the front and the rear of the car. 

Tires and Rims

 

Balance issues in tires and rims occur when Tire Width don’t match with the cars power requirements except when using full speed or full grip builds, see below. 

 

Each 100hp increase from cars stock power requires one tire width upgrade on the driven wheels, i.e. one rear tire width upgrade on RWD cars, one front tire width upgrade on FWD cars and one front and rear tire width upgrade on AWD cars. 

 

Each 200hp increase from cars stock power requires one tire width upgrade on the non-driven wheels, i.e. one front tire width upgrade on RWD cars and one rear tire width upgrade on FWD cars. 

 

Using a front tire width upgrade that is higher than the cars power require creates an understeer (-1) on the front of the car.

Using a front tire width upgrade that is lower than the cars power require creates an oversteer (+1) on the front of the car.

Using a rear tire width upgrade that is higher than the cars power require  creates an understeer (-1) on the rear of the car.

Using a rear tire width upgrade that is lower than the cars power require creates an oversteer (+1) on the rear of the car.

Example: car with 296hp power, 183hp stock power, stock front tire width, 3rd rear tire width upgrade creates an oversteer (+1) on the front of the car and an understeer (-1) on the rear of the car. 

 

Full Speed and Full Grip Builds

 

Full speed builds are considered builds with a car power that exceed cars stock power by at least 100hp and that use stock tire width front and rear and sport or race chassis reinforcement. 

 

Full grip builds are considered builds that use max tire width front and rear and sport or race chassis reinforcement. 

 

For cars that don’t offer any tire width or chassis reinforcement upgrades there are no full speed or full grip builds possible by definition. 

 

Full grip or speed builds require a sport or race transmission and never cause balance issues from tires by definition. 

General Stiffness Issues

General stiffness issues can be caused by platform and handling or tires and rims and are created on the front of the car, on the rear of the car or on both front and rear of the car depending on the upgrades causing the issues. 

 

Stiffness issues are given in +/- numbers for front and rear and simply add up across drivetrain and tires. 

 

Platform and Handling 

 

Stiffness issues in platform and handling occur when the Chassis Reinforcement upgrade doesn’t match with the car type and car weight except when using full speed or grip builds, see below. 

 

Street chassis reinforcement upgrade is required for street cars with 2500lb or more weight. 

Sport chassis reinforcement upgrade is required for sports cars with 2000lb or more weight. 

Race chassis reinforcement upgrade is required for race cars and high performance cars with 1500lb or more weight. 

 

Using a Chassis Reinforcement upgrade that is too low for the car type and weight creates a softness (-1) on the front of the car.

 

Using a Chassis Reinforcement upgrade that is too high for the car type and weight creates a stiffness (+1) on the front of the car.

Example: street car with 2600hp weight and sport chassis reinforcement creates a stiffness (+1) on the front of the car. 

Tires and Rims

Stiffness issues in tires and rims occur when Rim Style or Rim Size don’t match with the car type and weight except when using full speed or full grip builds, see below. 

 

Modern race and high performance cars require lightest rims, early modern race cars and modern productions cars require second lightest rims etc. until pre-war production cars that require heaviest rims. 

 

Using a rim style which weight class is too low for the car type creates a softness (-1) on the front and the rear of the car.

Using a rim style which weight class is too high for the car type creates a stiffness (+1) on the front and the rear of the car.

 

Stiffness issues on the rims also occur when the rim size doesn’t match with the cars weight except when using full speed or grip builds, see below. 

 

Each 100lb weight increase starting with 2500lb requires one rim size upgrade front and rear.

 

Using a front rim size which is lower than the cars weight requires creates a softness (-1) on the front of the car. 

Using a front rim size which is higher than the cars weight requires creates a stiffness (+1) on the front of the car. 

Using a rear rim size which is lower than the cars weight requires creates a softness (-1) on the rear of the car. 

Using a rear rim size which is higher than the cars weight requires creates a stiffness (+1) on the rear of the car.

Example: street car with 2600hp weight with lightest rims and stock front rim size and max rear rim size creates a softness (-1) and a stiffness (+1) on the front of the car and a softness (-2) on the rear of the car essentially neutralizing stiffness issues on the front.

 

Full Speed and Full Grip Builds

 

Full speed builds are considered builds with car power that exceed cars stock power by at least 100hp and that use stock tire width front and rear and sport or race chassis reinforcement upgrade. 

 

Full Grip builds are considered builds that use max tire width front and rear and sport or race chassis reinforcement upgrade. 

 

For cars that don’t offer any tire width or chassis reinforcement upgrades there are no full speed or full grip builds possible by definition. 

 

Full grip or speed builds require lightest rims for cars with a weight lower than 2500lb or heaviest rims for cars with a weight >= 2500lb. 

 

They also require max tire width front and rear except older cars (built before 1980) with a weight >= 2500lb require max front rim size and min rear rim size. 

Understanding Track Specific Balance and Stiffness Issues

When tuning for specific tracks there are additional track specific balance and stiffness issues that need to be considered.

Track specific balance and stiffness issues occur when the build does not match with the build requirements of a track.

 

The following table depicts which upgrade area can cause track specific balance or stiffness issues. For details please refer to the related section below.

|                                              Engine         Platform & Handling        Drivetrain       Aero & Appearance     Tires & Rims

Track Balance Issues                                                                                         ✓                               ✓                          

Track Stiffness Issues                                                ✓                                                                                                           ✓ 

Track Specific Balance Issues

Track specific balance issues can be caused by drivetrain and aero and appearance upgrades and are created on the front of the car, on the rear of the car or on both front and rear of the car depending on the upgrades causing the issues. 

 

Balance issues are given in +/- numbers for front and rear and simply add up across drivetrain and aero and appearance. 

Drivetrain

 

Track specific balance issues on the drivetrain occur when the Transmission does not match with the tracks transmission requirements.

Full size tracks require race transmission, shorter tracks require sport transmission.

Using a transmission that is higher than the tracks transmission requirements creates an understeer (-1) on the front and the rear of the car.

Using  a transmission that is lower than the tracks transmission requirements creates an oversteer (+1) on the front and the rear of the car.

Aero and Appearance

Track specific balance issues in aero and appearance occur when the Front Bumper and Rear Wing upgrades don't match with the tracks aerodynamic requirements. 

Most tracks require race front bumper and race rear wing except high speed tracks like Le Mans or Daytona.

Using a front bumper that is lower than the tracks aerodynamic requirements creates an understeer (-1) on the front of the car. Using a front bumper that is higher than the tracks aerodynamic requirements creates an oversteer (+1) on the front of the car.

Using a rear wing that is lower than the tracks aerodynamic requirements creates an understeer (-1) on the front of the car. Using a rear wing that is higher than the tracks aerodynamic requirements creates an oversteer (+1) on the front of the car.

Track Specific Stiffness Issues

Track specific stiffness issues can be caused by platform and handling and tires and rims upgrades and are created on the front of the car, on the rear of the car or on both front and rear of the car depending on the upgrades causing the issues. 

 

Stiffness issues are given in +/- numbers for front and rear and simply add up across platform and handling and tires and rims. 

 

Platform and Handling

Track specific balance issues in platform and handling occur when the Chassis Reinforcement upgrade does not match with the chassis stiffness requirements of the track.

Full race tracks require race chassis reinforcement, shorter race tracks require sport chassis reinforcement.

Full road tracks require street chassis reinforcement, shorter road tracks require stock chassis reinforcement.

Using a chassis reinforcement upgrade that is higher than the tracks chassis stiffness requirements creates a stiffness (+1) on the front of the car.

Using a chassis reinforcement upgrade that is lower than the tracks chassis stiffness requirements creates a softness (-1) on the front of the car.

Tires and Rims

 

Track specific balance issues on the tires occur when Tire Compound don’t match with the tracks tire compound requirements. 

 

Race tracks require race tire compound and road tracks require street tire compound.

Using a tire compound that is lower than the tracks tire compound requirements creates a stiffness (+1) on the front and the rear of the car.

Using a tire compound that is higher than the tracks tire compound requirements creates a softness (-1) on the front and the rear of the car.

Fixing Balance and Stiffness Issues

Fixing balance and stiffness issues simply means to apply the reverse setting across the affected tuning areas , e.g. a front understeer (-1) issue should be be corrected with a front oversteer (+1), a front understeer (-2) issue should be be corrected with front oversteer (+2) etc. 

The following table depicts which tuning areas are affected when correcting balance or stiffness issues. Please refer to the related section below for detailed explanations.

|                                    Tires       Alignment         ARBs            Springs           Dampers          Brakes       Diff

                                                                                           

Balance Issues                ✓                  ✓                     ✓                     ✓                       ✓                       ✓              ✓         

Stiffness Issues                                                           ✓                     ✓                       ✓                            

Tires

Adjusting tire pressures to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. increasing front tire pressure by 0.5 psi), a front understeer - 2 is corrected with front oversteer + 2 (i.e. increasing front tire pressure by 1.0 psi) etc.

Balance Issue                 Front Tire Pressure      Rear Tire Pressure 

Front Oversteer + 1                        -0.5                                  

Front Understeer -1                       +0.5

Rear Oversteer + 1                                                                -0.5

Rear Understeer  -1                                                              +0.5

Alignment

Adjusting alignment to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. decreasing front camber, increasing front toe and decreasing caster by 0.1), a front understeer - 2 is corrected with front oversteer + 2 (i.e. decreasing front camber, increasing front and decreasing caster by 0.2) etc.

Balance  Issue                  Front Camber     Rear Camber       Front Toe       Rear Toe         Caster

Front Oversteer + 1                  +0.1                                                       -0.1                                       +0.1

Front Understeer - 1                 -0.1                                                       +0.1                                       -0.1

Rear Oversteer - 1                                                    +0.1                                             +0.1                

Rear Understeer - 1                                                  +0.1                                              -0.1                

Anti-roll Bars

Adjusting anti-roll bars to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. decreasing front ARB by 0.1), a front understeer - 2 is corrected with front oversteer + 2 (i.e. decreasing front ARB by 0-2) etc.

Balance Issue                  Front ARB           Rear ARB

Front Oversteer + 1               +0.1                    

Front Understeer - 1              -0.1                     

Rear Oversteer - 1                                              -0.1

Rear Understeer -1                                            +0.1

Adjusting anti-roll bars to correct stiffness issues means to apply the reverse stiffness setting to compensate the stiffness issue. e.g. a front stiffness + 1 issue is corrected with a front softness + 1 (i.e. increasing front ARB by 0.5), a front stiffness + 2 is corrected with front softness - 2 (i.e. increasing front ARB by 1.0) etc.

Stiffness Issue                 Front ARB           Rear ARB

Front Stiffness + 1                 +0.1                    

Front Softness - 1                   -0.1                     

Rear Stiffness - 1                                                 +0.1

Rear Softness -1                                                   -0.1

Springs

Adjusting springs to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. decreasing front springs by 0.5), a front understeer - 2 is corrected with front oversteer + 2 (i.e. decreasing front springs by 1.0) etc.

Balance Issue                  Front Springs       Rear Springs

Front Oversteer + 1                +0.5                    

Front Understeer - 1               -0.5                     

Rear Oversteer - 1                                                   -0.5

Rear Understeer -1                                                 +0.5

Adjusting springs to correct stiffness issues means to apply the reverse stiffness setting to compensate the stiffness issue. e.g. a front stiffness + 1 issue is corrected with a front softness - 1 (i.e. decreasing front springs by 0.5), a front stiffness - 2 is corrected with front softness - 2 (i.e. decreasing front springs by 1.0) etc.

Stiffness Issue                 Front Springs       Rear Springs

Front Stiffness + 1                    -0.5                                      

Front Softness - 1                    +0.5                        

Rear Stiffness - 1                                                      -0.5

Rear Softness -1                                                      +0.5

Ride Height

Adjusting ride height to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. decreasing front ride height by 0.1), a front understeer - 2 is corrected with front oversteer + 2 (i.e. decreasing front ride height by 0.2) etc.

Balance Issue                  Front Ride Height       Rear Ride Height

Front Oversteer + 1                    +0.1                    

Front Understeer - 1                   -0.1                     

Rear Oversteer - 1                                                              -0.1

Rear Understeer -1                                                            +0.1

Adjusting ride height to correct stiffness issues means to apply the reverse stiffness setting to compensate the stiffness issue. e.g. a front stiffness + 1 issue is corrected with a front softness - 1 (i.e. increasing front ride height by 0.1), a front understeer - 2 is corrected with front oversteer + 2 (i.e. increasing front ride height by 0.2) etc.

Stiffness Issue                 Front Ride Height       Rear Ride Height

Front Stiffness + 1                      +0.1                    

Front Softness - 1                       -0.1                     

Rear Stiffness - 1                                                                 +0.1

Rear Softness -1                                                                  -0.1

Dampers

Adjusting dampers to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. decreasing front rebound and increasing rear bump by 0.1), a front understeer - 2 is corrected with front oversteer + 2 (i.e. decreasing front rebound and increasing rear bump by 0.2) etc.

Balance Issue                  Front Rebound       Rear Rebound       Front Bump       Rear Bump 

Front Oversteer + 1                +0.1                                                                                          -0.1

Front Understeer - 1               -0.1                                                                                          +0.1                     

Rear Oversteer - 1                                                         +0.1                        -0.1

Rear Understeer -1                                                        -0.1                        +0.1

Adjusting dampers to correct stiffness issues means to apply the reverse stiffness setting to compensate the stiffness issue. e.g. a front stiffness + 1 issue is corrected with a front softness - 1 (i.e. decreasing front dampers by 0.1), a front stiffness - 2 is corrected with front softness - 2 (i.e. decreasing front dampers by 0.2) etc.

Stiffness Issue                 Front Rebound       Rear Rebound       Front Bump       Rear Bump 

Front Stiffness + 1                    -0.1                                                                 -0.1                                      

Front Softness - 1                    +0.1                                                                +0.1                        

Rear Stiffness - 1                                                           -0.1                                                       -0.1

Rear Softness -1                                                           +0.1                                                       +0.1

Brakes

Adjusting brakes to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. decreasing brake distribution and increasing brake pressure by 1%), a front understeer - 2 is corrected with front oversteer + 2 (i.e. decreasing brake distribution and increasing brake pressure by 2%) etc.

Balance Issue                  Brake Distribution          Brake Pressue 

Front Oversteer + 1                    +1%                                    -1%

Front Understeer - 1                   -1%                                    +1%                     

Differential

Adjusting differential to correct balance issues means to apply the reverse balance setting to compensate the balance issue. e.g. a front understeer -1 issue is corrected with a front oversteer + 1 (i.e. decreasing diff decel by 1%), a front understeer - 2 is corrected with front oversteer + 2 (i.e. decreasing diff decel by 2%) etc.

Balance Issue                   Diff Accel      Diff Decel     

Front Oversteer + 1                                        +1%

Front Understeer - 1                                       -1%                     

Rear Oversteer - 1                  -2%

Rear Understeer -1                +2%

FWD Cars

For FWD cars don't adjust the Front Diff Decel, only adjust the Front Diff Accel.

AWD Cars

For AWD cars don't adjust the Front Diff Decel and Rear Diff Accel, only adjust the Front Diff Accel and rear Diff Decel. Apply the same adjustment for Diff Accel also for Diff Distribution.