Forza Motorsport 4 Tuning Guide and Car Upgrades

By   /   5 years ago


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. If you already had your bump

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