What brake bias actually does
Brake bias, also called brake balance, determines how the braking system distributes its action between the front and rear axles. It is not a control for braking harder: it changes the balance with which you brake.
Think about the work you request through a single pedal. Moving the bias forwards assigns a larger proportion of braking to the front axle. Moving it rearwards assigns a larger proportion to the rear. The precise response depends on how the simulator and car implement that adjustment.
It does not change the car’s weight distribution or physically move anything towards the nose. Nor does it determine wheel locking on its own. Available grip, pedal demand and steering input all matter.
How to read the percentage correctly
Many simulators display the front percentage. With that convention, a higher number moves the bias forwards; a lower number moves it rearwards. Check the car’s menu or manual before testing. Some cars show positions, offsets from a base setting or other scales.
For example, if the menu specifies front bias, changing from 60% to 59% reduces the front proportion by one percentage point. This explains the display; it is neither a recommended setting nor a prescribed test step. The appropriate value and the effect of each step depend on the car.
Do not read the number as an exact measurement of how much each tyre is braking on track. The control may represent hydraulic distribution or a control reference. Calipers, discs, ABS and other systems affect the force that ultimately reaches the road.
If the value represents front percentage: increasing it moves bias forwards; decreasing it moves bias rearwards. Check the convention before adjusting.
Where to find brake bias in AC, ACC and iRacing
Assetto Corsa. Brake bias appears in the setup menu as the front percentage, on cars that allow it. Many cars can also change it from the cockpit if you assign the brake balance controls. Each car brings its own default and its own range.
Assetto Corsa Competizione. It sits in the Mechanical Grip tab of the setup, also shown as front percentage. It can be adjusted while driving with the brake bias controls.
iRacing. It is in the garage, usually as brake pressure bias, and the section depends on the car. Many cars also allow changes from the in-car adjustment menu.
The same number does not mean the same thing in two simulators, or even in two cars of the same game. 58% in one car can behave very differently from 58% in another. Compare within the same car, never across them.
Why the two axles do not brake equally
During deceleration, vertical load increases at the front axle and decreases at the rear. Splitting braking equally is therefore not enough to make both axles work well. The appropriate distribution depends on the car and the situation.
Load transfer does not require obvious nose dive. Stiff suspension can limit body movement while load transfer still takes place. Confusing those effects makes brake behaviour harder to understand.
A tyre must also share its capacity between braking and turning. A brake application that works with straight steering may stop working when you turn with the same pedal pressure. Test bias throughout corner entry, rather than judging only the first hit of the pedal.
What happens with too much front bias
Without ABS, asking the front axle to do too much can make the front wheels lock before you use the rear axle’s braking capacity effectively. The car loses its ability to change direction, and you may need a longer braking distance.
With ABS, the system may contain that locking. This does not make every bias setting effective: excessive intervention can suggest too much demand on that axle. Do not diagnose bias from a dashboard light alone. Compare the car’s behaviour and the distance you need to slow down.
The useful evidence is a problem that repeats under comparable conditions. If front locking is repeatable at similar arrival speeds and the rear remains stable, a small rearward adjustment is worth testing. If you simply braked late or held too much pedal while turning, address that entry first.
What happens with too much rear bias
An unloaded rear axle has less margin to handle braking. Ask too much of it and the rear can lose grip while you are still slowing down. Without ABS, rear locking can be abrupt. Combining braking and steering usually leaves less margin.
Moving some bias rearwards can help certain cars rotate during entry. Moving it further back is not an automatic progression towards a faster setup. A steering correction, an uncertain braking phase or a compromised exit can erase any benefit.
If instability repeats under braking, test a small forward adjustment and compare. First rule out an early downshift, damage, rear tyres outside their working conditions or kerb contact. Brake bias cannot, by itself, fix a downshift that upsets the driven axle.
Three situations to separate
The car will not turn while I am still braking. You may be using the front tyres’ grip with the pedal, carrying too much speed or experiencing a bias-related problem. Repeat with a more controlled entry. If you confirm front locking and a stable rear axle, then test a small rearward shift.
The rear moves under braking or as I turn. Check whether it begins with the brake, a downshift or a bump. If excessive rear braking is involved, test more front bias. If it follows a downshift, work on the timing and execution of that shift first.
The car understeers after I release the brake. Stop moving brake bias to solve a steady cornering problem. It may be a consequence of your entry, but service brake bias has no direct action when those brakes are no longer applied. Review speed, line, tyres and chassis balance.
The Assetto Corsa understeer and oversteer guide helps separate those phases. A symptom needs a specific moment: “the car will not turn” is still too broad.
Brake bias and trail braking
Trail braking means continuing part of your braking into corner entry, reducing pressure as the demand for turning increases. It does not mean keeping heavy braking all the way to every apex.
Bias influences the distribution of that effort as the car begins to rotate. Too much front bias can hinder turning if you saturate the front tyres; too much rear bias can make the rear nervous. Speed, line and the way you release the pedal remain decisive.
If holding the entry requires constant correction, do not call the test successful just because the car seems to rotate more. Look for a response you can repeat. While learning, predictable bias is more useful than a setting that works only when every input is perfect.
What changes with ABS and other systems
ABS modulates braking to limit locking. It does not create grip or allow unlimited combinations of brake and steering. Bias is still worth evaluating on an ABS-equipped car, although the signals differ from those of a car without it.
Do not assume a higher ABS number always means more intervention: the scale and operation depend on the car and simulator. Also distinguish a game’s driving assist from the vehicle’s own system. Keep its configuration unchanged during a bias test so you can interpret the result.
With regenerative braking, adjustable engine braking or brake migration systems, effective balance can change through the braking phase. Read the car-specific documentation. The displayed percentage does not necessarily describe all rear-axle deceleration.
Engine braking is not the same as hydraulic brake bias. If a downshift unsettles the car, moving bias forwards may change the sensation without proving that you have fixed the cause.
How to adjust it in a practice session
Save a reference. Start with a known setup, no damage and settled tyres. Check pedal calibration, assists and what the control means. If the menu offers brake pressure as well as bias, leave pressure unchanged: they are different adjustments.
Choose a repeatable braking zone. Use a visible marker, comparable arrival speed and a clean line. Observe straight braking first, then entry with steering. Do not explore the limit of brake bias during a race lap in traffic.
Describe the problem. Record which axle loses grip, when it happens and whether it coincides with the pedal, steering, a gear change or a bump. If you cannot separate them, examine a replay or telemetry before choosing an adjustment direction.
Change only the bias. Make a small adjustment within that car’s scale. There is no universal number of clicks: the actual menu step matters. Repeat several comparable passes without changing technique, ABS or tyres at the same time.
Check the whole entry. Look at stability, trajectory, where you can release the brake and your position for accelerating. The best test is not necessarily the one with the highest minimum speed or latest braking point.
Keep or revert. If the benefit repeats without creating a problem in other braking zones, save the setting. If you manage only one good pass or introduce instability, return to the reference. The setup guide and tyre pressure guide help check your starting point before further adjustments.
If you drive the original Assetto Corsa, Track Engineer reads your stints and setup to propose changes, brake bias included, and checks them against the following runs. A proposal still needs confirming on track.
Should you change it during a race?
It can make sense if the car allows it and its behaviour changes with fuel, wear or track conditions. But there is no universal rule such as “less fuel means more rear bias”. Fuel tank location, tyres and the car’s systems matter.
In the wet, do not copy an adjustment direction out of habit either. Reduced grip narrows the margin and may change which axle limits braking. Start from a reference tested for those conditions, then observe before moving the balance.
First find a stable setting that lets you complete the run. Once your braking is repeatable, practise specific changes and check the dashboard value. A wheel control is useful when you understand the action it performs. Turning it routinely adds a task without necessarily solving a problem.
Mistakes that make testing confusing
Copying another car’s percentage, moving the bias after every missed braking point or changing ABS at the same time makes it hard to know what you learned. Comparing cold tyres with warm ones, or different arrival speeds, causes the same problem.
Do not chase dramatic rotation or deliberately locking both axles as a driving target. Aim to use the braking available, control the trajectory and reach the exit well positioned. If the car does that repeatedly, leave the bias alone and work on the rest of your lap.
Frequently asked questions
Does a higher percentage mean more front braking?
Only when the menu shows front percentage. Confirm the car’s convention: it may display a position or an offset from a base value.
Does rearward bias make the car brake harder?
It may use the rear axle more effectively if it was underused. It can also destabilise it. It does not create grip or guarantee a shorter stopping distance.
What is the best starting brake bias?
Use a known reference for that car and those conditions. Before copying a number, understand what it represents and which symptom you want to address.
Should I always move bias back if the fronts lock?
No. First rule out excessive pedal demand, too much entry speed and tyres outside their working conditions. With repeatable front locking and a stable rear, a small rearward shift is a reasonable test.
Is bias worth adjusting with ABS?
ABS does not remove the influence of bias. You can evaluate it, but keep ABS unchanged and do not judge only by the absence of visible locking.
Will brake bias fix oversteer under acceleration?
It does not directly control power delivery after you release the brake. Review the entry that left the car poorly positioned, throttle application and traction.
Sources and scope
The principles were checked against iRacing technical documentation. These references describe specific vehicles: their values and scales are not universal recommendations for other cars or simulators. No lap-time gains were measured and no optimum percentage is prescribed.
iRacing SRX User Manual — Brake Balance Bar · Skip Barber Formula 2000 — Set-up and Tuning