# ACC setup doctor: fix understeer & oversteer

> Describe your driving problem and get ranked ACC setup changes, each explained. Plus a safe beginner setup, the tyre pressure window and a parameter glossary.

Interactive tool and full version: https://pitlanecoach.com/en/setup

## In short

The setup doctor reverses the usual order: instead of downloading someone else's numbers, you describe how your car feels wrong — understeer on turn-in, oversteer on the throttle, instability under braking — and you get ranked, concrete changes, each with an explanation of what it does.

For a safe, forgiving car in ACC the directions are: tyre pressures inside the window (~26.5–27.0 psi hot), brake bias slightly forward, TC and ABS higher, more rear wing, softer anti-roll bars. Because ACC's physics has been unchanged since version 1.10.0 of 1 April 2024 — everything after that was content only — these directions no longer go stale with every patch.

## Common questions

### How do I fix understeer in ACC?

Check the front tyre pressure first (too much pressure kills the contact patch), then soften the front anti-roll bar, soften the front springs, add a little toe-out and move the brake bias slightly rearward for more rotation under trail braking.

### How do I fix oversteer on the throttle?

Lower the differential preload (the rear wheels start to differ earlier), raise the TC, soften the rear anti-roll bar, add more rear wing and increase rear rebound so the rear tyres stay loaded.

### What is the right tyre pressure in ACC?

Aim for about 26.5–27.0 psi hot on all four tyres. You start a few psi lower cold and let the pressure build over three or four laps. In the middle of the window you get the most grip and the most predictable behavior at the same time.

### Do I have to redo my setup after every ACC patch?

No. The last ACC patch with physics changes was version 1.10.0 on 1 April 2024; everything after it — up to the current 1.10.4 from December 2025 — only brought liveries, wheel presets and seasonal content. Only the occasional BoP adjustment shifts optimal pressures and ride heights slightly; the stability directions stay the same.