The aero tab in ACC has five settings: rear wing, splitter on some cars, front and rear ride height, and brake ducts. That is it. People make it sound harder than it is.
Every one of them is the same trade. Grip in fast corners against speed on the straight. Your job is to find how little downforce you can live with, then balance front against rear.
This page is part of the ACC setup guide, which covers every other tab.
What each aero setting does
| Setting | Raise it | Lower it |
|---|---|---|
| Rear wing | More rear downforce and more drag. Stable in fast corners, more high speed understeer, slower on the straight | Less drag and more top speed. The rear is lighter in fast corners |
| Splitter (some cars) | More front downforce. Sharper front in fast corners, a looser rear | Less front downforce. Safer, more high speed understeer |
| Front ride height | Less front downforce, more understeer. Kinder over kerbs and bumps | More front downforce and more rake. Risk of bottoming |
| Rear ride height | More rake. Aero balance moves forward, the car rotates more in fast corners | Less rake. More stable rear, more high speed understeer |
| Brake ducts | More cooling, slightly more drag | Hotter brakes and tyres, slightly less drag |
One thing first. Aero works with speed. In a hairpin a GT3 car makes very little downforce, so nothing on this tab will fix a slow corner. For that you need the bars and the diff, and I cover those in how to fix understeer and oversteer in ACC.
Rear wing
The wing is the first thing to set, because it decides the character of the car at that track.
More wing pushes the rear into the road. The car is planted in fast corners and under braking from high speed. You pay on the straight, and if you go too far the rear has so much more grip than the front that the car pushes in fast corners.
Less wing gives top speed. The rear moves around more and the car needs a calmer hand.
The range is different on every car. Do not copy a wing number from a Porsche to a BMW. Think in steps from the preset instead.
Ride height and rake
Rake is the rear ride height minus the front ride height. A GT3 car makes a lot of its downforce under the floor, and rake controls how hard the floor and the splitter work.
- Lower the front: more front downforce. The nose bites in fast corners.
- Raise the rear: more rake. Same effect on the balance, and the car rotates more.
- Lower the rear: less rake. The rear settles and the car is calmer.
The limit is the ground. Run the front too low and the car hits the track over bumps and kerbs, and under heavy braking when the nose dives. When that happens the grip goes away in an instant. If the car snaps for no reason at the same bump every lap, raise the front one step.
Ride height also changes the mechanical side. A lower car has a lower centre of gravity. So change it in small steps, and move front and rear together if you only want the car lower without touching the balance.
Splitter
Only some cars in ACC let you adjust the splitter. Where you can, it is the front version of the wing: more splitter is more front downforce.
Use it to balance the wing. If you added two clicks of wing for a fast track and the car now pushes, a step of splitter brings the front back without touching the ride height.
Brake ducts
Ducts are on the aero tab because open ducts cost a little drag. Mostly they are a temperature tool.
A higher number means more cooling. Aim for front brakes around 600 to 650 C and rears around 450 C. Brake heat also goes into the wheel and the tyre, so the ducts move your tyre pressures too. If your pressures come in low on a cold day, closing the ducts a step helps. The full method is in the ACC tyre pressure guide.
Where to start for each track
| Track type | Examples | Where I would start |
|---|---|---|
| Low downforce | Monza, Paul Ricard | Wing near the bottom of the range. Use rake to keep the front alive in the few fast corners |
| Medium downforce | Spa, Silverstone, Nurburgring, Barcelona | Wing in the middle. This is where most of the calendar sits |
| High downforce | Zolder, Hungaroring, Brands Hatch, Zandvoort | Wing in the upper half. Straights are short, so the drag costs little |
The order I would work in
Start from the aggressive preset. It is a sensible aero base for most tracks.
Then pick the wing. Drive five laps and look at two things: your speed at the end of the longest straight, and how the rear feels in the fastest corner. If the rear is solid and you are slow on the straight, take a click off. Repeat until the fast corner starts to feel nervous, then go back one.
Now balance the front with ride height and rake. Last, set the ducts from the brake temperatures.
Do the final check on race fuel. A full tank makes the car sit lower. A car that was fine in qualifying trim can touch the ground with 100 litres on board.
Fixing fast corner problems
| Problem in fast corners | First change | Second change |
|---|---|---|
| Understeer | One click less rear wing | Raise the rear ride height one step |
| Oversteer | One click more rear wing | Lower the rear ride height one step |
| Car bottoms out or snaps over bumps | Raise the front ride height one step | Raise the rear to keep the same rake |
| Slow on the straight, fine in corners | One click less rear wing | Add a little rake to get the front back |
| Front brakes over 650 C | Open the front ducts one step | Move the brake bias rearward a little |
If you are not sure whether the problem is aero or mechanical, compare a fast corner with a slow one. Wrong in both: mechanical. Wrong only when fast: aero. You can also see it in the data. The ACC MoTeC guide shows how to read ride heights and find where the car bottoms.
Qualifying, race and rain
For qualifying you can run a click less wing if the car stays driveable. It only has to last a lap or two.
For the race, think about traffic and tyres. A car with a little more wing is easier on the rear tyres over a stint. On the other side, a car that is slow on the straight cannot pass and cannot defend. At Monza I would give up some corner speed before I give up top speed.
In the rain, add wing and raise the car. Grip matters more than drag, and standing water under a low floor is a problem. More in the ACC wet weather guide.
FAQ
What does the rear wing do in ACC?
More rear wing adds rear downforce and drag. The car is more stable in fast corners and slower on the straight. Less wing does the opposite.
What is rake in ACC?
Rake is the difference between the rear and front ride height. More rake, with the rear higher than the front, moves the aero balance forward and helps the car turn in fast corners.
How do I fix high speed understeer in ACC?
Take one click off the rear wing or raise the rear ride height one step. If your car has an adjustable splitter, add a step there.
How do I fix high speed oversteer in ACC?
Add one click of rear wing or lower the rear ride height one step. Check that the front is not bottoming, because that can look like oversteer too.
How low should the ride height be in ACC?
As low as the car can run without hitting the ground on full fuel. If the car snaps over the same bump every lap, it is too low.
Do brake ducts affect top speed in ACC?
A little. Open ducts add a small amount of drag. Set them for brake temperature first, around 600 to 650 C at the front, and only then think about drag.
Is more downforce always faster?
No. Downforce costs drag. At tracks with long straights, less wing is usually faster over a lap and makes you much harder to pass.