Short answer: Start at 0° if you have little or no front aero, and around 5° if you're running a properly sized splitter. Tune from there based on how the car behaves in fast corners. If you need more rear downforce than 8° gives you, add a Gurney flap before you add more angle.
That's the quick version. Here's why, based on our own CFD and track testing.
More angle doesn't always mean more downforce
Our airfoil is a high lift-to-drag design. It started life on the Panoz Q9 GTR1 at Le Mans and runs roughly a 15:1 lift-to-drag ratio. That efficiency comes with a trade-off: high-efficiency wings stall more easily than draggy ones.
A stalled wing is one where the airflow breaks away from the underside of the wing. When that happens, downforce drops and drag climbs. The wing looks more aggressive and does less.
In open air, our airfoil keeps adding downforce past 5°. On a real car it's different. The air reaching the wing has already come over the roof and rear glass, so it doesn't arrive level, and the wing can see more angle than the number on your angle finder. When we developed our Miata Medium Downforce Kit, we kept adding angle until the wing started to stall. On that car, with the soft top, the limit was 5° with the wing alone.
The real goal is balance, not a big number
The right wing angle is the one that balances the car. Our target is aero balance within about 10% of the car's weight balance. Get that right and the car handles the same at low speed as it does at high speed. It won't suddenly change character as you cross 70 to 80 mph.
That's why wing angle depends on what's at the front of the car. A big wing at a big angle with no splitter just gives you high-speed understeer.
How to set your wing angle, step by step
1. Pick your starting point. Little or no front aero: 0°. A properly sized splitter or one of our downforce kits: 5°.
2. Measure the same way every time. Use a digital angle finder, measure from the same spot on the wing each time, and have the car on level ground at ride height. Write the number down.
3. Judge it in the fast corners. Slow corners tell you about mechanical grip. The fast stuff tells you about aero.
4. Adjust in small steps. High-speed understeer: take angle out. High-speed oversteer, or a nervous rear end in fast sweepers: add angle. Move one or two degrees at a time, and change only one thing per session.
5. Need more than 5° gives you? Add a Gurney flap first.
Gurney flap vs. more angle
Once you're near the stall limit, adding angle is a gamble. A Gurney flap, a small lip on the trailing edge, adds downforce by adding camber instead of angle, so you pick up grip without pushing the wing closer to stall. Our wings have a built-in Gurney flap relief, so it's a change that takes seconds.
If you still want more after that, you can go past 5°, but expect diminishing returns and a sharp rise in drag. The other option is more wing. On our first carbon wing test car, a 71" aluminum wing at 5° with a 3/4" Gurney flap gave the same balance as our 12"-chord Mega Carbon Wáng at just 2° with no Gurney.
How to tell if your wing is stalling
Tape short pieces of yarn to the underside of the wing and film them at speed. Yarn lying flat and pointing rearward means the air is attached. Yarn flapping around or pointing forward means the wing is stalled, and you should take angle out.
When to run less angle, or even negative
If the front end starts to feel light at speed, you don't have to chase more front downforce. On a high-mounted wing you can reduce angle, even into a negative setting, to pull rear downforce out and bring the car back into balance. We dig into this in our Drag Wing vs. High Wang test.
Quick guide by type of driving
Autocross: Speeds are low, so drag barely matters. You can run more angle.
Track days and time attack: Set angle for balance first, then add downforce front and rear together.
Tracks with long straights: Run the least angle that keeps the car balanced in the fast corners.
FAQ
What angle should a rear wing be set at?
For most cars running our wing, start at 0° with little front aero, or around 5° with a matched splitter. Then tune for balance.
Does more wing angle always mean more downforce?
No. Past the stall point, downforce drops and drag rises. On our Miata test car, the wing alone stalled at 5°.
Is a Gurney flap better than adding wing angle?
Near the stall limit, usually yes. It adds downforce without pushing the wing closer to stall.
How do I know if my wing is stalling?
Do a yarn tuft test on the underside of the wing. Flapping or forward-pointing tufts mean the flow has separated.
Should I add a wing without a splitter?
You can, but run low angle, around 0°, so you don't overload the rear and create high-speed understeer.
Want to see the numbers behind all this? Check out our CFD testing page, or browse our balanced downforce kits.