Downforce always costs drag

The permanent trade, and how teams decide where to sit on it.

Downforce always costs drag because both forces come from the same act of redirecting airflow around a shape. Any surface arranged to deflect air and push the car down is, by that same deflection, also generating a backward resistance that has to be paid for with engine power, and there is no way to keep one effect while discarding the other.

One deflection, two forces

Generating downforce means changing the direction and speed of air passing over a surface, and that requires exchanging momentum with the air: pushing some of it one way and, by simple reaction, being pushed back in return. Part of that reaction pushes the surface toward the road, which is the downforce being sought, and part of it inevitably pushes the surface backward, which is drag. A wing angled more steeply asks the air to change direction by a larger amount and gets more of both; a shallower angle gets less of each. A wing's angle is therefore a single dial controlling both quantities together.

Walking into the wind with an open umbrella shows this coupling through the arm holding it. The canopy's job is to turn the air and rain away from the person underneath, and that same turning is what drags backward on the arm. A smaller, flatter umbrella catches less rain and drags less, a larger, deeper one catches more and drags more, and closing it part way eases the pull at once, the two effects rising and falling together exactly as they do on a wing being adjusted.

Drag that has nothing to do with downforce

This pairing describes the drag that comes from generating downforce, sometimes called induced drag. A car also produces drag simply by pushing air out of the way and from the friction of air over its surfaces, and that baseline would exist on a car making no downforce at all. The two respond to different fixes. Baseline drag is reduced by smoothing and shrinking the car's overall shape, while induced drag falls only when the same downforce is produced by a more efficient combination of surfaces, or when less downforce is accepted in exchange.

Setting the trade for each track

Choosing how much downforce to run is a matter of matching the trade to the track. A circuit dominated by tight, slow corners rewards extra grip enough to justify the drag on its short straights, while a circuit with long straights and few demanding corners can lose more time on those straights than it gains in corners that were never difficult. Teams therefore change wing angles, and sometimes whole aerodynamic packages, between events. Working out roughly where to sit for an unfamiliar circuit, often before the car has turned a wheel there, is one of the most useful things a lap simulation does, weighing the time lost to drag on the straights against the time gained in the corners across a range of settings.