Ground Effect in F1 and How the Floor Pulls the Car to the Track

We bolted a flat aluminum undertray to our endurance car in 2016. Somebody on a forum had promised free lap time. We recorded no gain worth the trouble. Two events later a builder of sports racers looked along the side of the car, found the gaps where air was escaping, and told us we had installed a table. That night we riveted rubber strips down both edges in the paddock.

Next morning the car turned in differently. Nothing dramatic. The front stopped washing out in the quick left at the end of the back straight, and my times dropped about four tenths with nothing else changed.

Lotus found it first and the rules caught up

Colin Chapman’s team got there in 1977. The sidepods of that car were shaped underneath like upside down wings, and skirts along each side did the job our rubber strips did, on a budget with more zeros.

Cornering speeds went up fast enough that the governing body acted twice. Sliding skirts were prohibited from 1981. From 1983 the underbody between the wheels was required to be flat.

Forty years followed with downforce coming mostly from wings, which is the expensive way to buy it. A wing costs drag. It also leaves turbulence behind that makes life miserable for whoever is following.

What the 2022 rules brought back

Four eras of the F1 floor

Era	Underbody	What came of it
1977 to 1980	Venturi sidepods sealed by sliding skirts	Cornering speeds the rule book could not live with
1981 to 1982	Tunnels, skirts prohibited	Teams chasing the same seal by other means
1983 to 2021	Flat underbody required	Downforce bought from wings, and paid for in dirty air
2022 to 2025	Sealed tunnels return	Close racing on paper, porpoising in practice
2026	Flat central floor into a larger diffuser doing less work than the tunnels, 150 mm narrower	Downforce down about 30 percent, drag down 55
Compiled from the FIA rule texts, plus the explanatory material Formula 1 and Motorsport published around the 2022 and 2026 changes.

Compiled from the FIA rule texts, plus the explanatory material Formula 1 and Motorsport published around the 2022 and 2026 changes.

The cars introduced in 2022 carried two sealed tunnels running back along the underbody, and the load they made arrived without the wake problem.

On paper this was the fix for close racing. It also produced something nobody had budgeted for. Cars bounced down the straights, several impacts a second, from the opening weekends onward.

The mechanism is documented. Aerodynamic load builds, the car is drawn toward the surface, the flow beneath it separates, load is lost, the suspension returns the car to ride height and the sequence repeats. The phenomenon acquired a name within weeks. Intervention by the governing body followed during that same season.

Anyone who has run a stiff car over a bad crest knows a smaller version of the feeling. I did it to myself on borrowed springs one summer. The resemblance was close enough that I recognized the motion on television before the commentators named it.

The 2026 reset

What changed for 2026

2026 change	Number
Downforce against the previous generation	Down about 30 percent
Drag	Down 55 percent
Floor width	150 mm narrower
Wheelbase	200 mm shorter, now 3400
Width across the car	100 mm slimmer, now 1900
Minimum weight	768 kilograms, counted as 722 for the car and 46 for tires
Wing modes	Active front and rear wings, one setting for corners and one for straights
Overtaking aid	DRS replaced by extra electrical energy for the chasing car
Sources: Formula 1 and FIA materials on the 2026 regulations.

Sources: Formula 1 and FIA materials on the 2026 regulations.

The tunnels were removed for 2026. What sits under the car now is a flat central floor running back into a larger diffuser that still does less of the work than the tunnels did, and the floor lost 150 millimeters of width on top of that.

Total downforce came down by around 30 percent against the previous generation. Drag fell by 55. Both numbers are the ones Formula 1 published with the rules.

The cars themselves are smaller and lighter. DRS has been withdrawn and its functions distributed between two systems. Movable front and rear wings are permitted to switch between a cornering configuration and a low drag configuration, available to all competitors rather than to a car running within one second of another. The overtaking provision now takes the form of additional electrical energy, granted to the pursuing car and withheld from the leader.

Why trade away the cheap downforce

Because the cost was charged elsewhere. A floor operating at its optimum height, a couple of centimeters off the ground, requires stiff springs and tolerates curbs poorly. Circuits with uneven surfaces become a liability, and development expenditure is directed toward running lower than the competition without provoking a stall.

Four seasons of that loading were absorbed by the drivers. The 2026 answer transfers a greater share of the grip to wings under the driver’s control, and a smaller share to a surface liable to stall without warning.

Where the theory meets a student

Aero grip is the hardest thing I have ever had to explain from the right seat. It only shows up once you are going fast enough to have earned it, which is backwards from the way anybody learns to drive. Slow through a quick corner and the car feels like any other car. Quick through it and the thing is glued down. In between you have to keep your foot in while your gut argues with you.

I have ridden with people who lift in that exact spot, lap after lap, all day long. Nothing is wrong with their instincts. Every road car they have owned taught them to back off right there, and this one wants the opposite. Now hand a professional the same moment at three times the speed, with a floor that might stall under him.

What those rubber strips were worth

Our undertray never made real downforce. It made a small pressure difference, and most of that four tenths came from the front end finally getting a break in one corner.