How Does a Fan Car Hold Itself Down?

The Chaparral 2J raced at Watkins Glen on 12 July 1970 with two fans driven by a snowmobile engine, pulling air from under a car sealed to the track by sliding skirts. It is the first fan car to race, and nothing earlier turned up: a Chevrolet research vehicle tested the idea in 1968 and 1969 but never entered a race.

The 2J ran four events that season and was banned by the SCCA at the end of it. That ban is real, documented, and belongs to the Chaparral. It is not the ban most people are thinking of.

Then the idea went quiet for forty years. Between the Brabham’s single race in 1978 and Gordon Murray’s T.50 in 2020 there is almost nothing, which is itself worth noticing. Suction downforce was not suppressed by physics. It was suppressed by rulebooks, and it came back the moment somebody built a car that did not have to obey one.

Brabham brought the BT46B to the 1978 Swedish Grand Prix with a fan at the back. Niki Lauda won by half a minute. The car never raced again, and the story everyone tells is that it was banned immediately afterwards.

It was not. The stewards judged it legal, the result stood, and the governing body told Brabham’s designer Gordon Murray it could be run for the remainder of the season. Brabham withdrew it anyway, at Bernie Ecclestone’s request, under pressure from rival constructors. The regulations were reworded for the following year.

Brabham’s defence was that the fan’s primary job was cooling the engine, and that its aerodynamic effect was incidental. Whether anyone believed that is a separate question from whether it was ruled against, and it was not. The car even ran once more in fan form, in a timed trial at Donington in June 1979.

The distinction matters beyond trivia. A technology withdrawn under commercial pressure while legal has a different history from one outlawed on safety or fairness grounds, and only one of those things happened here.

Across six comparisons where a fan car and a conventional rival ran the same course, the fan car finished between 1.6 and 6.1 per cent ahead. Lauda won at Anderstorp by 34 seconds. The McMurtry Spéirling took the outright Goodwood hillclimb record in 2022 at 39.08 seconds, beating a time that had stood for 23 years.

Those margins are genuine, but they compare a car against a field, not a mechanism against itself. The Brabham was a good car with a good driver. The McMurtry is a purpose-built electric single-seater weighing under a tonne. How much of the gap is the fan is not something any of these results can tell you.

The measurement that would settle it is simple to describe and nobody has published it: the same car, on the same course, on the same day, with the fans running and then switched off. Fifty-six years, four manufacturers, and not one such figure exists in anything we could read.

Every fan car here claims a downforce-to-weight ratio above 1.0, which is the arithmetic condition for holding itself against gravity. Claiming it and doing it are different things.

McMurtry is the only one that has shown it. In April 2025 it ran a Spéirling on a rotating rig, inverted, from a standstill, for about five seconds and roughly a foot of travel, with what it described as independent adjudicators whom it did not name.

Tesla’s Roadster reached a 170 degree pitch on a curved ramp in October 2026, which is close to inverted and is not inverted. The Chaparral never attempted it; the idea that it could was inferred later by writers working from an estimate. Brabham never claimed it at all.

There is also a pattern in McMurtry’s own numbers worth noting. Its claimed downforce has stayed at 2,000 kg while the car has gained weight through development, so the ratio has fallen from 2.0 on the 2022 Goodwood car to 1.48 on the production version. The margin above the ceiling threshold is shrinking as the car becomes a real product.

The Roadster tops this chart at 2.76, and that figure deserves the least confidence of any on it. It divides a 4,700 kg reading from a screen at the reveal by a target weight of just under 1,700 kg that an executive gave in an interview. Neither number is a published specification.

Tesla also stated a different figure on stage: suction of up to 2 g, which is a ratio of 2.0. Those two numbers describe the same car and do not agree, and Tesla has not reconciled them. We have used both, kept them apart, and labelled which is which.

What the Roadster does bring that the racing cars did not is a road car with four fans and deployable skirts described in a 2025 patent, aimed at customers rather than a rulebook nobody will let it race under. Whether the production car carries any of it is still unannounced.