Roadster Track Mode explained: a robot-powered wing and fans that pull 2 g
Tesla says the new Roadster's Track Mode gives 'approaching F1' downforce. Here's how the moving wings, Optimus actuators and suction fans work, in plain words.
Track Mode is the Roadster getting ready to grip. The car drops lower, wings rise and swing out, and fans under the floor suck it down onto the road. Tesla says the result is "the best passive downforce package of any road car (approaching F1 levels!)", and the wings are moved by the same kind of actuators Tesla built for its Optimus robot (Drive Tesla, Electrek).
Tesla's Roadster film. Tap to play on YouTube.
What is downforce, and why does it matter?
A car can only turn, brake or speed up as hard as its tires can grip the road. Push a tire down harder and it grips harder. Downforce is air pushing the car down onto the road, so the tires can grip more without the car getting heavier.
Race cars get downforce from wings, which work like an airplane wing turned upside down. An airplane wing lifts the plane up; flip it over and it pushes the car down. The catch: a wing only works when the car is moving fast. At a crawl it does almost nothing.
The moving wings
The Roadster's rear wing changes its angle by itself as the car goes around a track (Tesla North, Electrek). Steep for grip in a corner, flatter for speed on a straight. Tesla's engineer Lars Moravy says the rear wing can make up to 2 g of downforce above 200 mph, meaning it presses down with about twice the car's weight at that speed (Tesla North).
It isn't the only moving part. Moravy says the front wings rotate up to 80 degrees, side panels pop out along the doors, and a vent above the hood opens (Tesla North).
The motors that move them are actuators made for Tesla's Optimus humanoid robot (Tesla North, Paultan). An actuator is simply the part that makes something move, like a muscle in your arm. Moravy says they're the robot's leg actuators with an added brake, so a wing holds its position under load, and that "nobody in the world is better at making the actuators than us" (Tesla North).
In Track Mode the car sits lower and the wings rise. In Road Mode, Paultan reports, the wing folds away for everyday driving (Paultan).
The fans: downforce without speed
This is the clever part, and the part that's easiest to picture with a hovercraft in mind. A hovercraft blows air down under itself, so it floats on a cushion of air. The Roadster runs that idea in reverse. Its fans suck the air out from under the car. Flexible skirts along the bottom edges seal the gap, the way the rim of a suction cup seals against glass. Now there's less air pushing up from underneath than there is pushing down from above, so the outside air presses the whole car against the surface (Electrek, Drive Tesla).
That surface doesn't have to be the road. It works the same against a wall or a ceiling, which is why the car could climb a curved ramp until it was nearly upside down without falling off.
Moravy says there are four fans, each about 20 kW (borrowed from the motor family Tesla uses in its heat-pump compressors), and four separate skirts. He calls the whole thing the "sucker system" (Tesla North).
The fans "can pull up to two g's" (Drive Tesla). Drive Tesla credits that line to Musk; Euronews credits it to Moravy (Euronews). Either way, it means pressing the car down with about twice its own weight. Tesla says that is enough to hold the car upside down, even when it's standing still (Electrek). Unlike a wing, the fans work at any speed, even parked. They run on the battery and use none of the thruster gas (InsideEVs).
The fans have two settings. At low speed they pull the car down for grip. At high speed, passages at the front and back open up to move more air under the car (Paultan, Drive Tesla).
