Spin Cycle: Tesla Engineer Says Cybercab Did Donuts on the Test Track

AUSTIN, Texas - Tesla's Cybercab is built to carry two passengers calmly across town with no steering wheel and no pedals. Before it got anywhere near a fare, one of the engineers behind it says, it was spinning donuts on a test track.

Yun-Ta Tsai, whose X profile lists him as a senior staff engineer at Tesla, shared the detail on Sunday evening. "One of the first things we did for Cybercab drivetrain and brake validation was doing donuts on the track," he wrote. "It can drive like a sports car. After all, Cybercab is very nimble."

The remark came in reply to a fan, Spencer, who posts as @scotsrule08 and had asked half in jest whether a "Cybercab Plaid trim" was coming, a nod to the name Tesla gives its fastest Model S and Model X. Tsai had opened the thread with a post about the Roadster, recalling how performance car experts once dismissed an electric sports car over battery weight and charging time, limits he said better engineering had overcome.

Donuts are more than a party trick for a test team. Holding a car in a tight, sustained spin puts heavy, uneven loads on the motor, the driveline and the brakes all at once, which is why the exercise makes sense early in validation, when engineers want to find weak points fast.

The brakes matter more than usual on this car. The Cybercab is Tesla's first brake-by-wire car, with an electric actuator at each caliper and no hydraulic lines or brake fluid, so proving that hardware under hard use is central to the case that a car with no pedals can be trusted with paying riders. Tesla has also put the cab through its crash lab.

Tsai did not say when the track sessions took place or where, and Tesla has not released footage of them. One follower replied that he wished there were a video of the Cybercab doing autonomous donuts.

What the public sees today is a much gentler machine. In Austin, community trackers logged a record 1,072 Cybercab sightings on Friday, most of them with nobody in the driver's seat, as the cabs move riders at city speeds. Tsai's point is that the calm on the street was earned on the track, and that the same small car has a good deal more in it than its passengers will ever ask for.