Valtteri Bottas has revealed a rear-wing stall caused his huge 350km/h spin at Mexico City’s Turn 1 during Friday's second practice session.
Bottas had just hit the brakes, which closed his Williams car's DRS flap, but the rear wing failed to provide the expected level of downforce, causing him to spin around and clatter against the concrete wall – travelling backwards for about 100 metres.
Amazingly, only the nose and front wing of Bottas' car was damaged, and he was able to rejoin the session after repairs.
"It was really sudden, we found it was a rear-wing stall under braking," Bottas told Motorsport.com.
"I was pretty surprised, obviously. I didn't know if the brakes had failed or what happened. Even though the DRS was closed, the wing was behaving like it was open.
"We changed the rear wing level and then it was fine. We've had it a couple of times, but with this high speed and heavy braking it's not good. It happened so quick, I guess I was lucky not to hit anything."
Enjoying the high speeds
Bottas is adamant that the track layout in Mexico City will produce good racing, especially on to the start/finish straight and the long drag exiting Turn 3.
But he admitted that the grip level in practice was extremely low and exaggerated by the thinner atmosphere at high altitude.
When asked if it was the most tricky track conditions he had ever experienced in F1, he replied: "Definitely! By far.
"Obviously we don't have that much downforce this high, on top of that the surface is massively slippery and it's difficult to get they tyres to bite. It was improving a bit. Let's hope it stays dry.
"I like the high speeds here, but the only thing we are missing is grip. The Esses seem nice but they will be even better with some more grip."