Mercedes has identified that a displaced guard over a switch that adjusts engine braking was to blame for Lewis Hamilton’s poor Q3 in Austin, Texas.
Hamilton could only qualify P5 for the United States Grand Prix after being nearly three tenths off the pole position time set by his team-mate Valtteri Bottas.
The now six-time World Champion said the poor performance was his fault and nothing to do with the car, but Mercedes have found evidence to the contrary.
“During the course of the lap, underneath his right hand, there’s a little rotary and that rotary adjusts the engine braking,” Mercedes strategy chief James Vowles said.
“Normally it has a guard on it, and what happened is the guard had accidentally been knocked off. As he went through the lap, every time he turned the steering wheel, he accidentally changed the engine braking and that caused him to lose performance towards the end of the lap.
“The mechanics spotted it immediately the second the car had come back in but obviously that first run was compromised as the result.”
The early Q3 malfunction proved to be more costly than usual, as track conditions slightly deteriorated ahead of the final hot laps.
Vowles added: “Come the second run you would’ve seen everyone went slower, the track in fact had slowed down slightly, small wind change, small track temperature change and Lewis wasn’t now able to compete at the front, ultimately sealing his place as fifth on the grid.”