Suspension upright to blame for loose wheel
Ferrari have explained that a suspension upright was to blame for Felipe Massa's loose wheel, which flew off his F138 during testing on Saturday.
The Brazilian was heading toward turn 10 in the closing stages of the penultimate day of pre-season testing when his front-left tyre flew free of the Ferrari.
The reason behind the failure left engineers at Ferrari confused, but the team later explained it was a suspension issue.
"A problem with the left front upright meant that Felipe had to stop the car on track, thus bringing a positive day to a slightly early end," they explained.
Further investigation will be done before Fernando Alonso gets behind the wheel on Sunday for the final days testing.
Video of the tyre failure: