Mercedes have admitted that their new package is proving difficult to get working, after struggling for pace and balance on the opening day of the Bahrain test.
Having raised eyebrows on Thursday morning as the team rolled out a heavily revised W13, with streamlined sidepods, the altered car proved a handful for both Lewis Hamilton and George Russell as they bedded in the upgrades.
With Hamilton running aero rakes in the morning to gather data, Russell worked through the afternoon to attempt to improve the balance and driveability of the car, with both drivers appearing to struggle on occasion to keep the car in check.
The team's best time of the day came courtesy of Russell, on the C3 Medium tyre, ending up two seconds away from the pace set by AlphaTauri's Pierre Gasly on the C5 soft tyre, while Hamilton's best was a further four-tenths adrift.
Viewed by others:
Mercedes with "quite a lot of work still to do"
"Compared to Barcelona, it's been harder to get the car well-balanced around the lap here," said Mercedes' Trackside Engineering Director Andrew Shovlin.
"We do seem
to have made a bit of progress through the day but it's always
difficult to judge accurately here as the falling temperature tends to
flatter everything you do later in the day.
"We've got quite
a lot of work still to do regarding validation of the update kit and
will continue the data collection programme over the next few days so
it's a bit early to say whether everything is working as expected.
"There is certainly more to find in getting the balance right between slow and high-speed corners, and there's also a bit too much tyre overheating.
"So, plenty to keep us busy for the next two days but we are on a steep learning curve with the new car and tyres – we'll analyse what we have from today and hopefully make a step forward for tomorrow."