Mercedes say that are exploring a range of set-up solutions as they look to stop their car from bouncing violently at the Bahrain International Circuit.
Lewis Hamilton cut a disappointed figure as he spoke to the media following a difficult day of running for his team in the heat and wind.
The seven-time World Champion accepted that most teams are in a "similar boat" but conceded that he believes Mercedes are lagging behind Ferrari and Red Bull.
Despite the problems, the Silver Arrows have racked up impressive mileage throughout the test and will spend some time on Saturday looking to cure the bouncing ahead of next weekend's 2022 Bahrain Grand Prix.
"[It was] a packed day with a mix of work on low and high fuel as we continue to learn about the car and tyres," explained Mercedes' Trackside Engineering Director, Andrew Shovlin.
"We're exploring a range of set-up options to try and improve the bouncing. We have some directions that are able to improve this, but finding the right balance between the bouncing and performance is clearly the challenge."
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Mercedes drivers to swap fuel loads on Saturday
Hamilton will swap places with George Russell on Saturday, with the 37-year-old set to get behind the wheel during the morning session before his younger teammate takes over in the afternoon.
The team's Friday running handed Hamilton the chance to put the car on track with a lower, lighter fuel load, resulting in him clocking the fourth-fastest time of the day on the Soft C5 tyre.
On Saturday, it will be Russell who is handed a more nimble, quicker Mercedes, as the team look to replicate their final day of testing in Barcelona from where they left with the fastest time of all.
Shovlin continued: "We've got a similar programme planned for tomorrow, but Lewis will do the higher fuel work and George the low fuel.
"We still have lots of work ahead of us but the car has been running reliably, which has helped us get good mileage in and run our programme."
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