Mercedes Formula 1 driver Valtteri Bottas has described the new W12 car’s rear end as “quite snappy and unforgiving” after his first meaningful test day.
Bottas fell victim to Mercedes’ first-morning gearbox issues, getting just six laps on Friday morning before Lewis Hamilton took over for the next two sessions.
Bottas returned to the car on Saturday afternoon to net 58 laps and set the fastest time of the test so far on the softest C5 tyre.
His late run allowed him to beat Pierre Gasly by 0.124s and is the first time the reigning champion team hit the front after a stop-start test in which it has covered the least mileage of any of the teams so far.
Earlier on Saturday seven-time champion Hamilton said Mercedes was “nowhere near” being worried about its progress but Bottas has raised fears over the car’s rear-end performance.
The W12 has looked unstable at times on track, with Hamilton causing a red flag by spinning into the gravel during the Saturday morning running.
“For sure it’s windier than we’ve had normally at the race but one of the bigger issues with the car is the rear end, it’s quite snappy and unforgiving,” said Bottas.
“Topped up with the new tyres, they feel quite sensitive to the sliding so we’re trying to calm the car down a bit and that way get some more pace.”
Bottas did temper those concerns by saying “I felt good with the car and confident and at least at times pretty fast”, having completed the equivalent of a race distance on Saturday.
Though teams have largely carried over their 2020 designs to 2021, regulation changes affecting the floor area have made a difference to rear downforce levels.
Asked how much he could read into being fastest today, Bottas played down the importance of the result.
“It’s so difficult to say, I can’t be jumping around being happy to be first – it is only testing,” he said.
“As always, we are just focused on getting through our programme and maximising the learning.
“Not really looking at lap times, we have no idea what other people are doing. You never know what fuel loads people are running.
“Hopefully [by the] end of tomorrow, we will have a better idea of where we are, long runs etc, but it’s only testing.”
Bottas is set to drive the Mercedes on the morning of the final day of pre-season testing on Sunday, with Hamilton due to take over in the afternoon.