SEPANG, Malaysia -- After struggling for performance during Friday practice, Mercedes opted to run different aerodynamic packages on its two cars during qualifying at the Malaysian Grand Prix.
The team brought a significant aero upgrade to the front of its car for the Malaysian Grand Prix, only for both drivers to complain of a lack of grip during Friday practice. On Saturday morning Hamilton reverted to older parts while Bottas stuck with the upgrade in an attempt to offer a comparison and gain a better understanding of the problems ahead of qualifying.
With Hamilton setting a slower time in FP3 and no obvious difference in the data, Mercedes opted to stick with the split aero packages for qualifying to avoid an overhaul of each car's setup.
"We obviously made a back-to-back test between the old aero package and the new one and there wasn't really a clear outcome," team boss Toto Wolff said. "Both packages had different underlying setups, so we felt it would be the safer way to not change the car too much and leave Valtteri and Lewis' cars just about in the same place for qualifying."
He added: "The first early indications state that the new aero update works as predicted."
Bottas felt there was more to be gained from the new aero package but after qualifying 0.682s down on his teammate he suspects it actually offers less downforce.
"We don't have confirmation about the performance differences between the two packages -- on paper my car should have had more downforce, but being 0.7s off the pace I'm not quite sure. There are many, many variables, but one things for sure is that you need to get the tyres into their sweet spot, which is something the result suggests I didn't quite get for Q3."
The biggest problem for the drivers is keeping the tyres in the correct temperature window for maximum performance. Up until qualifying the car had lacked grip, inducing slides through high-speed corners, which in turn overheated the tyres. The issue created a downward spiral in performance as the overheating tyres offered less grip and induced more slides, but with cooler track conditions for qualifying -- which started at 17:00 local time -- the problem was less severe.
"If you hit the sweetspot of the tyre the times are competitive," Wolff said. "If you out of that temperature window -- either too low or too high -- the times are not competitive and we have seen discrepancies between our drivers and you have seen large discrepancies between drivers of other teams. So there's science that needs to go into understanding the optimum operating window."
Bottas is concerned the tyre issues may reappear in the race, which is set to be held two hours earlier than qualifying.
"I think we are facing a difficult day tomorrow, I think that's a fact," he said. "What we've seen so far this weekend suggests that Ferrari's and Red Bull's race pace is stronger than ours, especially if it's going to be hot, if there are no clouds covering the sun, it's going to be trickier for us.
"I expect a very difficult day, but like we saw in Singapore, we were struggling but the cooler and mixed conditions helped us a lot and the race pace was really good. Perhaps a shower would help us but we can't count on that. We have to make our car work in every conditions but at the moment it's not working as well as some of the other cars in these conditions."