Mercedes suffers from an inherent weakness at Spa and a reversion to its previous-specification floor was not behind the team's solid Belgian Grand Prix qualifying result, according to George Russell.
Both Mercedes drivers appeared downbeat after Friday practice, having struggled with the W15 around the Spa-Francorchamps circuit, which preceded a decision to revert to its old floor after trialling a new specification in FP1 and FP2.
Russell and Lewis Hamilton broke into Q3 during a wet qualifying session, Hamilton moving up to a third-place grid slot for Sunday's race after the application of pole-winner Max Verstappen's 10-place penalty.
Asked if switching back to the old floor was the reason why Mercedes found performance on Saturday, Russell responded in the negative – actually suggesting that the new floor worked as anticipated, but that the team wanted a more familiar set-up to contend with a bogey circuit.
"No, not at all. We have struggled here the last three years and the fluctuation in performance of all the teams circuit to circuit is pretty substantial," Russell said.
"I think it was important for us to revert to something we know and see in the race tomorrow whether it is a challenge with Spa for us, because we are pretty confident it is, as opposed to the upgrade.
"The upgrades were nothing substantial, they are just part of the development over the course of the year – we're pretty confident those upgrades were working as expected."
Russell was at a loss to explain why Mercedes frequently struggles at Spa, and yet is able to perform at Barcelona and Silverstone – circuits with a similar mix of high- and low-speed corners.
He added that Red Bull had found the opposite and had always been strong at the undulating Belgian course.
"It has been three years in a row that we have been very quick in Silverstone – obviously this season exceptionally quick – and struggled at Spa," Russell explained.
"On paper, you would say they are not exactly the same types of circuit but they have high-speed [corners] here, a bit of low-speed, the same as Silverstone. We need to try and understand why that is.
"There seems to be something inherent in the cars that work at certain circuits. Red Bull are always flying here, as an example, this is always their strongest circuit of the season, along with Austria.
"For us, Silverstone and Barcelona are the sort of circuits we tend to go very well at as well. So we need to understand that one."
Speaking to Servus TV, Mercedes team principal Toto Wolff suggested that his team had got its sums wrong with the mechanical set-up of the car on Friday.
Along with the floor change, the Austrian stated that Mercedes had addressed a few other concerns heading into Saturday's sessions.
"We know that we did a few things wrong yesterday," said Wolff. "We changed that on the car and rebuilt it. And today the drivers said it was much better. We think it was more of a mechanical thing where we messed up."
