Spa-Francorchamps is the longest track on the F1 schedule and - along with Monza - is one of the sport's most power-hungry venues where top speeds reach their highest levels of the season.
But the Ardennes circuit's 7-kilometer layout isn't only about top velocity, as its blend of high-speed corners calls for the right compromise – and even more so in the rain – between straight-line speed and downforce levels.
In free practice on Friday, Mercedes' quest for the best possible balance, and the prospect of a wet weekend, led the team to mount a bigger rear wing on Lewis Hamilton's car.
But the end result were lap times that were similar to Valtteri Bottas' lower downforce set-up as anything lost on the straights was recouped with superior grip in the corners.
Spa's completely unpredictable nature means that determining the right aero compromise is a near impossible task given the weather factor.
However, based on Saturday's speed trap readings, topped by McLaren's Daniel Ricciardo and recorded on in the first part of Spa's Kemmel straight, Mercedes appear to be banking on a dry race, having opted for a lower downforce configuration, at least as far as Lewis Hamilton's set-up is concerned.
Poleman Max Verstappen was over 6 km/h slower than his title rival through the speed trap, which suggests that Red Bull are favouring – as has often been the case this season - a higher downforce approach to Sunday's race, an option that perhaps entails greater flexibility on a wet track.
But if its dry this afternoon, Max could be forced to take a back seat to the Hamilton freight train on the Kemmel straight.
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