THE HEIGHT OF THE MATTER

Under F1’s previous ruleset, rear ride height varied from 120mm to 140mm for the most extreme ‘high-rake’ designs. Now most cars operate in a narrow window around 60mm.

The science is simple: air passing at high speed under the car and through the twin venturi is generating a lowpressure area, in effect sucking the vehicle towards the ground. But that force will also draw air in from the side of the car, diminishing the suction effect. There is a balance to be struck because, if the car gets too low, the diffuser can stall, setting in motion the cyclical process of porpoising. This is a separate but related problem to the bouncing initiated by a low-riding, stiffly suspended car bottoming out.

With any ground-effect car some porpoising is inevitable. The skill of the designers and engineers is to make it less like a switch so the car is stable in as many conditions as possible.

Last year the FIA tried to reduce porpoising by reducing overall downforce. A proposal to raise the edges of the floors by 25mm was watered down to 15mm as the majority of teams reduced the impact of the problem by development.

While most teams took this opportunity to run their cars lower, achieving legality by raising the floor at the edge, Mercedes stuck to its late-2022 policy of optimising around a higher ride height, having been forced in that direction while curing the W13’s bouncing. While there were reasons for this – most teams agree simulations fall short in predicting bouncing – Merc quickly realised it was chasing limited gains.

“We placed value on the wrong things,” says technical director James Allison. “There was a debate: should we cash in that 15mm and drop the car down, operate in a window that’s 15mm smaller because the cars will be less bouncy inherently? Or should we do more of what has done us well over the course of the year [2022], which is force ourselves to keep looking for downforce where it’s difficult: high up?”

The mid-season revamp focused on undoing that decision but there were limits to what could be done, given the structural integration of the rear suspension and the gearbox casing. This year’s W15 features new front and rear suspension geometry and a new gearbox too.