MPH: The F1 hidden treasure that's key to Mercedes catching Red Bull

Mercedes F1 technical director James Allison’s articulate way of expressing technical matters always makes for an interesting interview – and in Brazil last year, as he talked us through the ’23 season, he made a few observations about why it has taken so long to understand the full implications of the venturi underbody regulations introduced a couple of years ago.

Although the conflict between good underbody downforce and the onset of mechanical bouncing (which is quite a separate phenomenon from aerodynamic porpoising) is widely known now, there’s more to it than just that, as he explains:

“There is this sort of treasure of downforce we have near the ground”

“There is a fundamental difficulty in these rules in that the car will generate more downforce the lower it goes  – but not without limit because you don’t want it to just magnet itself onto the ground at the end of the straight. Because at the end of the straight you’re generally not going around a corner and if that’s where your best downforce is, it’s just generating drag. So in order to cope with the load that is created at the end of the straights, you’re going to need stiff springs or higher ride heights – but if you have higher ride heights you’re not going to be where the downforce is. So that means stiff springs.

“Which all means that with these cars there is this sort of treasure of downforce we have near the ground. You can find lots of it there but you also have to survive the end of the straight. So there is a sort of a limit because this end-of-straight downforce consumes ride height which then punishes you in the low-speed corners.

“There comes a point where it’s no longer faster [over the lap] to have that end-of-straight downforce because of how much you’re hurting yourself in the slow corners. Everyone will be trying to get things that, at the end of the straight, don’t have quite as much load – but which right next door to that [at a slightly lower speed] have lots of load. Because the fast corners are right next door to the end-of-straight speeds. So you want it to hang onto an adequate amount in the slow speed despite the fact that the car just wants to shit all its downforce away as it raises off the ground.”

Downforce naturally wants to square with speed, but in that gap between the fastest corner and the fastest end-of-straight speed, you ideally want it to stop doing that. It will still inevitably create more downforce with more speed but if you can get that curve to tail off in that narrow speed range, it will be to your benefit. The drag increase will be less and the car will not be forced down quite so hard on its suspension, thereby creating the possibility of setting the static ride height a little lower – allowing it to run lower than before on slow corners, giving you an aero benefit there. It might also allow you to run just enough softer on the suspension that the dreaded bouncing is not triggered. The softer suspension will also help you in the slower corner and traction zones.

“You can have a car which is a bit more one-dimensional at the sort of one-dimensional tracks where there isn’t a big speed range,” continues Allison. “Then you can maybe set your car up such that the corner speeds coincide with where your good bit is. And you don’t suffer horribly as it drops away either side. But when you go to a place which is a bit more of a broad test of a car, an Austin for example where there is lots of fast stuff, some slow stuff and some in between stuff, some decent straights and some bumps, that’s going to test that bit [between end-of-straight and fast corners]. It’s going to need to stay strong in the fast corners and it’s hard to persuade the car to do all of those things with a set of rules which don’t want it to do anything but run near the ground.”