What’s all this then?
A Laguna with the agility of a Porsche Boxster. Through a slalom, it will turn in instantly, change direction with comparable speed – but not hint at the dreaded pendulum. Your hands will have steered just one, crisp input, and been met with firm, accurate response. How do we know? Renault laid on the comparison for us. The most bizarre press launch test – but, intriguingly valid. Welcome to Active Drive. Or, to cut marketing hype, the four-wheel-steer Laguna. The Japanese loved such technology in the ‘80s but primitivity and expense killed it off. Renault’s unexpectedly revived it, given it a modern twist, and will sell it to you next year for about a grand. The system will also appear on the forthcoming Laguna Coupe.
But is it as good as, let’s say, a 3-series?
Well, would you believe, Renault brought that along, too. Over a twisting hill route, the Laguna was comparably responsive. Of course, the BMW was ultimately more satisfying, but the Laguna seemed as alert, as keyed in; input directly transmitted action. What’s more, it had better mid-corner steering response and was less severe and more linear on turn-in. Interestingly, it also banishes the electric power-assisted steering's soggy indecision – while the BMW’s hefty rack had more feel, the Renault was more sensitive to fingertip inputs. Naturally, it’s very agile in town, cutting wheel-twirling, but you probably guessed that, just as you’d imagine it shows up the standard Laguna; no comparisons with the BMW valid there.
Well, I’ll be. So how does it work?
At slow speeds, the rear wheels turn up to 3.5deg counter to the front (earlier systems managed little more than 1deg). Above 37mph, they go in the same direction, for the ultimate passive rear steer effect. The technology is simple; actuator unit and redesigned hub knuckle with fancy bushing. It weighs 19kg and fits into an unmodified Laguna platform (the fuel tank of all Lagunas shrunk, so they wouldn’t need a specific 4WS one). It’s controlled by an ECU, calculating a set amount of speed-dependent steer, then correcting this with an added element of ‘dynamic’ steer, which adjusts according to yaw rate, speed of steering and so on. The latter is the trick bit.
But now I’m standing back. All well and good, but… why?
You betcha. We’ve seen papers showing Renault patented the technology back in 1991, but even the engineers admit the hardware is straightforward. Modelling the dynamic part is what took the time, painstakingly developed over four years by Renault and RenaultSport engineers. But it means rear steer is exact, not estimated. At any speed and dynamic load, the ideal degree of turn is dialled in. And that’s a first. It’s safer, too: already, there’s communication with the ESP (on which it’s less reliant). In the future, this can only be enhanced – has Renault pre-empted any EuroNCAP stability control tests? No wonder the chief engineer got a promotion out of it.
Renault seems wedded to the cheap-to-produce twist-beam rear suspension, as rivals’ embrace superior multi-link set-ups. With Active Drive, it can offer dynamics for those who want it, without bumping up low prices for those who don’t. But it’s also a modular system. Renault can fit it to anything sharing a similar rear: such as, say, the future Espace, with all the city-centre manoeuvrability benefits that would bring. That was from te mouth of the engineer, too. Oh, and think of how brilliantly agile a RenaultSport Megane or Clio with Active Drive could be. Lithe 205 GTI pointability but without the lemming tendencies? Bring it on.